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The molecular interaction between tetrabutylammonium iodide (TBAI) and cellulose and its potential application for the adsorption of chromium is discussed in this paper. The biosorbent was prepared under solvent free conditions using microwave irradiation. A subtle balance between electrostatic and the hydrophobic effects governs the interaction of biopolymer with the surfactant. The interaction between the biosorbent and chromium was comprehensively studied using spectroscopic, thermal and surface analysis techniques. The various analytical parameters that influence the adsorption were optimized, and the maximum adsorption capacity of Cr(VI) obtained from the Langmuir isotherm model was found to be 16.67 mg g(-1). The sorption thermodynamics indicated the spontaneity and exothermic nature of adsorption. The biosorbent could be effectively regenerated using NaOH, which imparts greener aspect to the overall process., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The molecular interaction of biopolymers with an array of substrates offers interesting insight into the adsorption phenomenon. The present work proposes the preparation and characterization of cellulose-methyltrioctylammonium chloride (MeTOACl)-a room temperature ionic liquid (IL) blend polymeric sorbent and its application for the adsorption of carcinogenic chromium(VI). The blend adsorbent material was synthesized in a relatively green solvent (methylisobutylketone) medium by ultrasonication. The mechanism of interaction of biopolymer with the ionic liquid could be conceptualized as electrostatic attraction, hydrogen bonding, and Van der Waals force of attraction with the hydroxyl groups of cellulose as a bilayer assembly. The composition, crystallinity, and the surface area of the prepared material were comprehensively characterized using FT-IR, solid-state (13)C NMR, TGA, XRD, SEM, EDX, XPS, and BET isotherm study. The adsorption capacity of chromium(VI) calculated from Langmuir isotherm model was found to be 38.94 mg g(-1) with adherence to the second-order kinetics. The study of thermodynamic parameters that affect the sorption process indicated the spontaneity and exothermic nature of adsorption. The green aspect in the methodology is brought out in the regeneration of the adsorbent, where Cr(VI) could be effectively reduced to the less toxic Cr(III) using ascorbic acid., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Biopolymer adsorbents are versatile in their application for removal of heavy metals. The present work is focused towards the preliminary study of the interaction of diphenylthiocarbazone (DTZ) complex of chromium(VI) in acidic medium with cellulose biopolymer. Chromium-DTZ complex could be quantitatively adsorbed on a cellulose column in the pH range 1.0-2.5 and the effect of various experimental parameters such as stability of the column and the complex, column breakthrough volume, and interfering ions have been studied in detail. The probable mechanism of adsorption of complex on the cellulose biopolymer was corroborated using Fourier transform infra-red spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and solid state 13C nuclear magnetic resonance techniques (CP-MAS). The pores formed due to the hydrogen bond between the cellulose layers and then the ensuing occupation of the complex between these layers and on the surface of the biopolymer layer through electrostatic attractive force and Π interaction of aromatic ring with cellulose are expected to play a vital role in the interaction. The cellulose column could be regenerated using environmentally benign polyethylene glycol-400 (PEG-400) in acidic medium. The cellulose biosorbent has been successfully tested to study the removal of chromium as its dithizone complex from synthetic and real waste water samples., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A simple, economical and green methodology has been developed for the adsorption of malachite green using cellulose powder as the adsorbent. Batch experimental procedures were conducted to investigate the adsorption ability of this bio-polymer to remove malachite green from aqueous medium. The adsorbed dye on cellulose was characterized by Fourier transform-infrared spectroscopy (FT-IR). The various analytical parameters such as the effect of contact time, pH, temperature, etc. were optimized. The adsorption was efficient at a neutral pH (7.2) and both Langmuir and Freundlich isotherm models showed good fit into the experimental data. The adsorption kinetics indicated that the adsorption proceeds according to pseudo-second-order model. The adsorption of malachite green was found to be exothermic and it was accompanied by decrease in the entropy. Column studies were performed and the regeneration of the adsorbent was done easily using environmentally benign polyethylene glycol-400.

Convergence of biotechnology and chemistry offers greener alternatives in environmental remediation. Hexavalent chromium is genotoxic and carcinogenic. The aim of the present study is to investigate the removal of hexavalent chromium from aqueous solution in batch and fixed bed column experiments using dead biomass of isolated Aspergillus fungal species immobilized in epichlorohydrin crosslinked cellulose. The biosorbent exhibited good potential to remove Cr(VI). Other parameters such as pH, isotherms, kinetics and temperature effect were studied with a view to understand the adsorption efficiency. Biomass as low as 0.4 g could adsorb completely a Cr(VI) concentration of 5 mg L −1 within 3 h from an aqueous volume of 30 mL. Optimum pH and temperature for Cr(VI) biosorption were 2.0 and 30 °C, respectively with a Langmuir adsorption capacity of 23.83 mg g −1 . Kinetic studies favour the pseudo second order model. The biosorbent–Cr(VI) interactions were corroborated by FTIR, SEM, EDAX and ESCA analysis. Emphasis is laid on various column modelling studies at different bed heights, flowrates, and concentrations of Cr(VI) and the experimental data obtained was in good agreement with Bed Depth Service Time (BDST) model. The synergism of Aspergillus and cellulose as a potential biosorbent was also validated in a synthetic mixture of diverse ions and a certified industrial effluent wastewater sample (BCR-715). [ABSTRACT FROM AUTHOR]

This work highlights the convergence of chemistry and biotechnology through the microwave assisted preparation of baker's yeast ( Saccharomyces cerevisiae ) immobilized in glutaraldehyde cross linked cellulose as a novel and green adsorbent for the removal of toxic Cr(VI). Microwave assisted preparation is a new approach to immobilize a microorganism and it ensured that just 200 s was enough for the incorporation of yeast in the biopolymer matrix. The yeast immobilized biopolymer acts as a good host to accommodate the Cr(VI) oxy anion. The hexavalent chromium could be adsorbed effectively at pH 2.5 and the functional groups present in the microbe and cellulose play a dominant role in the interaction. The proof of concept was established through FT-IR, SEM, EDAX, TGA and optical imaging techniques. Thermodynamic feasibility, second order kinetics and Langmuir isotherm model authenticates the experimental biosorption data. The yeast impregnated cellulose adsorbent could be regenerated using sodium hydroxide. Yeast and cellulose are non-toxic, inexpensive and easily obtainable and this lucid methodology provides a sustainable alternative for chromium remediation. [ABSTRACT FROM AUTHOR]

Inthis work, we present an interesting method for the adsorption ofHg(II) involving its interaction with cellulose and mercaptobenzothiazole(MBT). This affinity could be realized with cellulose and MBT actingas host and guest in the first instance followed by the subsequentcomplexation of Hg(II) with MBT. The soft–soft interactionbetween Hg(II) and sulfur enhances the effective complexation withMBT. The favorable experimental conditions, isotherm models, mechanismof interaction, and thermodynamics are discussed. The negative valuesof free energy obtained at various temperatures and the endothermicadsorption process affirms the spontaneity of adsorption. FT-IR, SEM,EDS, and XRD techniques were utilized to characterize the MBT impregnatedcellulose as well as the Hg(II)-loaded adsorbent. With a high adsorptioncapacity of 204.08 mg g–1a sample volume of 500mL could be quantitatively treated by column method. Potassium thiocyanatefunctions as a valuable reagent for the desorption of Hg(II). Thepractical application was tested for the adsorption of mercury vaporemanating from a used Compact Fluorescent Lamp (CFL). [ABSTRACT FROM AUTHOR]