Metals sorption from aqueous solutions by Kluyveromyces marxianus: Process optimization,equilibrium modeling and chemical characterization

The dead Kluyveromyces marxianus biomass, a fermentation industry waste, was used to explore its sorption potential for lead, mercury, arsenic, cobalt, and cadmium as a function of pH, biosorbent dosage, contact time, agitation speed, and initial metal concentration. The equilibrium data fitted the Langmuir model better for cobalt and cadmium, but Freundlich isotherm for all metals tested. At equilibrium, the maximum uptake capacity (Qmax) was highest for lead followed by mercury, arsenic, cobalt, and cadmium. The RL values ranged between 0–1, indicating favorable sorption of all test metals by the biosorbent. The maximum Kf value of Pb showed its efficient removal from the solution. However, multi-metal analysis depicted that sorption of all metals decreased except Pb. The potentiometric titration of biosorbent revealed the presence of functional groups viz. amines, carboxylic acids, phosphates, and sulfhydryl group involved in heavy metal sorption. The extent of contribution of functional groups and lipids to biosorption was in the order: carboxylic>lipids>amines>phosphates. Blocking of sulfhydryl group did not have any significant effect on metal sorption.     

226Ra, 238U and Cd adsorption kinetics and binding capacity of two cyanobacterial strains isolated from highly radioactive springs and optimal conditions for maximal removal effects in contaminated water

Biomass-based decontamination methods are among the most interesting water treatment techniques. In this study, 2 cyanobacterial strains, Nostoc punctiforme A.S/S4 and Chroococcidiopsis thermalis S.M/S9, isolated from hot springs containing high concentrations of radium (²²⁶Ra), were studied to be associated with removal of radionuclides (²³⁸U and ²²⁶Ra) and heavy metal cadmium (Cd) from aqueous solutions. The adsorption equilibrium data was described by Langmuir and Freundlich isotherm models. Kinetic studies indicated that the sorption of 3 metals followed pseudo-second-order kinetics. Effects of biomass concentration, pH, contact time, and initial metal concentration on adsorption were also investigated. Fourier-transform infrared spectroscopy revealed active binding sites on the cyanobacterial biomass. The obtained maximum biosorption capacities were 630 mg g^?1 and 37 kBq g^?1 for ²³⁸U and ²²⁶Ra for N. punctiforme and 730 mg g^?1 and 55 kBq g^?1 for C. thermalis. These 2 strains showed maximum binding capacity 160 and 225 mg g^?1, respectively for Cd adsorption. These results suggest that radioactivity resistant cyanobacteria could be employed as an efficient adsorbent for decontamination of multi-component, radioactive and industrial wastewater.     

Immobilization of blue green microalgae on loofa sponge to biosorb cadmium in repeated shake flask batch and continuous flow fixed bed column reactor system

Summary An indigenous strain of blue green microalga, Synechococcus sp., isolated from wastewater, was immobilized onto loofa sponge discs and investigated as a potential biosorbent for the removal of cadmium from aqueous solutions. Immobilization has enhanced the sorption of cadmium and an increase of biosorption (21%) at equilibrium was noted as compared to free biomass. The kinetics of cadmium biosorption was extremely rapid, with (96%) of adsorption within the first 5 min and equilibrium reached at 15 min. Increasing initial pH or initial cadmium concentration resulted in an increase in cadmium uptake. The maximum biosorption capacity of free and loofa immobilized biomass of Synechococcus sp. was found to be 47.73 and 57.76 mg g⁻¹ biomass respectively. The biosorption equilibrium was well described by Langmuir adsorption isotherm model. The biosorbed cadmium was desorbed by washing the immobilized biomass with dilute HCl (0.1 M) and desorbed biomass was reused in five biosorption–desorption cycles without an apparent decrease in its metal biosorption capacity. The metal removing capacity of loofa immobilized biomass was also tested in a continuous flow fixed-bed column bioreactor and was found to be highly effective in removing cadmium from aqueous solution. The results suggested that the loofa sponge-immobilized biomass of Synechococcus sp. could be used as a biosorbent for an efficient removal of heavy metal ions from aqueous solution.     

Arsenic(V) biosorption by charred orange peel in aqueous environments

Biosorption efficiency of natural orange peel (NOP) and charred orange peel (COP) was examined for the immobilization of arsenate (As(V)) in aqueous environments using batch sorption experiments. Sorption experiments were carried out as a function of pH, time, initial As(V) concentration and biosorbent dose, using NOP and COP (pretreated with sulfuric acid). Arsenate sorption was found to be maximum at pH 6.5, with higher As(V) removal percentage (98%) by COP than NOP (68%) at 4 g L^?1 optimum biosorbent dose. Sorption isotherm data exhibited a higher As(V) sorption (60.9 mg g^?1) for COP than NOP (32.7 mg g^?1). Langmuir model provided the best fit to describe As(V) sorption. Fourier transform infrared spectroscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy analyses revealed that the –OH, –COOH, and –N-H surface functional groups were involved in As(V) biosorption and the meso- to micro-porous structure of COP sequestered significantly (2-times) higher As(V) than NOP, respectively. Arsenate desorption from COP was found to be lower (10%) than NOP (26%) up to the third regeneration cycle. The results highlight that this method has a great potential to produce unique ‘charred’ materials from the widely available biowastes, with enhanced As(V) sorption properties.     

Phycoremediation of lead and cadmium by employing Nostoc muscorum as biosorbent and optimization of its biosorption potential

The present study reports the influence of different factors on the sorption of Pb and Cd by Nostoc muscorum. The results showed that extent of Pb and Cd removal by N. muscorum cells increased with increasing biosorbent dose, but exhibited decline in the adsorption capacity. The maximum sorption of Cd (85.2%) and Pb (93.3%) was achieved at 60 and 80 μg/ml concentrations of respective metal, within 30 and 15 min, respectively. The result revealed that optimum biosorption of Pb and Cd occurred at pH 5 and 6, respectively, at 40°C temperature. Presence of binary metals (both Pb and Cd) in a solution showed that the presence of one metal ion resulted into decreased sorption of other metal ion. The presence of Ca and EDTA showed significant decrease in the sorption of Pb and Cd, while other anions and cations did not show significant effect on the biosorption of both the metals. Maximum desorption of Pb and Cd was achieved in the presence of EDTA and HNO₃, respectively. Results also showed that the test biosorbent could be repeatedly used up to six biosorption/desorption cycles without significant loss of its initial metal adsorption capacity.     

Chromium Removal from Aqueous System and Industrial Wastewater by Agricultural Wastes

This study involved the development of formaldehyde-treated, deseeded sunflower head waste–based biosorbent (FSH) for the biosorption of Cr(VI) from aqueous solution and industrial wastewater. Batch-mode experiments were conducted to determine the kinetics, sorption isotherms, effect of pH, initial Cr(VI) concentration, biosorbent dose, and contact time. The results demonstrated that FSH can sequester Cr(VI) from the aqueous solution. The maximum sorption occurred at pH = 2.0, biosorbent dose = 4.0 g/L, concentration of 100 mg/L at 25°C at 180 rpm after 2 h contact time. The FSH had an adsorption capacity of 7.85 mg/g for Cr(VI) removal at pH 2.0. The rate of adsorption was rapid, and equilibrium was attained within 2 h. The equilibrium sorption data fitted the Langmuir isotherm model, which was further confirmed by the chi-square test.     

Uptake of Cr3+ from aqueous solution by lignite-based humic acids

Humic acid (HA) produced from brown coal, a relatively abundant and inexpensive material is currently being investigated as an adsorbent to remove toxic metals from aqueous solution. The influence of five parameters (contact time, solution pH, initial metal concentration, temperature and amount of adsorbent) on the removal at 20+/-1 degrees C was studied. HAs were prepared from lignites by using alkaline extraction, sedimentation and acidic precipitation. Adsorption equilibrium was achieved in about 60 min for Cr3+ ion. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The maximum adsorption capacity of 0.17 mmol for Ilgin (HA1), 0.29 mmol for Beysehir (HA2) and 0.18 mmol Ermenek (HA3) and 0.17 mmol of Cr3+/g for activated carbon (AC) was achieved, respectively at pH of 4.1. More than 84% of Cr3+ was removed by HA2, 54% by HA3 and 51% by HA1 and 50% by AC from aqueous solution. The adsorption was strongly dependent on pH but independent of ionic strength and metal ions. The adsorption of Cr3+ was higher between pH 4.1 and 5.1 for all HAs and maximum sorption was observed at pH 4.1. The rise in temperature caused a slight decrease in the value of the equilibrium constant (Kc) for the sorption of Cr3+ ion. Complex mechanisms including ion exchange, complexation and adsorption and size exclusion are possible for sorption of Cr3+ ion on HAs.     

Arsenic and fluoride removal by potato peel and rice husk (PPRH) ash in aqueous environments

Finding appropriate adsorbent may improve the quality of drinking water in those regions where arsenic (As) and fluoride (F^?) are present in geological formations. In this study, we evaluated the efficiency of potato peel and rice husk ash (PPRH-ash)-derived adsorbent for the removal of As and F from contaminated water. Evaluation was done in batch adsorption experiments, and the effect of pH, initial adsorbate concentration, contact time, and adsorbent dose were studied. Characteristics of adsorbents were analyzed using scanning electron micropcope (SEM) and Fourier transform infrared (FTIR) spectroscopy. Both the Langmuir and Freundlich isotherm models fitted well for F^? and As sorption process. The maximum adsorption capacity of adsorbent for As and F^? was 2.17 μg g^?1 and 2.91 mg g^?1, respectively. The As and Fi removal was observed between pH 7 and 9. The sorption process was well explained with pseudo-second order kinetic model. Arsenic adsorption was not decreased in the presence of carbonate and sulfate. Results from this study demonstrated potential utility of this agricultural biowaste, which could be developed into a viable filtration technology for As and F^? removal in As- and F-contaminated water streams.     

Regression model,artificial neural network,and cost estimation for biosorption of Ni(II)-ions from aqueous solutions by Potamogeton pectinatus

This study investigated the application of Potamogeton pectinatus for Ni(II)-ions biosorption from aqueous solutions. FTIR spectra showed that the functional groups of –OH, C–H, –C = O, and –COO– could form an organometallic complex with Ni(II)-ions on the biomaterial surface. SEM/EDX analysis indicated that the voids on the biosorbent surface were blocked due to Ni(II)-ions uptake via an ion exchange mechanism. For Ni(II)-ions of 50 mg/L, the adsorption efficiency recorded 63.4% at pH: 5, biosorbent dosage: 10 g/L, and particle-diameter: 0.125–0.25 mm within 180 minutes. A quadratic model depicted that the plot of removal efficiency against pH or contact time caused quadratic-linear concave up curves, whereas the curve of initial Ni(II)-ions was quadratic-linear convex down. Artificial neural network with a structure of 5 – 6 – 1 was able to predict the adsorption efficiency (R²: 0.967). The relative importance of inputs was: initial Ni(II)-ions > pH > contact time > biosorbent dosage > particle-size. Freundlich isotherm described well the adsorption mechanism (R²: 0.974), which indicated a multilayer adsorption onto energetically heterogeneous surfaces. The net cost of using P. pectinatus for the removal of Ni(II)-ions (4.25 ± 1.26 mg/L) from real industrial effluents within 30 minutes was 3.4 $USD/m³.     

Biosorption and Desorption of Lead(II) by Hydrilla verticillata

The potential of nonliving biomass of Hydrilla verticillata to adsorb Pb(II) from an aqueous solution containing very low concentrations of Pb(II) was determined in this study. Effects of shaking time, contact time, biosorbent dosage, pH of the medium, and initial Pb(II) concentration on metal-biosorbent interactions were studied through batch adsorption experiments. Maximum Pb(II) removal was obtained after 2 h of shaking. Adsorption capacity at the equilibrium increased with increasing initial Pb(II) concentration, whereas it decreased with increasing biosorbent dosage. The optimum pH of the biosorption was 4.0. Surface titrations showed that the surface of the biosorbent was positively charged at low pH and negatively charged at pH higher than 3.6. Fourier transform infrared (FT-IR) spectra of the biosorbent confirmed the involvement of hydroxyl and C?O of acylamide functional groups on the biosorbent surface in the Pb(II) binding process. Kinetic and equilibrium data showed that the adsorption process followed the pseudo-second-order kinetic model and both Langmuir and Freundlich isothermal models. The mean adsorption energy showed that the adsorption of Pb(II) was physical in nature. The monolayer adsorption capacity of Pb(II) was 125 mg g^?1. The desorption of Pb(II) from the biosorbent by selected desorbing solutions were HNO₃ > Na₂CO₃ > NaOH > NaNO₃.     

Evaluating the Adsorption Potential of Alachlor and Its Subsequent Removal from Soils via Activated Carbon

Alachlor, a globally used aniline herbicide, has great agronomic interest for controlling the development of broadleaved weeds and grasses. This research aspires to evaluate the sorption attributes of Alachlor through batch equilibrium method and its successive removal through biomass based activated carbon prepared from Sawdust (Cedrus deodara). Six soil samples were collected from selected regions of Pakistan to assess the adsorption and removal phenomena. Adsorption capacity for Alachlor varied in soils depending upon their physicochemical properties. Adsorption coefficient (K_d) values ranged from 12 to 31 µg ml^?1 with the highest K_d value observed in soil sample with highest organic content (1.4%) and least pH (5.62). The Gibbs free energy values ranged from ?17 to ?20 kJ mol^?1 proposing physio-sorption and exothermic interaction with soils. Values of R² (0.96–0.99) exhibited the best fit to linear adsorption model. Adsorption coefficient displayed a negative correlation (r = ?0.97) with soil pH and positive correlation with organic matter (r = 0.87). The effect of contact time and pesticide concentration on the removal efficiency by activated carbon was investigated. The highest removal percentages observed through activated carbon were 66% and 64% at concentrations of 5 and 7.5 ppm respectively. Activated carbon from sawdust (Cedrus deodara) was investigated as a suitable adsorbent for the removal of Alachor from selected soils. Biomass based activated carbon can prove to be an effective and a sustainable mean to remove pesticides from soil.     

Cadmium removal from simulated wastewater to biomass byproduct of Lentinus edodes

A kind of agricultural waste, the byproduct of brown-rot fungus Lentinus edodes, was used as an efficient biosorbent for the removal of cadmium from water in this paper. The sorption conditions, such as pH, the dose of biomass and the initial concentration of cadmium were examined. Three kinds of adsorption models were applied to simulate the biosorption data. Uptake of cadmium was higher in weak acid condition than in strong acid condition. Nearly no sorption of cadmium occurred when the pH value was lower than 2.5. Biosorption isothermal data could be well simulated by Freundlich model, and then Langmuir and Temkin model. Langmuir simulation of the biosorption showed that the maximum uptake of cadmium was 5.58mmol/g in weak acid condition, which was much higher than many other biosorbents. The exchanged proton was highly related to the uptake of cadmium in weak acid condition. Fourier transform infrared spectrums and energy-dispersive X-ray microanalyzer were used to reveal ion-exchange mechanism between cadmium and the functional groups or participated inorganic metal ions during biosorption.     

Equilibrium study of dried orange peel for its efficiency in removal of cupric ions from water

Excess of copper ion (>2 mg/L) in water is toxic to human beings and the ecosystem. Various water treatment technologies for copper remediation have been investigated in the past. Along with industrial effluents, Bordeaux mixture is also a noteworthy copper contamination source in the agricultural ecosystem. In our study, the biosorbent efficiency of dried orange peel was investigated through an environment-friendly process for the removal of cupric ions. Effects of pH, adsorbate concentration, adsorbent dosage, and temperature for the removal of Cu (II) were studied. Slightly acidic environment (pH = 6) was found to be optimum for removal of copper. The equilibrium data were well fitted with the Langmuir and Freundlich isotherms. The surface morphology of the adsorbent was studied using scanning electron microscope. Crystalline nonhomogenous surface was observed after copper adsorption. Desorption study indicated that 0.1N H₂SO₄ is the best eluent for the removal of adsorbed copper from the powdered dried orange peel.     

Microbial Waste Biomass for Removal of Chromium(VI) from Chrome Effluent

ABSTRACT

Microbial waste biomass, a by-product of the fermentation industry, was developed as a biosorbent to remove hexavalent chromium (Cr) from the acidic effluent of a metal processing industry. In batch sorption, 100% Cr(VI) removal was achieved from aqueous solution in 30 min contact at pH 4.0–5.0. The Cr(VI) sorption equilibrium was evaluated using the Langmuir and Freundlich models, indicating the involvement of ion exchange and physicochemical interaction. Fourier transform infrared (FTIR) analysis revealed the presence of amine, hydroxyl, and imine functional groups present on the surface of microbial biomass that are involved in Cr binding. In a continuous sorption system, 95 mg L^?1 of Cr(VI) was adsorbed before the column reached a breakthrough point of 0.1 mg L^?1 Cr(VI) at the column outlet. An overall biosorption capacity of 12.6 mg Cr(VI) g^?1 of dry microbial waste was achieved, including the partially saturated portion of the dynamic sorption zone. Insignificant change in metal removal was observed up to 10 cycles. In pilot-scale studies, 100% removal of Cr(VI) was observed up to 5 weeks, and the method was found to be cost-effective, commercially viable, and environmentally friendly, as it does not generate toxic chrome sludge.     

Biosorption of lead, cadmium, and zinc by Citrobacter strain MCM B-181: characterization studies

The biosorption process for removal of lead, cadmium, and zinc by Citrobacter strain MCM B-181, a laboratory isolate, was characterized. Effects of environmental factors and growth conditions on metal uptake capacity were studied. Pretreatment of biomass with chemical agents increased cadmium sorption efficiency; however, there was no significant enhancement in lead and zinc sorption capacity. Metal sorption by Citrobacter strain MCM B-181 was found to be influenced by the pH of the solution, initial metal concentration, biomass concentration, and type of growth medium. The metal sorption process was not affected by the age of the culture or change in temperature. Equilibrium metal sorption was found to fit the Langmuir adsorption model. Kinetic studies showed that metal uptake by Citrobacter strain MCM B-181 was a fast process, requiring <20 min to achieve >90% adsorption efficiency. The presence of cations reduced lead, zinc, and cadmium sorption to the extent of 11. 8%, 84.3%, and 33.4%, respectively. When biomass was exposed to multimetal solutions, metals were adsorbed in the order Co2+ < Ni2+ < Cd2+ < Cu2+ < Zn2+ < Pb2+. Among various anions tested, only phosphate and citrate were found to hamper metal sorption capacity of cells. Biosorbent beads prepared by immobilizing the Citrobacter biomass in polysulfone matrix exhibited high metal loading capacities. A new mathematical model used for batch kinetic studies was found to be highly useful in prediction of experimentally obtained metal concentration profiles as a function of time. Metal desorption studies indicated that Citrobacter beads could, in principle, be regenerated and reused in adsorption-desorption cycles. In an expanded scale trial, biosorbent beads were found to be useful in removal/recovery of metals such as lead from industrial wastewaters.     

Adsorption Evaluation of Herbicide Iodosulfuron Followed by Cedrus deodora Sawdust-Derived Activated Carbon Removal

The paucity of sorption studies of sulfonylurea herbicide Iodosulfuron has led to the current research for investigation of this imperative phenomena. Iodosulfuron adsorption capacity was evaluated through batch equilibrium experiments in six soil samples collected from distinct geographical regions of Pakistan. Activated carbon prepared from sawdust (Cedrus deodara) was investigated as an economical and sustainable adsorbent for the removal of Iodosulfuron from selected soils. Removal efficiency was studied as a function of contact time and pesticide concentration. Results exhibited a good adsorption capability of Iodosulfuron in different soils. Adsorption coefficient values ranged from 8.9 to 26 mL/g. Soil pH and organic matter greatly influenced the rate of adsorption. The linear adsorption model fitted best with the experimental results. Gibbs free energy values (?17 to ?20 kJ/mol) proposed physisorption and exothermic interaction of Iodosulfuron with selected soils. Analysis of variance and regression displayed a negative correlation of soil pH and K_d (R² = ?0.91) and positive correlation with organic matter (R² = 0.87). A good removal rate for was observed in soils by sawdust-derived activated carbon. Soil properties mainly; pH, organic matter and sand content greatly influenced Iodosulfuron removal phenomena. Biomass-derived activated carbon can thus be utilized as a sustainable remediation tool.     

Zinc removal from model solution and wastewater by Arthrospira (Spirulina) Platensis biomass

The biosorption of zinc from model solution as well as wastewater by Arthrospira (Spirulina) platensis biomass was studied. Adsorption capacity of the biosorbent was investigated as a function of contact time between adsorbent and zinc, the initial metals and sorbent concentration, pH value, and temperature. The ability of Arthrospira biomass for zinc biosorption exhibited a maximum at the pH range 4–8. Equilibrium data fitted well with the Langmuir model as well as the Freundlich model with maximum adsorption capacity of 7.1 mg/g. The pseudo second-order model was found to correlate well with the experimental data. Different thermodynamic parameters, ΔG°, ΔH° and ΔS° were evaluated and it has been found that the sorption was feasible, spontaneous, and endothermic in nature. The process of zinc removal from industrial effluent was studied at different time of sorbat–sorbent interaction and different sorbent dosage. Maximum zinc removal (83%) was obtained at sorbent concentration 60 g/L during 1-h experiment. The results indicate that Arthrospira platensis biomass could be effectively used for zinc removal from industrial effluents.     

Modeling of Pb(II) adsorption by a fixed-bed column

Removal of Pb(II) from an aqueous environment using biosorbents is a cost-effective and environmentally benign method. The biosorption process, however, is little understood for biosorbents prepared from plant materials. In this study, the biosorption process was investigated by evaluating four adsorption models. A fixed-bed column was prepared using a biosorbent prepared from the aquatic plant Hydrilla verticillata. The effect of bed height and flow rate on the biosorption process was investigated. The objective of the study was to determine the ability of H. verticillata to biosorb Pb(II) from an aqueous environment and to understand the process, through modeling, to provide a basis to develop a practical biosorbent column. Experimental breakthrough curves for biosorption of 50 mg L^?1 aqueous Pb(II) using a fixed-bed column with 1.00 cm inner diameter were fitted to the Thomas, Adams-Bohart, Belter, and bed depth service time (BDST) models to investigate the behavior of each model according to the adsorption system and thus understand the adsorption mechanism. Model parameters were evaluated using linear and nonlinear regression methods. The biosorbent removed 65% (82.39 mg g^?1 of biosorbent) of Pb(II) from an aqueous solution of Pb(NO₃)₂ at a flow rate of 5.0 ml min^?1 in a 10 cm column. Na₂CO₃ was used to recover the adsorbed Pb(II) ions as PbCO₃ from the biosorbent. The Pb(II) was completely desorbed at a bed height of 10.0 cm and a flow rate of 5.0 ml min^?1. Fourier transform infrared (FT-IR) analysis of the native biosorbent and Pb(II)-loaded biosorbent indicated that the hydroxyl groups and carboxylic acid groups were involved in the metal bonding process. The FT-IR spectrum of Pb(II)-desorbed biosorbent showed an intermediate peak shift, indicating that Pb(II) ions were replaced by Na⁺ ions through an ion-exchange process. Of the four models tested, the Thomas and BDST models showed good agreement with experimental data. The calculated bed sorption capacity N₀ and rate constant k_a were 31.7 g L^?1 and 13.6 × 10^?4 L mg^?1 min^?1 for the C_t/C₀ value of 0.02. The BDST model can be used to estimate the column parameters to design a large-scale column.     

Evaluation of Cr(VI) Exposed and Unexposed Plant Parts of Tradescantia pallida (Rose) D. R. Hunt. for Cr Removal from Wastewater by Biosorption

Phytoremediation is an efficient method for the removal of heavy metals from contaminated systems. A productive disposal of metal accumulating plants is a major concern in current scenario. In this work, Cr(VI) accumulating Tradescantia pallida plant parts were investigated for its reuse as a biosorbent for the removal of Cr(VI) ions. The effect of pH, contact time, sorbent dosage, Cr(VI) concentration and temperature was examined to optimize these process parameters. Results showed that Cr(VI) exposed/unexposed T. pallida leaf biomass could remove 94% of chromium with a sorption capacity of 64.672 mg g^?1. Whereas the kinetics of Cr(VI) biosorption was well explained by the pseudo second-order kinetic model, the Langmuir model better described the data on Cr(VI) sorption isotherm compared with the Freundlich model. The changes in the free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) were found to be ?5.276 kJ mol^?1, 0.391 kJ mol^?1 K^?1 and 11.346 kJ mol^?1, respectively, which indicated the process to be spontaneous, feasible and endothermic in nature. FTIR spectra of T. pallida leaf biomass revealed the active participation of ligands, such as ?NH, amide, hydroxyl and sulphonate groups present in the biomass for Cr(VI) binding, SEM analysis revealed a porous structure of the biosorbent for an easy uptake of Cr(VI).     

Cadmium removal from water environment by a fungus Volveriella volvacea

Biosorption technique was used for removal of cadmium under different conditions from water environment using a biosorbent, Volveriella volvaceas, locally growing fruit bodies of mushroom. Effects of different parameters like pH, sorbent concentration, ionic strength on the removal efficiency of cadmium by V. volvacea were carried out in continuation with adsorption kinetics and equilibrium isotherm experiments. From the kinetics studies it was found that nearly 95% of the total cadmium removal was achieved from cadmium spiked distilled water within first 15 minutes. Isotherm data was best fitted to linearised Langmuir equation and the sorption capacity was found to be varying from 9.13 to 9.33 mg/g for different sizes of sorbent. The uptake of cadmium(II) is a function of pH of the solution and increases with the increasing pH. Increasing ionic strength and the presence of soluble complexing agents such as ethylene diamine tetraacetic acid (EDTA) decrease the sorption of cadmium (II). The presence of other diavalent cations like calcium and magnesium impedes the uptake of cadmium (II). The presence of chloride ion has no significant effect on cadmium (II) removal. The spent biosorbent can effectively be regenerated with acid and can then be reused.The present work was carried out by the financial support in terms of fellowship under the cultural exchange programme of the Indo-Bangladesh government. Special thanks to the Director, Bangladesh Institute of Technology, Dhaka, Bangladesh, for providing leave, which enabled the author in carrying out the research work.