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.

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.

Biosorption of reactive black 5 by Corynebacterium glutamicum biomass immobilized in alginate and polysulfone matrices.

Corynebacterium glutamicum, a lysine fermentation industry waste, showed promise for the removal of Reactive black 5 (RB5). Due to practical difficulties in solid-liquid separation, the free biomass was immobilized in two polymer matrices: calcium alginate and polysulfone. Initially, the optimization of biomass loading in polymeric beads and bead dosage were examined. Of the different combinations examined, 4% (with bead dosage of 2 g per 40 ml) and 14% (with bead dosage of 1 g per 40 ml) in the case of alginate and polysulfone beads, respectively, were identified as the optimal conditions. According to the Langmuir model, at pH 1, the maximum RB5 uptakes of 352, 282 and 291 mg g(-1) were observed for free, alginate and polysulfone-immobilized biomass, respectively. According to the Weber-Morris model, intraparticle diffusion was found to be the potential rate limiting step for the immobilized beads. Regeneration experiments, with 0.01 M NaOH and Na(2)CO(3) as eluents, revealed that polysulfone beads exhibited invariable RB5 uptake capacity and very high mechanical stability even at the end of twentieth cycle, confirming the technical feasibility of the biosorption process for industrial applications.

Biosorption of cadmium by various types of dried sludge: an equilibrium study and investigation of mechanisms.

Batch equilibrium sorption experiments were used for screening for cost-effective four types of sludge, which were DWS (drinking water treatment plant sludge), LLS (landfill leachate sludge), ADSS (anaerobically digested sewage sludge), and SS (sewage sludge). SS removed cadmium most efficiently from aqueous solution (0.38 mmol/g), and showed the highest desorption efficiency (26.3%). Only the SS can be fitted by Langmuir isotherm model (r2 = 0.996). The FT-IR spectra of SS and cadmium loaded SS indicated that carboxyl groups were major binding sites of cadmium binding sites. In kinetic experiment, it was found that the uptake of the metal by the SS was accompanied with proton release, indicating that the metal binding occurs via an ion exchange as well as by electrostatic interaction between carboxylate groups and cadmium ions. This sorbent may have a potential for use as high-value biosorbent of heavy metals and it deserves further investigations into the details of practical application, for example on the development of desorption methods and on sorption process optimization.