Ganapati D. Yadav

Arsenic and fluoride contaminated groundwaters: A review of current technologies for contaminants removal.

Chronic contamination of groundwaters by both arsenic (As) and fluoride (F) is frequently observed around the world, which has severely affected millions of people. Fluoride and As are introduced into groundwaters by several sources such as water-rock interactions, anthropogenic activities, and groundwater recharge. Coexistence of these pollutants can have adverse effects due to synergistic and/or antagonistic mechanisms leading to uncertain and complicated health effects, including cancer. Many developing countries are beset with the problem of F and As laden waters, with no affordable technologies to provide clean water supply. The technologies available for the simultaneous removal are akin to chemical treatment, adsorption and membrane processes. However, the presence of competing ions such as phosphate, silicate, nitrate, chloride, carbonate, and sulfate affect the removal efficiency. Highly efficient, low-cost and sustainable technology which could be used by rural populations is of utmost importance for simultaneous removal of both pollutants. This can be realized by using readily available low cost materials coupled with proper disposal units. Synthesis of inexpensive and highly selective nanoadsorbents or nanofunctionalized membranes is required along with encapsulation units to isolate the toxicant loaded materials to avoid their re-entry in aquifers. A vast number of reviews have been published periodically on removal of As or F alone. However, there is a dearth of literature on the simultaneous removal of both. This review critically analyzes this important issue and considers strategies for their removal and safe disposal.

Magnetically separable sulfated zirconia as highly active acidic catalysts for selective synthesis of ethyl levulinate from furfuryl alcohol

Magnetically separable sulfated zirconia catalysts were prepared by a two-step approach. Coating of zirconia around the particles helps to increase the number of sites needed for sulfate ion loading and hence enhances the acidity of the catalyst. Different molar concentrations of chlorosulfonic acid were used for sulfonation. The prepared catalysts were used for selective synthesis of ethyl levulinate using renewable substrates: furfuryl alcohol and ethanol. Ethyl levulinate has many applications in different industries including as a potential blending component in biodiesel. The catalyst could be easily separated by the use of a magnet. The influence of different parameters was investigated to reach the optimum yield of ethyl levulinate. Detailed kinetics were established for scaling up purposes. The catalyst is robust and reusable.

Novel aluminium exchanged dodecatungstophosphoric acid supported on K-10 clay as catalyst: benzoylation of diphenyloxide with benzoic anhydride

A series of (20% w/w) aluminium exchanged dodeca-tungstophosphoric acids (DTP) (Alx-DTP, x = 0.33–1) supported on montmorillonite K-10 clay were synthesized and completely characterized by sophisticated techniques. These catalysts were used for the selective benzoylation of diphenyl oxide with benzoic anhydride to a mono acylated product. Al0.66-DTP/K-10 catalyst showed the best activity amongst other aluminium substituted catalysts and Cs2.5H0.5PW12O40 (Cs-DTP)/K-10. Different supports such as ZrO2, SnO2 and K-10 were used to study the effect of support on the acidic property and activity of Al0.66-DTP supported catalysts in the benzoylation reaction. The order of activity was Al0.66-DTP/K-10 > Al0.66-DTP/SnO2 > Al0.66-DTP/ZrO2. The effect of benzoylating agents such as benzoic anhydride, benzoyl chloride and benzoic acid on the conversion and rate was also studied. Benzoic anhydride showed the highest reactivity. Eley–Rideal mechanism was found to be consistent with the data. The activation energy for benzoylation of DPO was calculated as 22 kcal mol−1, which further supports that the reaction is kinetically controlled. Al0.66-DTP/K-10 was an active and robust catalyst.

Sustainability Assessment of Chemical Processes: Evaluation of Three Synthesis Routes of DMC

This paper suggested multicriteria based evaluation tool to assess the sustainability of three different reaction routes to dimethyl carbonate: direct synthesis from carbon dioxide and methanol, transesterification of methanol and propylene carbonate, and oxidative carbonylation of methanol. The first two routes are CO2-based and in a research and development phase, whereas the last one is a commercial process. The set of environmental, social, and economic indicators selected were renewability of feedstock, energy intensity, waste generation, CO2 balance, yield, feedstock price, process costs, health and safety issues of feedstock, process conditions, and innovation potential. The performance in these indicators was evaluated with the normalized scores from 0 to

Synthesis of Geraniol Esters in a Continuous-Flow Packed-Bed Reactor of Immobilized Lipase: Optimization of Process Parameters and Kinetic Modeling

With increasing demand for perfumes, flavors, beverages, and pharmaceuticals, the various associated industries are resorting to different approaches to enhance yields of desired compounds. The use of fixed-bed biocatalytic reactors in some of the processes for making fine chemicals will be of great value because the reaction times could be reduced substantially as well as high conversion and yields obtained. In the current study, a continuous-flow packed-bed reactor of immobilized Candida antarctica lipase B (Novozym 435) was employed for synthesis of various geraniol esters. Optimization of process parameters such as biocatalyst screening, effect of solvent, mole ratio, temperature and acyl donors was studied in a continuous-flow packed-bed reactor. Maximum conversion of ~xa087% of geranyl propionate was achieved in 15xa0min residence time at 70xa0°C using geraniol and propionic acid with a 1:1xa0mol ratio. Novozym 435 was found to be the most active and stable biocatalyst among all tested. Ternary complex mechanism with propionic acid inhibition was found to fit the data.

Selectivity engineering of O-methylation of hydroxybenzenes with dimethyl carbonate using ionic liquid as catalyst

Phenolic ethers are useful commercial entities which have been traditionally produced via polluting routes that could be replaced by benign catalytic processes. In the current work, O-methylation of mono-, di- and tri-hydroxy benzenes (phenolics), namely, phenol, catechol and pyrogallol, has been studied with dimethyl carbonate (DMC) as the etherification agent cum solvent in the presence of a phosphonium ionic liquid as catalyst. The co-products methanol and CO2 could be recycled to make DMC. The catalyst is recycled and thus the overall process is a green process. Ionic liquids possess many useful attributes and can be used as solvents and multi-functional catalysts, and some are amenable to recycling and reuse using clever strategies. Two different types of phosphonium-based ionic liquids were used – one group containing the trihexyl (tetradecyl) cation such as trihexyl (tetradecyl) phosphonium chloride (PC), trihexyl (tetradecyl) phosphonium bromide (PB), trihexyl (tetradecyl) phosphonium decanoate (PD), trihexyl (tetradecyl) phosphonium hexafluoro phosphate (HFP), and another symmetric reference containing the tetrabutyl phosphonium cation (tetrabutyl phosphonium bromide (TBPB)) – and were evaluated in the O-methylation of phenol, catechol and pyrogallol with DMC to the corresponding ethers. Depending on the number of hydroxyl groups on the benzene ring, different mono- and poly-ethers could be produced by using suitable process conditions such as molar ratio, catalyst, temperature and time. All of these intermediate and final ethers have different applications. Trihexyl (tetradecyl) phosphonium bromide (PB) was the best catalyst. Effects of various parameters on the rate of reaction, conversion and yield were studied including speed of agitation, catalyst concentration and reusability, reactant concentration and temperature. The best operating conditions were 200 °C, a 1u2006:u20066 mole ratio of reactant to DMC, and trihexyl (tetradecyl) phosphonium bromide (PB) as catalyst. A reaction mechanism is proposed and discussed to deduce the kinetics.

Synthesis of novel titania membrane support via combustion synthesis route and its application in decolorization of aqueous effluent using microfiltration

A simple preparation method for synthesizingxa0porous ceramic membrane support was developed from nanocrystalline titania powder using solution combustion synthesis. Different characteristics of combustion-synthesized titania membranes such as surface morphology, porosity, pore size, pure water and solvent permeability were measured using advanced characterization techniques. Novel titania membrane support sintered at 450xa0°C showed mean pore diameter 0.33xa0µm, porosity of about 77.5xa0%, and pure water permeability 20.31xa0×xa010−5xa0Lxa0h−1xa0m−2xa0Pa−1. Combustion-synthesized titania membrane supports were used in decolorization of commercial dye-based ink effluent using microfiltration. Effects of different parameters such as pressure, initial concentration of ink effluent, and pH on decolorization of ink effluent were studied. Furthermore, combustion-synthesized titania membranes operated at lower pressure (1xa0×xa0105xa0Pa) showed significant color removal (>99xa0%) and moderate chemical oxygen demand reduction with lower membrane fouling during decolorization of water-based ink effluent.Graphical Abstract

Green synthetic route for perfumery compound (2-methoxyethyl) benzene using Li/MgO catalyst

Ethers are one of the most prominent compounds among perfumery chemicals. (2-Methoxyethyl) benzene commonly known as phenyl ethyl methyl ether (PEME) is widely used in flavour and fragrance industries. Conventionally, synthesis of PEME involves the use of hazardous and polluting chemicals, which in turn affects the purity of perfumery compound. Thus, developing a green route to synthesise PEME without any hazardous chemicals is desirable. In the current work, a new process is developed for the synthesis of PEME using solid base catalysts including MgO and Li/MgO (with different loadings of lithium) and dimethyl carbonate (DMC) as a methylating agent as well as a solvent. Different kinetic parameters were studied to achieve the optimum yield of the desired product. At optimum reaction conditions i.e., 1000 rpm of speed,

Experimental and Modeling Assessment of Sulfate and Arsenic Removal from Mining Wastewater by Nanofiltration

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