Kailash Singh

Bio: Kailash Singh is an academic researcher from Malaviya National Institute of Technology, Jaipur. The author has contributed to research in topics: Reactive distillation & Adsorption. The author has an hindex of 17, co-authored 67 publications receiving 1252 citations.

Heavy metal removal from wastewater using various adsorbents: a review

Abstract: Heavy metals are discharged into water from various industries. They can be toxic or carcinogenic in nature and can cause severe problems for humans and aquatic ecosystems. Thus, the removal of heavy metals from wastewater is a serious problem. The adsorption process is widely used for the removal of heavy metals from wastewater because of its low cost, availability and eco-friendly nature. Both commercial adsorbents and bioadsorbents are used for the removal of heavy metals from wastewater, with high removal capacity. This review article aims to compile scattered information on the different adsorbents that are used for heavy metal removal and to provide information on the commercially available and natural bioadsorbents used for removal of chromium, cadmium and copper, in particular.

Cobalt exchanged zeolites for heterogeneous catalytic oxidation of phenol in the presence of peroxymonosulphate

Abstract: Several cobalt ion-exchanged zeolite catalysts based on ZSM-5, zeolite-A, and zeolite-X were prepared and tested for heterogeneous oxidation of phenol in the presence of various oxidants such as H2O2, persulphate, and peroxymonosulphate. It is found that Co-ZSM-5 is highly effective in heterogeneous activation of peroxymonosulphate to produce sulphate radicals but exhibits low activity for the activation of H2O2 and persulphate for organic oxidation in water. Co-zeolite-A and Co-zeolite-X show much faster reaction rate in homogeneous activation of peroxymonosulphate due to decomposition of the catalysts and leaching of Co ions into aqueous solution. Co-ZSM-5 also presents stable performance in heterogeneous activation of peroxymonosulphate for phenol degradation. The phenol degradation depends on catalyst loading, phenol concentration, oxidant concentration and temperature. Kinetic studies indicate that phenol degradation follows zero-order kinetics with an activated energy of 69.7 kJ/mol.

Study of catalytic behavior of KOH as homogeneous and heterogeneous catalyst for biodiesel production

Abstract: Increased industrialization and motorization are the major cause of environmental pollution and diminishing petroleum reserves. Biodiesel being renewable and environment friendly is one of the alternate sustainable energy sources having similar fuel properties as that of petroleum diesel. The objective of this study is to produce biodiesel from cheap raw material (waste cooking oil) and to get optimum reaction conditions for both homogeneous and heterogeneous catalytic transesterification. A comparison is also made to make the transesterification process techno-economically feasible. Potassium hydroxide (KOH) was selected as a homogeneous catalyst and KOH loaded on alumina as a heterogeneous catalyst. A yield of 96.8% fatty acid methyl ester (FAME) was obtained with heterogeneous catalyst at the optimum conditions of reaction temperature 70 °C, reaction time 2 h, catalyst concentration 5%, catalyst loading 15 wt%, and methanol to oil molar ratio 9:1, whereas 98.2% yield was obtained with homogeneous KOH catalyst at the optimum reaction conditions of reaction temperature 70 °C, reaction time 1 h, catalyst concentration 1%, and methanol to oil molar ratio 6:1. The fuel properties were also measured for biodiesel to observe its competitiveness with conventional diesel fuel. Reusability test of KOH loaded on alumina catalyst gave reasonable yield up to 3 cycles.

Methodologies for removal of heavy metal ions from wastewater: an overview

Abstract: Heavy metal is a serious problem nowadays. These heavy metals are discharged into water from various chemical industries. They are harmful for living organisms and it is necessary to eliminate these heavy metals to minimise risk of uptake by plants, animal and human. In the last few decades, several methods have been developed and extensively investigated for heavy metal removal. There are several methods for heavy metal removal: chemical precipitation, adsorption, ion exchange, membrane filtration, coagulation-flocculation and floatation. In this paper, an attempt is made to review various methodologies for heavy metal removal from wastewater with their advantages and disadvantages. It is evident from the literature survey that adsorption method is widely used over conventional methods, (i.e., chemical precipitation, ion exchange, membrane filtration, coagulation-flocculation and floatation) because of its low cost, availability and eco-friendly nature.

Generation of sulfate radical through heterogeneous catalysis for organic contaminants removal: Current development, challenges and prospects

Abstract: Sulfate radical-based advanced oxidation processes (SR-AOPs) employing heterogeneous catalysts to generate sulfate radical (SO4 −) from peroxymonosulfate (PMS) and persulfate (PS) have been extensively employed for organic contaminant removal in water. This article aims to provide a state–of–the–art review on the recent development in heterogeneous catalysts including single metal, mixed metal, and nonmetal carbon catalysts for organic contaminants removal, with particular focus on PMS activation. The hybrid heterogeneous catalyst/PMS systems integrated with other advanced oxidation technologies is also discussed. Several strategies for the identification of principal reactive radicals in SO4 −–oxidation systems are evaluated, namely (i) use of chemical probe or spin trapping agent coupled with analytical tools, and (ii) competitive kinetic approach using selective radical scavengers. The main challenges and mitigation strategies pertinent to the SR-AOPs are identified, which include (i) possible formation of oxyanions and disinfection byproducts, and (ii) dealing with sulfate produced and residual PMS. Potential future applications and research direction of SR-AOPs are proposed. These include (i) novel reactor design for heterogeneous catalytic system based on batch or continuous flow (e.g. completely mixed or plug flow) reactor configuration with catalyst recovery, and (ii) catalytic ceramic membrane incorporating SR-AOPs.

Cobalt-catalyzed sulfate radical-based advanced oxidation: A review on heterogeneous catalysts and applications

Abstract: Recently sulfate radical-based advanced oxidation processes (SR-AOPs) attract increasing attention due to their capability and adaptability in decontamination. The couple of cobalt and peroxymonosulfate (PMS) is an efficient way to produce reactive sulfate radicals. This article reviews the state-of-the-art progress on various heterogeneous cobalt-based catalysts for PMS activation, including cobalt oxides, cobalt-ferrite and supported cobalt by diverse substrates. We summarize the intrinsic properties of these catalysts and their fundamental behaviors in PMS activation, as well as synthetic approaches. In addition, influencing factors and synergistic techniques of Co/PMS systems in organic degradation and possible environmental applications are also discussed. Finally, we propose perspectives on challenges related to cobalt-based catalysts, heterogeneous Co/PMS systems and their potential applications in practical environmental cleanup.