Sun Beom Choi

Removal of 1-ethyl-3-methylimidazolium cations with bacterial biosorbents from aqueous media

This study aims to determine whether biosorption can be used for the removal of ionic liquids (ILs), especially their cationic parts, from aqueous media. As a model IL, 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) was used. Five types of bacterial biosorbents were prepared from fermentation wastes through chemical modification of the bacterial surface. Screening study was performed to compare the cationic [EMIM] biosorption capacity among the bacterial biosorbents, indicating that the succinated Escherichia coli biomass (SB-E) was the best biosorbent for removing [EMIM] cations. The [EMIM] biosorption performance of SB-E was evaluated in detail through various experiments. The optimal pH range for [EMIM] biosorption was from 7 to 10, and biosorption equilibrium was reached within 10 min. The maximum uptake of SB-E was also estimated to be 72.6 mg/g. Moreover, [EMIM] cations were easily desorbed from [EMIM]-sorbed SB-E by adding acetic acid.

Binding sites and mechanisms of cadmium to the dried sewage sludge biomass

The Cd biosorption on the dried sewage sludge biomass were experimentally evaluated and mathematically modeled at different pH values. The potentiometric titration of the biomass was well fitted by the four-site model, which consists of three-negative and one-positive sites. The main functional groups were identified through the FTIR study. The pH edge study showed that both the carboxyl and phosphonate groups played an important role in the binding of Cd. From the dynamic biosorption experiments, the H(+)/Cd(2+) exchange ratios at pH 4, 5 and 6 were estimated; thereby the binding mechanisms were established to be complexation with carboxyl and phosphonate groups. Finally, biosorption model was developed based upon the binding mechanism, which was successfully applied for predicting the isotherms and pH edges. Using the developed model equation, the contribution of each functional group on Cd binding could be predicted and visualized.

On the reason why acid treatment of biomass enhances the biosorption capacity of cationic pollutants

The present work is aimed at understanding the effect of acid treatment and demonstrating the reason for its effect. For this, Corynebacterium glutamicum biomass was used as a model biomass. Two cationic (cadmium and Methylene Blue) and one anionic (Reactive Red 4) pollutants were used to evaluate the sorption capacity by the biomass. Isotherm experiments showed that acid treatment of the biomass increased the uptake of the cationic pollutants, but decreased that of the anionic pollutant. Through the results of FTIR and potentiometric titrations, it was found that carboxyl groups on the biomass increased after acid treatment. The carboxyl groups seem to be generated likely through hydrolysis of esters in the biomass under the acidic condition. Therefore, increase of the carboxyl groups provided the binding sites for cationic pollutants, whereas it may interfere with the binding of anionic pollutants.