S. Ramalingam

Removal of cadmium(II) from aqueous solution by agricultural waste cashew nut shell

Cashew nut shell (CNS) is a low cost adsorbent that has been used for the removal of cadmium(II) from an aqueous solution. The effects of various parameters such as solution pH, CNS concentration, contact time, initial cadmium(II) concentration and temperature were examined. The CNS was effective for the quantitative removal of cadmium(II) ions in acidic conditions and equilibrium was achieved in 30 min. The experimental data were analyzed by two-parameter (Langmuir, Freundlich, Temkin and Dubinin-Radushkevich) and three-parameter models (Redlich- Peterson, Koble-Corrigan, Toth and Sips) by nonlinear regression analysis. The characteristic parameters for each isotherms and related correlation coefficients have been determined by using MATLAB 7.1. Thermodynamic parameters such as ΔGo, ΔHo and ΔSo have also been evaluated, and it was found that the sorption process was feasible, spontaneous and exothermic. Pseudo-first-order, pseudo-second-order, Elovich kinetic and intraparticle diffusion models were selected to follow the adsorption process. The results of the kinetic study show that the adsorption of cadmium(II) could be described by the pseudo-second order equation, suggesting that the adsorption process is presumably chemisorption. A single-stage batch adsorber was designed for different adsorbent dose-to-effluent volume ratios using the Freundlich equation. The results indicate that the cashew nut shell could be used to effectively adsorb cadmium(II) from an aqueous solution.

Lead(II) Adsorption onto Sulphuric Acid Treated Cashew Nut Shell

In this study, sulphuric acid treated cashew nut shell (STCNS) was used as adsorbent for the removal of lead(II) ions from the aqueous solutions. Adsorption studies were performed by varying the solution pH, contact time, and temperature. Experimental data were analyzed by the model equations such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms and it was found that the Freundlich isotherm model fits best with the experimental data at different temperatures studied. The maximum adsorption capacity of lead(II) on STCNS was determined as 408.6, 432, 446.3, and 480.5 mg/g, respectively, at different temperatures (30, 40, 50, and 60°C). The thermodynamic parameters (ΔGo, ΔHo, and ΔSo) were calculated and the thermodynamic properties of lead(II) ions-STCNS system indicate the exothermic process. Adsorption kinetic constants were determined using pseudo-first-order, pseudo-second-order, and the Elovich kinetic models at various temperatures. The adsorption results clearly showed that the adsorption of lead(II) ions onto STCNS followed pseudo-second-order model and the adsorption was both by film diffusion and by intraparticle diffusion. A single-stage batch adsorber was designed using the Freundlich equation.

Yttria-Zirconia–Based Lewis Acid Catalysis of the Biginelli Reaction: An Efficient One-Pot Synthesis of 3,4-Dihydropyrimidin-2-(1H)-ones

Abstract Yttria-zirconia–based Lewis acid efficiently catalyzes the three-component cyclocondensation reaction of aldehyde, β-keto ester, and urea or thiourea in refluxing acetonitrile to produce the corresponding dihydropyrimidones in high yields.

Efficient Removal of Nitrate and Phosphate Using Graphene Nanocomposites

The increase in demand for food products has forced production in agricultural sector at faster rate. Application of chemical fertilizers consisting of phosphorous, nitrates and potassium increased the yield with more negative impacts on environment. The run-off water from agriculture field with high concentration of nitrates and phosphates contaminate the water bodies such as rivers and lakes thus affecting the aquatic system and creatures. Algal growth and degradation occurs at faster rate and the microbes utilize the dissolved oxygen present in water. Lack of oxygen in water causes suffocation and death of living creatures resulting in eutrophication. Adsorption technique has been widely used to overcome these problems. Graphene nanocomposites find promising application in adsorbing and removing nitrates and phosphates from the water bodies. Graphene nanocomposites can be obtained from its derivatives such as graphene oxide, chemically and thermally reduced graphene oxides. They act as nanosorbents and are widely used owing to their properties such as biocompatibility, stability, high surface area to volume ratio, good conductivity and low-cost synthesis. It can be synthesised by solvent processing, melt processing or in situ polymerization methods. Studies reveal that graphene nanocomposites prove to be ideally potent in removing pollutants such as nitrates and phosphates.

A concise synthesis of (5R,6S)-tert-butyl 5-acetoxy-6-(hydroxymethyl)-5,6-dihydropyridine-1(2H)-carboxylate

An efficient synthesis of (5 R,6 S)-tert -butyl 5-acetoxy-6-(hydroxymethyl)-5,6-dihydropyridine- 1(2 H)-carboxylate 1, a common intermediate for various polyhydroxylated piperidines is reported in six steps with 32% overall yield starti ng from Garners aldehyde. The key steps include the diastereoselective nucleophilic additio n and intramolecular cyclization. (5 R,6 S)-tert - butyl 5-acetoxy-6-(hydroxymethyl)-5,6-dihydropyridine-1(2 H)-carboxylate is a common precursor for the synthesis of 1-deoxy- L-mannojirimycin, 1-deoxy-L-idonojirimycin, L- fagomycin and related analogues.