Veera M. Boddu

Adsorptive removal of copper and nickel ions from water using chitosan coated PVC beads.

A new biosorbent was developed by coating chitosan, a naturally and abundantly available biopolymer, on to polyvinyl chloride (PVC) beads. The biosorbent was characterized by FTIR spectra, porosity and surface area analyses. Equilibrium and column flow adsorption characteristics of copper(II) and nickel(II) ions on the biosorbent were studied. The effect of pH, agitation time, concentration of adsorbate and amount of adsorbent on the extent of adsorption was investigated. The experimental data were fitted to Langmuir and Freundlich adsorption isotherms. The data were analyzed on the basis of Lagergren pseudo first order, pseudo-second order and Weber-Morris intraparticle diffusion models. The maximum monolayer adsorption capacity of chitosan coated PVC sorbent as obtained from Langmuir adsorption isotherm was found to be 87.9 mg g(-1) for Cu(II) and 120.5 mg g(-1) for Ni(II) ions, respectively. In addition, breakthrough curves were obtained from column flow experiments. The experimental results demonstrated that chitosan coated PVC beads could be used for the removal of Cu(II) and Ni(II) ions from aqueous medium through adsorption.

Competitive adsorption of Cu (II), Co (II) and Ni (II) from their binary and tertiary aqueous solutions using chitosan-coated perlite beads as biosorbent

A new composite chitosan-coated biosorbent was prepared and was used for the removal and recovery of heavy metals from aqueous solution. In the present investigation, equilibrium adsorption characteristics of Cu (II), Ni (II), and Co (II) from their binary and tertiary solution on newly developed biosorbent chitosan-coated perlite beads were evaluated through batch and column studies. These beads were characterized by using FTIR, EDXRF and surface area analysis techniques. The effect of various biosorption parameters like effect of pH, agitation time, concentration of adsorbate and amount of adsorbent on extent of adsorption was investigated. The adsorption follows Lagergren first order kinetic model. The equilibrium adsorption data were fitted to Freundlich and Langmuir adsorption isotherm models and the model parameters were evaluated. Both the models represent the experimental data satisfactorily. The sorbent loaded with metal was regenerated with 0.1N NaOH solution. Furthermore the column dynamic studies indicate the re-usage of the biosorbent.

Adsorption of Chromium(VI) on Chitosan‐Coated Perlite

Chitosan‐coated perlite beads were prepared by drop‐wise addition of a liquid slurry containing chitosan and perlite to an alkaline bath. The beads were characterized by SEM and EDS x‐ray microanalysis. The chitosan content of the beads was 23%, as determined by a pyrolysis method. Adsorption of hexavalent chromium from aqueous solutions on chitosan‐coated perlite beads was studied under both equilibrium and dynamic conditions. The effect of pH on adsorption was also investigated. The data were fitted to the Langmuir adsorption isotherm. The adsorption capacity of chitosan‐coated perlite was found to be 104 mg/g of adsorbent from a solution containing 5000 ppm of Cr(VI). On the basis of chitosan, the capacity was 452 mg/g of chitosan. The capacity was considerably higher than that of chitosan in its natural and modified forms, which was in the range of 11.3 to 78 mg/g of chitosan. The beads loaded with chromium were regenerated with sodium hydroxide solution of different concentrations. A limited number of adsorption‐desorption cycles indicated that the chitosan‐coated beads could be regenerated and reused to remove Cr(VI) from waste streams.

Removal of Copper (II) and Nickel (II) Ions from Aqueous Solutions by a Composite Chitosan Biosorbent

Abstract A composite chitosan biosorbent (CCB) was prepared by coating chitosan on to ceramic alumina. The adsorption characteristics of the sorbent for copper and nickel ions were studied under batch equilibrium and dynamic flow conditions at pH 4.0. The equilibrium adsorption data were correlated with Langmuir, Freundlich, and Redlich‐Peterson models. The ultimate monolayer capacities, obtained from Langmuir isotherm, were 86.2 and 78.1 mg/g of chitosan for Cu(II) and Ni(II), respectively. In addition, dynamic column adsorption studies were conducted to obtain breakthrough curves. After the column was saturated with metal ions, it was regenerated with 0.1 M sodium hydroxide. The regenerated column was used for a second adsorption cycle.

Sorption of Triazine and Organophosphorus Pesticides on Soil and Biochar

Sorption and degradation are the primary processes controlling the efficacy and runoff contamination risk of agrochemicals. Considering the longevity of biochar in agroecosystems, biochar soil amendment must be carefully evaluated on the basis of the target agrochemical and soil types to achieve agricultural (minimum impact on efficacy) and environmental (minimum runoff contamination) benefits. In this study, sorption-desorption isotherms and kinetics of triazine (deisopropylatrazine) and organophosphorus (malathion, parathion, and diazinon) pesticides were first investigated on various soil types ranging from clayey, acidic Puerto Rican forest soil (PR) to heavy metal contaminated small arms range (SAR) soils of sandy and peaty nature. On PR, malathion sorption did not reach equilibrium during the 3 week study. Comparison of solution-phase molar phosphorus and agrochemical concentrations suggested that degradation products of organophosphorus pesticides were bound on soil surfaces. The degree of sorption on different soils showed the following increasing trend: deisopropylatrazine < malathion < diazinon < parathion. While sorption of deisopropylatrazine on SAR soils was not affected by diazinon or malathion, deisopropylatrazine suppressed the sorption of diazinon and malathion. Deisopropylatrazine irreversibly sorbed on biochars, and greater sorption was observed with higher Brunauer-Emmett-Teller surface area of biochar (4.7-2061 mg g(-1)). The results suggested the utility of biochar for remediation of sites where concentrations of highly stable and mobile agrochemicals exceed the water-quality benchmarks.

Hexavalent chromium removal mechanism using conducting polymers

We report detoxification of Cr(VI) into Cr(III) using electrochemically synthesized polyaniline (PANI), polypyrrole (PPY), PANI nanowires (PANI-NW) and palladium-decorated PANI (PANI-Pd) thin films. Percent Cr(VI) reduction was found to be decreased with an increase in pH from 1.8 to 6.8 and with initial Cr(VI) concentration ranging from 2.5 to 10mg/L. Efficacy of PANI increased at higher temp of 37 °C as compared to 30 °C. PANI-Pd was found to be most effective for all three initial Cr(VI) concentrations at pH 1.8. However, efficacy of PANI-Pd was significantly reduced at higher pHs of 5 and 6.8. Efficacy of PANI and PANI-NW was found to nearly the same. However, there was a significant reduction in effectiveness of PANI-NW at 10mg/L of Cr(VI) at all the three pHs studied, which could be attributed to degradation of PANI-NW by higher initial Cr(VI) concentration. PPY and PANI-NW were found to be highly sensitive with respect to pH and Cr(VI) initial concentration. Chromium speciation on PANI film was carried out by total chromium analysis and XPS, which revealed Cr(III) formation and its subsequent adsorption on the polymer. PANI-Pd and PANI are recommended for future sensor applications for chromium detection at low pH.

Equilibrium and column adsorption studies of 2,4‐dinitroanisole (DNAN) on surface modified granular activated carbons

2,4‐Dinitroanisole (DNAN) is used as a component extensively in the development of insensitive munitions. This may result in release of DNAN into the environment. Here, the results are reported of a study on the removal characteristics of DNAN through adsorption on granular activated carbon (GAC), chitosan coated granular activated carbon (CGAC), acid treated granular activated carbon (AGAC) and alkali treated granular activated carbon (BGAC) under equilibrium and column flow conditions. The effect of pH, contact time, concentration of DNAN, and presence of electrolytes on the uptake of DNAN by the adsorbents was investigated. The equilibrium data were fitted to different types of adsorption isotherms. The data were further analysed on the basis of Lagergren first‐order, pseudo second‐order and intraparticle diffusion kinetic models. Breakthrough curves were obtained based on column flow results. All the adsorbents were capable of removing about 99% of DNAN from aqueous media, except CGAC which adsorbed about 87% of DNAN.

Adsorption of Divalent Cobalt from Aqueous Solution onto Chitosan–Coated Perlite Beads as Biosorbent

Abstract Chitosan coated perlite beads are prepared by drop‐wise addition of a liquid slurry containing chitosan and perlite to an alkaline bath. The resulting beads are characterized using FTIR, SEM, EDXRF, and Surface area analysis and the chitosan content of the beads is 23% as determined by a pyrolysis method. Adsorption of Co (II) metal ions from aqueous solution on chitosan coated perlite beads is studied under both equilibrium and dynamic conditions. In the present investigation, a first order reversible rate equation is used to understand the kinetics of metal removal and to calculate the rate constants at different initial concentrations. The equilibrium characteristics of metal ion on newly developed biosorbent are studied and the experimental adsorption data are well fitted to Freundlich and Langmuir adsorption isotherm models and the model parameters are evaluated. The effect of pH, agitation time, concentration of adsorbate, and amount of adsorbent on the extent of the adsorption are investigated. The sorbent loaded with metal is regenerated with 0.10 mol dm−3 sodium hydroxide solution. The adsorption desorption cycles indicated that the chitosan coated perlite could be regenerated and reused to remove Co (II) from waste water.

Biosorption of Phenolic Compounds by Trametes Versicolor Polyporus Fungus

The use of non-living Trametes versicolor polyporus fungus to remove phenol, 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) from water under equilibrium and column flow experimental conditions was evaluated. The biomass was characterized by Fourier-transform infrared spectroscopy. The adsorption capacity of the biosorbent was investigated as a function of pH, contact time, initial concentration of adsorbate and amount of biomass employed. The adsorption process followed the pseudo-first-order kinetic model. The equilibrium data were analyzed in terms of the Freundlich, Langmuir and D–R adsorption isotherm models. The maximum monolayer adsorption capacity of Trametes versicolor polyporus fungus for phenol, 2-CP and 4-CP was found to be 50 mg/g, 86 mg/g and 112 mg/g, respectively. Desorption of phenolic compounds was achieved using 0.1 M NaOH solution. The experimental results demonstrated that the Trametes versicolor polyporus fungus could be used as a sorbent for immobilizing phenolic compounds.

Adsorption of uranium on a novel bioadsorbent-chitosan-coated perlite

Chitosan was coated on an inert substrate, perlite, and was prepared as spherical beads for adsorption of uranium from aqueous solutions. The uptake capacity of chitosan-coated perlite beads for uranium varied from 98.9 to 149 000 μg/g when the equilibrium concentration of uranium in the solution ranged from 11 ppb (11 μg/l) to 1000 ppm (10 × 106 μg/l) and the solution pH was 5. The adsorption capacity of chitosan-coated perlite beads for uranium decreased by 75% in the presence of 0.45 M NaCl, whereas the adsorption capacity decreased by 55% when TiO2 was added to the beads during their preparation. The adsorption capacity of TiO2-containing chitosan beads for uranium was found to be in the range of 2.5 to 40 μg of uranium per gram of beads when the concentration of uranium was 39 to 734 μg/l in the presence of 0.45 M NaCl. It was in the range of 18 to 302 μg of uranium per gram of beads when the concentration was 990 to 47 000 μg/l in the presence of 0.45 M Na2CO3. Chitosan-coated beads were found to preferentially adsorb uranium, Cd, and Cr from a mixture containing these ions along with Sr and Cs. Only a negligible amount of Sr and Cs was adsorbed by chitosan-coated beads. The data suggest that the chitosan-coated beads can be used for both extraction of uranium from waste streams and also from a highly acidic medium such as a reprocessing stream that uses nitric acid.