Use of a new zwitterionic cellulose derivative for removal of crystal violet and orange II from aqueous solutions.

This study describes the synthesis of a new bioadsorbent with zwitterionic characteristics and its successful application for removal of a cationic dye (crystal violet, CV) and an anionic dye (orange II, OII) from single component aqueous systems. The new bi-functionalized cellulose derivative (MC3) was produced by chemical modification of cellulose with succinic anhydride and choline chloride to introduce carboxylic and quaternary ammonium functional groups on the cellulose surface. MC3 was characterized by several wet chemical and spectroscopic methods. The effects of solution pH, contact time, and initial solute concentration on removal of CV and OII by MC3 were investigated. Studies of the desorption and re-adsorption of the dyes were also carried out. The isotherms for adsorption of CV and OII on MC3 were satisfactorily fitted using the Konda and Langmuir models. MC3 showed experimental maximum adsorption capacities of 2403 mg g-1 for CV and 201 mg g-1 for OII. The desorption and re-adsorption results showed that MC3 could be reused in successive adsorption cycles, which is essential for minimizing process costs and waste generation. The findings showed that MC3 is a versatile biosorbent capable of efficiently removing both cationic and anionic dyes.

Optimization of cellulose and sugarcane bagasse oxidation: Application for adsorptive removal of crystal violet and auramine-O from aqueous solution.

Cellulose (Cel) and sugarcane bagasse (SB) were oxidized with an H3PO4-NaNO2 mixture to obtain adsorbent materials with high contents of carboxylic groups. The oxidation reactions of Cel and SB were optimized using design of experiments (DOE) and response surface methodology (RSM). The optimized synthesis conditions yielded Cox and SBox with 4.8mmol/g and 4.5mmol/g of carboxylic acid groups, respectively. Cox and SBox were characterized by FTIR, TGA, PZC and solid-state 13C NMR. The adsorption of the model cationic dyes crystal violet (CV) and auramine-O (AO) on Cox and SBox in aqueous solution was investigated as a function of the solution pH, the contact time and the initial dye concentration. The adsorption of CV and AO on Cox was described by the Elovich equation and the pseudo-first-order kinetic model respectively, while the adsorption of CV and AO on SBox was described by the pseudo-second-order kinetic model. Adsorption isotherms were well fitted by the Langmuir and Konda models, with maximum adsorption capacities (Qmax) of 1117.8mg/g of CV and 1223.3mg/g of AO on Cox and 1018.2mg/g of CV and 682.8mg/g of AO on SBox. Desorption efficiencies were in the range of 50-52% and re-adsorption capacities varied from 65 to 81%, showing the possibility of reuse of both adsorbent materials.