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Current methods for the production of esters, including chemical synthesis and extraction from natural sources, are hindered by low yields and environmental pollution. The enzymatic synthesis of these compounds could help overcome these problems. In this study, phenethyl formate, a commercially valuable formate ester, was synthesized using commercial immobilized lipases. The effects of specific enzymes, enzyme concentration, formic acid:phenethyl alcohol molar ratio, temperature, and solvent were studied in order to optimize the synthesis conditions, which were identified as 15 g/L of Novozym 435 enzyme, a 1:5 formic acid:phenethyl alcohol molar ratio, a 40 °C reaction temperature, and 1,2-dichloroethane as the solvent. Under these conditions, phenethyl formate was obtained in a conversion yield of 95.92%. In addition, when 1,2-dichloroethane was replaced with toluene as the solvent, the enzyme could be recycled for at least 20 reactions with a steady conversion yield above 92%, testifying to the economic aspects of the process. The enzymatic synthesis of phenethyl formate using the proposed method is more environmentally friendly than methods currently employed in academic and laboratory settings. Moreover, the method has the potential to enhance the value-added properties of formic acid owing to its downstream use in the production of commercially essential esters.

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A combined ultrasound (US)/H2O2 process was used to oxidize arsenite to arsenate, yielding a synergistic effect value of 1.26. This showed that the combined process could be an effective method of oxidizing arsenite, instead of using either ultrasonic or H2O2 oxidation processes. This combined process was successfully modeled and optimized using a Box-Behnken design with response surface methodology (RSM). The effects of the US power density, the initial concentration of arsenite, and the H2O2 concentration on the sonochemical oxidation efficiency of arsenite were investigated. Analysis of variance indicated that the proposed quadratic model successfully interpreted the experimental data with coefficients of determination of R 2 = 0.95 and adjusted R 2 = 0.91. Through this model, we can predict and control the oxidation efficiency under different conditions. Furthermore, the optimal conditions for the oxidation of arsenite were found to be a US power density of 233.26 W L−1, an initial arsenite concentration of 0.5 mg L−1, and an H2O2 concentration of 74.29 mg L−1. The predicted oxidation efficiency obtained from the RSM under the optimal conditions was 88.95%. A confirmation test of the optimal conditions verified the validity of the model, yielding an oxidation efficiency of 90.1%.

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