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Journal ArticleDOI

A breakthrough biosorbent in removing heavy metals: Equilibrium, kinetic, thermodynamic and mechanism analyses in a lab-scale study

15 Jan 2016-Science of The Total Environment (Elsevier)-Vol. 542, pp 603-611

TL;DR: This novel MMBB can effectively be utilized as an adsorbent to remove heavy metal ions from aqueous solutions and calculated thermodynamic parameters indicated feasible, spontaneous and exothermic biosorption process.

AbstractA breakthrough biosorbent namely multi-metal binding biosorbent (MMBB) made from a combination of tea wastes, maple leaves and mandarin peels, was prepared to evaluate their biosorptive potential for removal of Cd(II), Cu(II), Pb(II) and Zn(II) from multi-metal aqueous solutions. FTIR and SEM were conducted, before and after biosorption, to explore the intensity and position of the available functional groups and changes in adsorbent surface morphology. Carboxylic, hydroxyl and amine groups were found to be the principal functional groups for the sorption of metals. MMBB exhibited best performance at pH 5.5 with maximum sorption capacities of 31.73, 41.06, 76.25 and 26.63 mg/g for Cd(II), Cu(II), Pb(II) and Zn(II), respectively. Pseudo-first and pseudo-second-order models represented the kinetic experimental data in different initial metal concentrations very well. Among two-parameter adsorption isotherm models, the Langmuir equation gave a better fit of the equilibrium data. For Cu(II) and Zn(II), the Khan isotherm describes better biosorption conditions while for Cd(II) and Pb(II), the Sips model was found to provide the best correlation of the biosorption equilibrium data. The calculated thermodynamic parameters indicated feasible, spontaneous and exothermic biosorption process. Overall, this novel MMBB can effectively be utilized as an adsorbent to remove heavy metal ions from aqueous solutions.

Topics: Biosorption (59%), Adsorption (50%), Sorption (50%)

Summary (4 min read)

1. Introduction

  • Heavy metals are discharged to aquatic environments from various industries such as paper, textile, plastic, ceramic and cement manufacturing, mining and electronics plating.
  • The significant difference between previous studies and current work is gaining the advantages and also using the biosorptive potentials of various biosorbents in a combination.
  • In addition, thermodynamic parameters were determined for the sorption of all metal ions to explain the process feasibility.

2.1. Preparation of adsorbents and heavy metal-containing effluent

  • All the reagents used for analysis were of analytical reagent grade from Scharlau and Chem-Supply Pty Ltd. .
  • The metal concentration was analyzed by Microwave Plasma-Atomic Emission Spectrometer, MP-AES, (Agilent Technologies, USA).
  • The biosorbents were applied in metal removal process for selecting the best ones in term of biosorption capacity sawdust (SD), sugarcane (SC), corncob (CC), tea waste (TW), apple peel (AP), grape stalk (GS), palm tree skin (PS), eucalyptus leaves (EU), mandarin peel (MP), maple leaves (ML) and garden grass (GG).
  • After using or removing their useable parts, they were washed by tap and distilled water to remove any dirt, color or impurity and then dried in the oven (Labec Laboratory Equipment Pty Ltd., Australia) at 105 °C overnight.

2.2. Biosorption studies in batch system

  • The tests were performed with synthetic multi-metal stock solution with concentration of 3000 mg/L for each metal, prepared by dilution in Milli-Q water.
  • Solution pH was adjusted with 1 M HCl and NaOH solutions.
  • After equilibration, to separate the biomasses from solutions, the solutions were filtered by Whatman™ GF/C-47 mm/circle (GE Healthcare, Buckinghamshire, UK) filter paper and final concentration of metal was measured using MPAES.
  • All the experiments were carried out in duplicates.
  • The statistical analysis was performed by analysis of variance .

2.3. Characterization of adsorbents by FTIR and SEM

  • To determine the functional groups involved in biosorption of Cd(II), Cu(II), Pb(II) and Zn(II) onto MMBB, a comparison between the Fourier Transform Infrared Spectroscopy (FTIR) before and after meal loading was done using Shimadzu FTIR 8400S (Kyoto, Japan).
  • Metal-loaded biosorbent were filtered and dried in the oven.
  • The small amount of samples was placed in the FTIR chamber on the KBr plates for analyzing the functional groups involving in biosorbent process by comparing with unused multi-metal biosorbent.

3.1. Selection of adsorbents

  • Eleven different natural biosorbents, namely sawdust, sugarcane, corncob, tea waste, apple peel, grape stalk, palm tree skin, eucalyptus leaves, mandarin peel, maple leaves and garden grass, individually were compared in regard to the biosorption capacities for Cd(II), Cu(II), Pb(II) and Zn(II) uptake in Fig.
  • The results indicate TW, ML and MP showed satisfying biosorptive capacity for all heavy metal ions (cadmiu , copper, lead and zinc).
  • TW:ML:MP combination was selected to apply for further batch experiments.
  • Apparently, there are no significant differences between the equal proportions of 1:1:1 and the others, especially for lead and copper.
  • This wadespite the fact that ANOVA results for each metal indicated the rejection of the null hypothesis due to P value was less than 0.05.

3.2. Characterization of adsorbents by FTIR

  • The FTIR spectrum of MMBB exhibited a large number of absorption peaks, indicating the complexity in nature of this adsorbent.
  • The shift of some functional groups bands and their intensity significantly changed after heavy metal biosorption (Table 1).
  • These shifts may be attributed to carboxylic (C O) and hydroxylic (O–H) groups on the MMBB's surface.

3.3. SEM analysis

  • From Table 1, SEM depicts the morphology changes of unloaded and loaded biosorbent.
  • After biosorption of heavy metal ions, the surface became smoother with less porosity with probable metal entrapping and adsorbing on biosorbent.
  • The SEM/EDS was reported in previous study (Abdolali et al., 2015).

3.4.1. Influence of pH

  • The initial pH values above 5.5 are not preferable du to the observed presence of metal hydroxide precipitation, so as the experiments were not conducted beyond pH 5.5.
  • The results indicated that the optimum pH value was 5.5 for all metals.

3.4.2. Influence of contact time

  • It is evident from Fig. 3(b) that the rate of metal uptake was very fast within first 30 min as a result of the exuberant number of available active sit s on adsorbent surfaces and then decreased until equilibrium was reached.
  • Biosorption capacity leveled off at equilibrium state within 180 min.
  • Therefore, the biosorption time was set to 180 min in each experiment.

3.4.3. Influence of adsorbent dose

  • Biosorption capacity was also affected by biosorptin dose and amount of available active sites and this effect is shown in Fig. 3(c).
  • The experimental results indicate that the percentage removal of all metal ions on MMBB represents an equilibrium pattern for biosorbent amounts of 5 g/L and more.
  • Furthermore, the removal efficien y decreased by increasing initial metal ion solution with similar trends.

3.4.4. Effect of biosorbent particle size

  • The effect of particle size of biosorbent was conducted for 5 g/L adsorbent dose and an initial concentration of 50 mg/L.
  • It was found that biosorpti n capacity did not significantly change by varying particle sizes.
  • The reason was that these particle size distributions were very small (less than 300 µm).
  • The smaller biosorbent size exhibits better performance in regard with metal removal due to a higher surface area for metal adsorption; however the mechanical stability reduces particularly in column (Liu et al., 2012).

3.5. Adsorption kinetics

  • A kinetic investigation was carried out to quantify the adsorption rate controlling steps in Cd(II), Cu(II), Pb(II) and Zn(II) uptake on MMBB.
  • The pseudo-first-order kinetic model known as the Lagergren equation and takes the form as: (2) where, qt and qe are the metal adsorbed at time t and equilibrium, respectively, and K1 (min− 1) is the first-order reaction rate equilibrium constant.
  • The experimental data and obtained parameters of these models were measured by MATLAB® and summarized in Table 2.
  • As shown in Table 2, with comparison between adsorption rate constants, the estimated q and the coefficients of correlation associated with the Lagergren pseudo-first-order and the pseudo-secnd-order kinetic models at room temperature for MMBB, it is obvious that both kinetic models well described all metal biosorption.
  • The coefficients of correlation (R2) of pseudo-second-order kinetic model were slightly larger than those of pseudo-first-order kinetic model for Cu in all initial concentrations.

3.6. Adsorption isotherm

  • The correlation between the adsorbed and the aqueous metal concentrations at equilibrium has been described by the Langmuir, Freundlich, Dubinin–Radushkevich, Sips, Redlich– Peterson and Khan adsorption isotherm models.
  • Furthermore, residual root mean square error (RMSE), error sum of square (SSE) and correlation of determination (R2) were used to measure the exactness of fitting.
  • Among three-parameter isotherm models, for Cu(II) and Zn(II), Khan isotherm describes biosorption conditions moderately better than Sips and Redlich–Peterson models, while for Cd(II) and Pb(II), the Sips model was found to provide the best correlation of the biosorption equilibrium data.
  • Various kinds of agro-industrial wastes and by-products were studied for heavy metal removal.
  • A comparison between maximum adsorptive capa ities of MMBB and some other adsorbents is shown in Table 4.

3.7. Biosorption mechanism

  • The main mechanisms known for metal sorption on ligocellulosic biosorbents are chelating, ion exchanging and making complexion with functional groups and releasing [H3O] + into aqueous solution.
  • Ionic exchange is known as a mechanism which involves electrostatic interaction between positive metallic cations and the negatively charged groups in the cell walls.
  • On the other hand, many characterization studies confirmed that ion exchange mechanism was included in heavy metal biosorption process rather than complexation with functional groups on the biosorbent surface and also showed the role of sodium, potassium, calcium and magnesium present in the adsorbent in ion exchange mechanism (Ding et al., 2012 and Akar et al., 2012).
  • In addition, the mean free energy of adsorption calcul ted from Dubinin– Radushkevich isotherm can evaluate sorption properties and main mechanism.
  • With respect to kinetic modeling, it also established that metal uptake by the micro-organisms takes place in two consecutive stages: a passive and quick uptake that follows by an active and very slow uptake.

3.8. Adsorption thermodynamics

  • The experimental results indicated dependency of adsorption on the temperature and are listed in Table 5.
  • The Gibbs free energy indicates the degree of spontaneity of sorption process, and the higher negative value reflects a more energetically favorable sorption.
  • ∆H° and ∆S° were obtained from the slop and intercept of the Van't Hoff plots (Fig. 5).
  • I addition, the low value of ∆S° may imply that no remarkable change in entropy occurred during the sorption of Cd, Cu, Pb and Zn ions on MMBB.

4. Conclusions

  • The present work explores a new economical and selective lignocellulosic biosorbent containing tea waste, maple leaves and mandarin peels as an alternative to costly adsorbents for the removal of Cd(II), Cu(II), Pb(II) and Zn(II) ions.
  • The low cost, rapid attainment of phase equilibrium (within 3 h) and high sorption capacity values may be cited among the main advantages.
  • Adsorption kinetics follows a pseudo-second-order kinetic model and negative values of ∆H° and ∆G° prove the exothermic and spontaneous nature of the biosorption phenomenon.
  • Hence, this novel MMBB can be a promising adsorbent to eliminate heavy metal ions from aqueous solutions.

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A breakthrough biosorbent in removing heavy metals: Equilibrium, kinetic,
thermodynamic and mechanism analyses in a lab-scale study
Atefeh Abdolali
a
, Huu Hao Ngo
a, *,
, Wenshan Guo
a
, Shaoyong Lu
b
, Shiao-Shing Chen
c
, Nguyen Cong
Nguyen
c
, Xinbo Zhang
d
, Jie Wang
e
, Yun Wu
e
a
Centre for Technology inWater and Wastewater, School of Civil and Environmental Engineering, University
of Technology Sydney, Broadway, NSW 2007, Australia
b
Chinese Research Academy of Environmental Science, Beijing 100012, China
c
Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1,
Sec. 3, Chung-Hsiao E. Rd, Taipei 106, Taiwan
d
Department of Environmental and Municipal Engineering, Tianjin Key Laboratory of Aquatic Science and
Technology, Tianjin Chengjian University, Jinjing Road 26, Tianjin 300384, China
e
School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China
*
Corresponding author at: School of Civil and Environmental Engineering, University of Technology, Sydney
(UTS), PO Box 123, Broadway, NSW2007, Australia.
E-mail address: h.ngo@uts.edu.au (H.H. Ngo).
Highlights
• A novel multi-metal binding biosorbent (MMBB) was studied.
• The biosorption of Cd
2 +
, Cu
2 +
, Pb
2 +
and Zn
2 +
on MMBB was evaluated.
• Hydroxyl, carbonyl and amine groups are involved in metal binding of MMBB.
• Equilibrium data were presented and the best fitting models were identified.
• The obtained results recommend this MMBB as potentially low-cost biosorbent.
Abstract
A breakthrough biosorbent namely multi-metal binding biosorbent (MMBB) made from a
combination of tea wastes, maple leaves and mandarin peels, was prepared to evaluate their
biosorptive potential for removal of Cd(II), Cu(II), Pb(II) and Zn(II) from multi-metal
aqueous solutions. FTIR and SEM were conducted, before and after biosorption, to explore
the intensity and position of the available functional groups and changes in adsorbent surface
morphology. Carboxylic, hydroxyl and amine groups were found to be the principal
functional groups for the sorption of metals. MMBB exhibited best performance at pH 5.5
with maximum sorption capacities of 31.73, 41.06, 76.25 and 26.63 mg/g for Cd(II), Cu(II),
Pb(II) and Zn(II), respectively. Pseudo-first and pseudo-second-order models represented the
kinetic experimental data in different initial metal concentrations very well. Among two-

parameter adsorption isotherm models, the Langmuir equation gave a better fit of the
equilibrium data. For Cu(II) and Zn(II), the Khan isotherm describes better biosorption
conditions while for Cd(II) and Pb(II), the Sips model was found to provide the best
correlation of the biosorption equilibrium data. The calculated thermodynamic parameters
indicated feasible, spontaneous and exothermic biosorption process. Overall, this novel
MMBB can effectively be utilized as an adsorbent to remove heavy metal ions from aqueous
solutions.
Keywords: Heavy metal; Biosorption; Isotherm; Kinetic; Thermodynamics; Lignocellulosic
waste
1. Introduction
Heavy metals are discharged to aquatic environments from various industries such as paper,
textile, plastic, ceramic and cement manufacturing, mining and electronics plating. These
poorly biodegradable pollutants are harmful for all plants, animals and human life due to high
environmental mobility in soil and water and also a strong tendency for bioaccumulation in
the living tissues along the food chain (Vargas-García et al., 2012, Akar et al.,
2012 and Bulut and Tez, 2007). In order to remediate polluted water and wastewater streams,
a wide range of treatment technologies are employed in industry (e.g. chemical precipitation,
extraction, ion exchange, filtration, reverse osmosis, membrane bioreactor and
electrochemical techniques) (Santos et al., 2015,Abdolali et al., 2014a, Montazer-Rahmati et
al., 2011 and Fu and Wang, 2011). Nonetheless, these methods are not effective enough in
low concentrations and might be very expensive as a result of high chemical reagent and
energy requirements, as well as the disposal problem of toxic secondary sludge (Bulut and
Tez, 2007 and Sud et al., 2008).
Therefore, introducing a properly eco-friendly and cost effective technology for wastewater
treatment has provoked many researchers into this matter in recent decades (Abdolali et al.,
2014b, Tang et al., 2013, Fu et al., 2013, Kumar et al., 2012, Hossain et al., 2012, Witek-
Krowiak et al., 2011, Gadd, 2009, Volesky, 2007 and Šćiban et al., 2007) to use cheap agro-
industrial wastes and by-products as biosorbents. Some of these materials include sawdust
and wood waste (Wahab et al., 2010, Bulut and Tez, 2007 and Šćiban et al., 2007), sugarcane
bagasse (Homagai et al., 2010, Martín-Lara et al., 2010 and Khoramzadeh et al., 2013),fruit
rind, pulp and seeds (Martín-Lara et al., 2010; Liu et al., 2012, Pehlivan et al.,
2012 and Schiewer and Patil, 2008), wheat or barley straw, rice husk, hull and straw (Asadi et
al., 2008), and olive pomace and stone (Blázquez et al., 2010, Blázquez et al., 2009 and Fiol
et al., 2006).
All of the previous attempts have been made to study the agro-industrial wastes and by-
products individually. The novelty of the present work is using combination of selected agro-
industrial multi-metal binding biosorbents for removal of cadmium, copper, lead and zinc
ions from synthetic aqueous multi-metal solutions. The significant difference between
previous studies and current work is gaining the advantages and also using the biosorptive

potentials of various biosorbents in a combination. The purpose of blending different
lignocellulosic materials is having all potentials of biosorbents for heavy metal uptake
(Abdolali et al., 2014a, Martín-Lara et al., 2010 and Martín-Lara et al., 2010). Also these
wastes were selected because of the good results reported in other literatures for heavy metal
removal (Abdolali et al., 2014a, Feng et al., 2011 and Amarasinghe and Williams, 2007).
Additionally, they are properly available in Australia and also all over the world.
Firstly, the adsorption studies were carried out to select the best combination of different
biosorbents, as mentioned hereinabove. Then the experiments were continued to compare the
effect of different contact times, pH, initial metal concentration, temperature, and biosorbent
dose and particle size on biosorptive potential of selected combination. The results were
mainly evaluated by two popular kinetic models of pseudo-first-order and pseudo-second-
order correlations and three two-parameter and three three-parameter adsorption models
(Langmuir, Freundlich, Dubinin–Radushkevich, Khan, Sips and Redlich–Peterson). In
addition, thermodynamic parameters were determined for the sorption of all metal ions to
explain the process feasibility.
2. Material and methods
2.1. Preparation of adsorbents and heavy metal-containing effluent
The stock solutions containing Cd, Cu, Pb and Zn were prepared by dissolving cadmium,
copper, lead and zinc nitrate salt, Cd(NO
3
)
2
·4H
2
O, Cu
3
(NO)
2
·3H
2
O, Pb(NO
3
)
2
and
Zn(NO
3
)
2
·6H
2
O in Milli-Q water. All the reagents used for analysis were of analytical
reagent grade from Scharlau (Spain) and Chem-Supply Pty Ltd. (Australia). The metal
concentration was analyzed by Microwave Plasma-Atomic Emission Spectrometer, MP-AES,
(Agilent Technologies, USA).
The biosorbents were applied in metal removal process for selecting the best ones in term of
biosorption capacity sawdust (SD), sugarcane (SC), corncob (CC), tea waste (TW), apple
peel (AP), grape stalk (GS), palm tree skin (PS), eucalyptus leaves (EU), mandarin peel
(MP), maple leaves (ML) and garden grass (GG). All biosorbents were collected from
Sydney area or local markets. After using or removing their useable parts, they were washed
by tap and distilled water to remove any dirt, color or impurity and then dried in the oven
(Labec Laboratory Equipment Pty Ltd., Australia) at 105 °C overnight. Having ground and
sieved (RETSCH AS-200, Germany) to different sizes (< 75 µm, 75–150 µm, 150–300 µm
and > 300 µm), the natural biosorbents were kept in a desiccator prior to use in future
experiments.
2.2. Biosorption studies in batch system
The tests were performed with synthetic multi-metal stock solution with concentration of
3000 mg/L for each metal, prepared by dilution in Milli-Q water. Solution pH was adjusted
with 1 M HCl and NaOH solutions.

A known weight of adsorbent (5 g/L) was added to a series of 200 mL Erlenmeyer flasks
containing 50 mL of metal solution on a shaker (Ratek, Australia) at room temperature and
the flasks were shaken at 150 rpm for 3 h. After equilibration, to separate the biomasses from
solutions, the solutions were filtered by Whatman™ GF/C-47 mm/circle (GE Healthcare,
Buckinghamshire, UK) filter paper and final concentration of metal was measured using MP-
AES. All the experiments were carried out in duplicates. The statistical analysis was
performed by analysis of variance (ANOVA).
The amount of heavy metal ion adsorbed, q (mg/g) was calculated from the following Eq.(1):
(1)
where, C
i
and C
f
(mg/L) are the initial and equilibrium metal concentrations in the solution,
respectively. v (L) the solution volume and m (g) is the mass of biosorbent.
2.3. Characterization of adsorbents by FTIR and SEM
To determine the functional groups involved in biosorption of Cd(II), Cu(II), Pb(II) and
Zn(II) onto MMBB, a comparison between the Fourier Transform Infrared Spectroscopy
(FTIR) before and after meal loading was done using Shimadzu FTIR 8400S (Kyoto, Japan).
Metal-loaded biosorbent were filtered and dried in the oven. The small amount of samples
was placed in the FTIR chamber on the KBr plates for analyzing the functional groups
involving in biosorbent process by comparing with unused multi-metal biosorbent.
Scanning Electron Microscopy (SEM) of the free and loaded MMBB was performed on
ZEISS EVO | LS15 (Germany) at an accelerating voltage of 10 kV and with the working
distance of 10 µm for MMBB to observe the porous properties of the biosorbents.
2.4. Influence of pH
In order to study the effect of pH on heavy metal adsorption, the initial pH of the solutions
varied from 2 to 5.5, by adding appropriate amounts of NaOH or HCl solutions. The batch
procedure at each pH was followed as above described using an initial concentration of
50 mg/L.
2.5. Influence of contact time
The contact time varied from 15 min to 5 h for the biosorption of Cd(II), Cu(II), Pb(II) and
Zn(II) adsorption on MMBB at different initial concentrations of 50 mg/L and room
temperature with similar procedures explained above.
2.6. Influence of adsorbent dose

The dependence of Cd(II), Cu(II), Pb(II) and Zn(II) adsorption on biosorbent dose was
studied at room temperature and optimum pH by varying biosorbent doses (0.2, 1, 2, 5, 10
and 20 g/L).
2.7. Influence of particle size
In order to study the effect of particle size on adsorption, batch experiments as above
described were carried out using the biosorbent with different particle sizes of < 75 µm, 75–
150 µm, 150–300 µm and > 300 µm and an initial metal concentration of 50 mg/L, at room
temperature.
2.8. Influence of temperature
The effect of temperature on the Cd, Cu, Pb, and Zn adsorption was investigated in the range
298–323 K (25–50 °C) in batch experiments already described and initial concentration of 1–
50 mg/L.
3. Results and discussion
3.1. Selection of adsorbents
Eleven different natural biosorbents, namely sawdust, sugarcane, corncob, tea waste, apple
peel, grape stalk, palm tree skin, eucalyptus leaves, mandarin peel, maple leaves and garden
grass, individually were compared in regard to the biosorption capacities for Cd(II), Cu(II),
Pb(II) and Zn(II) uptake in Fig. 1. The results indicate TW, ML and MP showed satisfying
biosorptive capacity for all heavy metal ions (cadmium, copper, lead and zinc). SD and CC
had quite less biosorptive potential in comparison with GG and GS and PS.AP, SC and EU
results for Pb, Zn, Cd and Cu were very unsatisfactory that this type of waste will not be
considered for study in combination with other biosorbents. TW:ML:MP combination was
selected to apply for further batch experiments.

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References
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Journal ArticleDOI
TL;DR: It is evident from the literature survey articles that ion-exchange, adsorption and membrane filtration are the most frequently studied for the treatment of heavy metal wastewater.
Abstract: Heavy metal pollution has become one of the most serious environmental problems today. The treatment of heavy metals is of special concern due to their recalcitrance and persistence in the environment. In recent years, various methods for heavy metal removal from wastewater have been extensively studied. This paper reviews the current methods that have been used to treat heavy metal wastewater and evaluates these techniques. These technologies include chemical precipitation, ion-exchange, adsorption, membrane filtration, coagulation-flocculation, flotation and electrochemical methods. About 185 published studies (1988-2010) are reviewed in this paper. It is evident from the literature survey articles that ion-exchange, adsorption and membrane filtration are the most frequently studied for the treatment of heavy metal wastewater.

5,658 citations


"A breakthrough biosorbent in removi..." refers background in this paper

  • ...chemical precipitation, extraction, ion exchange, filtration, reverse osmosis, membrane bioreactor and electrochemical techniques) (Santos et al., 2015; Abdolali et al., 2014a; Montazer-Rahmati et al., 2011; Fu and Wang, 2011)....

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  • ...…a wide range of treatment technologies are employed in industry (e.g. chemical precipitation, extraction, ion exchange, filtration, reverse osmosis, membrane bioreactor and electrochemical techniques) (Santos et al., 2015; Abdolali et al., 2014a; Montazer-Rahmati et al., 2011; Fu and Wang, 2011)....

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Journal ArticleDOI
TL;DR: Distinctive adsorption equilibria and kinetic models are of extensive use in explaining the biosorption of heavy metals, denoting the need to highlight and summarize their essential issues, which is the main purpose of this paper.
Abstract: Distinctive adsorption equilibria and kinetic models are of extensive use in explaining the biosorption of heavy metals, denoting the need to highlight and summarize their essential issues, which is the main purpose of this paper. As a general trend, up until now, most studies on the biosorption of heavy metal ions by miscellaneous biosorbent types have been directed toward the uptake of single metal in preference to multicomponent systems. In particular, Langmuir and Freundlich models are the most common isotherms for correlating biosorption experimental data though other isotherms, which were initially established for gas phase applications, can also be extended onto biosorption system. In kinetic modeling, the pseudo-first and -second order equations are considered as the most celebrated models.

1,273 citations


01 Jan 2008
TL;DR: Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions for heavy metal remediation.
Abstract: Heavy metal remediation of aqueous streams is of special concern due to recalcitrant and persistency of heavy metals in environment. Conventional treatment technologies for the removal of these toxic heavy metals are not economical and further generate huge quantity of toxic chemical sludge. Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions. The major advantages of biosorption over conventional treatment methods include: low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possibility of metal recovery. Cellulosic agricultural waste materials are an abundant source for significant metal biosorption. The functional groups present in agricultural waste biomass viz. acetamido, alcoholic, carbonyl, phenolic, amido, amino, sulphydryl groups etc. have affinity for heavy metal ions to form metal complexes or chelates. The mechanism of biosorption process includes chemisorption, complexation, adsorption on surface, diffusion through pores and ion exchange etc. The purpose of this review article is to provide the scattered available information on various aspects of utilization of the agricultural waste materials for heavy metal removal. Agricultural waste material being highly efficient, low cost and renewable source of biomass can be exploited for heavy metal remediation. Further these biosorbents can be modified for better efficiency and multiple reuses to enhance their applicability at industrial scale.

1,245 citations


"A breakthrough biosorbent in removi..." refers background in this paper

  • ...Nonetheless, these methods are not effective enough in low concentrations and might be very expensive as a result of high chemical reagent and energy requirements, aswell as the disposal problem of toxic secondary sludge (Bulut and Tez, 2007; Sud et al., 2008)....

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Journal ArticleDOI
Abstract: Heavy metal remediation of aqueous streams is of special concern due to recalcitrant and persistency of heavy metals in environment. Conventional treatment technologies for the removal of these toxic heavy metals are not economical and further generate huge quantity of toxic chemical sludge. Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions. The major advantages of biosorption over conventional treatment methods include: low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possibility of metal recovery. Cellulosic agricultural waste materials are an abundant source for significant metal biosorption. The functional groups present in agricultural waste biomass viz. acetamido, alcoholic, carbonyl, phenolic, amido, amino, sulphydryl groups etc. have affinity for heavy metal ions to form metal complexes or chelates. The mechanism of biosorption process includes chemisorption, complexation, adsorption on surface, diffusion through pores and ion exchange etc. The purpose of this review article is to provide the scattered available information on various aspects of utilization of the agricultural waste materials for heavy metal removal. Agricultural waste material being highly efficient, low cost and renewable source of biomass can be exploited for heavy metal remediation. Further these biosorbents can be modified for better efficiency and multiple reuses to enhance their applicability at industrial scale.

1,164 citations


Journal ArticleDOI
Abstract: Biosorption may be simply defined as the removal of substances from solution by biological material. Such substances can be organic and inorganic, and in gaseous, soluble or insoluble forms. Biosorption is a physico-chemical process and includes such mechanisms as absorption, adsorption, ion exchange, surface complexation and precipitation. Biosorption is a property of both living and dead organisms (and their components) and has been heralded as a promising biotechnology for pollutant removal from solution, and/or pollutant recovery, for a number of years, because of its efficiency, simplicity, analogous operation to conventional ion exchange technology, and availability of biomass. Most biosorption studies have carried out on microbial systems, chiefly bacteria, microalgae and fungi, and with toxic metals and radionuclides, including actinides like uranium and thorium. However, practically all biological material has an affinity for metal species and a considerable amount of other research exists with macroalgae (seaweeds) as well as plant and animal biomass, waste organic sludges, and many other wastes or derived bio-products. While most biosorption research concerns metals and related substances, including radionuclides, the term is now applied to particulates and all manner of organic substances as well. However, despite continuing dramatic increases in published research on biosorption, there has been little or no exploitation in an industrial context. This article critically reviews aspects of biosorption research regarding the benefits, disadvantages, and future potential of biosorption as an industrial process, the rationale, scope and scientific value of biosorption research, and the significance of biosorption in other waste treatment processes and in the environment. Copyright © 2008 Society of Chemical Industry

927 citations


"A breakthrough biosorbent in removi..." refers background in this paper

  • ...…many researchers into this matter in recent decades (Abdolali et al., 2014b; Tang et al., 2013; Fu et al., 2013; Kumar et al., 2012; Hossain et al., 2012; Witek-Krowiak et al., 2011; Gadd, 2009; Volesky, 2007; Šćiban et al., 2007) to use cheap agro-industrial wastes and by-products as biosorbents....

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  • ...Therefore, introducing a properly eco-friendly and cost effective technology for wastewater treatment has provoked many researchers into this matter in recent decades (Abdolali et al., 2014b; Tang et al., 2013; Fu et al., 2013; Kumar et al., 2012; Hossain et al., 2012; Witek-Krowiak et al., 2011; Gadd, 2009; Volesky, 2007; Šćiban et al., 2007) to use cheap agro-industrial wastes and by-products as biosorbents....

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Frequently Asked Questions (1)
Q1. What have the authors contributed in "A breakthrough biosorbent in removing heavy metals: equilibrium, kinetic, thermodynamic and mechanism analyses in a lab-scale study" ?

For Cu ( II ) and Zn ( II ), the Khan isotherm describes better biosorption conditions while for Cd ( II ) and Pb ( II ), the Sips model was found to provide the best correlation of the biosorption equilibrium data.