Removal of exhausted oils by adsorptiononmixed Ca and Mg oxides

Adsorption tests were performed on two different exhausted oils to reduce their polluting and health hazard potential: a ''water-insoluble oil'', utilised for automotive engine lubrication, and an ''emulsified'' oil, used as coolant for metal-cutting tools. Dolomite, a low-cost recovery material, was used to prepare two effective adsorbents: (a) a mixed Ca and Mg oxide obtained by thermal decomposition of dolomite at 18001C, and (b) an activated material obtained by submitting this product to chemical treatment with HCl. Preliminary tests carried out with an excess of the former material showed that the insoluble oil was adsorbed with lower yield (Y ¼ 0:40) thanthe soluble (emulsified) oil (Y ¼ 0:60). The material activationwith HCl remarkably improved the adsorptionof soluble oil organ ic fraction (Y > 0:90), while only a little increase in the removal yield was observed for the insoluble oil (Y ¼ 0:44). The results presented and discussed in this work pointed out that the products of dolomite calcination can successfully replace the conventional adsorbing materials in the removal of organic pollutants, with particular concern to exhausted soluble oils, which cannot usually be recycled, thus reducing the operational costs of their treatment. r 2002 Elsevier Science Ltd. All rights reserved.