Adsorption characteristic of Cs+ and Co2+ ions from aqueous solutions onto geological sediments of radioactive waste disposal site

Journal of Geochemical Exploration 206 (2019) 106366

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Adsorption characteristic of Cs+ and Co2+ ions from aqueous solutions onto geological sediments of radioactive waste disposal site

T

Mahmoud M. Goudaa, Yehia H. Dawoodb, Ahmed A. Zakia, Haneen A. Salam Ibrahima, ⁎ Mohamed R. El-Naggara, , Ahmed Gadb a b

Hot Laboratories Center, Atomic Energy Authority, Post Code 13759, Cairo, Egypt Ain Shams University, Faculty of Sciences, Geology Department, Abbassia, 11566 Cairo, Egypt

ARTICLE INFO

ABSTRACT

Keywords: Geochemistry Inshas sediments Modeling Radioactive waste disposal

The physico-chemical characteristics of clayey (CS) and brown sand (BSS1) sediments from the host geological formation of Inshas radioactive waste disposal site were explored and were correlated with the adsorption properties toward Cs+ and Co2+. Fe2O3 and SiO2 were the two most abundant chemical compounds in both sediments with greater percentage of the former in the CS which had platy surfaces (31.51 m2/g). FT-IR analyses evidenced the comparability between the contained low quantities of organic matter in both sediments. Geochemical study was carried out to investigate the weathering history and tectonic setting taken from the site area. Batch adsorption experiments of Cs+ and Co2+ reflected greater capacities of the CS which were correlated to the occurrence of hematite, kaolinite, vermiculite and plagioclase minerals, detected by XRD. All studied adsorption systems were kinetically controlled by the chemical sorption mechanism. The sorption isotherms ordered the adsorbed amounts to the following: Cs+/CS > Cs+/BSS1 > Co2+/CS > Co2+/BSS1. Langmuir, Freundlich, Dubinin-Radushkevitch and Temkin isotherm equations were applied to specify the affinities of CS and BSS1. Values of ΔH° reflected the exothermic natures for both systems of Cs+ and vice-versa regarding Co2+. Values of ∆G° revealed that the only spontaneous systems were the Cs+/CS at 298 and 313 K. The studied sediments gave good performance toward postponing the potential release of Cs+ and Co2+ into biosphere.

1. Introduction Management of radioactive wastes, including the disposal option, is mandatory to protect the environment from their essential disorders to human health. Egypt produces different kinds of such wastes among which aqueous operational forms are generated from two research reactors (ETRR-1 and ETRR-2) as well as production and applications of radioisotopes in medicine, research, education, … etc. (Abdel Rahman et al., 2005). Radionuclides of cesium and cobalt are among the majors that are presented in the radioactive wastes of a nuclear power or research reactors origin. Abdelhady (Abdelhady, 2013) mentioned the nuclide concentrations (Bq/m3) in the pool water of ETRR-2 where cesium (134Cs and 137Cs; t1/2 of 2.06 and ~ 30.0 y, respectively) and cobalt (60Co; t1/2 of 5.27 y) radionuclides were significantly represented. The adverse environmental impact, which may last long, of such radionuclides is due to the high solubility and mobility of cesium in the geosphere (Lebedev et al., 2003) beside the potential hazards of 60 Co as a high-energy gamma emitter (Zhu et al., 2014). The host geological formation is an essential complementary barrier ⁎

to postpone or prevent the release of the isolated radionuclides into the biosphere. The essentiality of such natural barriers depends on the fact that if the isolated radionuclides overcame the designed engineering barriers the prevention of their release into the biosphere will rely solely on the geochemical characteristics of the host site. Clay minerals, components of geological sediment, play a crucial adsorptive rule toward the long period potential release of radionuclides into radioactive waste disposal sites. Therefore, many researchers utilized the clay minerals in treatment of waste streams containing heavy metals, dyes and isotopes for instance (Adeyemo et al., 2017; Yin et al., 2017; AbdelKarim et al., 2016; Bentahar et al., 2016; Benedicto et al., 2014; Fan et al., 2014; Missana et al., 2014; Tournassat et al., 2013). The usage of clays as adsorbents have advantages upon many other commercially available ones in terms of low-cost, an abundant availability, high specific surface area, excellent adsorption properties, and large potential for ion exchange (Srinivasan, 2011) and a good ability to retain radionuclides by physicochemical adsorption that represent excellent natural barriers. Inshas locality is an authorized radioactive waste disposal area (~1.0 Km2) which located at longitudes of 31° 20′ & 31°

Corresponding author. E-mail address: [email protected] (M.R. El-Naggar).

https://doi.org/10.1016/j.gexplo.2019.106366 Received 19 March 2019; Received in revised form 19 August 2019; Accepted 23 August 2019 Available online 27 August 2019 0375-6742/ © 2019 Elsevier B.V. All rights reserved.

Journal of Geochemical Exploration 206 (2019) 106366

M.M. Gouda, et al.

longitudes of 31o 20′ and 31o 30′E) (Fig. 1) (Sultan et al., 2009). Three quaternary sediments of brown sand 1 (BSS1), brown sand 2 (BBS2) and yellow sand (YSS) were collected at depths of 1.5, 3.0 and 4.0, respectively. Two Miocene sediments of sandstone (SS) and clay (CS) were collected at depths of 5.0 and 6.5 m, respectively.

30′ E and latitudes of 30° 15′ & 30° 25′ N. Several studies have been done to evaluate the adsorption and mobility of radionuclides onto some quaternary deposits of such area (Abdel-Karim et al., 2019; AbdelKarim et al., 2016; Araffa et al., 2012; Seliman et al., 2012; Sultan et al., 2009; Kamel, 2002; Kamel and Navratil, 2002; Abdel-Aziz, 1996). Thus the present study aimed to the geochemical characterization of five sediments, collected from Inshas radioactive waste disposal site, to define their geological origin and the weathering conditions during their deposition. Further physico-chemical characterizations were carried out on two samples of them to be correlated to their adsorption properties toward cesium and cobalt ions from their aqueous solutions. Batch sorption experiments were designed and classical sorption models were used to propose retention parameters.

2.3. Characterizations The major and minor oxides percentages of the collected five sediments were determined using X-ray fluorescence (XRF-1800 SHIMADZU) technique, in Egyptian Atomic Energy Authority, with a rhodium tube and a 2.5 kW generator. The collected five sediments were subjected to the granulation test which was achieved by the dry sieve analysis method adopted by Ingram (1971) and Lewis and McConchie (1994). Organic matter (OM) and carbonate material (CM) were removed perior to the granulation test since the former is an important cementing agent in many sedimentary environments causing aggregation of sediments and the later are commonly in situ formed structures which alter the grain size and other textural data and complicate the interpretation. Removal of OM and CM was carried out using H2O2 (30%) and diluted HCl (10%), respectively. The physico-chemical characterizations were carried out on the as-received BSS1 and CS, without pre-treatments. A finely ground powder BBS1 and three oriented- particale mounts CS were subjected to X-ray diffraction to determine their non- clay and clay minerals. The later were used as untreated, glycolated and heated at 550 °C for 2 h (Bish and Post, 1989;

2. Experimental 2.1. Chemicals and sediments Chloride salts of cesium and cobalt are supplied from Sigma–Aldrich Co. Hydrochloric acid, hydrogen peroxide and sodium hydroxide pellets are products of Prolao Co. 2.2. Sediments Five samples were collected from Inshas disposal site (the northeastern part of Cairo, Egypt; latitudes of 30o 15′ and 30o 23′N and

Fig. 1. (a) Location map and (b) Litho-stratigraphic units of the borehole in Inshas radioactive waste disposal site with locations of the collected samples (Sultan et al., 2009). 2

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Środoń, 2006) The samples were determined using X-ray diffraction (Philips, XRD-PW1710), with monochromator of Cu-radiation (λ = 1.542 Å), supplied with powder diffraction files (PDF-2) as standard references, at 45 K.V., 35 M.A. and scanning speed 0.03o/s. were used in Egyptian Mineral Resources Authority. Fourier transforms infrared spectra and thermal analysis curves were collected by FT-IR (BOMEM, MB-Series) and DTA/TGA system (Shimadzu corporation, Kyoto-Japan), respectively. Total surface area of the studied sediments was determined using the BET-equation by means of Nova BET instrument (Quantachrome Corporation, USA), in which N2 adsorption/ desorption isotherms were constructed. Surface morphology of the BSS1 and CS was examined using the scanning electron microscopy (Philips, XL-30). Both the analyses of surface area and morphology were carried out in the Egyptian Atomic Energy Authority.

properties of a sorbent and its subsequent affinities (El-Kamash, 2008). Adsorption isotherms were constructed, in order to describe the adsorption mechanisms, depending on the relation between the amount of adsorbed ion (qe) and the final ion concentration at equilibrium (Ce) in the solution (Desta, 2013). Batches were designed using metal ion concentration range of 25–800 mg/L and each was overnight shaken with 0.1 g of an examined sample, at different temperatures. Langmuir (Langmuir, 1916), Freundlich (Freundlich, 1906), Dubinin–Radushkevich (Dubinin and Radushkevich, 1947) and Temkin (Temkin and Pyzhev, 1940) isotherm models are the most familiar tools to describe adsorption mechanisms. 2.4.2.1. Langmiur isotherm model.

qe =

2.4. Sorption experiments

2.4.2.2. Freundlich isotherm model.

qe = Kf Ce1/ n

2.4.2.3. Dubinin–Radushkevich isotherm model.

qt =

exp

2.4.2.4. Temkin isotherm model.

qe =

RT ln KT Ce bT

(7)

where T is absolute temperature of the aqueous solution, R is the gas constant (8.314 J/mol K), bT (J/mol) is the Temkin isotherm constant related to the heat of adsorption energy and KT (L/mg) is the equilibrium binding constant corresponding to the maximum binding energy. The evaluation of the fit in the isotherm to the experimental equilibrium data requires different error functions to define it. In this study, linear correlation coefficients, R2adjusted and a number of error functions such as root mean square error (RMSE) were used to rule the equilibrium model that calculated and Chi square (χ2) as similar RMSE as Eqs. (8)–(10) 2 Radjusted =1

RMSE = n

X2 = i=1

R2)(N

[(1 1×

(qexp .

P

1)]

(qexp .

qcalc.)

(8)

n

1 n

1)(N

1

i=1

(9)

qcalc.)2 qexp .

(10)

where P is the number of parameters, N is the total of points, Cexp. is the experimental data for adsorbed concentration, Ccal. is the calculation data by the model and n is the number of observations. Smaller value of indicates the better fit of the model.

(2)

k2 qe2 t 1 + k2 qe t

(6)

where Kp is a constant related to the sorption energy qm (mg/g), it is the theoretical saturation capacity and ε is the Polanyi potential.

(1)

k1 t )

kp 2

qe = qmexp

where Ct and Co are the metal ion concentration at time t and its initial concentration (mg/L), respectively. Both of the pseudo first- and pseudo second-order kinetic models are helpful for the prediction of adsorption rates, were applied according to Eqs. (2)–(3), respectively (Lagergren, 1898; Ho and McKay, 1999):

qt = qe (1

(5)

where Kf is constant indicative of the relative sorption capacity of the sorbent (mg/g) and 1/n is the constant indicative of the intensity of sorption process.

2.4.1. Sorption kinetic investigation These studies were performed at constants of pH (7 ± 0.1; to avoid the cation hydrolysis of cobalt) and fixed V/m (0.1) in order to examine the effects of contact time and initial metal ion concentration. Batches were designed using metal ion concentration range of 25–800 mg/L (to provide sufficient driving forces) and were shaken at different temperature (298–333 K). At different time intervals (2–120 min.), batches were centrifuged, liquid phase were collected, and the concentration of Cs+ and Co2+ were determined spectrophotometrically (Buck scientific model VGP 210) at wavelengths of 455 and 347 nm, respectively. The sorbed amounts of metal ions (qt, mg/g) were calculated by using:

qt = (Co

(4)

where Qo is the monolayer sorption capacity (mg/g) and b is the constant related to the free energy of adsorption.

Batch technique was selected to investigate the sorption behavior of the collected as-received CS (< 63 μm) and BSS1 (< 500 μm) toward cesium and cobalt ions, in triplets. Single component aqueous solutions containing either Cs+ or Co2+ were prepared using bi-distilled water to make an initial sorption assessment of the selected samples. The effect of solution pH on the sorption processes was explored at a range from 2.0 to 12.0 ± 0.02 by contacting 0.1 g sample (BSS1 or CS) with 10 mL aqueous solution of Cs+ or Co2+ (100 mg/L) in 25 mL bottles. Bottles were sealed and then shaken for 2 h at 298 K. The pH of the solutions were adjusted using 0.1 M NaOH and/or 0.1 M HCl and the pH values were measured using a digital pH meter of Hanna Instruments type. The choice of initial concentration and V/m, where V is the solution volume (L) and m is the mass of sorbent (g), was selected to provide sufficient driving force to overcome the mass transfer resistance between aqueous and solid phases. The optimum pH value (at which higher sorbed amounts, mg/g, of the studied metal ions were achieved) was applied to study the effect of different ratios V/m (0.02–0.2) on the sorbed amounts (mg/g) of the studied metal ions.

V Ct ) m

QobCe 1 + bCe

(3)

where qe is the amount of ion adsorbed at equilibrium (mg/g), k1 is Lagergren rate constant for adsorption (min−1), and k2 is pseudosecond order rate constant for adsorption (g/mg min).

3. Results and discussions

2.4.2. Sorption at chemical equilibrium Parameters of the adsorption steady states can express the surface

3.1.1. Elemental analysis The surface geology and stratigraphic description of the study area

3.1. Characterizations

3

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Table 1 Quantitative elemental analysis (%) of the different sediments taken from Inshas disposal site. Sediment

Depth

Na2O

MgO

Al2O3

SiO2

P2O5

Fe2O3

K2O

CaO

TiO2

SO3

MnO

CuO

Cl

LOI

Total

BSS1 BSS2 YSS SS CS

1.5 m 3.0 m 4.0 m 5.0 m 6.5 m

2.43 2.75 2.90 1.74 1.22

6.18 4.74 1.72 3.97 2.23

6.91 5.81 3.74 4.42 12.84

43.94 49.96 71.43 59.14 27.74

0.76 0.71 0.54 0.43 0.37

21.87 20.91 8.79 8.49 40.67

0.75 1.08 1.95 0.52 0.83

10.97 9.92 4.96 17.79 2.71

0.42 0.33 0.59 0.24 0.62

1.03 0.46 0.68 0.19 0.48

1.44 0.91 0.12 0.44 0.73

0.34 0.04 0.14 0.12 0.28

0.43 0.28 0.15 0.27 0.19

2.49 2.06 2.26 2.22 9.06

99.96 99.96 99.97 99.98 99.97

BBS1 = Brown sand sample 1; BBS2 = Brown sand sample 2; CS = clayey sample; LOI = Loss of ignition; SS = Sandstone sample; YSS = Yellow sand sample.

are covered by quaternary deposits which consistence by different formations such as, sand sheets that belong to Bilbies and Inshas formations (EGSMA, 1998). Data in Table 1 gave the chemical composition (%) in major and minor oxides of different samples, as determined by XRF spectroscopy. It is noticeable that, the major oxides were arranged as Fe2O3 > SiO2 > Al2O3 and SiO2 > Fe2O3 > CaO > Al2O3 > MgO in CS and BSS1, respectively. While, the minor oxides were arranged as CaO > MgO > Na2O and MnO > Na2O in CS and BSS1, respectively. The CS lost greater value (9.06%) of its weight, upon ignition, than the BBS1 (2.49%). This may be due to larger amount of organic matter in the CS, compared to the BBS1, as well as the dehydroxylation of kaolinite in O − H bond (Cravero et al., 2016).

was represented by kaolinite (one tetrahedral sheet fused to an octahedral sheet; 1:1 layer type), vermiculite (two tetrahedral sheets fused to one octahedral alumina or magnesia sheet; 2:1 layer type) and plagioclase (albite; sodium aluminum-silicates). Regarding the 1st and 2nd runs (untreated and glycerol, respectively) kaolinite was observed at 12.31° (7.17 Å) and 24.86° (3.58 Å), while it was disappeared due to its destruction upon heating and transformed into metakaolinite (ElNaggar, 2014; Greenlee et al., 2012). Vermiculite was observed at 6.22° (14.2 Å), 12.31° (7.17 Å) and 24.86° (4.57 Å) which was shifted by heating to be observed at 8.8° (10 Å) (Motokawa et al., 2014; Morimoto et al., 2012; Scarciglia et al., 2008). Quartz was detected at 20.85° (4.26 Å) and 26.7° (3.35 Å) and plagioclase (albite) was observed at 27.90° (3.196 Å). Regarding the BBS1 (Fig. 2b), the main structure of quartz (SiO2) was detected at 50.22° (1.817 Å), 26.70° (3.34 Å) and 20.85° (4.26 Å). Additionally, albite was observed at 29.43° (3.035 Å)

3.1.2. X-ray diffraction analysis X-ray diffraction patterns of the studied clayey sand sample (Fig. 2a)

Fig. 2. (a, b) X-ray diffraction patterns, (c, d) FT-IR spactra and (e, f) thermal analysis of CS and BSS1 of Inshas disposal site, respectively. BSS1 = brown sand sample 1; CS = clay sample. 4

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and 27.92° (3.196 Å). The co-associated quartz and albite minerals were detected at 42.60° (2.122 Å), 39.48° (2.28 Å) and 36.56° (2.458 Å). Calcite and magnesian were observed at 39.48° (2.28) and 29.43° (3.035 Å). This observation was in harmony with the obtained major value of CaO and MgO (Table 1).

Table 2 TGA dependent weight losses (%) of the clayey and brown sand sediments of Inshas disposal site. Temperature (K)

300–473 473–873 873–1173

3.1.3. FTIR spectral analysis Fig. 2c, d represents the FT-IR spectral analyses of CS and BSS1, respectively. Bands arising from 1032 to 1030 cm−1 and their associated band around 915 cm−1 may be due to the symmetric stretching band vibration of Si − O − T (T: Al or Si) and the associated hydrogen banding, respectively (Martinez et al., 2010). The better intensity and broadness of Si − O − T band was in the clayey sample (Fig. 2c) which may be attributed to the more substitution of aluminum into silicon (Zawrah et al., 2014). Bands arising at 468 cm−1 may be due to the bending vibration of Si − O − Si (Zawrah et al., 2014; Runliang et al., 2008; Van der Marel and Beutelspacher, 1976). The CeH bond vibrations of the presented organic matter were observed between 2929.8 and 2855.4 cm−1 (El-Naggar et al., 2018) with comparable intensities. This observation may indicate that both samples contain low amounts of organic matter. Bands at the range from 780.2 to 691.5 cm−1 may be attributed to the stretching bonding vibrations of Si − O with more expected its higher content of quartz in the BSS1 (Nirmala and Viruthagiri, 2014; Russell and Fraser, 1994; Hlavay et al., 1978). Hematite was evidenced in the clayey sample (Fig. 2c) through the observed band at 535 cm−1 (Farmer, 1974). Calcite mineral was also reflected in Fig. 2c, d via the appearance of CO32– bond vibrations at different wavenumbers (1440.1–1431.3, 1798.1–1797 and 2518.3–2516 cm−1). Since the BSS1 recorded higher amount of calcite (Table 1) than the CS one, its CO32– band was more intense with the associated band at 876 cm−1 (Senthil and Rajkumar, 2014; Ndukwe and Jenmi, 2008; Chester and Elderfield, 1967). The bending vibrations of H − OH were observed around 1642 cm−1 (Wan et al., 2017; Wang et al., 2013). The stretching bonding vibrations of water and surface hydroxyl groups were presented through the observed bands at the regions from 3697.1 to 3430.2 cm−1. The more broadened band that was recorded by the CS reflecting higher amounts of absorbed water and surface hydroxyls duo to clay minerals (Martinez et al., 2010).

Weight loss, % Clayey sample

Brown sand sample 1

8.41 4.65 4.02

2.37 1.42 0.72

3.1.5. Surface area analyses The quantity of N2 adsorbed per sample mass unit is represented as a function of the relative pressure (p/po), where p is the equilibrium pressure, and po is the saturation pressure of the adsorbate at 77 K. The values of the BET analysis regarding the specific surface area were found to be 31.51 m2/g for CS and 17.55 m2/g for BSS1 as shown in Fig. 3(a, b). Scanning electron micrographs (SEM) was performed to observe the particle morphology of the clay samples. The SEM of both samples in Fig. 3(c, d) show different porous sizes and platy structure and irregular shape of the clayey particles. The granulation in the grain size of the sediments in the study area was illustrated in Fig. 4. Such figure explained that the percent of silt and clay (< 63 μ) in clayey sand sample was 89.9% higher than in the BSS1 (17.40%) which affected in the adsorption process of the studied metal ions. 3.2. Geochemistry of the samples 3.2.1. Geochemical classification The sediment samples of the studied area were classified according to the log (SiO2/Al2O3) vs. log (Na2O/K2O) binary variation diagram (Pettijohn et al., 1972) into litharenite and graywake (Fig. 5a). In addition, the log (SiO2/Al2O3) vs. log (Fe2O3/K2O) binary variation diagram by Herron (1988), the taken samples were in Fe-sands and -shales as shown in Fig. 5b. These findings are in accordance with those in the elemental analysis, given in Table 1. Abdel-Karim and co-workers stated that the presence of high contents of iron oxides are more likely in controlling the adsorption of some radionuclides (Abdel-Karim et al., 2019). The Plots of Na2O vs. K2O of the studied sediments illustrated their intermediate quartz nature (Crook, 1974), as shown in Fig. 5c.

3.1.4. Thermal analysis Adsorbed water was detected at temperature range from 298 to 423 K (Fig. 2e, f). The quantity of adsorbed water onto CS was greater than that onto the BSS1. This may be due to the amount of physically absorbed water to the flat oxygen planes which resulted from Si eO – Si and Si – O – Al groups, as detected by FT-IR examinations. It was found that the broad endothermic peak at 367.67 K (94.67 °C) is greater than that at 339.08 K with continuous mass weight loss of 8.41 and 2.37% from 300 to 473 K in CS and BSS1, respectively. These endothermic peaks play crucial roles in the adsorption properties of samples. The endothermic peak at 779.61 K in CS appears broader than that at 779.20 K in the BSS1. This may be attributed to the dehydroxylation and desorption of the chemically bounded water in kaolinite [Al2Si2O5(OH)4.2H2O] and vermiculite [(Mg, Fe, Al)3·(Al, Si)4O10(OH)2. 4H2O] minerals (Yoshikawa et al., 2017; Cravero et al., 2016; Ptáček et al., 2011; Mathieson and Walker, 1954). The weight loss was 4.65% and 1.42% in a temperature range from 473 to 873 K in CS and BSS1, respectively. The weights lost during thermal treatment of both the samples were explained in Table 2. The total loss weight in the CS was higher than from the BSS1 because the dehydroxylation of OH bonds in clay minerals and iron hydroxide (high percent of Fe2O3) in the CS. There are studies indicated that this is the temperature most vermiculites start to loss hydroxyl water and begin to undergo structural changes (Walker, 1951).

3.2.2. Provenance Major elements were applied to infer the provenance of the taken samples. Roser and Korsch (1988), as given by Eqs. (11) & (12), used major element discriminant functions to discriminate four provenances, namely mafic, intermediate, felsic igneous rocks and quartzose recycled (Sahraeyan and Bahrami, 2012). They examined their data using discriminant function analysis in an attempt to improve separation between groups. This was achieved by setting a series of linear functions based on multiple variables, designed to achieve best separation between predefined groups of standard data. Application of discriminant function diagram into the present taken samples (Fig. 5d) indicated their mafic igneous sources except one sample which was of quartzose sedimentary provenance.

Discriminant function 1 = 9.09 + 0.607 Al2 O3 + 0.760 Fe2 O3 + 0.616 CaO + 0.509 Na2O 1.773 TiO2 MgO

5

1.224 K2O

0.50 (11)

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Fig. 3. (a, b) Adsorption-desorption curves of N2 at 77 K and (c, d) Scanning electron micrographs of CS and BSS1 of Inshas disposal site, respectively. BSS1 = brown sand sample 1; CS = clay sample.

addition, McLennan et al. (1980), recognizing the significance of Al and Ti in provenance studies, proposed a Al2O3 versus TiO2 bivariate discrimination diagram to constrain the provenance of siliciclastic rocks. The siliciclastic sediments of the study area plot between basalt and basalt-granite region was illustrated in Fig. 6d.

Discriminant function 2 = 0.445 TiO2 + 0.07 Al2 O3 + 0.438 CaO + 1.475 Na2O + 1.426 K2 O 1.142 MgO Fe2 O3

0.25

6.861 (12)

3.2.5. Weathering in the source area Geochemical parameters obtained from the analysis of sedimentary rocks are widely used to infer weathering and paleoweathering conditions of source areas. There are various factors affected in intensity of chemical weathering for examples: source rock composition, climatic conditions, duration of weathering and rates of tectonic uplift of source region (Akarish and El-Gohary, 2008). Table 3 illustrated the calculation of the chemical index of alteration (CIA; Nesbitt and Young, 1982), plagioclase index of alteration (PIA; Fedo et al., 1995) which are widely used to deduce the intensity of the source area weathering (ArmstrongAltrin and Machain-Castillo, 2016). The chemical index of weathering (CIW; Harnois, 1988), the source weathering of carbonate-bearing siliciclastic rocks a modified version of CIW (CIW′; Cullers, 2000) and index of chemical variability (ICV; Cox et al., 1995) were used to assess the weathering history of the source area and were given by:

The plots of CIA vs. Al2O3 depicted that most samples were of low degree of weathering of the source materials (CIA between 30 and 60%). While CS recorded a CIA value of 79.75% indicating its moderate to intensive weathering, as shown in Fig. 6a. 3.2.3. Maturity and climatic conditions during sedimentation Suttner and Dutta (1986) proposed a binary diagram of SiO2 vs. (Al2O3 + K2O + Na2O) weight percentages. Increasing in degree of chemical weathering may reflect the decreasing in tectonic activity and/or change in climate toward warm and humid conditions. Chemical maturity of the taken samples indicated that the CS was deposited under semiarid to humid conditions, as shown in Fig. 6b. 3.2.4. Tectonic setting The most favorable discrimination parameters which represented by the various tectonic settings through the plot of SiO2/Al2O3 vs. K2O/ Na2O are active continental and passive margins (Maynard et al., 1982). Most of the studied samples were formed between an active margin and a passive one Fig. 6c. Studies have shown that Al2O3/TiO2 ratios ranging from 3 to 8, 8–21 and 21–70 indicate mafic igneous, intermediate and felsic igneous rocks, respectively (Hayashi et al., 1997; Sugitani et al., 2006). The studied samples recorded values of Al2O3/TiO2 in the ranges of 6.38% and 20.84% with an average of 14.70% indicating that the taken samples were intermediate rocks. In

CIA =

Al2 O3 × 100 Al2 O3 + CaO + Na2 O + K2 O

(13)

CIW =

Al2 O3 × 100 Al2O3 + CaO + Na2O

(14)

PIA =

Al2 O3 K2 O Al2 O3 + CaO + Na2O

MIA = 2 × (CIA 6

50)

K2 O

× 100

(15) (16)

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determined and the results were along with CIW values. According to CIA values the degree of source weathering (31.83–79.85%; average of 53.24%), the high CIA values in CS indicated moderate weathering with a complete removal of alkali and alkaline earth elements and an increase in Al2O3. Additionally, CIA values reflected a low degree of chemical weathering and the average ICV values suggested immature sediments. PIA values indicated the intensity of alteration of source material varies from 22.78 to 57.07% (average of 52.17%). CIW values suggested the degree of source weathering (38.18–84.11%; average of 57.64%) and the values of CIW′ (56.36–91.37%; average of 72.25%) which indicated that low weathering at the source of sediments. The values of CIA, PIA, CIW and CIW′ in the samples of sediments reflect a low to moderate degree of chemical weathering except the CS where such values were 79.85, 83.22, 84.11, and 91.37%, respectively, indicating a moderate to intensive weathering in this sample. 3.3. Kinetic investigations In order to host a radioactive waste disposal, geological sediments require sorption properties able to limit the release of radionuclides into geosphere. Sorption properties of CS and BSS1 have been experimentally investigated toward the uptake of Cs+ and Co2+ from aqueous chloride solutions. Preliminary investigations were carried out to explore the effects of pH and V/m in sorption process (Fig. 7a, b) at constant temperature 298 K and initial metal ions concentrations (100 mg/L). Data revealed that uptakes of Cs+ and Co2+ were sharply increased until pH range from 7 to 8 with subsequent slowly decreasing where the pH of the solutions were adjusted using 0.1 M NaOH and/or 0.1 M HCl to avoid the cobalt hydroxylation at pH 8.0. In addition, a direct relation was observed between the sorbed amounts of Cs+ and Co2+ and their corresponding values of V/m. Additionally, factors like contact time and initial metal ion concentration, which may affect on the sorption parameters, were also investigated at different temperature values (298, 313 and 333 K). 3.3.1. Effect of contact time Fig. 7(c, d) showed the temperature dependent variation of the sorbed amounts of Cs+ and Co2+ as affected by sediment type, at constants of initial concentration (100 mg/L) and pH (7.0 ± 0.1). Data indicated that the CS sorbed greater amounts of both metal ions than the BSS1. These sorbed amounts were increased gradually by time (up to 120 min.). The equilibriums of Cs+ on both studied sediments were attained faster (30 min.) than those of Co2+ (60 min.). These findings reflect the ability of the studied sediments (especially the clayey one) to limit the transfer of Cs+ and Co2+ into the biosphere if they possibly leached from the disposed radioactive waste packages. 3.3.2. Effect of initial concentration The effect of initial concentration (25–800 mg/L) of both Cs+ and 2+ Co on the temperature dependent sorption behaviors of the examined CS and BSS1 was illustrated in Fig. 8(a,b) at constants of pH and V/m values. As expected, the higher concentrations recorded higher sorbed amounts for all studied systems with the associated favorability of the clayey sample. Additionally, lower temperatures favored the sorption of Cs+, vice versa regarding Co2+. Data also indicated that, the amounts of both metal ions those sorbed onto the clayey sample was greater than those sorbed onto BSS1. Fig. 4. Grain size analysis for the five samples of sediments in Inshas disposal site.

3.3.3. Kinetic modeling In order to clarify the kinetic characteristics of sorption of Cs+ and 2+ Co sorption onto the studied CS and BSS1 with time, an appropriate kinetic model is required. Toward achieving this goal, both pseudo firstand second-order kinetic models were applied to analyze the experimentally obtained data.

In case of the values of CIA are 100% that means complete weathering of a primary material into its equivalent weathered product. The low CIA value, approximately 50, implies an un-weathered upper crust or weak weathering. In Table 3, following the procedure of McLennan (1993), the CIA, PIA and CIW values of the studied sediments have been

3.3.3.1. Pseudo first-order kinetic model. Based on the sorption capacity, 7

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Fig. 5. The binary variation diagram of sediments as (a) Log (SiO2/Al2O3) − Log (Na2O/K2O) (after Pettijohn et al., 1972). (b) Log (SiO2/Al2O3) − Log (Fe2O3/K2O) (after Herron, 1988), (c) Plot of Na2O versus K2O of the studied sediments (after Crook, 1974), (d) Discriminant function diagram (after Roser and Korsch, 1988).

this model assumes that the reaction rate is limited by only one process or mechanism on a single class of sorbing sites and that all sites are of the time dependent type. The Lagergreen pseudo first-order expression as written as (Lagergren, 1898):

log (qe

qt ) = log qe

k1 t 2.303

3.4. Adsorption at chemical equilibrium Isotherms were constructed to express the adsorption of Cs+ and Co2+ onto CS and BSS1, at different temperatures (Fig. 10a,b), at the equilibrium conditions. Data revealed that, at 298 K, the adsorbed amounts followed the order of Cs+/CS > Cs+/BBS1 > Co2+/CS > Co2+/BSS1. Additionally, exothermic natures were observed for both adsorption systems of Cs+ and vice versa regarding Co2+. In order to identify the surface properties and affinities, four isotherm equations (Langmuir, Freundlich, Dubinin-Radushkevitch and Temkin) were applied.

(17)

The plotting of log(qe-qt) vs. t for Cs+ and Co2+ sorption onto the CS and BSS1, as affected by temperature (K), were shown in Fig. 9(a, b). Linearity of these figures was used to determine the first order rate constants (k1) and the calculated equilibrium sorption capacities (qe) and their corresponding correlation coefficients (Table 4).

3.4.1. Langmiur isotherm model The basic assumptions of this model are that adsorption takes place in monolayer coverage onto homogeneous surfaces that have energetically identical active sites with negligible interactions between the adsorbed molecules. For all studied systems, the linear form of Langmuir isotherm model (Eq. (19)) was utilized to calculate the numerical values of the monolayer sorption capacities (Qo) and the constant which related to the free energy of adsorption (b α e-ΔG/RT) (Table 5). These were obtained from slopes and intercepts of the linearized plots of (Ce/qe) vs. Ce (Fig. 11a, b).

3.3.3.2. Pseudo second-order kinetic model. A pseudo second-order rate model can be applied to describe the kinetics of the sorption of ions onto the adsorbent materials. This model can be expressed as:

t 1 1 = + t qt qe k2 qe2

(18)

Plotting of t/qt vs. t for Cs+ and Co2+ sorption onto the studied CS and BSS1 were shown in Fig. 9(c, d), respectively. The closeness of the correlation coefficients (R2) of the linear fits to unity (0.999) suggested the strong relationships between their parameters. The kinetic parameters of this model were calculated from the slopes and intercepts (Table 4) beside the initial sorption rates (h = k2qe2). It is possible to suggest that the sorption of Cs+ and Co2+ followed the pseudo-second order kinetic model, for all studied systems, to be controlled by the chemical sorption mechanism.

Ce 1 1 = o + o Ce qe Qb Q

(19) o

+

Data in Table 5 indicated that the Q values of Cs are relatively higher than that of Co2+ for both sediments. The Langmuir constants Qo and b for the sorption of both ions decreased with increasing temperature as in case of Cs+, but these values increased with increasing temperature in case of Co2+. One of the essential characteristics of this 8

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Fig. 6. (a) Chemical index of alteration (CIA) versus Al2O3, (b) Plot of SiO2 versus (Al2O3 + K2O + Na2O) showing the chemical maturity (after Suttner and Dutta, 1986), (c) relation between SiO2/Al2O3 versus K2O/Na2O (after Maynard et al., 1982) and (d) Al2O3 vs. TiO2 bivariate diagram (after McLennan et al., 1980).

3.4.2. Freundlich isotherm model The Freundlich sorption isotherm is the one of the most widely used mathematical descriptions and usually fits the experimental data over a wide range of concentrations. The Freundlich model is an empirical equation and can be applied for non-ideal sorption on heterogeneous surfaces and multilayer sorption (Freundlich, 1906). It says that the ratio of the amount of solute adsorbed onto a given mass of sorbent to the concentration of the solute in the solution is not constant at different concentrations. The Freundlich model is linearized as follows:

Table 3 Weathering and alteration indices and other module in the samples. Index

SiO2/Al2O3 K2O/Na2O K2O/Al2O3 Al2O3/TiO2 CIA PIA CIW CIW′

Samples BSS1

BBS2

YSS

SS

CS

6.37 0.31 0.11 16.82 55.19 55.91 58.73 74.00

8.63 0.39 0.19 18.09 46.84 46.18 51.28 67.80

19.10 0.67 0.52 6.38 31.83 22.78 38.18 56.36

13.41 0.30 0.12 18.38 52.44 52.78 55.89 71.71

2.16 0.67 0.06 20.84 79.85 83.22 84.11 91.37

log qe = log Kf +

model explained in terms of a dimensionless separation factor constant, RL, that expressed as:

1 1 + bCo

(21)

where, Kf is constant indicative of the relative sorption capacity of the sorbent (mg/g) and 1/n is the constant indicative of the intensity of sorption process from the relation between log qe vs. log Ce as shown in Fig. 11(c, d) for CS and BSS1, respectively. The numerical values of the constants 1/n and Kf are computed from the average values of slopes and intercepts where two slopes and intercepts were recognized which may be due to the presence of fast and slow sorption processes at lower and higher initial metal ions concentrations, respectively. The numerical values were calculated by means of the linear least square fitting method and were given in Table 5. The 1/n value is usually dependent on the nature and strength of sorption process as well as on the distribution of active sites. The cases of n are as follow, n = 1 describe the adsorption to be linear, n > 1 describe adsorption to be a chemical process and n < 0 indicates adsorption process to be a physical process (Desta, 2013). For this study, it was found that, the values of n for sorption of both Cs+ and Co2+ onto both sediments were > 1. A feature indicating an increase tendency for sorption with increased the concentration. In

BBS1 = Brown sand sample 1; BBS2 = Brown sand sample 2; CS = clayey sample; SS = Sandstone sample; YSS = Yellow sand sample.

RL =

1 log Ce n

(20)

where, Co is the highest initial metal ion concentration (mg/L). The RL value indicates the shape of the isotherm as follows: To be irreversible (RL = 0), favorable (0 < RL < 1), linear (RL = 1) and unfavorable (RL > 1) (Mohan and Singh, 2002). The calculated value of RL indicated that the sorption of Cs+ and Co2+ onto both sediments was favorable, as shown in Table 5. In addition, smaller value of R2adjusted, RMSE and χ2 indicated a better fit of the model.

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M.M. Gouda, et al.

Fig. 7. Adsorbed amounts of Cs+ and Co2+ onto CS and BSS1 of Inshas disposal site as affected by (a, b) pH and V/m at constant temperature of 298 K and (c, d) contact time at constant pH 7 and V/m 0.2 mL/g at different temperatures with error bars. BSS1 = brown sand sample 1; CS = clay sample.

addition, the Kf value for Cs+ and Co2+ in the CS was greater than in the BSS1 and the smaller value of R2adjusted, RMSE and χ2 indicated a better fit of the model.

= RT ln 1 +

2

(23)

where, R is the gas constant (kJ/mol. K) and T is the temperature (K). The sorption energy illustrated by using the following relationship:

3.4.3. Dubinin-Radushkevich isotherm model The Dubinin-Radushkevich (D-R) isotherm model describes sorption on a single type of uniform pores. This model can be used to analyze the equilibrium data to estimate the mean free energy of adsorption (E). The linear form of D–R model can be represented by the equation:

ln qe = ln qm

1 Ce

E=( 2 )

(24)

1/2 2

+

2+

The D–R plots of Ln qe vs. ε for the sorption of Cs and Co at different temperatures resulted in the derivation of qm, β, E and the correlation factor (R2) which were given in Table 5. The D-R plots for the sorption of Cs+ and Co2+ at different temperatures were illustrated in Fig. 11(e, f) for CS and BSS1. The magnitude of mean free energy of sorption (E) can be related to the reaction mechanism. If E is in the range of 8–16 kJ/mol, sorption is governed by ion exchange (Helfferich, 1962). In the case of E < 8.0 kJ/mol, physical forces control the sorption mechanism. As illustrated the in Table 5, values of E for Cs+

(22)

where, qe is the number of metal ions sorbed per unit weight of sorbent (mg/g), qm is the maximum sorption capacity, β is the activity coefficient related to mean sorption energy and ε is the Polanyi potential:

Fig. 8. Effect of initial metal ion concentration on the adsorbed amounts of (a) Cs+ and (b) Co2+ onto CS and BSS1 of Inshas disposal site, at different temperatures with error bars. BSS1 = brown sand sample 1; CS = clay sample. 10

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Fig. 9. Pseudo 1st- (a, b) and 2nd-order (c, d) kinetic modeling of the adsorbed amounts of Cs+ and Co2+ onto CS and BSS1 of Inshas disposal site, at different temperatures. BSS1 = brown sand sample 1; CS = clay sample.

and Co2+ lied between 8.333 and 13.87 kJ/mol explaining that the reaction mechanisms were ion exchange reaction. On contrary the values of Cs+ at 298, 313 K in the BSS1 were 7.72 and 7.96 kJ/mol, respectively, indicating that the physical forces may affect the sorption mechanism.

qe =

RT RT ln KT + ln Ce bT bT

(25)

The constant bT is related to the heat of adsorption. Plots of qe vs. Ln Ce for Cs+ and Co2+ adsorption onto CS and BSS1 were illustrated in Fig. 11(g, h). Isotherm constants, bT and KT, were calculated from the slope and the intercept of the plot, and were given in Table 5. The values of bT were decreased in Cs+ and were increased in Co2+ with increasing in temperature in both of CS and BSS1.

3.4.4. Temkin isotherm model Temkin and Pyzhev adsorption isotherm model explains the indirect interaction of adsorbent and adsorbate on adsorption system (Temkin and Pyzhev, 1940). The Temkin adsorption isotherm model is depend on the heat of different metal ions adsorption during the interaction between the adsorbate and adsorbent. It assumes that the energy of adsorption of molecules decreases linearly due to interaction in the adsorbent surface. The linear form of Temkin isotherm model can be expressed as:

3.5. Thermodynamic studies The values of the thermodynamic equilibrium constant (Kc) at different studied temperatures were determined as products of the

Table 4 Temperature dependent pseudo 1st- and 2nd-order kinetic models parameters for the adsorption of Cs+ and Co2+ onto CS and BSS1 of Inshas disposal site. Sediments

CS

Metal ion

Cs+ Co2+

BSS1

Cs+ Co2+

Temp., K

298 313 333 298 313 333 298 313 333 298 313 333

Pseudo 1st-order kinetic model parameters

Pseudo 2nd-order kinetic model parameters

qeexp., mg/g

K1 , min−1

qecal., mg/g

R2

K1, g/mg.min

qecal., mg/g

h, mg/g.min

R2

0.045 0.058 0.057 0.037 0.035 0.035 0.039 0.043 0.044 0.061 0.051 0.047

1.968 1.917 1.816 5.985 7.002 10.297 3.699 2.984 2.268 2.278 3.775 4.664

0.940 0.971 0.979 0.994 0.998 0.981 0.989 0.977 0.972 0.999 0.997 0.991

0.083 0.096 0.109 0.015 0.013 0.008 0.024 0.035 0.050 0.055 0.026 0.021

18.12 17.67 17.15 12.95 14.66 18.90 6.99 5.88 4.94 3.66 5.78 7.93

27.32 30.12 32.15 2.58 2.70 2.76 1.17 1.20 1.23 0.74 0.86 1.30

0.999 0.999 0.999 0.998 0.997 0.996 0.997 0.998 0.999 0.999 0.998 0.998

BBS1 = Brown sand sample 1; CS = clayey sample. 11

18.00 17.59 17.05 12.43 14.03 17.88 6.60 5.61 4.75 3.48 5.42 7.49

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Fig. 10. Isotherm data of the adsorbed amounts of (a) Cs+ and (b) Co2+ onto CS and BSS1 of Inshas disposal site, at different temperatures with error bars. BSS1 = brown sand sample 1; CS = clay sample.

Langmuir equation parameters Q° and b (Panayotova, 2001). The Gibbs free energy change, ΔG°, is the fundamental criterion of spontaneity. The free energy of the sorption reaction as given by:

Go =

in Fig. 12(a, b). The Kc values were decrease with increasing of temperatures in case of Cs+ and were increased with increasing temperatures in case of Co2+.

(26)

RT ln K c

ln K c =

where, Kc is the sorption equilibrium constant, R is the gas constant (kJ/mol. K) and T is the absolute temperature (K). Reactions occur spontaneously at a given temperature if ΔG° is a negative quantity and non-spontaneous when the value is positive. There is another process to obtain the enthalpy changes (∆H°) and entropy change (∆S°) which can be deduced from the slope and intercept in both of metal ions by plotting Ln Kc versus 1/T (Eq. (27)), as shown

So R

Ho RT

(27)

The free energy of the sorption reaction as given according to the following the equation:

Go =

Ho

(28)

T So °

°

°

+

The thermodynamic parameters (ΔH , ∆G and ΔS ) for Cs and Co2+ sorbed onto the studied CS and BSS1 were given in Table 6. The enthalpy change (ΔH°) for Cs+ was found to be negative for the all

Table 5 Temperature dependent Langmuir, Freundlich, D-R and Temkin isotherm models parameters for the adsorption of Cs+ and Co2+ onto CS and BSS1 of Inshas disposal site. Clayey sample

Brown sand sample 1

+

Cs

Langmuir isotherm model Qo, mg/g b × 10−2, L/mg RL R2 R2adjusted RMSE χ2 Freundlich isotherm model n Kf, mg/g R2 R2adjusted RMSE χ2 D-R isotherm model β × 10−3, mol2/kJ2 qm, mol/g E, kJ/mol R2 R2adjusted RMSE χ2 Temkin isotherm model KT, L/mg bT, KJ/mol R2 R2adjusted RMSE χ2

Co

2+

Cs+

Co2+

298 K

313 K

333 K

298 K

313 K

333 K

298 K

313 K

333 K

298 K

313 K

333 K

68.03 1.84 0.05 0.99 0.99 0.18 0.31

66.23 1.40 0.07 0.98 0.98 0.27 0.52

64.94 1.10 0.08 0.98 0.97 0.38 0.82

18.83 3.20 0.03 0.99 0.99 0.47 0.48

23.92 3.50 0.03 0.99 0.99 0.46 0.38

30.12 4.40 0.02 0.99 0.99 0.41 0.95

67.11 0.19 0.34 0.81 0.73 1.45 2.57

58.82 0.17 0.37 0.89 0.84 1.28 1.51

48.08 0.15 0.40 0.89 0.86 1.54 1.56

12.84 0.53 0.16 0.97 0.96 3.08 5.09

15.13 0.79 0.11 0.99 0.99 1.31 1.37

17.18 1.28 0.07 0.99 0.99 0.69 0.59

1.967 3.42 0.91 0.88 0.12 0.12

1.902 2.78 0.91 0.87 0.12 0.12

1.831 2.24 0.90 0.86 0.12 0.14

3.168 2.74 0.88 0.83 0.08 0.05

3.212 3.59 0.90 0.86 0.08 0.06

3.504 5.39 0.80 0.72 0.12 0.14

1.316 0.31 0.97 0.96 0.07 0.70

1.288 0.23 0.98 0.99 0.04 0.03

1.279 0.16 0.99 0.99 0.03 0.02

1.932 0.37 0.98 0.98 0.03 0.02

2.067 0.62 0.98 0.97 0.04 0.02

2.324 0.91 0.95 0.94 0.06 0.03

5.2 3.38 9.81 0.94 0.92 0.22 0.67

5.0 3.26 10.00 0.94 0.91 0.23 1.14

4.6 3.19 10.43 0.93 0.89 0.25 0.39

3.9 0.56 11.32 0.92 0.89 0.15 0.12

3.4 0.69 12.13 0.94 0.92 0.14 0.09

2.6 0.83 13.87 0.84 0.77 0.26 0.32

8.4 2.72 7.72 0.96 0.95 0.19 0.11

7.9 2.39 7.96 0.98 0.98 0.13 0.05

7.2 1.85 8.33 0.99 0.98 0.10 0.03

6.7 0.39 8.64 0.98 0.97 0.09 0.00

5.7 0.49 9.37 0.99 0.98 0.06 0.02

4.4 0.57 10.66 0.98 0.97 0.09 0.04

0.341 0.21 0.98 0.98 2.37 3.75

0.263 0.22 0.98 0.97 2.67 3.72

0.205 0.24 0.97 0.97 2.86 2.63

0.715 0.80 0.93 0.91 1.32 1.49

0.926 0.70 0.98 0.98 0.82 0.55

2.040 0.66 0.94 0.91 2.22 4.65

0.053 0.27 0.90 0.86 3.08 7.92

0.053 0.32 0.91 0.86 2.70 5.85

0.052 0.41 0.89 0.85 2.28 4.14

0.073 1.00 0.95 0.92 0.74 1.46

0.102 0.87 0.97 0.97 0.62 0.85

0.168 0.83 0.98 0.97 0.64 0.67

BBS1 = Brown sand sample 1; CS = clayey sample; RMSE = Root mean square error; χ2 = Chi square. 12

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Fig. 11. Isothermal modeling for the adsorbed amounts of Cs+ and Co2+ onto CS and BSS1 of Inshas disposal site, at different temperatures: (a, b) Langmuir (c, d) Freundlich (e, f) D-R and (g, h) Temkin plots. BSS1 = brown sand sample 1; CS = clay sample.

values of ∆G° in the most determinations indicated the non-spontaneous nature of Cs+ and Co2+ onto both sediments, but only ∆G° is negative in case of Cs+ with CS at 298 K and 313 K the sorption reaction is of spontaneous nature. The values of the ΔS° are was the very small, indicated that Cs+ and Co2+ would be more stable on the adsorption site at the solid–solution interface during the fixation of the ion on the surface of the sorbent.

adsorbents used confirming the exothermic nature of the sorption processes but in case of Co2+ it was found to be positive for both sediments, confirming their endothermic natures. The reason of this behavior could be originated from thermal destabilization, which causes an increase in the mobility of Cs+ ions on the surface of the solid and decreased in sorption with increasing temperature. In the case of Co2+, ΔH° increased in sorption with increasing the temperature. The positive

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Fig. 12. Relationship between Ln Kc and 1/T for the adsorption of Cs+ and Co2+ onto CS and BSS1 of Inshas disposal site. BSS1 = brown sand sample 1; CS = clay sample. Table 6 Thermodynamic parameters for the adsorption of Cs+ and Co2+ onto CS and BSS1 of Inshas disposal site. Sediments

Metal ion

Temp. (K)

Kc

ΔG°, kJ/mol

ΔH°, kJ/mol

ΔS°, J/mol.K

CS

Cs+

298 313 333 298 313 333 298 313 333 298 313 333

1.253 0.940 0.718 0.607 0.825 1.329 0.131 0.102 0.072 0.067 0.120 0.220

−0.558 0.161 0.918 1.236 0.500 −0.787 5.044 5.944 7.286 6.679 5.517 4.187

−13.085

−0.042

18.528

0.058

−14.075

−0.064

27.848

0.071

Co2+ BBS1

Cs+ Co2+

BBS1 = Brown sand sample 1; CS = clayey sample.

sorption experiments of Cs+ and Co2+ onto the BSS1 and CS samples was found to be temperature dependent where lower temperatures favored the adsorption of Cs+, vice versa regarding Co2+. Kinetic modeling of the experimentally obtained data suggested that sorption of both metal ions were controlled by the chemical sorption mechanism. Langmuir, Freundlich, Dubinin-Radushkevitch and Temkin isotherm equations were used to calculate the sorption parameters at equilibrium. Sorption of both metal ions was favorable onto both sediments and was found to be controlled by chemical reaction mechanism. Values of the mean free energy of sorption for Cs+ and Co2+ explained their ion exchange controlled reaction. The enthalpy change (ΔH°) for Cs+ was found to be negative at all confirming the exothermic nature and vice versa regarding Co2+. The values of ΔG° revealed the nonspontaneous natures except for Cs+ when sorbed onto CS at 298 K and 313 K. The values of the ΔS° are was the very small, indicated that Cs+ and Co2+ would be more stable on the adsorption site at the solid–solution interface during the fixation of the ion on the surface of the sorbent. The obtained data indicated a an opportunity of examined sediments to postpone Cs+ and Co2+ making Inshas area to meet the requirements posed by the International Atomic Energy Agency for shallow disposal.

4. Conclusions The principal for disposal option includes potential sites that are evaluated on the basis of their ability to contribute to the isolation of the waste and limit radionuclide emissions to minimize potential adverse impacts on humans and the environment. Five sediments were collected from Inshas radioactive waste disposal site. Three quaternary sand samples of brown sand 1 (BSS1), brown sand 2 (BBS2) and yellow sand (YSS) were collected at depths of 1.5, 3.0 and 4.0, respectively. Two Miocene sediments of sandstone (SS) and clay (CS) were collected at depths of 5.0 and 6.5 m, respectively. The collected samples were quantitatively analyzed in regard to their major and minor oxide percentages. The geochemical studies revealed that the collected samples can be classified as Fe-sands and Fe-shales of a mafic igneous source and one sample in quartzose sedimentary provenance. The most of sand samples indicated a low degree of weathering of source materials while the clayey sample indicated a moderate to intensive weathering. Studies of the chemical maturity indicated that the collected samples were deposited under semiarid to humid conditions and most of samples were formed between a passive margin and active margin of tectonic setting. The BSS1 and CS were selected for further physico-chemical characterizations perior to their examinations toward the sorption of Cs+ and Co2+ from aqueous solutions. Mineralogical studies indicated that the BSS1 was composed mainly of quartz co-associated with albite minerals while kaolinite, vermiculite and plagioclase minerals were detected in the CS sample. The structural bond vibrations like Si – O – T (T = Si or Al) of these minerals were detected in FT-IR spectra. SEM analyses explained a platy structure with irregular shape of the CS surface which when examined by BET technique recorded a specific area of 31.51 m2/g versus 17.55 m2/g for the BSS1. The batch

Acknowledgments Authors are acknowledged stuff members of Radioactive Waste Management Dept., Hot Lab. Center, Egyptian Atomic Energy Authority. Authors also acknowledged stuff members of Geology Department, Faculty of Sciences, Ain Shams University.

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References

12913–12920. https://doi.org/10.1021/es303037k. Harnois, L., 1988. The CIW index a new chemical index of weathering. J. of Sedimentary Geology 55, 319–322. https://doi.org/10.1016/0037-0738(88)90137-6. Hayashi, K., Fujisawa, H., Holland, H., Ohmoto, H., 1997. Geochemistry of ~1.9 Ga sedimentary rocks from northeastern Labrador, Canada. Geochim. Cosmochim. Acta 61 (19), 4115–4137. https://doi.org/10.1016/S0016-7037(97)00214-7. Helfferich, F., 1962. Ion Exchange. McGraw-Hill, New York. Herron, M.M., 1988. Geochemical classification of terrigeneous sands and shales from core or log data. J. Sediment. Petrol. 58, 820–829. https://doi.org/10.1306/ 212F8E77-2B24-11D7-8648000102C1865D. Hlavay, J., Jonas, K., Elek, S., Inczedy, J., 1978. Characterization of the particle size and the crystallinity of certain minerals by IR spectro- photometry and other instrumental methods; II, investigations on quartz and feldspar. Clay Miner. 26, 139–143. https:// doi.org/10.1346/CCMN.1978.0260209. Ho, Y.S., McKay, G., 1999. Pseudo-second order model for sorption processes. Process Biochem. 34, 451–465. https://doi.org/10.1016/S0032-9592(98)00112-5. Ingram, R.L., 1971. Sieve analysis. In: Carver, R.E. (Ed.), Procedures in Sedimentary Petrology. Wiley and Sons, New York, USA, pp. 49–67. Kamel, N.H.M., 2002. The behaviour of 134Cs, 60Co, and 85Sr radionuclides in marine environmental sediment. The Scientific World J 2, 1514–1526. https://doi.org/10. 1100/tsw.2002.290. Kamel, N.H.M., Navratil, D.J., 2002. Migration of 134Cs in unsaturated soils at a site in Egypt. J. of Radioanal. and Nucl. Chem. 254 (3), 421–429. https://doi.org/10.1023/ A:1021669500684. Lagergren, S., 1898. About the theory of so-called adsorption of soluble substances. Kung. Svenska Vetenskap. 24, 1–39. Langmuir, I., 1916. The constitution and fundamental properties solids and liquids. J. Am. Chem. Soc. 38, 2221–2295. https://doi.org/10.1021/ja02268a002. Lebedev, V.N., Melʼnik, N.A., Rudenko, A.V., 2003. Sorption of cesium on titanium and zirconium phosphates. Radiochem 45 (2), 149–151. Lewis, D.W., McConchie, D., 1994. Analytical Sedimentology. Springer, Netherlands (197p.). Martinez, R.E., Sharma, P., Kappler, A., 2010. Surface binding site analysis of Ca2+homoionized clay-humic acid complexes. J. Colloid Interface Sci. 352, 526–534. https://doi.org/10.1016/j.jcis.2010.08.082. Mathieson, A.McL., Walker, G.F., 1954. Crystal structure of magnesium-vermiculite. Amer. Min. 39, 231–255. Maynard, J.B., Valloni, R., Yu, H.S., 1982. Composition of modern deep-sea sands from arc related basins. In: Leggett, J.K. (Ed.), Trech-Forearc Geology Sedimentation and Tectonics on Modern and Ancient Active Plate M Argins. Geol. Soc. London. Spec. Publ, pp. 10551–10561. McLennan, S.M., 1993. Weathering and global denudation. J. Geol. 101, 295–303. https://doi.org/10.1086/648222. McLennan, S.M., Nance, W.B., Taylor, S.R., 1980. Rare earth element-thorium correlation in sedimentary rocks and the composition of the continental crust. Geochim. Cosmochim. Acta 44, 1833–1839. https://doi.org/10.1016/0016-7037(80)90232-X. Missana, T., Benedicto, A., García-Gutiérrez, M., Alonso, U., 2014. Modeling cesium retention onto Na-, K- and Ca-smectite: effects of ionic strength, exchange and competing cations on the determination of selectivity coeffcients. Geochem. Cosmochim. Acta 128, 266–277. https://doi.org/10.1016/j.gca.2013.10.007. Mohan, D., Singh, K.P., 2002. Single and multi-component adsorption of cadmium and zinc using activated carbon derived from bagasse, an agricultural waste. Water Res. 36, 2304–2318. https://doi.org/10.1016/S0043-1354(01)00447-X. Morimoto, K., Kogure, T., Tamura, K., 2012. Desorption of Cs+ ions intercalated in vermiculite clay through cation exchange with Mg2+ ions. Chem. Lett. 41, 1715–1717. https://www.journal.csj.jp/doi/10.1246/cl.2012.1715. Motokawa, R., Endo, H., Yokoyama, S., 2014. Mesoscopic structures of vermiculite and weathered biotite clays in suspension with and without cesium ions. Langmuir 30, 15127–15134. https://doi.org/10.1021/la503992p. Ndukwe, N.A., Jenmi, F.O., 2008. Effects of vehicular exhaust fumes on urban air pollution in Lagos metropolis. Pollut. Res. 27 (3), 539–543. Nesbitt, H.W., Young, G.M., 1982. Early Proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature 299, 715–717. https://doi.org/10. 1038/299715a0. Nirmala, G., Viruthagiri, G., 2014. FT-IR characterization of articulated ceramic bricks with wastes from ceramic industries. Spectrochim. Acta A Mol. Biomol. Spectrosc. 126, 129–134. https://doi.org/10.1016/j.saa.2014.01.143. Panayotova, M.I., 2001. Kinetics and thermodynamics of copper ions removal from wastewater by use of zeolite. Waste Manag. 21, 671–676. https://doi.org/10.1016/ S0956-053X(00) 00115-X. Pettijohn, F.J., Potter, P.E., Siever, R., 1972. Sand and Sandstone. Springer-Verlag, New York, pp. 618. https://doi.org/10.4319/lo.1973.18.1.0182. Ptáček, P., Šoukal, F., Opravil, T., Havlica, J., Brandštetr, J., 2011. The kinetic analysis of the thermal decomposition of kaolinite by DTG technique. Powder Technol. 208, 20–25. https://doi.org/10.1016/j.powtec.2010.11.035. Roser, B.P., Korsch, R.J., 1988. Provenance signatures of sandstone-mudstone suites determined using discrimination function analysis of major element data. Chem. Geol. 67, 119–139. https://doi.org/10.1016/0009-2541(88)90010-1. Runliang, Z., Lizhong, Z., Jianxi, Z., Xu, L., 2008. Structure of cetyltrimethylammonium intercalated hydrobiotite. Appl. Clay Sci. 42, 224–231. https://doi.org/10.1016/j. clay.2007.12.004. Russell, J.D., Fraser, A.R., 1994. Infrared methods. In: Wilson, M.J. (Ed.), Clay Mineralogy: Spectroscopic and Chemical Determinative Methods. Chapman & Hall, London, pp. 11–67 (Chapter 2). Sahraeyan, M., Bahrami, M., 2012. Geochemistry of Sandstones from the Aghajari Formation, Folded Zagros Zone, Southwestern Iran: Implication for Paleoweathering

Abdel Rahman, R.O., El Kamash, A.M., Zaki, A.A., El Sourougy, M.R., 2005. Disposal: a last step towards an integrated waste management system in Egypt, International Conference on the Safety of Radioactive Waste Disposal, Tokyo, Japan, IAEA-CN135/81, 317–324. https://inis.iaea.org/search/search.aspx?orig_q=RN:38002499. Abdel-Aziz, M.A., 1996. Site Assessment for Disposal of Low and Intermediate Levels Radioactive Wastes Inshas Area. Ph.D. Thesis. Ain Shams University. Abdelhady, A., 2013. Radiological performance of hot water layer system in open pool type reactor. Alex. Eng. J. 52, 159–162. https://doi.org/10.1016/j.aej.2012.12.008. Abdel-Karim, A.M., Zaki, A.A., Elwan, W., El-Naggar, M.R., Gouda, M.M., 2016. Experimental and modeling investigations of cesium and strontium adsorption onto clay of radioactive waste disposal. Appl. Clay Sci. 132-133, 391–401. https://doi.org/ 10.1016/j.clay.2016.07.005. Abdel-Karim, A.M., Zaki, A.A., Elwan, W., El-Naggar, M.R., Gouda, M.M., 2019. Geological and contaminant transport assessment of a low level radioactive waste disposal site. J. Geochem. Explor. 197, 174–183. https://doi.org/10.1016/j.gexplo. 2018.12.011. Adeyemo, A.A., Adeoye, I.O., Bello, O.S., 2017. Adsorption of dyes using different types of clay: a review. Appl Water Sci 7, 543–568. https://doi.org/10.1007/s13201-0150322. Akarish, A.I.M., El-Gohary, A.M., 2008. Petrography and geochemistry of lower Paleozoic sandstones, East Sinai, Egypt: implications for provenance and tectonic setting. J. Afr. Earth Sci. 52, 43–54. https://doi.org/10.1016/j.jafrearsci.2008.04.002. Araffa, S.A.S., Santos, F.A.M., Hamed, T.A., 2012. Delineating active faults by using integrated geophysical data at northeastern part of Cairo, Egypt. NRIAG J. Astron. Geophys. 1, 33–44. https://doi.org/10.1016/j.nrjag.2012.11.004. Armstrong-Altrin, J.S., Machain-Castillo, L.M., 2016. Mineralogy, geochemistry, and radiocarbon ages of deep-sea sediments from the Gulf of Mexico, Mexico. J. S. Am. Earth Sci. 71, 182–200. https://doi.org/10.1016/j.jsames.2016.07.010. Benedicto, A., Missana, T., Fernández, A.M., 2014. Interlayer collapse affects on cesium adsorption onto illite. Environ. Sci. Technol. 48 (9), 4909–4915. https://doi.org/10. 1021/es5003346. Bentahar, Y., Hurel, C., Draoui, K., Khairoun, S., Marmier, N., 2016. Adsorptive properties of Moroccan clays for the removal of arsenic (V) from aqueous solution. Appl. Clay Sci. 119, 385–392. https://doi.org/10.1016/j.clay.2015.11.008. Bish, D.L., Post, J.E., 1989. Modem Powder Diffraction. Reviews in Mineralogy 20. Mineralogical Society of America, Washingon, D.C. (369p.). Chester, R., Elderfield, H., 1967. The application of infrared absorption spectroscopy to carbonate mineral. Sedimentology 9, 5–21. https://doi.org/10.1111/j.1365-3091. 1967.tb01903.x. Cox, R., Lower, D.R., Cullers, R.L., 1995. The influence of sediment recycling and basement composition on evolution of mud rock chemistry in the southwestern United States. Geochim. Cosmochim. Acta 59, 2919–2940. https://doi.org/10.1016/00167037(95)00185-9. Cravero, F., Fernández, L., Marfíl, S., Sánchez, M., Maiza, P., Martínez, A., 2016. Spheroidal halloysites from Patagonia, Argentina: some aspects of their formation and applications. Appl. Clay Sci. 131, 48–58. https://doi.org/10.1016/j.clay.2016. 01.011. Crook, K.A.W., 1974. Lithogenesis and tectonics: the significance of com-positional variations in flysch arenites graywackes. In:Dott RH, Shaver RH (eds) Modern and ancient geosynclinal sedimentation. Soc Econ Paleontol Mineral Spec Pub 19, 304–310. Cullers, R.L., 2000. The geochemistry of shales, siltstones and sandstones of Pennsylvanian–Permian age, Colorado, U.S.a.: implications for provenance and metamorphic studies. Lithol 51, 181–203. https://doi.org/10.1016/S0024-4937(99) 00063-8. Desta, M.B., 2013. Batch sorption experiments: Langmuir and Freundlich isotherm studies for the adsorption of textile metal ions onto teff straw (Eragrostis tef) agricultural waste. J. Thermodynamics. https://doi.org/10.1155/2013/375830. Dubinin, M.M., Radushkevich, L.V., 1947. The equation of the characteristic curve of the activated charcoal. Proc. Acad. Sci. USSR Phys. Chem. Sec. 55, 331–333. El-Kamash, A.M., 2008. Evaluation of zeolite A for the sorptive removal of Cs+ and Sr2+ ions from aqueous solutions using batch and fixed bed column operations. J. Hazard. Mater. 151, 432–445. https://doi.org/10.1016/j.jhazmat.2007.06.009. El-Naggar, M.R., 2014. Applicability of alkali activated slag-seeded Egyptian Sinai kaolin for the immobilization of 60Co radionuclide. J. of Nucl. Mat. 447, 15–21. https://doi. org/10.1016/j.jnucmat.2013.12.020. El-Naggar, M.R., El-Sherief, E.A., Mekhemar, H.S., 2018. Performance of geopolymers for direct immobilization of solvent extraction liquids: Metakaolin/LIX-84 formulations. J. Hazard. Mater. 360, 670–680. https://doi.org/10.1016/j.jhazmat.2018.08.057. Fan, Q.H., Tanaka, M., Tanaka, K., Sakaguchi, A., Takahashi, Y., 2014. An EXAFS study on the effects of natural organic matter and the expandability of clay minerals on cesium adsorption and mobility. Geochem. Cosmochim. Acta. 135, 49–65. https://doi.org/ 10.1016/j.gca.2014.02.049. Farmer, V.C., 1974. The IR Spectra of Minerals. vol. 42. Mineral. Soc, London, pp. 308–320. Fedo, C.M., Nesbitt, H.W., Young, G.M., 1995. Unraveling the effects of Kmetasomatism in sedimentary rocks and paleosols with implica-tions for palaeoweathering conditions and provenance. Geology 23, 921–924. https://doi.org/10.1130/00917613(1995)023<0921:UTEOPM>2.3.CO;2. Freundlich, H.M.F., 1906. Over the adsorption in solution. J. Phys. Chem. 57A, 385–470. Geological Survey of Egypt (EGSMA), 1998. Geology of Inshas area, geological survey of Egypt, (Internal Report). Greenlee, L.F., Torrey, J.D., Amaro, R.L., Shaw, J.M., 2012. Kinetics of zero valent iron nanoparticle oxidation in oxygenated water. Environ. Sci. Technol. 46,

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Journal of Geochemical Exploration 206 (2019) 106366

M.M. Gouda, et al. condition, Provenance, and Tectonic setting. Intern. J. of Basic and Applied Sciences 1 (4), 390–407. https://doi.org/10.14419/ijbas.v1i4.244. Scarciglia, F., De Rosa, R., Vecchio, G., Apollaro, C., Robustelli, G., Terrasi, F., 2008. Volcanic soil formation in Calabria (southern Italy): the Cecita Lake geosol in the late Quaternary geomorphological evolution of the Sila uplands. J. Volcanol. Geotherm. Res. 177, 101–117. https://doi.org/10.1016/j.jvolgeores.2007.10.014. Seliman, F., Borai, E.H., Lasheen, Y.F., DeVol, T.A., 2012. Remobilization of 60Co, 85Sr, 137 Cs, 152Eu, and 241Am from a contaminated soil column by groundwater and organic ligands. Transp. Porous Med. 93, 799–813. https://doi.org/10.1007/s11242012-9983-2. Senthil, K.R., Rajkumar, P., 2014. Characterization of minerals in air dust particles in the state of Tamilnadu, India through FTIR, XRD and SEM analyses. Infrared Phys. Technol. 67, 30–41. https://doi.org/10.1016/j.infrared.2014.06.002. Srinivasan, R., 2011. Advances in application of natural clay and its composites in removal of biological, organic, and inorganic contaminants from drinking water. Adv. Mater. Sci. Eng. 2011, 1–17. https://doi.org/10.1155/2011/872531. Środoń, J., 2006. Identification and quantitative analysis of clay minerals. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science. Developments in Clay Science. vol. 1 Elsevier. Sugitani, K., Fumiaki, Y., Tsutomu, N., Koshi, Y., Masayo, M., Koichi, M., Kazuhiro, S., 2006. Geochemistry and sedimentary petrology of Archean clastic sedimentary rocks at Mt. Goldsworthy, Pilbara Craton, Western Australia: evidence for the early evolution ofcontinental crust and hydrothermal alteration. Precambrian Res. 147, 124–147. https://doi.org/10.1016/j.precamres.2006.02.006. Sultan, S.A., Santos, F.A.M., Helaly, A.S., 2009. Integrated geophysical interpretation for the area located at the eastern part of Ismailia Canal, Greater Cairo, Egypt. Arab. J. Geosci. 4, 735–753. https://doi.org/10.1007/s12517-009-0085-6. Suttner, L.J., Dutta, P.K., 1986. Alluvial sandstone composition and paleoclimate. L. Framework mineralogy. J. Sediment. Petrol. 56, 329–345. Temkin, M.J., Pyzhev, V., 1940. Kinetics of ammonia synthesis on promoted iron catalysts. Acta Physiochim. URSS 12, 217–222. https://doi.org/10.1007/s12517-009-

0085-6. Tournassat, C., Grangeon, S., Leroy, P., Giffaut, E., 2013. Modeling specific pH dependent sorption of divalent metals on montmorillonite surfaces. A review of pitfalls, recent achievements and current challenges. Am. J. Sci. 313, 395–451. https://doi.org/10. 2475/05.2013.01. Van der Marel, H.W., Beutelspacher, H., 1976. Atlas of Infrared Spectroscopy of Clay Minerals and their Admixtures. Elsevier Scientific Pub. Co, Amsterdam. https://doi. org/10.1180/claymin.1977.012.3.11. Walker, G.F., 1951. Vermiculite sand some related mixed-layer minerals. In: Brindley, G.W. (Ed.), X-Ray Identification and Crystal Structures of Clay Minerals. Mineral. Soc, London, pp. 199–223. Wan, Q., Rao, F., Song, S., Cholico-González, D.F., Ortiz, N.L., 2017. Combination formation in the reinforcement of metakaolin geopolymers with quartz sand. Cem. Concr. Composite. 80, 115–122. https://doi.org/10.1016/j.cemconcomp.2017.03. 005. Wang, W., Zheng, B., Deng, Z., Feng, Z., Fu, L., 2013. Kinetics and equilibriums for adsorption of poly(vinyl alcohol) from aqueous solution onto natural bentonite. Chem. Eng. J. 214, 343–354. https://doi.org/10.1016/j.cej.2012.10.070. Yin, X., Wang, X., Wu, H., Ohnuki, T., Takeshita, K., 2017. Enhanced desorption of cesium from collapsed interlayer regions in vermiculite by hydrothermal treatment with divalent cations. J. Hazard. Mater. 326, 47–53. https://doi.org/10.1016/j.jhazmat. 2016.12.017. Yoshikawa, N., Mikoshiba, S., Sumi, T., Taniguchi, S., 2017. Model experimental study on Cs removal from clay minerals by ion exchange under microwave irradiation. Chem. Eng. Process. https://doi.org/10.1016/j.cep.2017.01.006. Zawrah, M.F., Khattab, R.M., Saad, E.M., Gado, R.A., 2014. Effect of surfactant types and their concentration on the structural characteristics of nanoclay. Spectrochim. Acta A Mol. Biomol. Spectrosc. 122, 616–623. https://doi.org/10.1016/j.saa.2013.11.076. Zhu, Y., Hu, J., Wang, J., 2014. Removal of Co2+ from radioactive wastewater by polyvinyl alcohol (PVA)/chitosan magnetic composite. Prog. Nucl. Energy 71, 172–178. https://doi.org/10.1016/j.pnucene.2013.12.005.

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