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

Clean Technologies and Environmental Policy, May 2018

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 (qm) 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.

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

Potentiometric titration data on the enhancement of sorption capacity of surface‑modified biosorbents: functional groups scanning method Sok Kim 0 Chul Woong Cho 0 Myung‑Hee Song 0 John Kwame Bediako 0 Yeoung‑Sang Yun 0 Yoon‑E Choi 0 0 Division of Semiconductor and Chemical Engineering, Chonbuk National University , Jeonju 54896 , Republic of Korea 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 (qm) 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. Biosorption; Potentiometric titration; Biomass; Surface modification; Biosorbent; Buffering capacity Introduction Biosorption has been introduced as an environmental-friendly and cost-effective method. It can replace conventional methods such as precipitation, membrane filtration, ion exchange, solvent extraction, oxidation, and coagulation for treatment of pollutants in the aqueous effluents (Wei et al. 2015) . In the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10098-018-1542-2) contains supplementary material, which is available to authorized users. Division of Environmental Science and Ecological Engineering, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea biosorption process for the removal of ionic pollutants, various biotic materials such as bacteria, fungi, algae, agricultural, and industrial byproducts, and other biomaterials can be applied as biosorbents (Won et al. 2014) . According to Volesky (2007) , these biomasses possess various functional groups (e.g., carboxyl, amine, hydroxyl, and sulfonate) on their surface. These binding sites can bind ionic materials like metals and dyes by complex physicochemical mechanisms including ion exchange, complexation/coordination, surface precipitation, adsorption, electrostatic interaction, and chelation (Vijayaraghavan and Yun 2008) . Recently, as per the acquired knowledge on biosorption mechanisms, various methods of functional group modification such as addition of binding sites, removal of interfering sites, and coating/composite with ionic polymers have been applied to improve the sorption capacity (Kim et al. 2016a) . Among these modification methods, cases of the sorbents-applied ionic polymers such as polyethylenimine (PEI) (Cho et al. 2016) , poly(allylamine hydrochloride) (PAA HCl) (Mao et al. 2010), and poly(methacrylic acid) (PMA) (Yu et al. 2009) showed a drastic enhancement in the sorption capacity because ionic polymers possess a large number of binding sites in their chemical structures for target pollutants. Since amounts and kinds of binding sites in biosorbents are important factors for determining the sorption capacity of biosorbents, quantitative and qualitative characteristics evaluation of functional groups on the biosorbents should be essential in biosorption research area. To determine the characteristics of functional groups on the biosorbents, various surface analyses including Fourier-transform infrared spectroscopy (FT-IR) (Ramrakhiani et al. 2011) , X-ray photoelectron spectroscopy (XPS) (Kim et al. 2018) , and potentiometric titration methods (Bhatnagar et al. 2012) have been applied. Of these analytical methods, potentiometric titration method can be available for the simultaneous qualitative and quantitative analyses of functional groups in the biosorbents. The potentiometric titration curves of biosorbents present the surface characteristics (pKa positions) depending on the possessed functional groups in the biosorbents (biomasses). In addition, the amounts of functional groups in the biomasses have been estimate (...truncated)


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Sok Kim, Chul Woong Cho, Myung-Hee Song, John Kwame Bediako, Yeoung-Sang Yun, Yoon-E Choi. Potentiometric titration data on the enhancement of sorption capacity of surface-modified biosorbents: functional groups scanning method, Clean Technologies and Environmental Policy, 2018, pp. 1-9, DOI: 10.1007/s10098-018-1542-2