Hexavalent Chromium removal from simulated and real effluents using Artocarpus heterophyllus peel biosorbent - Batch and continuous studies

Accepted Manuscript Hexavalent chromium removal from simulated and real effluents using Artocarpus heterophyllus peel biosorbent - Batch and continuous studies

N. Saranya, Abhishek Ajmani, V. Sivasubramanian, N. Selvaraju PII: DOI: Reference:

S0167-7322(18)31854-3 doi:10.1016/j.molliq.2018.06.094 MOLLIQ 9292

To appear in:

Journal of Molecular Liquids

Received date: Revised date: Accepted date:

9 April 2018 4 June 2018 23 June 2018

Please cite this article as: N. Saranya, Abhishek Ajmani, V. Sivasubramanian, N. Selvaraju , Hexavalent chromium removal from simulated and real effluents using Artocarpus heterophyllus peel biosorbent - Batch and continuous studies. Molliq (2018), doi:10.1016/ j.molliq.2018.06.094

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.

ACCEPTED MANUSCRIPT Hexavalent Chromium Removal from Simulated and Real Effluents Using Artocarpus Heterophyllus Peel Biosorbent- Batch and Continuous Studies Saranya Na, Abhishek Ajmanib, Sivasubramanian Va, Selvaraju Nb,

SC

02.06.2018

RI

PT

a- Department of Chemical Engineering, National Institute of Technology Calicut, Kozhikode, Kerala, India b- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Assam, India

NU

Corresponding author

AC

CE

PT E

D

MA

Dr. Selvaraju Narayanasamy, Assistant Professor, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India - 781039. Ph: +91-361-2583210 (O) ; +91-361-2585210 (R) Mob:+91-9446021424; Fax:+91-361-2582249

1

ACCEPTED MANUSCRIPT ABSTRACT Cr(VI) removal was studied with Artocarpus heterophyllus peel as a biosorbent in batch and continuous mode. Parameters influencing the maximum removal efficiency like biosorbent dose, contact time, pH, temperature, agitation speed, initial chromium concentration have been optimized in batch studies. Cr(VI) removal was observed to be 99.92 percentage and the residual Cr(VI) concentration was 0.036 mg/L with 50 mg/L initial concentration, 0.3 g of

PT

biosorbent at 100 rpm, pH 2.0 and 35°C. Elemental analysis, Porosity and surface area of the biosorbent were determined using CHNS analysis and Mercury Intrusion Porosimetry (MIP)

RI

respectively. The characteristics and interaction of the sorbent before and after treatment with Cr(VI) were analyzed using Fourier Transform Infrared Spectrometry (FTIR), Scanning

SC

Electron Microscopy-Energy Dispersive X-ray Spectrometry (SEM-EDXS), Electron Spin Resonance (ESR) spectrometry, X-ray Photoelectron Spectroscopy (XPS) and Atomic

NU

Adsorption Spectroscopy (AAS). Adsorption-coupled reduction was observed to be the predominant mechanism behind Cr(VI) removal. Isotherm and kinetic analysis were

MA

performed, Qo value was found to be 64.47±3.7 mg/g and pseudo-second-order model fitted better than the other models analyzed. Thermodynamic parameters revealed that the process was thermodynamically feasible and endothermic. Effect of co-existing ions was also done to

D

check the feasibility of Artocarpus heterophyllus biosorbent in removing Cr(VI) from real

PT E

effluents. Continuous column studies at different feed flow rates, initial feed Cr(VI) concentration and Column bed height were optimized using simulated and tannery effluents. Considerable performances were noted from Desorption-regeneration experiments with

CE

simulated Cr(VI) solution up to 3 consequent runs. Results of the present study depicted that AH biosorbent can be utilized for removal of Cr(VI) from simulated and real effluents.

AC

Keywords: Artocarpus heterophyllus peels, adsorption-coupled reduction, isotherms, kinetics, continuous column studies

2

ACCEPTED MANUSCRIPT

1. INTRODUCTION Chromium with its half-filled electronic configuration is toxic to the ecosystem when exceeds permissible limit. Cr(VI) and Cr(III) are the two stable forms prevail in aqueous solutions [1]. As far as the toxicity is concerned, Cr(VI) is considered to be more toxic than that of Cr(III) because of its high mobility[2]. Several industries like electroplating, metal polishing, leather

PT

tanning, wood preserving, chemical production industries use Cr(VI) and Cr(III) salts [3]. Though effluents containing toxic chemicals released from industries have been treated, they

RI

are not under permissible limits which cause serious problems to soil, water, air and their

SC

habitats [4]. Permissible limit of chromium in ground water is 0.5 mg/L and in drinking water is 0.05 mg/L [5]. Though several techniques have been utilized to treat toxic heavy metals

NU

from industrial effluents like precipitation, membrane separation, sedimentation, etc, adsorption played an excellent role for this purpose due to its simplicity in application and less sludge production with the possibility of metal recovery [6, 7]. Plant materials like

MA

leaves, stem, fruit pods, seeds, shells and peels have been used as biosorbents for Cr(VI) removal from aqueous solutions for several decades by researchers [8-12]. Artocarpus

D

heterophyllus, commonly known as jack fruit is a deciduous evergreen tree belongs to mulberry family cultivated in south-east Asia for their delicious fruit. The external cortex,

PT E

peels or rinds of the fruit are hard, horny and non-edible composed of conical carpel apices which are blunt envelop a thick rubbery whitish to yellowish wall [13]. The peels of the fruit found to contain immense phytochemicals like phenolic acids, hydroxybenzoic acids,

CE

flavanols with anti-inflammatory, anti-allergic, anti healing and anticancer properties reported by several researchers [14-17]. The peels of jack fruit being inedible are generally

AC

considered as waste without any economical value and also create a big problem of disposal due to its bulky nature. Earlier studies with jack fruit peels were performed for the removal of Cd(II), rhodamine dye and methylene blue [18-20]. Hence this study attempted to exploit the peels for the removal of Cr(VI) from simulated and real effluents. Industrial effluents are more critical with several heavy metals, acids and alkalis that pose high COD, BOD, turbidity, salinity and colour which cause severe damage and imbalance to ecosystem. Among the Cr(VI) releasing industries, tanneries and electroplating units are considered as major sources of Cr(VI) pollution to the environment. According to the CPCB report [21] from Government of India 2009, 2500 tanneries are distributed in and around Tamilnadu, 3

ACCEPTED MANUSCRIPT Uttar Pradesh and west Bengal. Tanneries use several chemicals including CrCl3 salts for the tanning and processing of hides. Due to the post tanning operations with several chemicals, Cr(VI) got released from the processing units as effluent. The effluent has to be treated and Cr(VI) has to be removed before discharge into the environment [22]. This work utilized Artocarpus heterophyllus peel particles for the removal of Cr(VI) from simulated and real effluents. Also the study focused on determining the influencing parameters and possible

PT

mechanism behind Cr(VI) removal. Effect of co-existing ions and desorption experiments were done to analyze the efficacy of AH biosorbent in removing Cr(VI) from real effluents and re-usability. Continuous packed bed column performance of the biosorbent at different

RI

experimental conditions was also performed using simulated and real tannery effluents.

SC

2. MATERIALS AND METHODS

NU

2.1. Preparation of Biosorbent

Artocarpus heterophyllus peels collected from NITC campus, Kozhikode, India, were cut into

MA

smaller pieces, washed several times in deionized water and sun dried to get a hard material. The dried pieces were then placed in a hot air oven at 60°C to remove excess moisture, pulverized in an electric blender and sieved to particles less than 1 mm, called as Artocarpus

D

heterophyllus (AH) biosorbent. The particles were stored in air tight plastic bags for further

PT E

use.

2.2. Preparation of simulated Cr(VI) solution

CE

Stock solution of Cr(VI) was prepared by diluting 2.828 g of potassium dichromate in 1000 ml of deionized water. Working solutions of different concentrations were prepared by

AC

appropriate dilutions of the stock solution in deionized water. All chemicals used in this study are of analytical grade. 2.3. Characterization of biosorbent Biosorbent properties like elemental composition (C-H-N-S %) were determined using C-HN-S analyzer (Vario EL III, Elementar, Germany). Textural characteristics like total intruded area, pore volume and porosity were determined by Mercury Intrusion porosimetry (MIP) (Quantachrome ASAP 2200, Micromeritics, USA). Surface functional groups of the biosorbent before and after Cr(VI) contact and possible interactions between them have been 4

ACCEPTED MANUSCRIPT analyzed by FTIR (Nicolet Nexus 670,USA) between 400 cm-1 to 4000 cm-1. Surface morphology and Cr binding over the biosorbent surface were analyzed by SEM (JSM – 6390LV, JEOL, USA) and EDXS (JED–2300, JEOL, USA). Reduction of Cr(VI) into Cr(III) in terms of their oxidation states is confirmed with the “g-values” calculated from electron spin resonance analysis with the aid of ESR spectrometer (JEOL, JES X3 series A system, USA) with frequency 9.44 GHz, microwave power 0.995 mW, magnetic field of 490.00 mT,

PT

a field amplitude 10mT, modulation frequency 100 kHz, modulation width 0.1mT, time constant 0.03 sec, and sweep time of 30 sec.

RI

Speciation of Cr was checked using K-Alpha XPS (Thermo Scientific MULTILAB 2000, USA), with a monochromatic Al Kα incident X-ray beam. The survey spectra were obtained

SC

from 1350 to -10 eV binding energy and the Cr2p high resolution spectra was obtained from 594 to 568 eV. Point of zero charge (PZC) of the biosorbent was determined by agitating 0.1

NU

g of biosorbent with 0.1 N KNO3 solution (pH 1.0 to 10.0) overnight. Plot between initial pH (pHo) and difference between final and initial pH (ΔpH= pHf –pHo) was made and PZC was

MA

determined from the point at which ΔpH is zero. Determination of total phenols present in the biosorbent was performed by standard Folin-Ciocalteu method using gallic acid as standard

2.4. Cr(VI) removal studies

D

by UV-visible spectrophotometer (Perkin-Elmer Lambda 650, USA) at 760 nm[23].

PT E

Batch studies of Cr(VI) removal were done in stoppered conical flasks with 50 ml working volume. The flasks were agitated in an incubator shaker at desired rpm and temperature. pH of the solutions were adjusted with 0.1M HCl and 0.1M NaOH and measured using a digital

CE

pH meter. Cr(VI) concentration in the residual filtrate after contacting with 1,5-Diphenyl carbazide in acidic environment was determined by UV-Visible spectrophotometer at 540

AC

nm. Total chromium concentration in the filtrate was determined using AAS (iCE 3300 series, Thermo Scientific,India) under air-acetylene flame and a hollow-cathode chromium lamp was used as radiation source. Cr(III) concentrations were determined by subtractive method between total Cr and Cr(VI) concentrations. The experiments were repeated independently twice and the results are reproducible with 5% error. The removal % of Cr(VI) was determined using the following equation as

 C  Ce   100 %Removal  o C o  

(1)

5

ACCEPTED MANUSCRIPT , where C0 is the initial Cr(VI) concentration (mg/L) and Ce is the residual Cr(VI) concentration at equilibrium (mg/L). The amount of adsorbed Cr(VI) adsorbed at any time ‘t’ was calculated using the formula:

qt 

C0  Ct V

(2)

m

PT

where qt is the adsorption capacity of the biosorbent at time ‘t’(mg/g), C0 is the initial Cr(VI) concentration (mg/L), Ct is the Cr(VI) concentration at time ‘t’ (mg/L), m is the mass of the

RI

biosorbent (g) and V is the volume of Cr(VI) solution (L).

SC

2.5. Desorption experiments

50 ml of 0.1 N NaOH was used as desorbing agent for 0.25 g of Cr adsorbed biosorbent and

Cdes 100 Cads

(3)

MA

%Desorption

NU

the desorption percentage was calculated as

Where, Cdes is the Cr(VI) desorbed at equilibrium time ‘t’ (mg/L), Cads is the Cr(VI)

D

adsorbed at time ‘t’ (mg/L).

PT E

2.6. Effect of other metal ions over Cr(VI) removal Combined effect of other cations and anions upon Cr(VI) removal was studied by mixing up 25 ml of 50 mg/L Cr(VI) solution with 25 ml of the same concentration of MgSO 4.7H2O,

CE

CoCl2, CaCl2,NaCl2,NaF,NaNO3, Na2HPO4 solutions separately and allowed to contact it for about 2 h at 100 rpm. The residual Cr(VI) concentration was measured using UV-Visible

AC

spectrophotometer as specified before. 2.7. Column experiments Continuous column studies were performed with simulated and real effluents in a borosilicate glass column of length 35 cm and inner diameter of 1.25 cm. Cr(VI) concentrations of 50 mg/L, 150 mg/L and 250 mg/L were selected for the continuous study. Experiments were done at different heights of AH biosorbent (5 cm, 7 cm, 9 cm) packed into the column with glass beads (1 mm dia) and cotton as supporting materials on both sides. The solutions were pumped into the column at a desirable flow rate (5 ml/min, 10 ml/min, 15 ml/min) using a peristaltic pump (Meclins PP 20 ex, India) in up-flow direction. Cr(VI) and Cr(III) from the 6

ACCEPTED MANUSCRIPT outlet of the column were determined as mentioned before. Efficacy of the biosorbent in removing Cr in real effluent was also tested with tannery effluent collected from chrome tanning industry in Ambur, India. The initial physico-chemical parameters of the industrial effluent including total Cr and Cr(VI) were determined by standard methods. 3. RESULTS AND DISCUSSION

PT

3.1. Characteristics of AH biosorbent From the analysis, it was found that the PZC value is 2.0, which implies that the AH

RI

biosorbent has highly protonated surface which is prone to anionic chromium binding. The pH of the KNO3 solutions from 3.0 to 10.0 reduced to 2.0 ± 0.25 after addition of AH

SC

biosorbent at a temperature of 35°C and 100 rpm for 2 h. This might be due to the release or interaction of various acidic groups from the biosorbent into the residual solution.

NU

Hence further modification of the biosorbent through chemical means and activation has

MA

not been done.

8

D

7

PT E

6 5 4 3

CE

pHinitial - pHfinal

PZC

2

AC

1 0

0

1

2

3

4

5

6

7

8

9

10

11

pHinitial

Fig.1 - Plot for determination of point of zero charge for the AH biosorbent From the elemental analysis it was observed that the biosorbent has high carbon and sulphur content (Table.1). The higher sulphur content might be mainly due to the sulphonic acids, proteins and amino acids present in the biosorbent [16].

7

ACCEPTED MANUSCRIPT

Table 1- Characteristics of AH biosorbent AH biosorbent

C% H% N% S% Total pore volume (cc/g)

65.36 6.76 1.22 7.22 7.83

Total surface area (m2/g) Total porosity % Total phenols

8.83 15.67

RI

PT

Parameters

NU

SC

38.32 mg GAE/g of extract

MIP data showed that the biosorbent has considerable pore volume and surface area suitable

MA

for ligand binding. Total phenolic content was found to be high with ethanolic extract (38.32 mg/g) which may serve as natural electron donor for Cr(VI) reduction [25].

D

Fig 2 showed the FTIR spectra of AH biosorbent before and after contacting with Cr(VI) ions

PT E

which deliberately revealed the functional groups participated in Cr(VI) removal. Broad peak at 3336.87 cm-1 showed the presence of -OH groups of alcohols and phenols of the biosorbent[26]. Shift in the peak after adsorption represents the involvement of -OH groups

CE

in Cr removal process. Shift at 2922.20 cm-1 represents the C–H stretch of alkanes composing

AC

the cellulosic part of the biosorbent [27].

8

ACCEPTED MANUSCRIPT

AH Cr loaded AH

100

60

40

20

3500

3000

2500

2000

1500

1000

-1

500

0

SC

Wavenumber (cm )

RI

4000

PT

% Transmittance

80

Fig. 2- FTIR spectra of AH biosorbent before and after contacting with Cr(VI)

NU

Sharp peak at 1722 cm-1 represents the carbonyl stretch of ketones or saturated aliphatics and disappearance of the peak after adsorption confirmed the participation of carbonyl groups in Cr(VI) removal [28]. A narrow shift in the peak at 1625 cm-1 represents the N–H bend of

MA

amines. Shift at the position 1438.8 cm-1 revealed that the C–C stretch of aromatic compounds present in the biosorbent took part in interaction with the chromium ions. Sharp and narrow shift at 1155.5 cm-1 denotes the interaction of S=O stretch of sulphonic acids.

D

Also a narrow shift at 1025.0 cm-1 represents the involvement of –SO3H group of Phenols

PT E

and proteins [29]. Disappearance of a sharp peak after adsorption at 872.2 cm-1 depicts the involvement of C–C stretch of Alkanes. Hence the possible mechanism of interaction may be of adsorption-coupled reduction since –COO, –OH, –SO3H groups mainly involved in the

CE

process of Cr(VI) removal [30,31] as shown below.

AC

3CxOH + Cr2O72- + 4H+ = 3CxO + HCrO4- + Cr3+ + H2O

CxSO3H + Cr2O72- = CxO + SO42- + HCrO4- + Cr3+ + H2O RCOOH + 2H2O + HCrO4- = RCO3H4O3Cr + ROH-

Scanning electron microscopy along with Energy dispersive X-ray spectroscopy revealed the morphology of the biosorbent. The biosorbent has a highly complex surface with several pores on it and irregular in nature. EDXS plot depicted the elemental composition of the biosorbent (Fig 3a). After adsorption, the surface seemed to be smooth with distinct visibility

9

ACCEPTED MANUSCRIPT of Cr ions clinged over it. This has been confirmed by the EDXS plot showing separate peaks

AC

CE

PT E

D

MA

NU

SC

RI

PT

for Cr at distinct energy levels of 0.57 KeV and 5.4 KeV (Fig 3b).

Fig 3- a) SEM-EDXS image of AH biosorbent before contacting with Cr(VI) b) after contacting with Cr(VI)

10

ACCEPTED MANUSCRIPT 3.2. Determination of oxidation state of chromium using ESR and XPS Electron spin resonance is a technique used to identify the oxidation states by the “g-value” obtained from the plot between intensity and magnetic field. ESR has been done for the AH biosorbent before and after Cr(VI) adsorption. From Fig. 4, the g-value is observed as 2.008 at magnetic field 333.53 mT for the untreated biosorbent which is meant for free radicals or lignins [32]. After Cr(VI) adsorption, the AH biosorbent is showing a small peak at around

PT

340 mT with a g -value of 1.972 which is specifically meant for Cr(III) [33]. Similar trend has been noted in the work of Escudero [34] using grape stalks as biosorbent for removing

RI

Cr(VI). Hence from the ESR analysis it has been confirmed that Cr(VI) after contacting with AH biosorbent is undergoing reduction which converts Cr(VI) into Cr(III) by the functional

NU

SC

groups present in the biosorbent.

MA

400

-200

-400

-600

g=2.008, Free radicals

g=1.972, Cr(III)

D

0

PT E

Field Intensity (MHz)

200

untreated AH Cr treated AH

250

275

300

325

350

375

Magnetic field (mT)

AC

CE

225

Fig 4. ESR plot of AH before and after adsorption.

11

ACCEPTED MANUSCRIPT

5200

Cr2P scan A

Cr2P scan B

4800

PT

4600

4400

RI

Counts/s (Residuals *0.5)

5000

595

590

585

580

SC

4200

575

570

565

NU

Binding energy (eV)

Fig 5. XPS analysis of AH biosorbent after Cr(VI) adsorption

MA

The oxidation state of Cr after adsorption was analyzed using XPS and shown in Fig 5. Survey scan in the broad range of binding energy showed the elements present in the AH

D

biosorbent after adsorption of Cr(VI) with atomic percentages ( S1 and table S1). Significant bands obtained at binding energies between 590 to 570 eV specifically at 575.6 eV and

PT E

585.06 eV are attributed to Cr(III) corresponding to Cr2P3/2 and Cr2P1/2 respectively [35,36]. This imply that the adsorbed Cr(VI) over the acidic groups of AH biosorbent get reduced to Cr(III) with the aid of electron donating groups of AH and get attached to it. The low atomic

CE

percentage of Cr(III) at AH biosorbent surface showed that most of the reduced Cr(III) got released into the aqueous solution which was determined by AAS analysis. Hence the

reduction. 3.3.

AC

mechanism of Cr(VI) removal by AH biosorbent is confirmed as adsorption-coupled

Effect of biosorbent dose

0.1 to 0.5 g of AH biosorbent were taken and allowed to contact with 50ml of 50 mg/L Cr(VI) solution at pH 2.0 agitated at 100 rpm for 2 h. With 0.1 g of biosorbent, the residual Cr(VI) concentration in the filtrate was 1.906 mg/L whereas the total Cr and Cr(III) concentrations were found to be 12.72 mg/L and 10.81 mg/L respectively. In Fig 6 it was shown that if the biosorbent dose increased, the residual Cr(VI) concentration gradually 12

ACCEPTED MANUSCRIPT decreased and reached below the permissible limit of 0.036 mg/L with 0.3 g of biosorbent. Total Cr and Cr(III) gradually increased with the increase in the biosorbent and reached almost same concentration at 0.3 g of biosorbent. Hence for further studies, 0.3 g of AH biosorbent has been taken as the optimum dose for removing Cr(VI) since there is no

PT

appreciable increase in the total Cr concentration above 0.3g of biosorbent.

50

RI

Cr(VI) Total Cr Cr(III)

SC

30

NU

20

10

0

-10 0.0

0.1

MA

Residual Cr Concentration (mg/L)

40

0.2

0.3

0.4

0.5

0.6

D

Dose (g)

PT E

Fig. 6 - Effect of biosorbent dose on Cr(VI), Cr(III) and Total Cr 3.4. Effect of contact time

CE

One of the important influencing parameter in Cr(VI) removal is the contact time between the adsorbent and adsorbate. The AH biosorbent showed 99.92 % Cr(VI) removal at a equilibrium time of 90 min at 100 rpm, pH 2.0. Cr(VI) got reduced gradually whereas total

AC

Cr and Cr(III) concentration increased and attained its maximum at 90 min (Fig.7). Presence of phytochemicals and immense functional groups might have assisted the adsorptioncoupled reduction of Cr(VI) into Cr(III) within a short span of 90 min. Hence the AH biosorbent can be a promising biosorbent for abstracting Cr(VI) from aqueous solutions.

13

ACCEPTED MANUSCRIPT Cr(VI) Total Cr Cr(III)

50

30

PT

20

10

RI

Concentration (mg/L)

40

0

30

SC

0

60

90

120

150

NU

Contact time (min)

MA

Fig. 7- Effect of contact time upon Cr(VI) removal in terms of Cr(III) and total Cr using AH biosorbent 3.5. Effect of agitation speed

D

Influence of contact speed upon Cr(VI) removal using AH biosorbent was determined at 6

PT E

different agitation speeds, from 25 to 150 rpm using an orbital shaker maintained at 35 °C. As shown in Fig.8, at 25 rpm the removal percentage was only 2.75, however it gradually increased with the increase in the agitation speed and reached a maximum of 99.85 % at 100

CE

rpm. The adsorption capacity of the AH biosorbent also increased with increasing agitation speed and reached a maximum of 8.32 mg/g at 100 rpm. The removal percentages were

AC

almost same at 125,150 and 100 rpm, revealed that 100 rpm can be optimum agitation speed for the complete removal of Cr(VI) from 50 mg/L solution.

14

ACCEPTED MANUSCRIPT % removal Adsorption capacity

100

80

60

PT

4 40

2

RI

Cr(VI) removal %

6

0

40

60

80

100

120

0

140

160

NU

20

SC

20

Adsorption capacity (mg/g)

8

MA

Agitation speed (rpm)

Fig. 8- Effect of agitation speed upon Cr(VI) removal and adsorption capacity of AH biosorbent

D

3.6. Influence of pH

PT E

The very detrimental parameter in Cr(VI) removal from aqueous solutions is the initial pH of the solution as it determines the speciation, stability and solubility of ions. Cr behaves critically in different pH environments. Cr exists as dichromate and chromate anions in

CE

aqueous solutions. When the pH is lower than the PZC of the biosorbent, the surface becomes more protonated which tend to make interaction with anionic Cr ions [37]. The surface of AH

AC

biosorbent was found to be more positive in PZC analysis. Cr(VI) solutions of various initial pH ranges from 1.0 to 9.0 have been prepared and allowed to contact with 0.3 g of AH biosorbent for 1.5 h agitated at 100 rpm. Interestingly the final pH of the Cr solution after contacting with the AH biosorbent became acidic (2.00 ± 0.75). This might be due to the immense acid containing functional groups like phenolic acids, hydroxybenzoic acids, ellagic acids, hydroxycinnamic acids [15] that would have released protons while contacting with the Cr(VI) solutions. The removal percentage of Cr(VI) and adsorption capacity of AH biosorbent at pH 1.0 to 8.0 was almost same as 99.88 and 8.32 mg/g respectively where at pH 9.0 they were slightly reduced to 97% and 8.1 mg/g (Fig.9(a)). Also presence of electron 15

ACCEPTED MANUSCRIPT donating groups of phytochemicals such as polyphenols, amino acids, proteins, oxylipins, flavonoids and lignocelluloses would have assisted the mechanism of reduction by donating electrons to the system [38]. The residual Cr(VI) concentrations at acidic pH were very low around 0.03mg/L and as the pH was increased the residual concentration decreased and reached a maximum of 1.33 mg/L at pH 9.0. However the total Cr and Cr(III) concentration gradually increased in the same manner with the increase in the pH till pH 7.0 and slightly

PT

reduced above it (Fig.9b). This might be due to the less availability of protons and electrons at higher pH for adsorption-coupled reduction to happen [39]. pH study with the AH biosorbent revealed that the biosorbent with its highly protonated surface groups and

RI

naturally containing inbound phytochemicals readily discharge protons and electrons for

SC

adsorption and reduction of toxic Cr(VI) into less toxic Cr(III) at a wide range of pH from 1.0 to 7.0. This adds an advantage of using AH biosorbent for Cr(VI) removal at physiological

MA

NU

pH, which most of the plant based biosorbents cannot be utilized for.

100

% Removal of Cr(VI) (a) qe (mg/g)

10

D

PT E

8

4

40

2

0

20

AC

pH initial pH final

6

60

CE

% Removal of Cr(VI)

80

0

2

4

6

8

10

0 0

1

2

3

4

5

pH

16

6

7

8

9

10

ACCEPTED MANUSCRIPT

(b) 40 35 30

Cr(VI) Total Cr Cr(III)

20

PT

Cr(VI)

25

15

RI

10

0 1

2

3

4

5

6

7

8

9

10

NU

0

SC

5

MA

pH

Effect of initial Cr(VI) concentration

PT E

3.7.

D

Fig. 9(a)- Effect of pH upon % removal of Cr(VI) and adsorption capacity of AH biosorbent (insert- initial and final pH of Cr(VI) solution before and after contacting with biosorbent for 2hrs) (b)- Effect of pH upon residual concentrations of Cr(VI), Cr(III) and total Cr

Wide range of initial Cr(VI) concentrations were selected from 50mg/L to 500mg/L for

CE

determining its effect on removal percentage of Cr(VI) and adsorption capacity of AH biosorbent. The removal percentage was maximum at 50 mg/L to 200 mg/L with 99.9 and 97.3 % respectively but decreased with the further increase in the initial concentration and

AC

attained 75% at 500 mg/L. As shown in Fig.10, the adsorption capacity of the AH biosorbent was low at lower concentration, however it gradually increased with the increase in initial Cr(VI) concentration. At all initial concentrations, the adsorption capacity attained its equilibrium at around 120 min. The fact behind this behavior might be due to the depletion of Cr(VI) ions at low concentration since almost all Cr(VI) ions have been adsorbed over the surface and got detoxified by the reducing elements of AH biosorbent. As the initial concentration of Cr ions were increased, the number of sites prone to Cr binding and reducing groups depleted and become unavailable for detoxifying available Cr(VI) ions in solution. Similar results were obtained for Cr(VI) removal using natural and ZnCl2 activated Sterculia 17

ACCEPTED MANUSCRIPT guttata shell by Rangabhashiyam and Selvaraju[40]. Hence, 50 mg/L is considered as optimum concentration for 99.99% removal with a residual concentration of 0.036mg/L which is less than that of the permissible limit with 0.3g of AH biosorbent at 2.0 pH, 35°C and 100 rpm.

PT

70

60

RI

50

SC

40

qe (mg/g)

50 mg/L 100 mg/L 200 mg/L 300 mg/L 400 mg/L 500 mg/L

30

NU

20

MA

10

0 0

50

100

150

200

PT E

D

Time (mins)

Fig. 10- Effect of initial Cr(VI) concentrations upon adsorption capacity of AH biosorbent Isotherm studies

CE

3.8.

Isotherm analysis reveals whether the adsorbent-adsorbate interaction is monolayer or

AC

multilayer with similar or varying affinity towards the ligands. Langmuir adsorption isotherm relies on per molecule one layer concept with the assumption that all ions have the same affinity towards adsorbent surface [41]. The isotherm is given by

qe 

Q0 KLCe 1  KLCe

(4)

Where, Ce is the Cr(VI) concentration at equilibrium (mg/L), qe is the biosorbent adsorption capacity at time ‘t’ (mg/g), Q0 is the monolayer adsorption capacity (mg/g) and KL is the Langmuir isotherm constant. RL is a dimensionless constant represented as 18

ACCEPTED MANUSCRIPT RL 

1 1  kLC0

(5)

The adsorption process is said to be favorable if the RL value is between 0 and 1, unfavorable if it is 1 and irreversible if its value is 0. Non linear isotherm plot is shown in Fig.11 and the isotherm parameters are given in Table 2. Q0 value was found to be 64.47±3.7 mg/g with regression value 0.965. Also the RL value of 0.102 represents that the Cr(VI) removal process

PT

is favorable and involves monolayer adsorption. Freundlich isotherm rely on multilayer adsorption with the assumption that the adsorbent

RI

surface is heteregenous with varying affinity towards ligands which is represented as 1

SC

qe  K F Ce n

(6)

NU

Where, KF is the Freundlich isotherm constant (mg/g)(L/mg)1/n and n is the Freundlich exponent (dimensionless) which depicts the magnitude of adsorption at biosorbent surface [42]. Low Value of 1/n, 0.25±0.043 represented that the adsorption of Cr(VI) over AH is

MA

favourable. KF value was found to be 20.17±2.99 with regression value 0.943. Dubinin–Radushkevich model is given by

D

2

(7)

PT E

qe  Qm expK

which is based on Polyani potential theory that describes about the nature and forces acting in the adsorption process. Qm is the maximum adsorption capacity (mg/g), K is the activity

CE

coefficient (mol/J), ε is Polanyi potential which is equal to RT [ln(1+(1/Ce)], T is the absolute temperature (K) and R is the gas constant (J/mol.K). Calculation of apparent energy of

E

1 2k

AC

adsorption ‘E’ from the activity coefficient value K, which is given by (8)

identify the involvement of physical, chemical forces and ion exchange mechanisms in the adsorption process [43]. Physical adsorption prevails if the E value is less than 8 kJ/mol, chemical adsorption occurs if the value is higher than 16 kJ/mol, ion exchange predominates if the value lies between 8 and 16 kJ/mol. From the non linear analysis, the Qm value was found to be 57.77±6.20 with regression value of 0.802 represents that the model does not fit well for the process. From the isotherm studies, Langmuir model fitted well with the 19

ACCEPTED MANUSCRIPT equilibrium data rather than the other isotherms like Freundlich and DR models evaluated, which depicted the involvement of Monolayer adsorption predominantly.

65 60 55

PT

50

RI

40 35 30

SC

qe (mg/g)

45

25 20

NU

15

Experimental Langmuir Freundlich DR

10

-25

0

25

MA

5 50

75

100

125

150

D

Ce (mg/L)

PT E

Fig. 11- Isotherm analysis of AH biosorbent for Cr(VI)

CE

Table 2 Isotherm parameters

Isotherm

AC

Langmuir

Freundlich

D-R

Parameters Qo (mg/g) KL (L/mg) RL at 50 mg/L R2 KF ((mg/g)(l/mg)1/n 1/n R2 Qm(mg/g) E(kJ/mol) K(mol2/J2) R2

3.9. Kinetic analysis 20

Values 64.47±3.7 0.17±0.04 0.102 0.965 20.17±2.99 0.25±0.043 0.943 57.77±6.20 0.163 24.97±14.20 0.802

ACCEPTED MANUSCRIPT The linear pseudo-first-order kinetic model is given as

log(qe  q)  logq e 

k1 t 2.303

(9)

Where, qt is adsorption capacity (mg/g) at time ‘t’ (sec), qe is equilibrium adsorption capacity (mg/g) and k1 is pseudo-first-order rate constant (min-1) [44]. By plotting log(qe  qt ) vs t, the kinetic parameters were calculated and showed in Table 3. The Regression values are

PT

lower than that of pseudo second order kinetics and the calculated qe values didn’t well

RI

matched with the experimental values which imply that the model was not matching for the whole range of contact time. This might be due to the boundary layer limitations and excess

SC

resistance which controls start of Cr(VI) removal process [45]. Linear form of pseudo-second order model is given as:

(10)

NU

t 1 t   2 qt K 2 qe qe

MA

where, k2 is the pseudo-second-order rate constant, (g/mg/min) [46,47]. Fig.12 showed that the plot of pseudo-second-order kinetic model at different initial Cr(VI) concentrations in the range of 50 to 500 mg/L. The qe values calculated from the model were well correlated with

D

experimental values and regression values are comparatively higher depicted that the process

PT E

of Cr(VI) removal followed pseudo-second order kinetics. Rate controlling steps limiting the biosorption process can be represented using the intraparticle diffusion model [48] in the following equation qt  Kidt1/ 2  C

CE

(11)

Where, kid is the rate constant for intra-particle diffusion (mg/g/min1/2) and C is the intercept.

AC

Multi linear curve obtained by plotting t1/2 and qt represented that the process of adsorption was not diffusion limited [49]. From the kinetic analysis it was known that pseudo second order kinetic model fitted better than the other kinetic models like pseudo first order and intraparticle diffusion models on the analysis over a wide range of concentration at regular time intervals.

21

ACCEPTED MANUSCRIPT

50 mg/L 100 mg/L 200 mg/L 300 mg/L 400 mg/L 500 mg/L

20 18 16

12 10 8 6

PT

t/qt, (min.g/mg)

14

4

RI

2

-2 -20

0

20

40

60

80

100

120

140

160

NU

time (mins)

SC

0

Table 3 Kinetic parameters

0.064 0.047 0.035 0.055 0.022 0.026

3.10.

Pseudo second order k2 qe R2 (g/mg/ min) (mg/g)

PT E

D

8.32 16.37 32.31 47.22 57.39 62.93

7.823 8.994 17.418 46.665 39.174 44.360

CE

(mg/g) 50 100 200 300 400 500

(mg/g)

Pseudo first order k1 qe R2 -1 (min ) (mg/g)

qe exp

0.999 0.846 0.807 0.897 0.825 0.849

0.052 0.049 0.013 0.007 0.003 0.003

8.47 16.66 32.25 47.62 66.66 66.66

0.998 0.999 0.998 0.997 0.992 0.992

Intraparticle diffusion kid C R2 (mg/g/min1/2) (mg/g) 0.616 1.256 2.275 3.508 4.251 4.985

2.107 3.844 9.187 11.376 11.170 10.299

AC

C0

MA

Fig. 12-Pseudo second order plot for different initial Cr(VI) concentration

Thermodynamic studies

Spontaneity of the process, heat of reaction and degree of randomness of the adsorption process can be determined by calculating the thermodynamic parameters like Gibbs free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) using the following. The parameters were calculated by the following equations

G  RT ln KC

(12) 22

0.770 0.715 0.751 0.781 0.886 0.843

ACCEPTED MANUSCRIPT where, ‘R’ is gas constant (8.314 J/mol/K), ‘T’ is absolute temperature (K) and and Kc is the distribution coefficient given by

H  S  ln KC    RT R

(13)

qe Ce

(14)

PT

KC 

Plot between 1/T vs ln Kc was made for different concentrations and the parameters were

RI

shown in Table 4. Negative ΔG values showed that the process is taking place in a spontaneous manner and the values tend to increase with the increase in the concentration.

SC

Positive values of ΔH revealed that the reaction is endothermic. Same trend has been shown by adsorption coupled reduction reactions of Cr(VI) using several biosorbents [50, 51].

NU

Positive values of ΔS at lower concentrations showed that the degree of randomness at the sorbent-sorbate interface is higher due to the increased movement of ions.

AC

CE

100

PT E

50

Temperature (K) 298 303 308 313 298 303 308 313 298 303 308 313 298 303 308 313

D

C0 (mg/L)

300

500

MA

Table 4 Thermodynamic parameters ΔG (kJ/mol) -8.641 -13.699 -13.925 -11.288 -4.602 -5.445 -5.744 -5.428 -0.128 -0.814 -2.668 -0.712 1.556 1.688 1.702 1.770

23

ΔH (kJ/mol)

ΔS (kJ/mol K)

41.096

0.173

12.113

0.057

21.998

0.075

2.375

-0.013

ACCEPTED MANUSCRIPT

3.11.

Effect of coexisting ions

Effect of co-existing ions in Cr(VI) removal have been studied with 50 mg/L Cr(VI) solutions. The percentage removal of Cr(VI) have been determined and shown in the Fig.S3. It was found that the cations like Mg2+, Cu2+, Ca2+, Co2+, K+ reduced removal of Cr(VI). Nitrates, Fluorides and Chlorides have slightly reduced Cr(VI) removal percentage by 72.84,

PT

79.36 and 64.73 respectively. Sulphate ions found to reduce the removal percentage by 56.77. This might be due to the competitive binding of anions to the positively charged surface

Desorption-regeneration experiments

SC

3.12.

RI

functional groups that would have made the Cr(VI) ions to stay in the residual solution.

NU

Desorption studies were done by dispersing the adsorbed biosorbent with 50mg/L of Cr(VI) solution into 50 ml 0.1 N NaOH solution and allowed to agitate at 100 rpm upto 2 h. Samples were taken intermittently once in every half an hour and analyzed for Cr(VI). The results

MA

obtained (Table S2) were appreciable upto 3 runs of desorption-regeneration cycles. Hence the AH biosorbent can be regenerated and reused for industrial purposes. Continuous column studies with simulated and real effluents

D

3.13.

PT E

Continuous column studies have been carried out by modifying the significant column parameters such as feed flow rate (5 mL/min, 10 mL/min, 15 mL/min), column height (5 cm, 7 cm, 9cm) and initial feed concentration (50mg/L, 150 mg/L, 250 mg/L) with simulated

CE

Cr(VI) solution. The physico-chemical parameters of the tannery effluent are given in Table 5. The breakthrough curves obtained for each of the experiment are shown in the figure 11.

q total 

AC

The total column capacity packed with AH biosorbent, qtotal (mg) is calculated by FA F t  t total  Cadsdt  1000 1000 t 0

(15)

Where ttotal is the total time of flow (min), F is the feed flow rate (mL/min) and A is the area under the breakthrough curve (cm2). Equilibrium adsorption capacity qe(exp) (mg/g), can be determined using q

e(exp)



q total M

(16) 24

ACCEPTED MANUSCRIPT Where M is the mass of the AH biosorbent packed inside the column (g) corresponding to the height. Total amount of Cr(VI) entering into column, mtotal, (g) is calculated by

mtotal 

C0 Ft total 1000

(17)

qtotal 100 mtotal

(18)

RI

Y(%)

PT

and the removal percentage of Cr(VI) ions can be calculated by

SC

The total treated volume, Veff (mL) in the column was calculated from equation:

NU

Veff  Ft total (19)

Total Dissolved solids Total suspended solids

10570.0 186.0

Sulphates Chlorides

8208.0 864.67

Iron BOD COD

5.75 1935.0 9504.0

PT E

pH Turbidity, NTU

effluent 4.48 37.0

CE AC

Tannery

D

Parameters

MA

Table 5-Physico-chemical parameters of industrial effluents

Total chromium Chromium (VI)

767.0 53.2 mg/L

The effect of column bed height, initial feed flow rate and the initial feed concentration is shown in the Fig 11. It was found that the column got saturated at about 660 min at bed depth of 5cm at a constant flow rate of 5 ml/min, whereas the saturation time increased with the increase in the bed depth from 840 min for 7 cm and 1170 min for 9 cm [Fig 13(a)]. The 25

ACCEPTED MANUSCRIPT maximum removal percentage was 79.71 with 9 cm bed height when compared to 72.45 and 67.27 with 7 cm and 5 cm respectively. The reason behind this could be due to the increase in the axial dispersion of Cr(VI) ions along the lengthy bed height due to the increased mass transfer zone. Also the number of active or binding sites will be large enough to convert Cr(VI) into Cr(III) [52]. Fig 13(b) shows the effect of initial Cr(VI) concentration with a constant flow rate of 5

PT

ml/min and bed depth of 9cm. The breakthrough time decreased with the increase in the Cr(VI) concentration. 50 mg/L initial Cr(VI) feed attained its breakthrough time at 960 min

RI

and saturated at almost 1170 min, whereas with 150 mg/L and 250 mg/L feed concentrations the breakthrough time decreased to 270 min and 120 min respectively and the curve became

SC

more steeper. The removal percentages at 150 mg/L and 250 mg/L were also less than that at 50 mg/L at constant flow rate and bed height. The adsorption capacity got increased with the

NU

increase in concentration (Table 5). This might be attributed to the increased driving force at the interface between the sorbent-sorbate due to the increased concentration gradient owing

MA

to increase in the Cr(VI) ions [53].

Effect of feed flow rate at constant Cr(VI) feed concentration of 50 mg/L and bed height of 9

D

cm is shown in Fig 13(c). If the feed flow rate is 5 ml/min, the breakthrough time, saturation time and the removal percentage are higher. The removal percentage decreased and the

PT E

breakthrough curve became steeper within a short span of time with 10 ml/min and 15 ml/min. The reason behind the fact is that more residence time would be there for Cr(VI) ions along the mass transfer zone of the column to contact with functional groups of AH

CE

biosorbent which converts Cr(VI) into less toxic state. Also the mass transfer resistance due to the external film diffusion decreases with increase in the flow rate [54]. The breakthrough

AC

curve for tannery effluent with initial Cr(VI) concentration of 53.2 mg/ml was shown in S2. The removal percentage was 49.37 with 9 cm AH biosorbent column bed height and 5 mg/L feed flow rate. The break through time was very less, about 30 mins with a saturation time of 240 mins. The effective volume of the real effluent was only 1200 ml which is very less compared to simulated Cr(VI) solutions. This might be due to the prevalence of other co existing anions especially sulphates, phosphates, fluorides, chlorides, dissolved and suspended solids which compete with the binding sites on AH biosorbent.

26

ACCEPTED MANUSCRIPT

5 cm 7 cm 9 cm

(a) 1.0

50 mg/L 150 mg/L 250 mg/L

(b)

1.0

0.8 0.8

0.6

0.4

0.2

0.2

0.0

0.0

0

150

300

450

600

750

900

1050

PT

0.4

0

1200

150

RI

Ct/Co

Ct/Co

0.6

300

450

SC

contact time (mins

(c)

NU

1.0

750

900

1050

1200

5 ml/min 10 ml/min 15 ml/min

MA

0.8

0.6

0.4

D

Ct/C0

600

Time (mins)

PT E

0.2

0.0

0

150

300

450

600

750

900

1050

1200

Time (mins)

CE

-150

AC

Figure 13- Breakthrough curve at a) different bed heights b) initial Cr(VI) concentrations c) feed flow rate Table 5- Column parameters Z

(cm)

Flow rate

C0

qtotal

(mg/L) (mg)

qexp

ttotal

Mtotal

Cr(VI)

Veff

(mg/g)

(min)

(mg)

removal (%)

(ml)

(ml/min) 5

5

50

80.615 12.40

480

120

67.179

2400

7

5

50

163.03 18.62

840

210

72.45

4200

9

5

50

233.15 21.19

1170

292.5

79.71

5850

27

ACCEPTED MANUSCRIPT 9

5

150

245.45 22.04

570

427.5

56.71

2850

9

5

250

278.77 25.34

420

525

53.12

2100

9

10

50

236.25 21.47

690

345

68.47

6900

9

15

50

224.03 20.36

540

405

55.30

8100

63.84

49.37

1200

5

53.2

31.519 2.865

240

RI

9

PT

Tannery effluent containing Cr(VI)0 = 53.2 mg/L Cr(VI)

SC

4. CONCLUSION

In the study, peels of Artocarpus heterophyllus were used as biosorbent and analyzed for

NU

Cr(VI) removal. The biosorbent was characterized using FTIR, CHNS, MIP, XPS, ESR and AAS in order to determine the basic mechanism of the process. Adsorption-coupled reduction was found to be the mechanism behind Cr removal. Batch biosorption influencing parameters

MA

were optimized as pH 2.0, AH biosorbent dose of 0.3 g, contact time of 90 min, temperature of 35°C, initial concentration of 50mg/L, agitation speed of 100 rpm. The residual Cr(VI) concentration after contacting with 50 mg/L Cr(VI) solution was found to be under

D

permissible limit of 0.036 mg/L with total Cr and Cr(III) concentrations of 43.77 mg/L and

PT E

43.73 mg/L respectively. Also the biosorbent was found to remove considerable amount of Cr(VI) at a wide range of pH from 2.0 to 7.0. Equilibrium data well correlated with Langmuir Isotherm model and pseudo-second-order kinetic model. Effect of other co-existing ions have

CE

been analyzed and found that anionic pollutants tend to decrease the removal percentage of Cr(VI). Column studies in continuous mode were performed and the significant column

AC

parameters were optimized for maximum removal of 79.71% at bed height 9 cm, feed flow rate 5 ml/min, initial Cr(VI) concentration of 50mg/L. Tannery effluent containing 53.2 mg/L of initial Cr(VI) concentration was treated in the AH biosorbent loaded column where 49.37% removal was obtained. Desorption and regeneration studies produced fair results upto 3 runs. Hence Artocarpus heterophyllus biosorbent can be a potential biosorbent for detoxifying simulated and real industrial effluents containing hexavalent chromium.

5. ACKNOWLEDGEMENT 28

ACCEPTED MANUSCRIPT The authors would like to thank Kerala State Council for Science, Technology and Environment, India (Grant No. ETP/02/2014/KSCSTE), for their financial support to perform the research. The authors would like to thank the anonymous reviewers and Editors for their suggestions and comments which improved the quality of the manuscript. 6. REFERENCES

AC

CE

PT E

D

MA

NU

SC

RI

PT

[1]. Jacques Guertin, James A. Jacobs, Cynthia P. Avakian, Chromium(VI) Handbook, CRC Press, USA, 2004 [2]. Dinesh Mohan, Charles U Pittman Jr, Review: activated carbons and low cost adsorbents for remediation of tri and hexavalent chromium from water, J. Hazard. Mater. 137 (2006) 762–811. doi:10.1016/j.jhazmat.2006.06.060 [3]. D.E. Kimbrough, Y. Cohen, A.M. Winer, L. Creelman, C.A. Mabuni, Critical assessment of chromium in the environment, Crit. Rev. Environ.Sci. Technol. 29 (1) (1999) 1–46. [4]. Status of trace and toxic metals in Indian rivers, Central Water Commission, Government of India report 2014. [5]. EPA Environmental Pollution Control Alternatives EPA/625/5-90/25, EPA/625/489/023, Environmental Protection Agency Cincinaati, OH, USA, 1990. [6]. T.A. Kurniawan, G.Y.S. Chan, W.H. Lo, S. Babel, Physico-chemical techniques for wastewater laden with heavy metals. Chem. Eng. J. 118 (2006), 83-98. [7]. B. Volesky, A. Mucci, A review of the biochemistry of heavy metal biosorption by brown algae. Water Res. 37 (2003) 4311-4330. [8]. H. Gao, Y. Liu, G. Zeng, W. Xu, T. Li, W. Xia, Characterization of Cr(VI) removal from aqueous solutions by a surplus agricultural waste—rice straw. J Hazard Mater 31(2008) 446–452. [9]. M.K. Uma , Nagpal, V. Ashok, Bankar & J Namdeo, Pawar & P Balu, Kapadnis & S Smita, Zinjarde, Equilibrium and Kinetic Studies on Biosorption of Heavy Metals by Leaf Powder of Paper Mulberry (Broussonetia papyrifera),Water Air Soil Pollut (2011) 215 (2008):177–188,DOI 10.1007/s11270-010-0468-z. [10]. N. Feng, X. Guo, S. Liang, Y. Zhu, J. Liu, Biosorption of heavy metals from aqueous solutions by chemically modified orange peel. J Hazard Mater 185 (2011) 49–54. [11]. C. Namasivayam, M.V. Sureshkumar, Removal of chromium(VI) from water and wastewater using surfactant modified coconut coir pith as a biosorbent, Bioresource Technol, 99 (2008) 2218–2225. [12]. S. Rangabhashiyam, N. Selvaraju ,Evaluation of the biosorption potential of a novel Caryota urens inflorescence waste biosorbent for the removal of hexavalent chromium from aqueous solutions, Journal of the Taiwan Institute of Chemical Engineers 47 (2015) 59–70. 29

ACCEPTED MANUSCRIPT

AC

CE

PT E

D

MA

NU

SC

RI

PT

[13]. C.R. Elevitch and H.I. Manner, Artocarpus heterophyllus (jackfruit), ver. 1. 1v. In Elevitch C R (ed.) Species Profiles for Pacific Island Agroforestry, Permanent Agriculture Resources, Hawaii. Available from: http://www.agroforestry.net/tti/A.heterophyllusjackfruit.pdf [Accessed 18 June 2010] [14]. A.S. Saxena, P.S. Bawa, Raju, Postharvest Biology and Technology of Tropical and Subtropical Fruits Cocona to Mango, A volume in Woodhead Publishing Series in Food Science, Technology and Nutrition, Pages 275–298, 299e, chapter 12 – Jackfruit (Artocarpus heterophyllus Lam.), 2011. [15]. Anubhuti Sharma & Priti Gupta & A. K. Verma, Preliminary nutritional and biological potential of Artocarpus heterophyllus L. shell powder, J Food Sci Technol, 52 (2015) 1339–1349,.DOI 10.1007/s13197-013-1130-8. [16]. Lu Zhang , Zong-cai Tu, Xing Xie, Hui Wang, Hao Wang , Zhen-xing Wang , Xiaomei Sha , Yu Lu, Jackfruit (Artocarpus heterophyllus Lam.) peel: A better source of antioxidants and a-glucosidase inhibitors than pulp, flake and seed, and phytochemical profile by HPLC-QTOF-MS/MS, Food Chemistry 234 (2017) 303– 313. [17]. Dharman Govindaraj, Mariappan Rajan, Abdullah A.Alarfaj, Murugan A.Munusamy, From Waste to High- Value Product: Jackfruit Peel Derived Pectin/Apatite Bionanocomposites for Bone Healing Applications, International Journal of Biological Macromolecules 106 (2018) 293–301. [18]. B.S. Inbaraj, N. Sulochana, Carbonised jackfruit peel as an adsorbent for the removal of Cd(II) from aqueous solution, Bioresour. Technol. 94 (2004) 49–52. [19]. M. Jayarajan, R. Arunachalam, G. Annadurai, Agricultural wastes of jackfruit peel nano-porous adsorbent for removal of Rhodamine dye, Asian J. Appl. Sci.4 (2011) 263–270. [20]. B.H. Hameed, Removal of cationic dye from aqueous solution using jackfruit peel as non-conventional low-cost adsorbent, J. Hazard. Mater. 162 (2009) 344–350. [21]. CPCB, Annual Report, Central Pollution Control Board, Ministry of Environment & Forests, Government of India, 2009. [22]. Changqing Zhao, Qinhuan Yang, Wuyong Chen, and Bo Teng, Removal of hexavalent chromium in tannery wastewater by Bacillus cereus, Can. J. Microbiol. Vol. 58 (2012) 23-28. [23]. Ainsworth, E.A.; Gillespie, K.M.: Estimation of total phenolic content and other oxidation substrates in plant tissues using Folin- Ciocalteu reagent. Nat. Protoc. 2 (2007) , 875–877. [24]. C. Mystrioti, D. Sparis, N. Papassiopi, A. Xenidis, D. Dermatas, M. Chrysochoou,Hexavalent chromium reduction with polyphenolcoated nano zero valent iron.CRETE. 3rd International Conference on industrial and hazardous wastemanagement, pp. 1–8. 2012. [25]. Saranya Kuppusamy, Palanisami Thavamani, Mallavarapu Megharaj, Ravi Naidu, Bioremediation potential of natural polyphenol rich green wastes: A review of current research and recommendations for future directions, Environmental Technology & Innovation, 4 (2015. )17–28, doi:10.1016/j.eti.2015.04.001. 30

ACCEPTED MANUSCRIPT

AC

CE

PT E

D

MA

NU

SC

RI

PT

[26]. Vaishakh Nair, Ajitesh Panigrahy, R. Vinu, Development of novel chitosan–lignin composites for adsorption of dyes and metal ions from wastewater, Chemical Engineering Journal 254 (2014) 491–502. [27]. Radia Labied, Oumessaad Benturki, AdhYa Eddine Hamitouche, Adsorption of hexavalent chromium by activated carbon obtained from a waste lignocellulosic material (Ziziphus jujuba cores): Kinetic, equilibrium, and thermodynamic study, Adsorption Science & Technology 0(0) 1–34 . DOI: 10.1177/0263617417750739. [28]. O. Martins, Omorogie, O. Jonathan, I. Babalola, Emmanuel, Unuabonah,Weiguo Song , Jian Ru Gong, Efficient chromium abstraction from aqueous solution using a low-cost biosorbent: Nauclea diderrichii seed biosorbent waste, Journal of Saudi Chemical Society 20 (2016) 49–57, [29]. S.Chen, J. Zhang, H. Zhang, X.Wang, removal of hexavalent chromium from contaminated wter by Chinese herb-extraction residues, Water Air Soil Pollution, 4 (2017) 1-13 . https://doi.org/10.1007/s11270-017-3329-1. [30]. P.Miretzky A. Fernandez Cirelli, Cr(VI) and Cr(III) removal from aqueous solution by raw and modified lignocellulosic materials: A review, J. Hazard. Mater. 180 (2010) 1-19. [31]. Shahid Ul-Islam ,Advanced Materials for Wastewater Treatment, ISBN: 978-1-11940776-8, Oct 2017 [32]. Parinda Suksabye, Akira Nakajima, Paitip Thiravetyan, Yoshinari Baba,Woranan Nakbanpote,Mechanism of Cr(VI) adsorption by coir pith studied by ESR and adsorption kinetic, J. Hazard. Mater. 161 (2009) 1103–1108. [33]. L. Xu, M. Luo, W. Li, X. Wei, K. Xie, L. Liu, C. Jiang, H. Liu, Reduction of hexavalent chromium by Pannonibacter phragmitetus LSSE-09 stimulated with external electron donors under alkaline conditions. J. Hazard. Mater. 185 (2011) 1169-1176,. [34]. Carlos Escudero, Nuria Fiol, Isabel Villaescusa, Jean-Claude Bollinger, Effect of chromium speciation on its sorption mechanism onto grape stalks entrapped into alginate beads, Arabian Journal of Chemistry 10 (2017) S1293–S1302, [35]. Amtul Nashim and Kulamani Parid, n-La2Ti2O7/p-LaCrO3: a novel heterojunction based composite photocatalyst with enhanced photoactivity towards hydrogen production,: J. Mater. Chem. A,43 (2014) 18405-18412. [36]. Donghee Park, Yeoung-Sang Yun, Ji Hye Jo, JongMoon Park, Mechanism of hexavalent chromium removal by dead fungal biosorbent of Aspergillus niger,Water Research 39 (2005) 533–540. [37]. H. Niu, B Volesky, Characteristics of anionic metal species biosorption with waste crab shells. Hydrometallurgy 71 (2003) 209–215. [38]. Donghee Park, Yeoung-Sang Yun, JongMoon Park, Reduction of Hexavalent Chromium with the Brown Seaweed Ecklonia Biosorbent, Environ. Sci. Technol., 38 (2004) 4860-4864. [39]. Erick Aranda-García & Eliseo Cristiani-Urbina, Effect of pH on hexavalent and total chromium removal from aqueous solutions by avocado shell using batch and continuous systems, Environ Sci Pollut Res, DOI 10.1007/s11356-017-0248-z 31

ACCEPTED MANUSCRIPT

AC

CE

PT E

D

MA

NU

SC

RI

PT

[40]. S. Rangabhashiyam, N. Selvaraju, Adsorptive remediation of hexavalent chromium from synthetic wastewater by a natural and ZnCl2 activated Sterculia guttata shell, Journal of Molecular Liquids 207 (2015) 39–49. [41]. I. Langmuir, The adsorption of gases on plane surfaces of glass, mica and platinum, J Am. Chem. Soc. 40 (1918) 1361–1368. [42]. H. Freundlich : Adsorption in solution, Phys Chem Soc. 40 (1906) 1361–1368. [43]. M.M. Dubinin: Modern state of the theory of volume filling of micropore adsorbents during adsorption of gases and steams on carbon adsorbents. Russ J Phys Chem.39 (1965) 1305–17, [44]. S. Lagergren, About the theory of so-called adsorption of soluble substances, K.Svenska Vetenskapsakad. Handl. 24 (1898) 1–39. [45]. S Chen, Q Yue, B Gao, et al. Removal of Cr(VI) from aqueous solution using modified corn stalks: characteristic, equilibrium, kinetic and thermodynamic study. Chem Eng J 168 (2011) 909–917. [46]. G. Blanchard, M. Maunaye, G. Martin, Removal of heavy metals from waters by means of natural zeolites, Water Res. 18 (1984) 1501–1507. [47]. Y.S. Ho, G. McKay, Pseudo-second order model for sorption processes, ProcessBiochem. 34 (1999) 451–46. [48]. W.J. Weber, J.C. Morris, Advances inwater pollution research: removal of biologically resistant pollutants from waste waters by adsorption, Proceedings of International Conference on Water Pollution Symposium, 2, Pergamon Press, Oxford 1962, pp. 231–266. [49]. Sami Guiza, Biosorption of heavy metal from aqueous solution using cellulosic waste orange peel, Ecological Engineering 99 (2017) 134–140. [50]. Marta López-García, Pablo Lodeiro, Roberto Herrero, José L. Barriada, Carlos ReyCastro,Calin David, Manuel E. Sastre de Vicente, Experimental evidences for a new model in the description of the adsorption-coupled reduction of Cr(VI) by protonated banana skin, Bioresource Technology 139 (2013) 181–189. [51]. Ahmad B. Albadarin, Yoann Glocheux, M.N.M. Ahmad, Gavin M. Walker, Chirangano MangwandiNovel comparison of kinetic models for the adsorptioncoupled reduction of Cr(VI) using untreated date pit biomaterial, Ecological Engineering 70 (2014) 200–205. [52]. Atefeh Abdolali, Huu Hao Ngo, Wenshan Guo, John L. Zhou, Zhang, Shuang Liang,Soon W. Chang, Dinh Duc Nguyen, Yi Liu, Application of a breakthrough biosorbent for removing heavy metals from synthetic and real wastewaters in a labscale continuous fixed-bed column, Bioresource Technology 229 (2017) 78–87. [53]. Z. Aksu, S.S. Çagatay, F. Gönen, Continuous fixed bed biosorption of reactive dyes by dried Rhizopusarrhizus: determination of column capacity. J. Hazard. Mater. 143 (2007) 362–371. [54]. S. Rangabhashiyam, E. Suganya & N. Selvaraju, Packed bed column investigation on hexavalent chromium adsorption using activated carbon prepared from Swietenia

32

ACCEPTED MANUSCRIPT Mahogani fruit shells, Desalination and Water Treatment (2015) 1–8. DOI:

AC

CE

PT E

D

MA

NU

SC

RI

PT

10.1080/19443994.2015.1055519.

33

ACCEPTED MANUSCRIPT

AC

CE

PT E

D

MA

NU

SC

RI

PT

Graphical abstract

34

ACCEPTED MANUSCRIPT Highlights:

Artocarpus heterophyllus peel biomass was used to detoxify Cr(VI) from aqueous solutions at a wide range of pH.



The mechanism of adsorption was determined by ESR, FTIR, XPS and AAS and found to be adsorption -coupled reduction. Isotherm, kinetic and thermodynamic analysis were performed



Effect of other co-existing ions, desorption- regeneration studies were conducted in

PT



CE

PT E

D

MA

NU

SC

Continuous column studies were done using simulated and real effluents.

AC



RI

batch mode

35