No abstract

This work reports the transesterification of soybean oil with ethanol using two commercial immobilized lipases under the influence of ultrasound irradiation. The experiments were performed in an ultrasonic water bath, following a sequence of experimental designs to assess the effects of temperature, enzyme and water concentrations, oil to ethanol molar ratio and output irradiation power on the reaction yield. Results show that ultrasound-assisted lipase-catalyzed transesterification of soybean oil with ethanol might be a potential alternative route to conventional alkali-catalyzed method, as high reaction yields (~90 wt.%) were obtained at mild irradiation power supply (~100 W), and temperature (60 °C) in a relatively short reaction time, 4h, using Lipozyme RM IM as catalyst. The repeated use of the catalyst under the optimum experimental condition resulted in a decay in both enzyme activity and product conversion after two cycles. The use of Novozym 435 led to lower conversions (about 57%) but the enzyme activity was stable after eight cycles of use, showing, however, a reduction in product conversion after the forth cycle.

This study investigated the chemical composition of five different extracts of

In this work, the use of ultrasound energy for chromium removal from residual tannery leather was investigated. The following parameters were evaluated: complexation temperature (60–90 °C), chromium/complexant molar ratio (1:0 to 1:6), complexation time (30–120 min), washing steps (1–14), washing temperature (25–80 °C), and washing time (1–10 min). For all evaluated conditions, chromium removal was monitored by flame atomic absorption spectrometry. The residual tannery leather after different extraction strategies were characterized using a scanning electron microscopy. For the proposed method, the optimized conditions were: 3 g of residual tannery leather to be treated, 100 mL of extraction solution (chromium/complexant molar ratio of 1:3), at 80 °C and 30 min of sonication. To complete the chromium removal, only five washing cycles (50 mL of water at 50 °C) of 3 min were required. Using these conditions, a chromium removal higher than 98% was achieved. Under the same reaction conditions, the results were compared with mechanical stirring (100 rpm), which allowed observing the significant effects of ultrasound for chromium removal. Comparing to the conventional method, the total time of the process (including extraction and washing steps) was decreased from 150 to 45 min and the water volume for the washing was reduced from 450 to 250 mL. Therefore, the proposed ultrasound-assisted process can be considered as a suitable alternative for chromium removal from residual tannery leather.

-In Brazil, the species Maytenus aquifolia and Maytenus ilicifolia are widely used in popular medicine in the form of teas for stomach and ulcer illness treatment. Despite the great interest in Maytenus aquifolia therapeutic properties and the fact that it is an abundant and native plant growing in Brazil, there is a lack of information in the literature concerning the extraction at high pressures. In this context, this work is focused on the mathematical modelling of the packed-bed extraction of Maytenus aquifolia with compressed CO 2 . Three mathematical models were used to represent the experimental data. The experiments were performed in a laboratory-scale unit, evaluating the effects of temperature (293 to 323 K), pressure (100 to 250 bar), and extraction time on the yield of the extracts. Results show that the extraction temperature and solvent density exerted a pronounced effect on yield. The mathematical model of Sovová was the most suitable to represent the experimental extraction data of M. aquifolia.