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)