John Kwame Bediako
Chonbuk National University
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Publication
Featured researches published by John Kwame Bediako.
Journal of Hazardous Materials | 2015
John Kwame Bediako; Wei Wei; Sok Kim; Yeoung-Sang Yun
In this study, an outstanding performance of chemically modified waste Lyocell for heavy metals treatment is reported. The sorbent, which was prepared by a simple and concise method, was able to bind heavy metals such as Pb(II), Cu(II) and Cd(II), with very high efficiencies. The binding mechanisms were studied through adsorption and standard characterization tests such as scanning electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses. Adsorption kinetics was very fast and attained equilibrium within 5 min in all metals studied. The maximum single metal uptakes were 531.29±0.28 mg/g, 505.64±0.21 mg/g, and 123.08±0.26 mg/g for Pb(II), Cd(II) and Cu(II), respectively. In ternary metal systems, Cu(II) selectivity was observed and the underlying factors were discussed. The sorbent by its nature, could be very effective in treating large volumes of wastewater with the contact of very little amount.
Journal of Hazardous Materials | 2016
Wei Wei; Shuo Lin; D. Harikishore Kumar Reddy; John Kwame Bediako; Yeoung-Sang Yun
Poly(styrenesulfonic acid)-impregnated alginate capsule (PSSA-AC) was prepared using a simple fabrication process, and used for selective separation of Pd(II) and Pt(IV) from their mixture. Evaluation of the pH effect revealed that PSSA-AC had good Pd(II) selectivity especially when the pH was between 3 and 5 at which neutral species Pd(OH)2 are present. Experiments on metal penetration through the Ca(2+)-alginate film showed that anionic species hardly penetrate through the alginate film (acting as an ionic barrier). The selective sorption mechanism is proposed as the following steps: (1) selective penetration of the neutral Pd(OH)2 through the ionic barrier (Ca(2+)-alginate shell) and then (2) chelation reaction of the neutral Pd(OH)2 with the SO3(-) groups of PSSA in the core. The maximum Pd(II) uptake was 291.19±17.48mg/g, which was about 32 times higher than that of Pt(IV). The results of the sorption/desorption test indicated that the PSSA-AC has good reusability potential. Even through one cycle of sorption/desorption, Pd(II) and Pt(IV) were successfully separated from their mixture with significantly high purities of 98.65% Pd(II) and 98.71% Pt(IV). This study reports for the first time the feasibility and potential of ionic barrier-based sorbents as selective separation of precious metals which have different speciations.
Journal of Hazardous Materials | 2017
Myung-Hee Song; Sok Kim; D. Harikishore Kumar Reddy; Wei Wei; John Kwame Bediako; Sang-Won Park; Yeoung-Sang Yun
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.
Journal of Materials Chemistry | 2017
Shuo Lin; D. Harikishore Kumar Reddy; John Kwame Bediako; Myung-Hee Song; Wei Wei; Jeong-Ae Kim; Yeoung-Sang Yun
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.
Science of The Total Environment | 2018
Jong-Won Choi; Yufeng Zhao; John Kwame Bediako; Chul-Woong Cho; Yeoung-Sang Yun
TCAs are known to be toxicants and endocrine disrupting agents. Generally, after being used, TCAs are passed through wastewater treatment plants (WWTPs) to be treated. However, still trace amounts (ng/L to μg/L) of TCAs have been founded even in the treated water. Therefore, the aim of this study is to elucidate the environmental behaviors of TCAs in the sewage water from WWTPs (Jeonju, Korea). For the experiments, seven TCAs (amitriptyline, imipramine, clomipramine, desipramine, protriptyline, nortriptyline, and doxepin) were selected. Hydrolysibility, biodegradability, and adsorbability of the selected seven TCAs were evaluated. Based on the results, it was concluded that TCAs are not readily hydrolyzed in water and also not biodegraded by aerobic sludge. The 60% to 85% of TCAs were adsorbed immediately onto the activated sludge within 1 s via electrostatic and hydrophobic interactions. It was clearly observed that adsorption affinities were dependent on the types of activated sludge (i.e. anaerobic and aerobic sludge). The affinities of aerobic and anaerobic sludge towards the TCAs at trace concentrations e.g., 1 to 10 μg/L, were estimated to be in the range from 0.021 ± 0.000 to 0.087 ± 0.000 L/μg and from 0.001 ± 0.000 to 0.108 ± 0.001 L/μg, respectively.
Journal of Hazardous Materials | 2018
Yufeng Zhao; Jong-Won Choi; John Kwame Bediako; Myung-Hee Song; Shuo Lin; Chul-Woong Cho; Yeoung-Sang Yun
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.
Clean Technologies and Environmental Policy | 2018
Sok Kim; Chul Woong Cho; Myung-Hee Song; John Kwame Bediako; Yeoung-Sang Yun; Yoon-E Choi
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.
Solid State Phenomena | 2017
Myung Hee Song; D. Harikishore Kumar Reddy; John Kwame Bediako; Shuo Lin; Yeoung Sang Yun
Magnetic MnFe2O4 nanoparticles (MNPs) were fabricated and entrapped in amine-rich chitosan (CS) sorbents containing multi-walled carbon nanotubes (MWCNTs) or polyethyleneimine (PEI). Magnetic polymer composite sponges (MPCSs) and magnetic polymer composite fibers (MPCFs) were prepared through mixing each of MWCNT and PEI with MNPs-CS solution. The successful fabrication of MPCSs and MPCFs was confirmed through FTIR and VSM analyses. The as-fabricated MPCSs and MPCFs were used for adsorptive recovery of Pt (IV) from acidic solution. The maximum uptakes of Pt (IV) ions by the MPCSs and MPCFs were estimated to be 218.2 ± 8.3 and 371.4 ± 16.8 mg/g, respectively. Moreover, the Pt (IV)-loaded MPCSs and MPCFs were easily separated from aqueous solution under magnetic field after sorption process.
Solid State Phenomena | 2017
John Kwame Bediako; Myung Hee Song; Yeoung Sang Yun
High-capacity polyethylenimine (PEI)/Ca-alginate blended hydrogel fibers were fabricated via three steps, viz. electrostatic blending of PEI and alginate, ionotropic gelation of alginate and CaCl2, and fixing of PEI into the Ca-alginate matrix, using glutaraldehyde (GA) as a crosslinker. Two crosslinking approaches resulted in different stabilities and gold uptake capacities of the prepared sorbents. Post-crosslinking approach was more efficient than pre-crosslinking likely owing to the better crosslinking efficiency, leading to better stability and sorption capacity. Furthermore, X-ray diffraction (XRD) study revealed the reduction of Au (III) to metallic gold, Au (0) in the crosslinked fibers. The Au (0) predominancy was confirmed with a metal desorption study. The present study thus demonstrates the possibility of recovering metallic gold from aqueous solutions by direct adsorption-coupled-reduction approach using GA-crosslinked PEI/Ca-alginate fibers.
Journal of Molecular Liquids | 2016
Wei Wei; Chul-Woong Cho; Sok Kim; Myung-Hee Song; John Kwame Bediako; Yeoung-Sang Yun