Biodiesel purification by water washing has been proved to be an unattractive process from an economic and environmental point of view. In this work, we propose the use of regenerated cellulose membranes from peanut shell as an alternative in the biodiesel purification. The preparation of the membranes was optimized from a central composite design, resulting in dense and non-porous membranes. However, in contact with biodiesel, the membranes undergo expansion due to the retention of methanol, water, and glycerol molecules, allowing the permeation of fatty acid methyl esters. The filtered biodiesel presents quality parameters, such as total ester content of 98.3 ± 1.4% and free glycerol content < 0.02%, in agreement with the main regulatory agencies. The regenerated cellulose membranes from peanut shell are easily prepared, with high repeatability (relative standard deviation (RSD) < 1.8%) and are presented as an economical and environmental solution for the biodiesel purification.

O catalisador nanoestruturado SiO2/ZrO2 foi preparado pelo método sol-gel e apresentou uma área superficial de 131,50 ± 14 m² g-1. As imagens de microscopia eletrônica de varredura mostraram que o catalisador apresentou partículas muito homogêneas de 250 nm de diâmetro. Este material foi aplicado na transesterificação do óleo de soja para a produção de biodiesel. A conversão do óleo em biodiesel teve um rendimento de 96,2 ± 1,4 % em 3 h de reação de transesterificação catalisada pelo material SiO2/ZrO2 (SiZr). O catalisador foi recuperado e reutilizado por seis vezes, mantendo uma eficiência catalítica de 84,1%.

Nanosized SiO2/ZrO2 catalyst with high surface area (131.50 ± 14 m² g-1) was prepared by the sol-gel method. The material presented highly homogeneous particles with an average diameter of 250 nm according to SEM images. It was applied in the transesterification of soybean oil for biodiesel production. The biodiesel conversion reached a yield of 96.2 ± 1.4 % after 3 h of transesterification reaction catalised by SiO2/ZrO2 (SiZr). The catalyst was recovered and reused six times, maintaining a catalytic efficiency of about 84.1 %.

The silica gel was obtained from sand and its surface was modified with POCl3 to produce Si-Cl bonds on the silica surface. Ethylenediamine was covalently bonded onto the chlorinated silica surface. The adsorption of the chlorides of divalent cobalt, nickel and copper was qualitatively studied to show that the bonding of ethylenediamine onto the silica gel surface produces a solid base capable of chelating metal ions from solution. The experiments illustrate the extraction of silica gel, its reactivity, the development of modified surfaces and its application in removing metal ions from water and are deigned for undergraduate inorganic chemistry laboratories.