Keywords: Spent bleaching earth; waste lubricating oil; heat regeneration process; number of cycles; solid loading; pore size

Abstract

In this study, the properties of waste lubricating oil (WLO) were investigated upon the regeneration of spent bleaching earth (SBE). Acid treatment to recover WLO to its base oil form and remove contaminants was carried out using glacial acetic acid. The characterization of the recovered WLO samples was conducted on water content, sludge formation, absorbance, and presence of the functional groups in the WLO samples by using Fourier-transform infrared spectroscopy (FTIR). The results of the water content level showed positive in five different samples of WLO and its removal percentage was within the range of 3.63% to 11.01%. After the acetic acid treatment, the mass of sludge produced for 10 mL of WLO was within the range of 0.13 g to 0.89 g. The characterization of the regenerated SBE was done using oil removal analysis, scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR). Number of cycles in solvent extraction and regeneration heat treatment temperature on the regeneration of SBE were studied and tested to recover WLO. In addition, the response surface methodology (RSM) was used to obtain optimum values of number of cycles, regeneration temperature of SBE, and amount of SBE solid loading required for better adsorption efficiency. From the results, it was found that the optimized set of parameters were 8 cycles in Soxhlet extraction, 400^oC of SBE heat treatment process, and 40 g of SBE loading in 10 mL of WLO.