Kinetics of oil extraction from clay used in the lubricating oil re-refining processes and re-activation of the spent bleaching clay

Oil extraction and re-activation of spent bleaching clay issued from re-refining of waste-lubricating oil in Sulaimani city, was studied under the three stages of solvent extraction, calcination, and acid activation processes. A set of different response parameters was considered such as (i) the extraction kinetics and the quality of the re-refined oil depending on the type of solvent used, (ii) the bleaching efficacy of re-activated spent bleaching clay, (iii) the effect of calcination time and temperature on the properties of re-activated spent bleaching clay, and (iv) the effect of additional acid activation of the spent bleaching clay. After oil recovery, calcination without acid treatment was sufficient to recover most of the clay activity (with respect to bleaching performance). Hexane and heptane were found to be the best solvents regarding the quantity and quality of the extracted oil. The results point out to a beneficial remediation of Tanjaro landfill from thousands of tons of dumped oily spent bleaching clay by de-oiling and calcination to recover the oil and re-activate the spent clay in an economic manner.