Supercapacitor performance of carbon supported Co₃O₄ nanoparticles synthesized using Terminalia chebula fruit

Edison, T.N.J.I.,Atchudan, R.,Sethuraman, M.G.,Lee, Y.R. Elsevier BV ; C/o Dept. of Chemical Engineering, N 2016 JOURNAL- TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Vol.68 No.-

Carbon supported cobalt oxide nanoparticles (Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs) were synthesized by simple thermolysis of cobalt(II) acetate tetrahydrate and Terminalia chebula (T. chebula) fruit. The synthesized Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs were characterized using attenuated total reflection conjunction with Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) techniques. The specific surface area of Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs was measured by N<SUB>2</SUB> adsorption-desorption isotherm. The ATR-FTIR analysis revealed that the phytoconstituents of T. chebula were carbonized and supports the Co<SUB>3</SUB>O<SUB>4</SUB> NPs. The synthesized Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs were highly crystalline with carbon support, exposed by the XRD patterns. As inferred from microscopic images, the particle size of Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs is in the range of 15-25nm with distorted spherical shape. The EDS results confirmed the presence of three major elements such as Co, O and C in the synthesized Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs. The calculated specific surface area of Co<SUB>3</SUB>O<SUB>4</SUB> NPs is 22m<SUP>2</SUP>/g. The supercapacitor performance of synthesized Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs in 2M aqueous KOH was analyzed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) methods. The Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs showed a maximum specific capacitance of about 642F/g at 1 A/g of discharging current density between 0 and 0.50V (vs. Ag/AgCl). The high specific capacitance of Co<SUB>3</SUB>O<SUB>4</SUB>Γ NPs could be attributed to the combination of both double layer capacitance and pseudocapacitance.

Novel improvement of CO₂ adsorption capacity and selectivity by ethylenediamine-modified nano zeolite

Pham, T.H.,Lee, B.K.,Kim, J. Elsevier BV ; C/o Dept. of Chemical Engineering, N 2016 JOURNAL- TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Vol.66 No.-

In this study, nano zeolite (NZ) was modified with ethylenediamine (EDA) to improve the CO<SUB>2</SUB> adsorption-desorption properties. The CO<SUB>2</SUB> adsorption capacity of NZ-EDA increased as the temperature was increased from 20<SUP>o</SUP>C to 70<SUP>o</SUP>C, but then decreased as the temperature was further increased from 70 <SUP>o</SUP>C to 100<SUP>o</SUP>C. The CO<SUB>2</SUB> adsorption capacity of NZ-EDA was 7.48mmol/g, which is 2.6-fold more than that by NZ. The mechanism of CO<SUB>2</SUB> adsorption onto NZ is entirely physical interaction. With NZ-EDA, however, chemical interaction between CO<SUB>2</SUB> and NZ-EDA becomes the key adsorption mechanism. The adsorption selectivity of CO<SUB>2</SUB> over N<SUB>2</SUB> by NZ-EDA was influenced by temperature and peaked at 56.01 at 50<SUP>o</SUP>C. The cyclic adsorption and desorption of CO<SUB>2</SUB> showed that the adsorbed CO<SUB>2</SUB> could be desorbed from the surface of NZ at 60<SUP>o</SUP>C and NZ-EDA at 85<SUP>o</SUP>C. The adsorption-desorption percentages of NZ and NZ-EDA remained above 80% even after 15 cycles. This stability of CO<SUB>2</SUB> adsorption-desorption characteristics after repeated cycling indicates that NZ-EDA can be a cost-effective sorbent for CO<SUB>2</SUB> capture.

Continuous treatment of dairy effluent in a downflow anaerobic filter packed with slag grains: Reactor performance and kinetics

Jo, Y.,Kim, J.,Lee, C. Elsevier BV ; C/o Dept. of Chemical Engineering, N 2016 JOURNAL- TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Vol.68 No.-

A downflow anaerobic filter packed with blast-furnace slag (BFS) grains was evaluated for treating cheese whey, a high-strength dairy effluent. The reactor demonstrated effective and stable biomethanation of whey in continuous mode without pH control. The chemical oxygen demand (COD) removal remained at around 80%, with the reactor pH being maintained neutral without buffering, in the organic loading rate (OLR) range of 0.8-2.4g COD/l@?d. Although the COD removal decreased down to below 60% at higher OLRs along with acid accumulation, the methane production rate continued to increase with increasing OLR. On the other hand, the methane yield was maintained at 0.28-0.34l/g COD throughout the experiment. The substrate removal and methane production kinetics were successfully described by the modified Stover-Kincannon model. The overall results suggest that BFS grains could be used as economic filter media for anaerobic treatment of cheese whey and other easily acidifying waste streams.

Understanding the synergistic between optimum dopant loading and charge transfer kinetics in platinum-mediated nanostructured hematite thin films

Phuan, Y.W.,Chong, M.N.,Egamparan, K.,Lee, B.K.,Zhu, T.,Chan, E.S. Elsevier BV ; C/o Dept. of Chemical Engineering, N 2016 Journal of the Taiwan Institute of Chemical Engine Vol.66 No.-

Photoelectrochemical (PEC) water splitting process has received immense attention owing to its ability in sustainably producing solar hydrogen from water. The main aim of this study was to systematically optimise the Platinum (Pt) dopant loadings and understand its synergistic role in enhancing the photoactivity in nanostructured hematite (α-Fe<SUB>2</SUB>O<SUB>3</SUB>) thin films. Through the optimisation study, it was found the 3mol% Pt-doped nanostructured hematite thin film exhibited the highest photocurrent density of 0.91mA/cm<SUP>2</SUP> at 0.7V vs Ag/AgCl in 1M NaOH. In comparison with the bare hematite film, this was a 3-fold enhancement in terms of measured photocurrent density. Such an enhancement in the measured photocurrent density was attributed to the increased donor density caused due to the incorporation of optimum Pt dopant. Further EIS analysis revealed that the flat-band potential of hematite was shifted to a more negative potential by 30mV while the charge transfer resistance was considerably reduced through the incorporation of Pt dopant. All these suggested that the successful doping of optimum Pt loading will lead to a visible active, lower charge transfer resistance and an enhanced separation efficiency of the photogenerated charge carriers in nanostructured hematite thin films.

Application of chlorine dioxide (ClO₂) to reverse osmosis (RO) membrane for seawater desalination

Oh, J.H.,Jang, A. Elsevier BV ; C/o Dept. of Chemical Engineering, N 2016 Journal of the Taiwan Institute of Chemical Engine Vol.68 No.-

There are justifiable concerns about reverse osmosis (RO) performance deterioration and carcinogenic by-products from disinfection in water treatment facilities. Traditional disinfectant chlorine (Cl<SUB>2</SUB>) has been replaced with stable and safe disinfection processes. Chlorine dioxide (ClO<SUB>2</SUB>) as an alternative disinfectant has been increasingly adopted in various water treatment facilities. To identify the applicability of ClO<SUB>2</SUB> to RO desalination process, lab-scale experiments were designed by simulating actual oxidant exposure circumstances. In the experiment, Cl<SUB>2</SUB> or ClO<SUB>2</SUB> solution was injected separately into a working RO system. Our results showed that Cl<SUB>2</SUB> dosage greatly decreased permeate flux slope. However, instant flux increase of approximately 5% was observed when ClO<SUB>2</SUB> was injected. ATR FT-IR and EDX analysis for exposed membranes showed that Cl<SUB>2</SUB> deformed amide peaks and attached Cl atom onto the membrane, indicating chlorination. However, none of these results was observed in ClO<SUB>2</SUB> exposure cases. In addition, immediate sodium bisulfite application alleviated flux decrease under Cl<SUB>2</SUB> chlorination.

Controlled synthesis of heterostructured Ag&n.diameter;gI/ZnS microspheres with enhanced photocatalytic activity and selective separation of methylene blue from mixture dyes

Reddy, D.A.,Choi, J.,Lee, S.,Kim, T.K. Elsevier BV ; C/o Dept. of Chemical Engineering, N 2016 Journal of the Taiwan Institute of Chemical Engine Vol.66 No.-

Novel heterostructured Ag&n.diameter;gI/ZnS microspheres were fabricated through a soft chemical route using polyvinylpyrrolidone (PVP). Their formation was confirmed by SEM, TEM, XRD, XPS, and FTIR analyses, which revealed that the Ag&n.diameter;gI/ZnS nanocomposites comprised Ag, AgI, and ZnS nanoparticles. Luminescence quenching in the Ag&n.diameter;gI/ZnS nanocomposites indicated that the hetero-junction between Ag&n.diameter;gI and ZnS effectively accelerated charge separation and transferred electrons from the AgI to Ag and ZnS nanostructures. The photocatalytic activity was evaluated via the decomposition of organic dyes and phenol oxidation under simulated sunlight irradiation. All the Ag&n.diameter;gI/ZnS heterostructures exhibited better photocatalytic performance than the pure AgI and ZnS nanostructures. Ag&n.diameter;gI-ZnS (5wt%) possesses the optimal photocatalytic degradation efficiency, and colorless phenol oxidation performance. More specifically, in the presence of the nanocomposite, 95% degradation rate was achieved within 80min of sunlight irradiation, while AgI, only reached 64.12%. The enhanced photocatalytic activity is associated with effective transfer and separation of photogenerated electron-hole pairs at the interface of the Ag&n.diameter;gI/ZnS nanocomposite because of their matching band positions. The nanocomposites exhibit good photocatalytic stability with almost no loss of photocatalytic activity after five recycles. These nanostructures show the best catalytic activity for selective separation of methylene blue (MB) dye from mixed organic dyes. Photocatalytic experiments with MB-RhB as the target pollutants, within 70min of irradiation time 96.44% of MB and 64.68% of RhB were degraded, and the rate constants were 0.044 and 0.013min<SUP>-1</SUP> for RhB and MB, respectively. MB-MO as the target pollutant within 80min of irradiation time, 95.29% of the MB and 41.37% of the RhB were degraded. The rate constants were 0.031 and 0.005min<SUP>-1</SUP> for MB and MO, respectively. This work will promote further interest in the fabrication of various heterostructured nanocomposites and their applications as sunlight-driven photocatalysts for purifying polluted water resources.