Use of Raphanus sativus L. press cake, a solid residue from biodiesel processing, in the production of adsorbents by...

The objective of this study was to evaluate the performance of an adsorbent, based on a solid residue arising from biodiesel production, for the removal of cationic dyes from wastewaters. The adsorbent was produced by microwave thermal activation. The Freundlich model provided the best fit for equilibrium data, indicating heterogeneous adsorption. The adsorption capacity increased in comparison to the adsorbent obtained by thermal processing of the same residue in a conventional oven, showing that microwave processing is an attractive alternative for adsorbent production, given the significant reduction in processing time (decreased from 60 min to 3 min). Both the removal efficiency and the removal capacity decreased with an increase in temperature, pointing towards the exothermic nature of the removal process.