Myung-Hee Song

Selective biosorption behavior of Escherichia coli biomass toward Pd(II) in Pt(IV)–Pd(II) binary solution

This study reports a new finding that the industrial waste biomass of Escherichia coli is capable of selective binding of Pd(II) in the Pd(II)-Pt(IV) bimetal solution. Batch sorption experiments with E. coli were carried out at different initial metal concentrations in single and bimetal systems. In the single metal systems, the maximum sorption capacities of E. coli for Pt(IV) and Pd(II) were found to be 45.65 ± 2.04 and 38.87 ± 2.08 mg/g, respectively. Meanwhile, in the bimetal system, the maximum sorption capacities for Pd(II) and Pt(IV) were 33.16 ± 1.53 and 7.32 ± 0.29 mg/g, respectively, which corresponded to 4.53 times of selective adsorption toward Pd(II). In order to understand the underlying reason, ion exchange resins (TP214 and Amberjet 4200) with different amine types were compared with the E. coli biomass. As a result, it was found that the sorbents containing primary amine groups could selectively adsorb Pd(II) more easily in the binary mixture.

Development of polyethyleneimine-loaded core-shell chitosan hollow beads and their application for platinum recovery in sequential metal scavenging fill-and-draw process

Polyethyleneimine (PEI)-loaded chitosan hollow beads (CHBs) were fabricated through the ionotropic gelation process using sodium tripolyphosphate (TPP) as a counter polyanion. The CHBs were loaded with hydrophilic PEI in pre- and/or post-loading methods. Hence, the sorbent could possess a large number of amine groups which were able to function as the binding sites to recover platinum metal ions. The enhancement of the amine groups was confirmed by Fourier transform infrared spectroscopy (FTIR). Isotherm and kinetic studies were carried out to evaluate the sorption performance of the sorbents. The maximum Pt(IV) uptake by the PEI-loaded CHBs was estimated to be 815.2±72.6mg/g, which was much higher than that of a commercial ion exchange resin, Lewatit® MonoPlus TP214 (330.2±16.6mg/g). A sequential metal scavenging fill-and-draw process was operated using the PEI-loaded CHBs sorbents for ten cycles and the Pt(IV) recovery efficiency was kept above 97.4% even after the last cycle. These results indicated that the ionic polymer-loaded hydrogel hollow beads can be a novel platform to design high-performance sorbents able to recover and/or scavenge anionic precious metal ions even from trace metal solutions.

Fabrication of Stable and Regenerable Amine Functionalized Magnetic Nanoparticles as a Potential Material for Pt(IV) Recovery from Acidic Solutions

MnFe2O4@SiO2-NH2 magnetic nanocomposite (AFMNC) adsorbent with a particle size of ∼50 nm was successfully synthesized using a facile approach. The as-prepared composite particles showed a fast binding of Pt(IV) with easy magnetic solid-liquid separation. The kinetic data were fitted to both pseudo-first and second-order rate models, indicating that AFMNC exhibited a much higher rate of Pt(IV) binding (0.125 g mg-1 min-1) compared to that of commercial ion-exchange resin Amberjet 4200 (0.0002 g mg-1 min-1). The equilibrium adsorption data were fitted to the Langmuir isotherm model with a relatively high sorption capacity of 380 mg/g. Scanning transmission electron microscopy analysis demonstrated the presence of platinum chloride after sorption on AFMNC, suggesting an adsorbate-adsorbent anion-exchange interaction. In addition, due to its magnetic characteristics, AFMNC can be easily separated from the aqueous medium after the sorption process. The novel nanocomposite may facilitate recovery of Pt(IV) from waste solutions.

Effective adsorption of Pd(II), Pt(IV) and Au(III) by Zr(IV)-based metal–organic frameworks from strongly acidic solutions

Separation of precious metal ions from acidic solutions is of great importance due to their cumulative supply risk and environmental concern. However, their separation is still challenging as they are often present in extremely low pH solutions. Metal–organic frameworks (MOFs) have attracted extensive curiosity for adsorption owing to their fascinating physicochemical features including tunable pore sizes, active functional sites, and porosity. Here, two Zr-based MOFs of UiO-66 and UiO-66-NH2 with an 8-ligand-connected Zr6 node were fabricated and tested for adsorption of Pd(II), Pt(IV) and Au(III) anions (PdCl42−, PtCl62− and AuCl4−) in strongly acidic solutions. Both MOFs were tested for uptake time and adsorption capacities and showed rapid and high precious metal adsorption performances. Inner-sphere complexation between the precious metal anions and the incompletely coordinated Zr atoms in the MOFs was the key mechanism involved in the precious metal adsorption. In the case of UiO-66-NH2, additional electrostatic attraction was found between the protonated amine group (–NH3+) and the precious metal anions, as well as partial reduction of the bound precious metal ions. Moreover, the pathway of adsorption–reduction–crystallization–precipitation for the interaction of UiO-66-NH2 and AuCl4− resulted in extremely high recovery efficiency for gold.

Three degradation pathways of 1-octyl-3-methylimidazolium cation by activated sludge from wastewater treatment process.

The biodegradability and degradation pathways of 1-octyl-3-methylimidazolium cation [OMIM](+) by microbial community of wastewater treatment plant in Jeonju city, Korea were investigated. It was found that [OMIM](+) could be easily degraded by the microbial community. New degradation products and pathways of [OMIM](+) were identified, which are partially different from previous results (Green Chem. 2008, 10, 214-224). For the analysis of the degradation pathways and intermediates, the mass peaks observed in the range m/z of 50-300 were screened by using a tandem mass spectrometer (MS), and their fragmentation patterns were investigated by MS/MS. Surprisingly, we found three different degradation pathways of [OMIM](+), which were separated according to the initially oxidized position i.e. middle of the long alkyl chain, end of the long alkyl chain, and end of the short alkyl chain. The degradation pathways showed that the long and short alkyl chains of [OMIM](+) gradually degraded by repeating oxidation and carbon release. The results presented here shows that [OMIM](+) can be easily biodegraded through three different degradation pathways in wastewater treatment plants.

Adsorptive interaction of cationic pharmaceuticals on activated charcoal: Experimental determination and QSAR modelling

Due to high mobility and specific toxic actions of the ionizable pharmaceuticals in surface water with a normal range of pH, the pharmaceuticals should be removed before being discharged. Therefore, this study investigated the adsorptive interactions between cationic pharmaceuticals and a popular adsorbent (i.e., activated charcoal) frequently used in water treatment processes. For that, we performed isotherm experiments and then the results were plotted by Langmuir model to determine the adsorption affinity (b) and capacity (qm). Afterwards, to interpret the adsorption behaviors, two simple prediction models were developed based on quantitative structure-activity relationships (QSAR). In the modelling, molecular weight (MW), polar surface area (PSA), and octanol-water partitioning coefficient (log P) were used as model parameters. In the results, the combinations of these three parameters could predict the adsorption affinity and capacity in R2 of 0.85 and 0.80, respectively. The robustness of models was validated by leave-one-out cross-validation (Q2LOO) and the estimated Q2LOO values were 0.60 and 0.55 for the adsorption affinity and capacity, respectively, which are higher than the acceptability of standard i.e., 0.5.

Fabrication of high performance amine-rich magnetic composite fibers for the recovery of precious Pt(IV) from acidic solutions

Magnetic nanoparticles (MNPs) possessing a high surface to volume ratio, copious chemically active sites, and ease of separation from aqueous solutions are emerging materials for water treatment. Further encapsulation of these nanoparticles (NPs) with polymeric materials may protect these NPs from direct contact with the aqueous environment and also enhance their sorption efficiency. In the case of polymer fibers, breakage will occur depending on environmental conditions, and the addition of MNPs in fibers will provide an opportunity for the complete recovery of fibers after the sorption process. In the present study, a mixed solution of amine-rich chitosan (CS) and polyethyleneimine (PEI) containing magnetic MnFe2O4 nanoparticles was utilized for fabricating versatile and robust magnetic polymer composite fibers (MPCFs) in a facile methodology. The effective fabrication of MPCFs was confirmed by using analytical techniques such as FTIR, XRD, VSM, FE-SEM, and TEM. Morphological characterization demonstrated that MnFe2O4 nanoparticles were well distributed in the composite fibers. Detailed batch sorption experiments revealed that MPCFs exhibited significant improvement in adsorption efficiency compared with bare MnFe2O4 nanoparticles. The MPCFs exhibited high adsorption capacity (371.35 ± 16.79 mg g−1) and fast equilibrium (within 30 min). The Pt-loaded MPCFs were easily separated from aqueous solution under an external magnetic field. It can be concluded that MPCFs with amine-rich functional groups and magnetic properties are promising for Pt adsorption from aqueous solutions.

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 (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.