Sung Wook Won

Biosorbents for recovery of precious metals

Biosorption is a promising technology not only for the removal of heavy metals and dyes but also for the recovery of precious metals (PMs) from solution phases. The biosorptive recovery of PMs from waste solutions and secondary resources is recently getting paid attractive attention because their price is increasing or fluctuating, their available deposit is limited and maldistributed, and high-tech industries need more consumption of PMs. The biosorbents for recovery of PMs require specifications which differ from those for the treatment of wastewaters containing heavy metals and dyes. In this review, the previous works on biosorbents and biosorption for recovery of PMs were summarized. Especially, we discuss and suggest the required specifications of biosorbents for recovery of PMs and strategies to give the required properties to the biosorbents. We believe this review will provide useful information to scientists and engineers and hope to give insights into this research frontier.

Cationic polymer-immobilized polysulfone-based fibers as high performance sorbents for Pt(IV) recovery from acidic solutions.

This work reports a novel concept for the development of a polysulfone (PS)-based fiber as a high-performance acid-tolerant adsorbent for the recovery of platinum group metals (PGMs), particularly Pt(IV), in acidic media. Polyethylenimine (PEI)-coated PS-Escherichia coli biomass composite fiber (PEI-PSBF) was prepared by spinning biomass-PS blends in water, coating with PEI and cross-linking with glutaraldehyde. The E. coli biomass on the fiber was executed as a functional group donor for binding PEI. PS fiber (PSF), PS-biomass composite fiber (PSBF), and PEI-modified PSF (PEI-PSF) were also prepared and compared with PEI-PSBF. The results of SEM and FTIR analyses revealed the presence of PEI on the surface of PEI-PSBF. Kinetic and isotherm experiments showed the negligible sorption capacity of PSF. In contrast, adsorption equilibrium on PSBF and PEI-PSBF was attained after 40 min and 6h, respectively. The maximum Pt(IV) uptake of PEI-PSBF was 6.6 times higher than that of PSBF. Pt(IV) ions were completely recovered from loaded PEI-PSBF by 0.1M thiourea in 1M HCl solution. The PEI-PSBF was also stable in 0.1M and 1M HCl solutions. The PEI-PSBF exhibited promising properties as an adsorbent for PGMs-containing acidic wastewaters.

The role of biomass in polyethylenimine-coated chitosan/bacterial biomass composite biosorbent fiber for removal of Ru from acetic acid waste solution

The present study is aimed at understanding the role of bacterial biomass in functionalizing polyethylenimine (PEI)-coated bacterial biosorbent fiber (PBBF). To make PBBF, chitosan/biomass composite fiber was coated with PEI and then cross-linked by glutaraldehyde. The role of biomass in the fiber was investigated through sorption experiments and SEM, FTIR and XPS analyses with differently prepared fiber sorbents. In the case that the chitosan fiber was made without the biomass, it could not be coated with PEI. Meanwhile, the chitosan/biomass composite fiber could successfully coated with PEI and primary amine groups were significantly increased on the surface of the fiber. Therefore, the biomass should be essential to make PEI-reinforced chitosan fiber.

Adsorptive characteristics of the polyurethane-immobilized Corynebacterium glutamicum biosorbent for removal of Reactive Yellow 2 from aqueous solution

Polyurethane (PU) was evaluated for its possibility as an immobilization matrix for the raw biomass of Corynebacterium glutamicum. Initially, different blending ratios of the raw biomass to PU weight were tested, and the ratio of 7: 3 was identified as the optimal condition. PU-immobilized biosorbent (PUIB) with a particle size ranging from 0.425 to 0.18mm was selected for the adsorption of Reactive Yellow 2 (RY2). The uptake of RY2 on the PUIB was favorable at acidic pH, especially below 3. According to the Langmuir model, the maximum RY2 uptakes were estimated to be 104.0, 93.3, and 87.3mg/g at pH 2, 3, and 4, respectively. The pseudo-first-order and pseudo-secondorder models were applied to fit the biosorption kinetic data; the latter model fitted the data well with a high coefficient of determination (R2) and low average percentage error (ε) values. The RY2-sorbed PUIB was able to be regenerated and reused for five cycles of the adsorption and desorption processes.

Polyethylenimine-coated polysulfone/bacterial biomass composite fiber as a biosorbent for the removal of anionic dyes: Optimization of manufacturing conditions using response surface methodology

This study aim was to optimize the manufacturing conditions polyethylenimine-coated polysulfone/bacterial biomass composite fiber (PEI-PSBF) to remove anionic pollutants from aqueous solution. The contents of biomass, PEI, and glutaraldehyde (GA) were selected as independent variables, and the response was defined as Reactive Yellow 2 (RY2) uptake. The manufacturing conditions were optimized by response surface methodology (RSM) with the full factorial central composite design (CCD). The determined coefficient of determination (R2) value of the reduced quadratic model was 0.9551, and the optimal manufacturing conditions were predicted as 4.145 g of biomass, 1.104 g of PEI and 3.9 μL of GA, at where the predicted RY2 uptake was 543.78 mg/g. For validating the RSM-predicted results, the RY2 sorption capacity of the optimized PEI-PSBF was evaluated through isotherm experiments. The experimentally confirmed maximal uptake was comparable to predicted one. From these studies, the manufacturing conditions for PEI-PSBF were well optimized and its sorption capacity was 3.83 times higher than that of the PSBF.

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.