Effect of nanoparticles on kinetics release and fractionation of phosphorus

Accepted Manuscript Title: Effect of nanoparticles on kinetics release and fractionation of phosphorus Author: Marzieh Taghipour Mohsen Jalali PII: DOI: Reference:

S0304-3894(14)00790-0 http://dx.doi.org/doi:10.1016/j.jhazmat.2014.09.045 HAZMAT 16293

To appear in:

Journal of Hazardous Materials

Received date: Revised date: Accepted date:

1-7-2014 14-9-2014 15-9-2014

Please cite this article as: M. Taghipour, M. Jalali, Effect of nanoparticles on kinetics release and fractionation of phosphorus, Journal of Hazardous Materials (2014), http://dx.doi.org/10.1016/j.jhazmat.2014.09.045 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Effect of nanoparticles on kinetics release and fractionation of phosphorus Marzieh Taghipour and Mohsen Jalali

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Department of Soil Science, College of Agriculture, Bu-Ali Sina University, Hamedan, Iran

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Highlights

 Pseudo second- order model described well P release.

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 We examined the effect of nanoparticles on release and fractionation of P in soils.

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 PHREEQC could simulate the P release very well in all studied treated soils.  After P release, the percentage of organic matter and sulphide–P fraction increased.

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 This result reflected that the NPs caused immobilization of P in soils.

Abstract

In this study, we examined the effect of nanoparticles (Al2O3 and TiO2) on kinetics release, fractionation and speciation of phosphorus (P) in some calcareous soils of western Iran. The maximum (average of five soils) (40.3 mg kg−1) and the minimum (10.5 mg kg−1) P were released by control soils and soils plus 3% TiO2, respectively. Pseudo second- order model described well P release. In order to predict and model the effects of NPs on P release, surface 

Corresponding author: E-mail address: [email protected], Tel: +988134502726

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complexation model in PHREEQC program was used. The model could simulate the P release very well in all soils. After P release, the percentage of organic matter and sulphide–P fraction increased markedly following NPs addition, while carbonated-P fraction remained the most

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dominant fraction in all soils. In the initial stage of P release the solution samples in all soils and treatments were saturated with respect to strengite, and undersaturated with respect to other

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phosphate minerals. At the end of P release, all solutions were saturated with respect to

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hydroxyapatite and strengite and undersaturated with respect to other phosphate minerals. These results reflected that the NPs caused immobilization of P in soils and reduced the bioavailable P,

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thus, reducing their environment risk.

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Keywords: Phosphorus, Nanoparticles, Fractionation, Release, Speciation, PHREEQC

1. Introduction

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Although phosphate (P) is an essential element for plant growth in soils, excess P release may

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lead to eutrophication and hence deteriorate the water quality [1, 2]. Phosphorus is discharged to

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aquatic environments by several ways such as discharging from wastewater treatment plants, agricultural activities, and weathering rocks. To date, however, most of the previous studies have focused on enhanced P removal in wastewater treatment plants [3-4]. Because it is the only engineering source that can be significantly reduced. Soil is another important P source. Many soils in Iran have received large amounts of P fertilizers and consequently contain high level of available P [5]. The presence of P in groundwater in western Iran was reported by Jalali [6]. Water and soil pollution by P is in rise, and therefore, there is an increasing demand for the removal of P from water and soil. The adsorption of P onto material significantly affects their mobility in natural environments. Some natural materials have been applied to remediate P in soils and aqueous solutions.

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Successful results have been achived using aluminum oxide [7], iron oxide [8-10], fly ash [11], silicates [12-14], and gas concrete [15]. With the rapid development of nanotechnology, nanoparticles (NPs) have been applied in wastewater and soil remediation due to their small

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sizes, large surface areas, and special chemical reactivity. NPs have a large surface-to-volume ratio compared to other bulk materials therefore, enhanced adsorption properties are achieved by

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their use [16]. Metal oxide nanoparticles, such as titanium dioxide (TiO2), aluminum oxide

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(Al2O3) have received increasing interests due to their widespread industrial, medical and military applications [17-18]. Despite the widespread use of NPs in various fields, there is

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limited information about P immobilization by these nanoparticles [16-22], especially in soil. Thus, the objectives of the present study were to determine the effects of NPs (TiO2 and Al2O3)

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on P release rate, fractionation and speciation in some calcareous soils. Moreover, an adsorption

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2.1. Soils and nanoparticles

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2. Materials and methods

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model with PHREEQC program was used to simulate the experimental results.

The five soil samples used in this study were collected from the surface (0-30 cm) soil of Hamadan, western Iran. After being air-dried, the soil samples were passed through a 2 mm sieve. Soil properties were measured by routine methods [23] and reported by Jalali and Ahmadi Mohammad Zinli [24]. Selected chemical and physical properties of the studied soils are given in Table 1. The Olsen-P value ranged from 21.4 to 112.0 mg kg−1, while total P varied from 1079.1 to 1911.9 mg kg−1. Nano-structured TiO2, Al2O3 were purchased (purity, 99.5%) from Tecnan (www.tecnan nanomat.es, Spain) and Nabond (www.nabond.com, China). Characteristics of the NPs were previously reported by Mahdavi et al. [25]. In summary, the particle sizes of TiO2 and Al2O3

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were 12 nm and 11 nm, respectively. The specific surface area (BET) was 45.4 m2 g-1 for TiO2 and 105.8 m2 g-1 for Al2O3.

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2.2. Experiment design Different treatments were used to evaluate the effects of NPs on kinetics release and P

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fractionation. Two NPs (Al2O3 and TiO2) were added to the soil at a rate of 1 and 3%. At the

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first, 1.98 and 1.94 g soil was put into a 50 ml centrifuge tube, then mixed with 0.02 (1% NPs) and 0.06 g (3% NPs) Al2O3 and TiO2, respectively. There were five treatments with 2 replicates:

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control soil (Cs), soil plus 1% Al2O3 (Al-1), soil plus 3% Al2O3 (Al-3), soil plus 1% TiO2 (Ti-1) and soil plus 3% TiO2 (Ti-3). The NPs was completely mixed with the soil to obtain

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homogeneity.

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2.3. Kinetics release of P

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Treated and untreated soils (2 g) were extracted with 20-mL of a 10 mM CaCl2 solutions. The suspensions were shaken for 30 min at 200 rpm in shaking machine, then equilibrated for 0.5, 1,

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4, 16, 28, 40, 52, 64, 76 and 88 h at 25°C, centrifuged at 5000 rpm for 10 min. Afterward, the P concentration in the supernatant was determined by molybdate blue spectrometry method [26].

2.4. Kinetic data analysis

Two kinetic models (pseudo-first-order, pseudo-second-order) were used in order to investigate the release of P with time. The pseudo-first-order can be determined by the following equation [27]: log(



−



) =









−



1 2.303

(1)

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where qt (mg kg-1) is the amount of P released at time t (h), qe (mg kg-1) is cumulative P released at time t and k1 (h−1) is the rate constant of pseudo-first-order model. The pseudo-second-order model can be expressed in the form [28]:

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1 1

= + 2





2









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(2)

where k2 is the rate constant of second-order adsorption in mg kg-1 h.

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The best fit among the kinetic models is assessed by the linear coefficient of determination (r2)

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and non-linear Chi-square (χ2). The Chi-square test measures the difference between the experimental and model data. This test can be expressed as:



,





−



,









,







2

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χ2 = ∑

(3)

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where qe,exp is measured P released and qe,cal is the fitted P release from a model. If χ2 were small,

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it would indicate that data from the model are similar to experimental data [29].

2.5. Modelling of P release

In order to predict P release in treated soils, we used surface complexation model in PHREEQC program (version 2.17) [30]. The parameters used to run the model were indicated in Table 2.

2.6. P fractionation

Phosphorus fractionation was carried out before and after release of P from control and treated soils. Soils were sequentially extracted based on the modified Tessier method described by Lucho-Constantino et al. [31]. Phosphorus was separated into four fractions by this method. Easily soluble and exchangeable fractions were extracted by 1 N MgCl2 at pH 7 and P bound to

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carbonates was extracted by CH3COOH/CH3COONa at pH 5. Residue from the previous step was extracted with 0.04 M NH2OH. HCl in 25% CH3COOH and represented the fraction bound to Fe and Mn oxides. Phosphorus bound to organic matter and sulphides were extracted with 8.8

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M H2O2 in 0.02 M HNO3, for 5 h at 85oC followed by addition of a solution of 3.2 M CH3COONH4 in 25% HNO3. After each successive extraction, separation was accomplished by

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centrifugation at 5000 rpm for 10 min and then the P concentration in the supernatant was

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determined.

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2.7. P speciation

The program visual MINTEQ was chosen in this paper as a chemical speciation model for

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calculating saturation index (SI) and P species [32]. Phosphorus speciation was carried out before and after release of P from soils. As input values soil pH, and the concentrations of SO42-,

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NO3-, P, Al, Fe, K, Na, Mg and Ca were used. The MINTEQ runs were performed at 25oC.

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Oversaturation is indicated if SI>0, whereas the solution is under saturated with respect to the

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solid if SI<0. There is an apparent equilibrium with respect to the solid when SI=0 (or more correctly -0.5
3. Results and discussion

3.1. Effects of nanoparticle treatment on kinetic of P release Phosphorus release from control and treated soils with TiO2 and Al2O3 NPs is shown in Figures 1, 2 and 3, respectively. The initial release witnessed a rapid period continued for 1 to 4 h followed by a slower rate, which had also been reported by Zhang et al. [35]; Jalali and Ahmad Mohamad Zinli [24] and Pan et al. [36]. The rapid and slower release rate can be attributed to the mobile and less mobile P, respectively.

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Cumulative P released from control soils were in a range of 30.4 to 53.3 mg kg-1 (average 40.3 mg kg-1) (Table 3). The release of P in soils treated with NPs was significantly lower than the control soils (the decrease in P release was not significant in soils 1 and 3). Cumulative P

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released from soils treated with 1 and 3% Al2O3 were in a range of 10.9 to 22.9 mg kg-1 and 9.5

of 10.1 to 18.4 and 9.0 to 12.6 mg kg-1, respectively (Table 3).

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to 15.7 mg kg-1, respectively, while the corresponding data with 1 and 3% TiO2 were in a range

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The surface hydroxyl group of NPs provides the ability to bind with P released from soils. Thus, addition of NPs to soil reduced P release with time. Pan et al. [36] indicated that the adsorption

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of P on Fe3O4 particles was very fast and the equilibrium was reached within 2 h. The maximum amount of P (average of five treated soils = 16.9 mg kg–1) was released in soils treated with 1%

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Al2O3 (Fig. 1), whilst, the minimum (10.5 mg kg–1) P was released in soils treated with 3% TiO2.

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Increasing of the NP percent in the soils increased sorption sites and therefore reduced release of

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P from the soils. This result revealed that P release from soils could be reduced by 31.4% and

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27.6% when the soil was amended with 3% Al2O3 and TiO2, respectively. Walker [37] observed that P sorption by Al-WTR applied to a soil impacted with dairy effluent was low, only about 22% P was removed with surface applied Al-WTR at 5% rate. Codling et al. [38] reported that incorporating Al-WTR and Fe-rich residue at the rate of 10 g kg-1 in three litter amended soils reduced the Bray and Kurtz no.1-extractable P concentrations by 24% and 8%, respectively. Yang et al. [39] showed that the amounts of leachate reactive P, the potentially bioavailable P pool, from a sandy soil in Florida was significantly reduced by addition of CaCl2, CaCO3, or CaCl2+CaCO3, which was 36.0%, 17.5%, and 40.4%, respectively, while mill mud and mill mud + Al(OH)3 increased reactive P leached. Moharami and Jalali [40] studied the effect of amendments on P loss from a sandy soil and showed that the highest percentage of P

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retention in soil was produced when Al2O3 (38.5 %) and TiO2 (24.0 %) NPs were used for soil amendment, followed by calcite (20.1 %), bentonite (14.1 %), kaolinite (13.8 %), and zeolite (10.5 %). Results showed that amount of P sorbed on these NPs are higher than the values

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reported in some literatures for other adsorbents. But it should be noted that due to the scarcity of consistent cost information, cost comparisons are difficult to make. This study was carried out

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with the aim of finding an alternative approach for removing P from soil using NPs. Although

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efficiency of NPs is more costly than the other techniques and its widespread use is restricted due to high cost, but this study suggest that NPs also can use to decrease of P release from soils. It

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should be noted that the adsorption of P on NPs is relatively irreversible and the bonding between the active sites and the adsorbed P is so strong. Therefore, they can be a favor sorbent.

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To evaluate the kinetics of P release, the pseudo first-order and pseudo second-order models

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were tested to interpret the experimental data. The parameters of both empirical equations are

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given in Table 4. The value of pseudo first-order model parameters (k1 and qe) were calculated using the slope and the intercept of plots of log (qe −qt) versus t (Fig. 4) and pseudo second-order

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model parameters (qe and k2) were determined by plotting t/qt versus t (Fig. 5). The correlation coefficients (r2) for the pseudo second-order kinetic model fits are > 0.82 (average of treated and control soils = 0.92). Fitted cumulative P release from soils derived from Eq. (2) is similar with those observed experimentally. Good agreement between model fit and observed cumulative P release, in addition with the large correlation coefficients, suggests that P release in all soils and treatments well fitted using pseudo second-order kinetic model. Furthermore, the lower χ2 value (Eq. 3) for the pseudo-second order model (0.09, 0.09, 0.09, 0.06 and 0.45 in Al-1, Al-3, Ti-1, Ti-3 and Cs, respectively) also suggests that the release of P in soils and soil plus NPs followed the pseudo-second order kinetic model. The higher χ2 values (2.37, 0.32, 0.38, 0.15 and 3.01 in

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Al-1, Al-3, Ti-1, Ti-3 and Cs, respectively) for the pseudo-first order model suggests poor pseudo-first order fit to the data for P release. Successful presentation of the pseudo-second order kinetic model for P removal from aqueous solution by magnetic Fe–Zr binary oxide has been

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reported by Long et al. [41].

Although, the addition NPs in soils can reduce the P release, but it also increases the potential

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risk of NPs release to the environment. The purpose of this work was not to assess the NPs toxic

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effects, but the evaluation of NPs negative effects on microorganisms, plant and pollution of groundwater is important. The knowledge of the solubility and transport of NPs in soil is

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important for developing an understanding of their mobility potential in the soil environment and their potential risks to groundwater. Stability and transport of NPs are influenced by factors such

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as pH and zeta potential, ionic strength, and organic matter [42]. Fang et al. [43] investigated the

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transport of TiO2 in saturated homogeneous soil columns. It was observed that retention of TiO2

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was favored in soils containing higher clay content. Godinez and Darnault [44] reported that the hydrophobic characteristics and aggregation tendencies of some NPs will prevent their dispersal

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in natural environments and increase their deposition onto porous media thus limiting their transport. Moharami and Jalali [40] investigated the transport of TiO2, Fe3O4 and Al2O3 in soil columns and observed that retention of these NPs were favored in soil. On the hand, pH is one of the most important parameters in the dissolution of NPs. Brookins [45] indicated that Ti due to the high stability has very low mobility under almost all environmental conditions (except below pH 2). Pourbaix [46] found that Al2O3 will get dissolved and form aluminum ions in solutions with pH values lower than 4.25 or higher than 10.25. In this study, the pH of the soils amended with Al2O3 and TiO2 NPs were 6.5 and 8.3. Thus, performed experiments were not in the pH range of the dissolution of NPs. Although, information obtained

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from other research indicated that the solubility and transport of NPs in soils are low, but to prevent NPs toxicity on environment health and minimize pollution of the soils and groundwater,

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best management strategies should be applied.

3.2. Modelling of P release

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In order to predict the effect of NPs on P release from treated soils, modeling was performed

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using PHREEQC with the database of WATEQ4F. Table 2 indicates the surface parameters and the surface complexation reactions according to the diffuse double layer model proposed by

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Dzombak and Morel [47]. The initial P content has been measured using the equilibration of control soils with 10 Mm CaCl2 after 88 h of interaction and this amount was used as P solution

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in model. In the initial stage of modelling, surface sites of NPs is mixed with 10 mM CaCl2. Then, the results of this simulation were used as new surface composition in the next stage of

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modelling. The results of modeling for the treated soils with TiO2 and Al2O3 NPs are presented

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in Figures 2 and 3. The agreement between modeled and experimental results was very good.

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The modeling results showed that the amount of P released in the treated soils with Al2O3 is higher than in the treated soils with TiO2. Coincidence of experimental and modeled data indicated that surface complexation model was successful in predicting P adsorption by NPs and P release from soils treated with NPs. Thus, surface complexation process was controlled adsorption of P in this studied NPs. Moharami and Jalali [19] indicated that the adsorption of P from aqueous solutions using TiO2, Al2O3 and Fe3O4 nanoparticales follows pseudo-secondorder kinetics. They reported that TiO2 more effective than Al2O3 and Fe2O3 in adsorption of P from aqueous solution and surface complexation model was the main mechanism for the adsorption of P onto these NPs. Zach-Maor et al. [48] by studying the adsorption of P on nano-

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sized magnetite layer reported that P was bonded onto the surface of the nFe-GAC predominantly through bidentate complexation.

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3.3. Effect of nanoparticle treatment on P Fractionation Phosphorus behavior in soils for eutrophication can be evaluated based on the P fractions,

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instead of the total P content. Figure 6 shows the changes in fractions in the five control soils and

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the soils treated with two different doses of the nanoparticles (1% and 3%). The average distributions of P fractions are listed in Table 5 (Dunkan test, P < 0.05).

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In the control soils, the percentage of P fractions decreased as: carbonated-P (73.6%) > organic matter and sulphide-P (17.8%) > Fe-Al oxides–P (7.2%) > exchangeable-P (1.4%) (Fig. 6).

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These results were similar to the results observed by Zhang et al. [35; Jalali and Ranjbar [49]; Halajnia et al. [50] and Alvarez-Rogel et al. [51] who found that P was bounded to carbonates,

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fraction for P in soils.

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whereas Motavalli and Miles [52] and Richards et al. [53] reported that Fe-Al bound was largest

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After P release, distribution of P in control soils follows the sequence of: carbonated-P (62.5% to 77.1%) > organic matter and sulphide -P (16.4% to 37.4%) > Fe-Al oxides–P (4.3% to 7.2%) > exchangeable-P (0.2% to 1.3%). With the increase of NPs, the exchangeable, Fe-Al bound and carbonated-P decreased from 1.1% (control) to 0.85% (3% TiO2), 5.4% (control) to 3.5% (3% TiO2) and 67.5% (control) to 56.2% (3% TiO2), respectively, while the organic matter and sulphide-P were increased from 25.9% (control) to 39.4% (3% TiO2). Thus, carbonated- P fraction remained the most dominant fraction in all soils and all treatments and organic matter and sulphide–P fraction increased markedly following NPs addition. This result reflected that the NPs caused immobilization of P in soils and reduced the available P, consequently reducing their environment risk.

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Liu and Zhao [54] studied the effects of iron phosphate NPs on Pb2+ fraction in soils. They found that NP treatments resulted in significant shift in soil-bound Pb2+ fraction from more easily extractable Pb2+ to the least available form (the residual Pb2+). Cui et al. [55] reported that the

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applications of nano hydroxyapatite in a contaminated soil significantly decreased exchangeable fraction of Cu and Cd and transformed them from active to inactive fractions. There are no

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published data on the effect of NPs on P fractionation in soils, thus, these results cannot be

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compared.

The relationships between the released P from soils (Cs, Al-1 and Ti-1) and different P fractions

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in the soils were shown in Figure 7. It seemed that the amounts of P released was significantly correlated with total- P (r = 0.66 to 0.88) and Fe- Al oxide- P (r = 0.31 to 0.33), but was not

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correlated with exchangeable, carbonated and organic matter and sulphide- P fractions.

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Furthermore, in treated soils with 3% of Al2O3 and TiO2, the amount of P released was correlated

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with total- P and Fe- Al oxide- P fractions (data not shown). This means that Fe- Al oxide- P might be easily released from the soils, and it was main contributors to the P-release source in

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the control and treated soils. This was very similar to the previous studies [35; 56].

3.4. Effect of nanoparticle treatment on P speciation in soils In all soils treated with NPs and in control soils, in the initial stage of P release the solution samples were saturated with respect to strengite (Fe(OH)2 H2PO4) (SI= 1.23) and undersaturated with respect to other phosphate minerals. At the end of P release, all solutions were saturated with hydroxyapatite (HA, Ca5(PO4)3OH) (SI= 5.61) and strengite (SI= 2.38). Taghipour and Jalali [57] investigated P species controlling P release by organic acids. They indicated that soil P release was controlled by a combination of octacalcium phosphate, dicalcium phosphate dehydrate, dicalcium phosphate and magnesium phosphate minerals.

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The percentage distribution of P species in control and treated solutions (initial stage and end of P release) from the MINTEQ output is summarized in Table 6. In the initial stage of release of P between 47.9 (Ti-1) to 85.5% (Ti-1), 4.6 (Ti-1) to 26.7% (Ti-3) and 3.4% (Ti-1) to 19.2% (Ti-1)

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of total P in solutions present as H2PO4-, HPO42- and CaHPO4, respectively. At the end of P release, the percentage of HPO42- and CaHPO4 in all soils and all treatments increased, while the

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percentage of H2PO4- decreased. Our results therefore apparently suggest a decrease of

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availability of P after the addition of NPs in the soils.

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4. Conclusion

The present study was conducted to evaluate the effect of NPs on kinetics release and

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fractionation of P in some calcareous soils. The addition of NPs to soil reduced P release with time. Kinetic analyses indicated that the time-dependent P release followed pseudo-second-order

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kinetics. We used surface complexation model to simulate the release of P from treated soils.

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The amount of P bounded with organic matter and sulphide (stable fraction) were increased

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following NPs addition. Thus, the results indicated that the addition of NPs reduces P release from soil and reduces its environment risk. But it should be noted that although application of these materials can be more efficient than other adsorbents for P removal from soils and aqueous solution, but some problems with Al and Ti toxicity may arise after their application. In order to provide an adequate explanation for the effects of TiO2 and Al2O3 NPs on the release of P, it is inevitable to analyze the release of Al, Ti and their effects on plants, microorganisms and groundwater pollution.

Acknowledgement

The authors express their sincere thanks to the reviewers.

Reference

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[1] Y. Zhao, J. Wang, Z. Luan, X. Peng, Z., Liang, L. Shi, Removal of phosphate from aqueous solution by red mud using a factorial design. J. Hazard. Mater. 165 (2009) 1193-1199. [2] L.E. de-Bashan, J.P. Hernandez, T. Morey, Y. Bashan, Microalgae growth-promoting

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bacteria as “helpers” for microalgae: a novel approach for removing ammonium and phosphorus from municipal wastewater. Water Res. 38 (2004) 466–474.

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[3] D. Wang, X. Li, Q. Yang, W. Zheng, Y. Wu, T. Zeng, G. Zeng, Improved biological the sole carbon source. Water Res. 46 (2012) 3868-3878.

us

phosphorus removal performance driven by the aerobic/extended-idle regime with propionate as

an

[4] D. Wang, W. Zheng, X. Li, Q. Yang, D. Liao, G. Zeng, Evaluation of the feasibility of alcohols serving as external carbon sources for biological phosphorus removal induced by the

M

oxic/extended-idle regime. Biotechnol. Bioeng. 110 (2013) 827–837. [5] M. Jalali, Phosphorous status and sorption characteristics of some calcareous soils of

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Hamadan, western Iran. Environ. Geol. 53 (2007) 365-374.

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[6] M. Jalali, Phosphorous concentration, solubility and species in the groundwater in a semi-arid

Ac ce p

basin, southern Malayer, western Iran. Environ. Geol. 57 (2009) 1011–1020. [7] B.B. Johnson, A.V. Ivanov, O.V. Antzutkin, W. Forsling, 31P nuclear magnetic resonance study of the adsorption of phosphate and phenyl phosphates on Al2O3. Langmuir 18 (2002) 1104-1111.

[8] S.H. Lin, H.C. Kao, C.H. Cheng, R.S. Juang, An EXFAS study of the structures of copper and phosphate sorbed onto geotite. Colloids Surf. 234 (2004) 71-75. [9] R.S. Juang, J.Y. Chung, Equilibrium sorption of heavy metals and phosphate from singleand binary sorbate solutions on goethite. J. Colloid Interf. Sci. 275 (2004) 53-60. [10] X. Huang, Intersection of isotherms for phosphate adsorption on hematite. Colloid Interf. Sci. 271 (2004) 296-307.

Page 14 of 32

[11] N.M. Agyei, C.A. Strydom, J.H. Potgieter, An investigation of phosphate ion adsorption from aqueous solution by fly ash and slag. Cement Concrete Res. 30 (2000) 823-826. [12] S. Moharami, M. Jalali, Removal of phosphorus from aqueous solution by Iranian natural

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adsorbents. Chem. Eng. J. 223 (2013) 328-339. [13] E.W. Shin, J.S. Han, M. Jang, S.H. Min, J.K. Park, R.M. Rowell, Phosphate dsorption on

cr

aluminumim pregnated mesoporous silicates: surface structure and behavior of adsorbents.

us

Environ. Sci. Technol. 38 (2004) 912-917.

[14] T. Kasama, Y. Watanabe, H. Yamada, T. Murakami, Sorption of phosphates on Al-pillared

an

smectites and mica at acidic to neutral pH. Appl. Clay Sci. 25 (2004) 167-177. [15] E. Oguz, A. Gurses, N. Canpolat, Removal of phosphate from wastewaters. Cement

M

Concrete Res. 33 (2003) 1109-1112.

[16] A. Zach-Maor, R. Semiat, H. Shemer, Fixed bed phosphate adsorption by immobilized

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nano-magnetite matrix: experimental and a new modeling approach. Adsorption 17 (2011a) 929–

te

936.

Ac ce p

[17] A. Miziolek, Nanoenergetics: an emerging technology area of national importance. Amptic. Quart. 6 (2002) 43–48.

[18] R.E. Serda, S. Ferrati, B. Godin, E. Tasciotti, X.W. Liu, M. Ferrari, Mitotic trafficking of silicon microparticles. Nanoscale 1 (2009.) 250–259. [19] S. Moharami, M. Jalali, Effect of TiO2, Al2O3, and Fe3O4 nanoparticles on phosphorus removal from aqueous solution. Environ. Prog. (In Press). [20] S.A. Kang, W. Li, H.E. Lee, B.L. Phillips, Y.J. Lee, Phosphate uptake by TiO2: Batch studies and NMR spectroscopic evidence for multisite adsorption. J. Colloid Interf. Sci. 364 (2011) 455–461.

Page 15 of 32

[21] Z. Guo, C. Yan, J., Xu, W. Wu, Sorption of U(VI) and phosphate on γ-alumina: Binary and ternary sorption systems. Colloids and Surfaces A: Physicochem. Eng. Aspects 336 (2009), 123– 129.

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[22] P. Bingjun, J. Wu, B. Pan, L. Lv, W. Zhang, L. Xiao, X. Wang, X. Tao, S. Zheng, Development of polymer-based nanosized hydrated ferric oxides (HFOs) for enhanced phosphate

cr

removal from waste effluents. Water Res. 43 (2009) 4421–4429.

[23] D.L. Rowell, Soil Science: Methods and Applications. Longman Scientific & Technical,

us

Essex, UK, 1994.

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[24] M. Jalali, N. Ahmadi Mohammad Zinli, Kinetics of phosphorus release from calcareous soils under different land use in Iran. J. Plant Nutr. Soil Sci. 174 (2011) 38–46.

M

[25] S. Mahdavi, M. Jalali, A. Afkhami, Heavy metals removal from aqueous solutions using TiO2, MgO, and Al2O3 Nanoparticles. Chem. Eng. Comm. 200 (2013) 448-470.

d

[26] J. Murphy, J.P. Riley, A modified single solution method for determination of phosphate in

te

natural waters. Analytica Chimica Acta 27 (1962) 31–36.

Ac ce p

[27] S. Lagergren, Zur theorie der sogenannten adsorption geloester stoffe, Kungliga Svenska, Vetenskapsakad Handl. 24 (1898) 1–39. [28] Y.A. Aydin, N.D. Aksoy, Adsorption of chromium on chitosan: Optimization, kinetics and thermodynamics. Chem. Eng. J. 151 (2009) 188-194. [29] H.K. Boparai, M. Joseph, D.M. O’Carroll, Kinetics and thermodynamics of cadmium ion removal by adsorption onto nano zerovalent iron particles. J. Hazard. Mater. 186 (2011) 458– 465. [30] D.L. Parkhurst, C.A.J. Appelo, User's Guide to PHREEQC (Version 2)-A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations. United States Geological Survey, Water Resources Investigations Report 99-4259, Washington, DC, 1999.

Page 16 of 32

[31] C.A. Lucho-Constantinoa, M.A. lvarez-Sua´rez, R.I. Beltra´n-Herna´ndez, F. Prieto Garcı´a, H.M. Poggi-Varaldo, A multivariate analysis of the accumulation and fractionation of major and trace elements in agricultural soils in Hidalgo State, Mexico irrigated with raw wastewater.

ip t

Environ. Int. 31 (2005) 313– 323. [32] J.P. Gustafsson, Visual MINTEQ, ver 2.32. Stockholm: Royal Institute of Technology,

cr

2005.

[33] M. Jalali, H. Arfania, Leaching of heavy metals and nutrients from calcareous sandy-loam

us

soil receiving municipal sewage sludge, J. Plant Nutr. Soil Sci. 173 (2010) 407–416.

an

[34] J.D. Allison, D.S. Brown, K.J. Novo-Gradac, MINTEQA2/PRODEFA2, A Geochemical Assessment Model for Environmental Systems: Version 3.0 Users Manual. US Environmental

M

Protection Agency, Athens, GA. (EPA/600/3-91/021), 1991.

[35] B. Zhang, F. Fang, J. Guo, Y. Chen, Z. Li, S. Guoa. Phosphorus fractions and phosphate sorption-release characteristics relevant to the soil composition of water-level-fluctuating zone of

te

d

three gorges reservoir. Ecol. Eng. 40 (2012) 153– 159. [36] G. Pan, L. Li, D. Zhao, H. Chen, Immobilization of non-point phosphorus using stabilized

Ac ce p

magnetite nanoparticles with enhanced transportability and reactivity in soils. Environ. Pollut. 158 (2010) 35–40.

[37] L.C. Walker, Vertical mobility and dynamics of phosphorus from fertilizer and manure in sandy soils. M.Sc Thesis, Univ. Fl., Gainesville, Fl, 2004. [38] E.E. Codling, R.L. Chaney, C.L. Mulchi, Use of aluminum- and iron-rich residues to immobilize phosphorus in poultry litter and litter-amended soils. J. Environ. Qual. 29 (2000) 1924-1931. [39] J. Yang, Z. He, Y. Yang, P. Stoffella, X. Yang, D. Banks, S. Mishra, Use of amendments to reduce leaching loss of phosphorus and other nutrients from a sandy soil in Florida. Environ. Sci. Pollut. Res. 14 (2007) 266–269.

Page 17 of 32

[40] S. Moharami, M. Jalali, Phosphorus leaching from a sandy soil in the presence of modified and un-modified adsorbents. Environ. Monit. Assess. 186 (2014) 6565–6576. [41] F. Long, J.L. Gong, G.M. Zeng, L. Chen, X.Y. Wang, J.H. Deng, Q.Y. Niu, H.Y. Zhang,

ip t

Z.R. Zhang, Removal of phosphate from aqueous solution by magnetic Fe–Zr binary oxide. Chem. Eng. J. 171 (2011) 448– 455.

cr

[42] R.A. French, A.R. Jacobson, B. Kim, S.L. Isley, R.L. Penn, P.C. Baveye, Influence of ionic strength, pH, and cation valence on aggregation kinetics of titanium dioxide nanoparticle.

us

Environ. Sci. Technol. 43 (2009) 1354-1359.

[43] J. Fang, X.Q. Shan, B. Wen, J.M. Lin, G. Owens, Stability of titania nanoparticles in soil

an

suspensions and transport in saturated homogeneous soil columns. Environ. Pollut. 157 (2009)

M

1101-1109.

[44] I.G. Godinez, Ch.J.G. Darnault, Aggregation and transport of nano-TiO2 in saturated porous

d

media: Effects of pH, surfactants and flow velocity. Water Research 45 (2011) 839-851.

te

[45] D.G. Brookins, Eh-pH diagrams for geochemistry. New York, Springer-Verlag, 1988. [46] M. Pourbaix, Atlas of electrochemical equilibria in aqueous solutions, NACE International,

Ac ce p

Houston, USA, 1974.

[47] D.A. Dzombak, F.M.M. Morel, Surface complexation modeling—hydrous ferric oxide: New York, John Wiley. 1990.

[48] A. Zach-Maor, R. Semiat, H. Shemer, Adsorption–desorption mechanism of phosphate by immobilized nano-sized magnetite layer: Interface and bulk interactions. J. Colloid Interf. Sci. 363 (2011b) 608–614.

[49] M. Jalali, F. Ranjbar, Aging effects on phosphorus transformation rate and fractionation in some calcareous soils. Geoderma 155 (2010) 101–106. [50] A. Halajnia, G.H. Haghnia, A. Fotovat, R. Khorasani, Phosphorus fractions in calcareous soils amended with P fertilizer and cattle manure. Geoderma 150 (2009) 209–213.

Page 18 of 32

[51] J. Alvarez-Rogel, F.J. Jimenez-Carceles, C. Egea-Nicolas, Phosphorus retention in a coastal salt marsh in SE Spain. Sci. Total Environ. 378 (2007) 71–74. [52] P.P. Motavalli, R.J. Miles, Soil phosphorus fractions after 111 years of animal manure and

ip t

fertilizer applications. Biol. Fertil. Soils 36 (2002) 35–42. [53] J.E. Richards, T.E. Bates, S.C. Sheppard, Changes in the forms and distribution of soil

cr

phosphorus due to long-term corn production. Can. J. Soil Sci. 75 (1995) 311–318.

us

[54] R. Liu, D. Zhao, Reducing leachability and bioaccessibility of lead in soils using a new class of stabilized iron phosphate nanoparticles. Water Res. 41 (2007) 2491–2502.

an

[55] H. Cui, J. Zhou, Q. Zhao, Y. Si, J. Mao, G. Fang, J. Liang, Fractions of Cu, Cd, and enzyme activities in a contaminated soil as affected by applications of micro- and nanohydroxyapatite. J.

M

Soils Sediments 13 (2013) 742–752.

[56] L.M. Ma, M. Zhang, Y.H. Teng, Characteristics of phosphorous release from soil in

d

periodic alternately waterlogged and drained environments at WLFZ of the three gorges

te

reservoir. Environ. Sci. 29 (2008) 1035- 1039.

Ac ce p

[57] M. Taghipour, M. Jalali, Effect of low-molecular-weight organic acids on kinetics release and fractionation of phosphorus in some calcareous soils of western Iran. Environ. Monit. Assess. 185 (2013) 5471-82.

[58] A. Torrents, Ph.D. Thesis, Department of Geography and Environmental Engineering, The Johns Hopkins University, Baltimore, MD, 1992. [59] A.T. Stone, A. Torrents, J. Smolen, D. Vasudenvan, J. Hadley, Adsorption of organic compounds possessing ligand donor groups at the oxide/water interface. Environ. Sci. Technol. 27 (1993) 895-909. [60] J.P. Morel, N. Marmier, C. Hurel, N. Morel-Desrosiers, Effect of temperature on the acid– base properties of the alumina surface: Microcalorimetry and acid–base titration experiments. J. Colloid Interface Sci. 298 (2006) 773-779.

Page 19 of 32

pH

EC

OM

Clay

dS m-1

Sand

CaCO3

Olsen-P

Total P

mg kg-1

%

cr

Soil no.

ip t

Table 1 Some chemical and physical properties of studied soils [24]

6.7

0.1

2.1

15.2

61.4

3.7

21.4

1079.1

2

7.1

0.2

1.2

19.2

51.4

13.3

71.0

1674.1

3

7.5

0.3

3.1

45.8

24.2

19.6

70.0

1137.5

4

7.3

0.2

1.1

24.8

59.0

8.5

112.0

1911.9

5

7.1

0.2

1.9

23.2

59.7

4.9

94.0

1818.0

Ac ce p

te

d

M

an

us

1

Page 20 of 32

Table 2 Surface parameters of NPs and equilibrium constants used to simulate P desorption

TiO2

Al2O3

45.4a

105.8a

Surface parameters

ip t

Specific surface area (m2 g-1) Site density (sites nm-2)

cr

2.5b 1.7c

Surface complexation reactions

us

SurfcOH + H+ = SurfcOH2+

SurfcOH + PO4-3 + 3H+ = SurfcH2PO4 + H2O

M

SurfcOH + PO4-3 + 2H+ = SurfcHPO4- + H2O

an

SurfcOH = SurfcO- + H+

[58]

c

[21]

d

[59]

-9.2 g

15.6 e

14.2 e

22.1 e

24.4 e

29.7f

26.5 f

te

[25]

b

-8.7 d

Ac ce p

a

7.9 g

d

SurfcOH + PO4-3 + H+ = SurfcPO4-2 + H2O

3.9 d

e

[19]

f

Obtained from Fitting

g

[60]

Page 21 of 32

ip t

Table 3 Amounts of P released (mg kg−1) (± SD) from soils (Cs=untreated soil, Al-1=1% Al2O3 plus soil, Al-3= 3% Al2O3 plus soil, Ti-1= 1% TiO2 plus soil, Ti-3=3% TiO2 plus soil) Soil no.

Cs

Al-1

Al-3

Ti-1

1

34.9 ± 1.8a

11.8 ±3.5b

10.2 ±4.7b

10.7 ±3.5b

2

40.6 ± 3.5a

18.3 ±4.3b

11.9 ±3.6d

14.5 ±1.8c

3

30.4 ± 2.3a

10.9 ±5.3b

9.6 ± 0.7b

10.1 ±3.9b

4

42.6 ± 3.4a

19.5 ±6.4b

13.0 ±3.1d

16.0 ±0.3c

11.2 ±0.8d

5

53.3 ± 2.9a

22.9 ±3.2b

15.8 ±2.1d

18.5 ±2.7c

12.6 ±2.3e

Ti-3

9.6 ±0.9b

9.0 ±2.4b

an

us

cr

10.2 ±3.9d

Ac ce p

te

d

M

Data followed by the same letter in the row are not significantly different at the P <0.05 level, according to Duncan’s test (p<0.05)

Page 22 of 32

ip t

us

cr

Table 4 Kinetic parameters for the release of P from soils (Cs=untreated soil, Al-1=1% Al2O3 plus soil, Al-3= 3% Al2O3 plus soil, Ti-1= 1% TiO2 plus soil, Ti-3=3% TiO2 plus soil)

Pseudo-second-order q e,cal k2 -1 mg kg mg kg-1h-1

R

2

Pseudo-first-order q e,cal k1 -1 mg kg h-1

R2

1 2 3 4 5

34.87 40.63 30.45 42.56 53.26

36.63 41.32 33.33 43.85 55.24

0.001 0.001 0.001 0.002 0.002

0.95 0.96 0.96 0.94 0.96

33.12 35.22 30.04 38.21 44.82

0.025 0.026 0.022 0.028 0.034

0.88 0.93 0.83 0.92 0.96

Al-1

1 2 3 4 5

11.80 18.35 10.89 19.47 22.96

11.97 19.19 11.47 19.57 22.17

0.005 0.003 0.004 0.003 0.004

0.95 0.95 0.95 0.95 0.96

10.42 17.32 10.39 17.24 17.33

0.022 0.024 0.022 0.022 0.022

0.91 0.90 0.83 0.89 0.93

Al-3

1 2 3 4 5

10.61 12.40 9.97 12.75 15.03

0.005 0.003 0.004 0.004 0.003

0.95 0.92 0.95 0.92 0.93

9.55 11.54 9.14 12.09 14.22

0.022 0.021 0.021 0.018 0.016

0.85 0.80 0.79 0.80 0.80

Ti-3

ed

ce pt

Ti-1

10.22 11.93 9.57 13.04 15.77

Ac

Cs

M an

Soil no

q e,exp mg kg-1

1 2 3 4 5

10.66 14.53 10.11 15.98 18.46

10.66 14.95 10.61 16.42 19.38

0.005 0.003 0.004 0.003 0.002

0.88 0.85 0.82 0.86 0.87

9.36 13.52 9.72 14.85 17.66

0.022 0.022 0.022 0.022 0.025

0.89 0.85 0.82 0.86 0.87

1 2 3 4 5

9.64 10.22 9.00 11.24 12.64

10.10 10.92 9.27 11.48 13.64

0.004 0.003 0.004 0.003 0.003

0.95 0.91 0.94 0.93 0.93

9.21 10.12 8.55 10.76 12.50

0.022 0.022 0.020 0.018 0.022

0.82 0.80 0.81 0.80 0.80 Page 23 of 32

ip t

Al-1 Initial After P stage release

Ti-1 Initial After P stage release

Ti-3 Initial stage

After P release

32.9

6.4

31.6

85.5 3.4 5.7

31.6 18.2 1.7

81.6 5.2 6.2

38.4 21.8 2.5

41.6 15.8 27.0 1.0

25.0 47.9 19.2 7.1

42.4 15.7 21.6 0.8

17.2 66.5 9.7 3.5

43.9 13.0 22.1 0.6

After P release

8.1

28.8

9.4

26.9

7.2

40.2

4.6

H2PO4 CaHPO4 CaH2PO4+

80.6

45.4

5.0 4.9

17.8 2.6

79.5 6.1 4.6

53.3 16.3 2.9

80.9 5.6 6.0

19.1 25.9 1.2

HPO4-2 H2PO4CaHPO4 CaH2PO4+

14.3 70.7 8.4 3.8

46.2 17.8 25.7 0.9

16.4 64.2 13.9 5.0

43.2 16.6 29.8 1.1

16.7 63.2 12.5 4.6

Species

1 HPO4-2 -

HPO4-2 H2PO4CaHPO4 CaH2PO4+ 4

16.9 64.7 11.3 4.1

45.8 17.8 26.1 0.9

19.3 59.6 13.6 13.9

42.6 20.4 27.6 1.3

19.2 58.2 12.7 3.7

40.8 24.3 21.1 1.2

19.3 61.3 12.1 3.5

41.1 15.6 22.3 0.8

23.3 59.2 13.7 2.8

53.2 12.9 22.5 0.5

12.4 73.7 7.5 4.4

43.7 20.5 26.7 1.2

10.0 78.0 5.9 4.2

46.7 17.9 25.3 0.9

17.2 66.4 11.7 4.3

44.1 16.8 29.1 1.1

11.9 74.3 8.6 4.9

49.9 19.0 21.2 0.8

26.7 50.1 16.1 3.0

47.5 18.8 23.0 0.8

11.1 69.7 9.6 4.1

44.2 23.7 23.2 1.8

19.1 64.1 11.3 7.2

43.4 19.2 22.0 2.0

18.5 51.1 11.1 4.6

40.0 17.7 22.1 1.0

18.3 69.3 11.6 5.8

40.6 16.0 19.4 0.7

21.6 57.6 9.1 3.1

49.2 11.7 22.7 0.6

Ac

HPO4-2 H2PO4CaHPO4 CaH2PO4+

ce pt

3

HPO4-2 H2PO4CaHPO4 CaH2PO4+

ed

2

5

Al-3 Initial After P stage release

us

Cs Initial stage

M an

Soil no.

cr

Table 6 Phosphorus species distribution (%) in the soil solutions in the initial and final stage of P release (Cs=untreated soil, Al-1=1% Al2O3 plus soil, Al-3= 3% Al2O3 plus soil, Ti-1= 1% TiO2 plus soil, Ti-3=3% TiO2 plus soil)

Page 24 of 32

ip t

Figure

cr us

50 40

an

30

20

0 0

20

40

M

10

60

80

Soil No.1

Soil No.2 Soil No.3 Soil No.4 Soil No.5

100

te

d

Time (h)

Fig. 1 Cumulative of P released by time in control soils

Ac ce p

Cumulative P released (mg kg-1)

60

Page 25 of 32

Soil 1 + 1% TiO2

Soil 1 + 3% TiO2

20

Cumulative P released (mg kg-1)

16 12 8 4

16 12 8 4

0

0 0

20

40

60

80

100

0

20

40

Time (h)

Soil 2 + 1% TiO2

8 4

12 8 4 0

0 0

20

40

60

80

0

100

20

Cumulative P released (mg kg-1)

Cumulative P released (mg kg-1)

80

100

80

100

80

100

Soil 3 + 3% TiO2

20

12

M

12

16

8 4

8 4 0

0 40

60

80

Time (h)

te

Soil 4 + 1% TiO2

20 16

Ac ce p

12

0

100

8 4

20

40

60

80

40

16 12 8 4 0

100

0

20

40

Time (h)

60 Time (h)

Soil 5 + 1% TiO2

Soil 5 + 3% TiO2

20

Cumulative P released (mg kg-1)

20

60

Soil 4 + 3% TiO2

20

0

0

20

Time (h)

Cumulative P released (mg kg-1)

20

d

0

Cumulative P released (mg kg-1)

60

an

Soil 3 + 1% TiO2

16

Cumulative P released (mg kg-1)

40

Time (h)

Time (h)

20

100

cr

12

16

us

16

80

Soil 2 + 3% TiO2

20

Cumulative P released (mg kg-1)

Cumulative P released (mg kg-1)

20

60 Time (h)

ip t

Cumulative P released (mg kg-1)

20

16 12 8 4 0

16 12 8 4 0

0

20

40

60 Time (h)

80

100

0

20

40

60

80

100

Time (h)

Fig. 2 Cumulative of P released by time in soils plus 1% and 3% TiO2 nanoparticle. Black diamonds represent experimental data and the open diamonds corresponds to the modelling results.

Page 26 of 32

Cumulative P released (mg kg-1)

20 15 10 5

20 15 10 5 0

0 0

20

40

60

80

0

100

20

Soil 2 + 1% Al2O3

15 10 5

20 15 10 5 0

0 40

60

80

0

100

Soil 3 + 1% Al2O3 Cumulative P released (mg kg-1)

15 10

20

80

100

80

100

80

100

80

100

15

10

5

d

5

0

0

20

40

60

80

100

Soil 4 + 1% Al2O3

25

15 10 5 0 0

Ac ce p

20

20

40

60

0

te

Time (h)

80

20

40

Soil 4 + 3% Al2O3

25 20 15 10 5 0

100

0

20

40

15 10 5

Soil 5 + 3% Al2O3

25

Cumulative P released (mg kg-1)

20

60 Time (h)

Soil 5 + 1% Al2O3

25

60 Time (h)

Time (h)

Cumulative P released (mg kg-1)

60

M

20

Cumulative P released (mg kg-1)

Cumulative P released (mg kg-1)

40

Soil 3 + 3% Al2O3

25

0

Cumulative P released (mg kg-1)

20

Time (h)

Time (h) 25

100

an

20

80

cr

20

0

60

Soil 2 + 3% Al2O3

25

Cumulative P released (mg kg-1)

Cumulative P released (mg kg-1)

25

40

Time (h)

Time (h)

us

Cumulative P released (mg kg-1)

Soil 1 + 3% Al2O3

25

ip t

Soil 1 + 1% Al2O3

25

20 15 10 5 0

0 0

20

40

60 Time (h)

80

100

0

20

40

60 Time (h)

Fig. 3 Cumulative of P released by time in soils plus 1% and 3% Al2O3 nanoparticle. Black diamonds represent experimental data and the open diamonds corresponds to the modelling results.

Page 27 of 32

(b)

1.4

1.2

1.2

1 0.8 0.6

ip t

1.6

1.4

log (qe - qt)

log (qe - qt)

1.8

(a)

1.6

1 0.8 0.6

0.4

0.4

0.2

0.2 0

0 0

20

40

60

80

0

100

20

60

80

100

80

100

us (d)

1.6

1.4

1.4

1.2

1.2

an

log (qe - qt)

log (qe - qt)

1.8

(c)

1.6

40

Time (h)

Time (h)

1.8

cr

1.8

1 0.8

1

0.8 0.6

0.6

0.4

0.4

0.2

M

0.2

0

0 0

20

40

60

80

100

1.8

20

40

60 Time (h)

(e)

1.6

te

1.4

1.2 1 0.8

Ac ce p

log (qe - qt)

0

d

Time (h)

soil No.1 soil No.2

0.6

soil No.3

0.4

soil No.4

0.2

soil No.5

0

0

20

40

60

80

100

Time (h)

Fig. 4 Relationship between observed and predicted P release kinetics as described by pseudo first- order models in: (a) soil plus 1% Al2O3, (b) soil plus 3% Al2O3, (c) soil plus 1% TiO2 (d) soil plus 3% TiO2 and (e) control soils

Page 28 of 32

14

(a)

12

12

10

10

8

8

t/qt

6

(b)

6

4

4

2

2

0

0 0

20

40

60

80

100

0

20

40

Time (h)

60

80

100

80

100

cr

Time (h) 14

12

12

10

10

8

8

6

4

4

an

6

(d)

us

(c)

t/qt

t/qt

14

ip t

t/qt

14

2

2

0

0 0

20

40

60

80

0

100

20

14

60 Time (h)

(e)

12

soil No.1

d

10

t/qt

40

M

Time (h)

8

soil No.3

te

6

soil No.2

4

Ac ce p

2

soil No.4 soil No.5

0

0

20

40

60

80

100

Time (h)

Fig. 5 Relationship between observed and predicted P release kinetics as described by pseudo secondorder models in: (a) soil plus 1% Al2O3, (b) soil plus 3% Al2O3, (c) soil plus 1% TiO2 (d) soil plus 3% TiO2 and (e) control soils

Page 29 of 32

Soil 2 100%

80%

80%

P contribution (%)

60% 40%

60% 40%

0%

0% Cs (before P release)

Cs (after P release)

Al-1

Al-3

Ti-1

Cs (before P release)

Ti-3

Cs (after P release)

Soil 3

Al-3

Ti-1

Ti-3

Soil 4

100%

P contribution (%)

60% 40%

20%

80% 60% 40%

0%

an

20%

us

100%

80% P contribution (%)

Al-1

ip t

20%

20%

cr

P contribution (%)

Soil 1 100%

0%

Cs (after P release)

Al-1

Al-3

Ti-1

Ti-3

Soil 5

80%

Cs (after P release)

Al-1

Al-3

Ti-1

Ti-3

Organic matter and sulphide-P

60%

Carbonated-P

d

40%

20%

0%

Cs (after P release)

Al-1

Al-3

Fe-Al oxids-P Exchangeable-P Ti-1

Ti-3

Ac ce p

Cs (before P release)

te

P contribution (%)

100%

Cs (before P release)

M

Cs (before P release)

Fig. 6 Effects of NPs applications on percentage of P fractions in five soils (Cs=untreated soil, Al-1=1% Al2O3 plus soil, Al-3= 3% Al2O3 plus soil, Ti-1= 1%TiO2 plus soil, Ti-3=3% TiO2 plus soil)

Page 30 of 32

60 50

40 30

y = 0.1448x + 37.196 R² = 0.0212

Linear (Al-1)

y = 0.1583x + 13.244 R² = 0.0706

Linear (Ti-1)

20 y = 0.0927x + 11.927 R² = 0.0516

10

Linear (Cs)

40 30

0

40

40 y = 0.0038x + 12.373 R² = 0.0861

30 20

50

Linear (Al-1)

y = 0.0026x + 10.919 R² = 0.0901

Linear (Ti-1)

Linear (Cs)

40 30 20

an

10

us

y = 0.0076x + 31.66 R² = 0.1248

Released P (mg kg-1)

Released P (mg kg-1)

50 100 150 Fe- Al oxide- P (mg kg-1)

60

50

10

0

Linear (Ti-1)

Linear (Cs)

200

cr

0

60

y = -0.0741x + 24.794 R² = 0.3233

y = -0.0496x + 19.366 R² = 0.3083

10 10 20 30 Exchangeable- P (mg kg-1)

Linear (Al-1)

20

0 0

y = -0.1233x + 53.827 R² = 0.3204

ip t

50

Released P (mg kg-1)

Released P (mg kg-1)

60

y = -0.0314x + 48.167 R² = 0.083

Linear (Al-1)

y = -0.0107x + 19.346 R² = 0.0267

Linear (Ti-1)

y = -0.0105x + 16.557 R² = 0.055

Linear (Cs)

0

500 1000 1500 Carbonated- P (mg kg-1)

2000

0

60

d

40 30

10 0

te

Released P (mg kg-1)

50

20

100 200 300 Organic matter and sulphide- P (mg kg-1)

M

0

500

Ac ce p

0

1000 1500 Total P (mg kg-1)

2000

y = 0.0181x + 12.827 R² = 0.6605

Linear (Al-1)

y = 0.0125x - 2.3614 R² = 0.884

Linear (Ti-1)

y = 0.0085x + 1.0166 R² = 0.8673

Linear (Cs)

400

2500

Fig. 7 Relationship between the amounts of P released and different P fractions (Cs=untreated soil, Al1=1% Al2O3 plus soil, Ti-1= 1%TiO2 plus soil)

Page 31 of 32

Table 5 Effects of NPs on P fractions in control and treated soils (Cs=untreated soil, Al-1=1% Al2O3 plus soil, Al-3= 3% Al2O3 plus soil, Ti-1= 1% TiO2 plus soil, Ti-3=3% TiO2 plus soil) Before P release

After P release

ip t

Fractionation (mg kg-1)

Cs

Al-1

Al-3

Ti-1

Ti-3

21.8 ± 3.2a

15.9 ± 1.8a

15.8 ±0.5a

16.2 ±2.4a

14.0 ±1.3a

13.9 ±2.5a

109.3 ±12.3a

78.9 ±1.7ab

73.5 ± 3.6ab

67.9 ±5.2ab

61.9 ±3.2b

56.5 ±3.8b

Bound to carbonate

1146.1 ± 25.3a

982.6 ± 10.6a

908.3 ± 11.5a

893.8 ±8.9a

896.5 ±5.1a

880.9 ±5.4a

Bound to organic matter

248.6 ± 14.7c

351.7 ±12.0bc

456.9 ± 6.1ab

519.5 ±10.3a

533.8 ±6.5a

579.0 ±3.1a

Bound to Fe and Al oxides

an

and sulphides

us

Exchangeable

cr

Cs

Ac ce p

te

d

M

Results are presented as means of concentration of P in different P fractions of five control and treated soils (± SD) The superscript letters denote statistically different fraction within each category before and after P release according to Duncan’s test (p<0.05)

Page 32 of 32