CdS microspheres composed of nanocrystals and their photocatalytic activity.

Rengaraj, Selvaraj,Jee, Sun Hee,Venkataraj, Selvaraj,Kim, Younghun,Vijayalakshmi, Selvaraj,Repo, Eveliina,Koistinen, Arto,Sillanp??, Mika American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.3

<P>A simple and template-free solution phase synthesis method has been developed for the preparation of novel CdS hollow microspheres using cadmium nitrate and thioacetamide precursors. In this manuscript, we demonstrate that process parameters such as the reaction time, precursor ratio, and reaction temperature strongly influence the morphology of the final product. The synthesized products have been characterized by a variety of methods, including X-ray powder diffraction (XRD), Raman spectroscopy, high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray diffraction (EDX) analysis, X-ray photoelectron spectroscopy (XPS), and UV-visible diffused reflectance spectroscopy (UV-DRS). XRD analysis confirmed the cubic structure of the CdS microspheres, which has also been further supported by Raman spectroscopy. The HR-SEM measurements revealed the spherical morphology of the CdS microspheres which has been evolved by the oriented aggregation of the primary CdS nanocrystals. The TEM measurements confirmed the hollow shell-like structure of the spheres; the formation of their hollow interiors can be explained by the Ostwald ripening mechanism. UV-DRS studies showed that the band gap of the CdS microspheres increased with increasing cadmium-nitrate-to-thioacetamide ratio. Furthermore, studies of photocatalytic activity revealed that the synthesized CdS hollow microspheres exhibit an excellent photocatalytic performance in rapidly degrading methyl tert-butyl ether (MTBE) in aqueous solution under visible-light illumination. These results suggest that CdS microspheres will be an interesting candidate for photocatalytic detoxification studies under visible light radiation.</P>

Batch Adsorptive Removal of Copper Ions in Aqueous Solutions by Ion Exchange Resins: 1200H and IRN97H

Selvaraj Rengaraj,최경희,이종협,김영훈,Cheol Kyun Joo 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.1

The removal of copper from aqueous solution by ion exchange resins, such as 1200H and IRN97H, is described. Effect of initial metal ion concentration, agitation time and pH on adsorption capacities of ion exchange resins was investigated in a batch mode. The adsorption process, which is pH dependent, shows maximum removal of copper in the pH range 2-7 for an initial copper concentration of 10 mg/L. The experimental data have been analyzed by using the Freundlich, Langmuir, Redlich-Peterson, Temkin and Dubinin-Radushkevich isotherm models. The batch sorption kinetics have been tested for a first-order, pseudo-first order and pseudo-second order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated. Results showed that the intraparticle diffusion and initial sorption into resins of Cu(II) in the ion exchange resins was the main rate limiting step. The uptake of copper by the ion exchange resins was reversible and thus has good potential for the removal/recovery of copper from aqueous solutions. We conclude that such ion exchange resins can be used for the efficient removal of copper from water and wastewater.

Batch Adsorptive Removal of Copper Ions in Aqueous Solutions by Ion Exchange Resins : 1200H and IRN97H

Rengaraj, Selvaraj,Kim, Younghun,Joo, Cheol Kyun,Choi, Kyunghee,Yi, Jongheop 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.1

The removal of copper from aqueous solution by ion exchange resins, such as 1200H and IRN97H, is described. Effect of initial metal ion concentration, agitation time and pH on adsorption capacities of ion exchange resins was investigated in a batch mode. The adsorption process, which is pH dependent, shows maximum removal of copper in the pH range 2-7 for an initial copper concentration of 10㎎/L. The experimental data have been analyzed by using the Freundlich, Langmuir, Redlich-Peterson, Temkin and Dubinin-Radushkevich isotherm models. The batch sorption kinetics have been tested for a first-order, pseudo-first order and pseudo-second order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated. Results showed that the intraparticle diffusion and initial sorption into resins of Cu(Ⅱ) in the ion exchange resins was the main rate limiting step. The uptake of copper by the ion exchange resins was reversible and thus has good potential for the removal/recovery of copper from aqueous solutions. We conclude that such ion exchange resins can be used for the efficient removal of copper from water and wastewater.

Preparation of nanoporous alumina using aluminum chloride via precipitation templating method for CO adsorbent

염창주,Rengaraj Selvaraj,김영훈 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.67 No.-

A cost-effective preparation method is proposed to prepare nanoporous alumina (NA) using aluminum chloride as a precursor with a lower cost than aluminum butoxide. In addition, the surfactant template was replaced with magnesium stearate, which has a lower unit cost in stearate acid. The adsorption isotherm test for the CO gas was carried out to compare the adsorption performance of the NA adsorbents prepared using post-hydrolysis (NA) and cost-effective precipitation (C-NA). In addition, C-NA exhibited a similar uptake capacity as NA, and the maximum uptake capacity of Pd/C-NA increased 1.3 times via Pd nanodots loading.

Synthesis of paper-based porous gold electrode for electrocatalytic oxidation of ethanol

오승연,Rengaraj Selvaraj,김영훈 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.26 No.-

Herein, to apply porous gold electrode for the electrooxidation of ethanol, we proposed a simple and facile method for the synthesis of paper-based porous gold (PAu) with large surface area using gold nanoparticles (AuNPs) and filter paper. The results showed that Pd/PAu exhibited a large electrochemical surface because of pore size of 100 nm and high electrochemical reaction compared to smooth Au foil and PAu. The as-prepared Pd/PAu electrode exhibited high activity and stability for ethanol electrooxidation in alkaline solution and was reusable even after 100 cycles

Enhancement of visible-light-driven photocatalytic reduction of aqueous Cr(VI) with flower-like In3+-doped SnS2

박성묵,Rengaraj Selvaraj,Mohammed A. Meetani,김영훈 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.45 No.-

Microwave-assisted synthesis is a facile approach for overcoming critical disadvantages of conventionalheating process, such as high temperature/pressure and longer heating/cooling time as well as lowphotocatalytic efficiency. Herein, 3Dflower-like In3+-doped SnS2 (InSnS2) was successfully prepared by amicrowave-assisted solvothermal method. InSnS2 was applied to photocatalytic reduction of aqueous Cr(VI) under LED visible-light. The enhanced photocatalytic activity was attributed to indium doping,which can cause low recombination rate of photogenerated electron–hole pairs. Novel metal depositionon the photocatalyst surface and addition of organic acid as hole scavenger increased photocatalyticefficiency for the reduction of Cr(VI) under LED visible-light irradiation.

Preparation of nanoporous alumina using aluminum chloride via precipitation templating method for CO adsorbent

Yeom, Changju,Selvaraj, Rengaraj,Kim, Younghun THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.67 No.-

<P><B>Abstract</B></P> <P>A cost-effective preparation method is proposed to prepare nanoporous alumina (NA) using aluminum chloride as a precursor with a lower cost than aluminum butoxide. In addition, the surfactant template was replaced with magnesium stearate, which has a lower unit cost in stearate acid. The adsorption isotherm test for the CO gas was carried out to compare the adsorption performance of the NA adsorbents prepared using post-hydrolysis (NA) and cost-effective precipitation (C-NA). In addition, C-NA exhibited a similar uptake capacity as NA, and the maximum uptake capacity of Pd/C-NA increased 1.3 times via Pd nanodots loading.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanoporous alumina (NA) was prepared by cost-effective (C) method. </LI> <LI> C-NA showed uniform pore size, interlinked pore system, and large surface area. </LI> <LI> C-NA exhibited 6–7 times higher uptake for CO than commercial adsorbents. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

High-efficiency photothermal sterilization on PDMS film with Au@CuS yolk-shell nanoparticles

Eunhae Park,Rengaraj Selvaraj,김영훈 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.113 No.-

Since the global COVID-19 pandemic, the development of biocide-free antibacterial surfaces based onother sterilization mechanisms has gathered momentum. It however faces significant challenges. Photothermal sterilization based on photothermal agents (PTA), which can convert light energy to heatunder near-infrared (NIR) irradiation, has been proposed as an attractive method to prevent bacterialinfections and contamination. Gold nanoparticles (AuNPs) with localized surface plasmon resonance,which cause a photothermal effect via high photothermal conversion from light to heat energy, are generallyused as PTA, and CuS as a p-type semiconductor with a narrow band gap is an emerging PTA. Therefore, in this study, an Au@CuS yolk-shell with inner gaps was prepared via the Kirkendall effect,and its photothermal performance was tested under NIR irradiation. Polydimethylsiloxane (PDMS) wasused as the supporting substrate with low surface energy. Photothermal sterilization effect was exploredby inactivating E. coli using Au@CuS/PDMS films. Effective inactivation of E. coli was observed in the0.025 wt% Au@CuS/PDMS film within 10 s of NIR irradiation. The results show that the dramatic inactivationof E. coli is caused by the photothermal effect generated by the coupling of CuS and AuNPs.

Enhanced solar photocatalytic activity of Er3+:YAlO3-loaded BiPO4 composite

Yunfan zhang,Rengaraj Selvaraj,Mika Sillanpaa,김영훈,Cheuk Wai Tai 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.24 No.-

Er3+:YAlO3 loaded BiPO4 were successfully synthesized by a simple heat treatment approach in order to enhance the photocatalytic efficiency of BiPO4. Comparing with the simple substance of BiPO4, the composite system showed the better efficiency on photodegradation of Methlyene Blue (MB) solution under a simulated solar light irradiation. The relationship between loading amount and degradation rate was also investigated. It is found that the optimal loading amount of Er3+:YAlO3 is 7 wt%. The recycling test of selected sample was carried out to study the stability of the Er3+:YAlO3 loaded BiPO4 system. The composite materials were finally characterized by field-emission scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV–visible diffuse reflectance spectroscopy (UV–vis DRS). Based on the findings a possible mechanism has been proposed. The existence of luminescence agent (Er3+-doped YAlO3) and the occurrence of upconversion luminescence process have been related with the enhanced photodegradation of MB over composite system.

Facile microwave-assisted synthesis of SnS2 nanoparticles for visible-light responsive photocatalyst

박성묵,박지홍,Rengaraj Selvaraj,김영훈 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.31 No.-

A facile and rapid microwave-assisted method was proposed to prepare tin disulfides (SnS2) for use asvisible-light responsive photocatalysts with narrow band gap ( 2.1 eV). The photocatalytic activity ofSnS2 was evaluated by photodegradation of methylene orange (MO) under visible light irradiation(455 nm of LED lamp). SnS2-M show enhanced photocatalytic activities compared to SnS2-A andconventional TiO2, and the mineralization ratio of MO by SnS2-M showed highest value (0.025) ascompared to literature data. To confirm the photoreduction mechanism, Au or Ag dots as inhibitor fordirect reduction of MO were decorated on the SnS2 surface.