Potentiometric titration data on the enhancement of sorption capacity of surface-modified biosorbents: functional groups scanning method

In the present study, the relationship between the amount of anionic or cationic binding sites and adsorption capacities of biosorbents is discussed through potentiometric titration and mathematical model equations (proton-binding models). The poly(acrylic) acid-modified biomass (PAAB) and polyethylenimine-modified biomass (PEIB) derived from raw biomass (RB) Corynebacterium glutamicum (C. glutamicum) were used as cationic and anionic binding site-enhanced biosorbents, respectively. To obtain the sorption capacities of biomasses for anionic and cationic pollutants, isotherm tests were carried out using Basic Blue 3 (BB3, at pH 9) and Reactive Red 4 (RR4, at pH 2) as model anionic and cationic pollutants, respectively. The maximum sorption capacity (q_m) of PAAB was 1.28 times higher than RB for BB3. In the case of PEIB, the sorption capacity was found to be 3.27 times higher than RB for RR4. A quantitative information of functional groups could be estimated by the application of proton-binding models to potentiometric titration results. In addition, the buffering capacities of functional groups were obtained from the parameters of pK models. An increasing ratio of sorption capacities was similar to that of the buffering capacities of modified biosorbents obtained from all conditions of pK models. Therefore, the fact that the sorption capacity of modified biomass can be predicted by comparing it with the buffering capacity of biosorbents was confirmed.