USED LUBRICATING OIL TREATMENT USING ACID ACTIVATION CLAY AS ADSORBENT FOR OIL RECOVERY

The aim of this study was to assess the effectiveness of activated clay as an adsorbent in the recycling of used lubricating oil (ULO). To accomplish this, the research primarily concentrated on identifying the optimal parameters for the application of organic acids—specifically acetic acid and citric acid—in the acid activation of clay during the adsorption process. Montmorillonite K-10 clay served as the adsorbent and was activated to facilitate ULO recovery. According to the experimental findings, citric acid at a concentration of 1.0 mol/L for a reaction time of 45 minutes proved to be the most effective for ULO recovery. The optimal activated clay exhibited a viscosity of 95.10 cP and a density of 0.663 g/mL, achieving a water removal rate of 0.036% and sludge removal of up to 9.20%. Moreover, clay treated with citric acid produced a current of 1.3293 A, in comparison to 1.5721 A for acetic acid under identical conditions, as measured by Ultraviolet-visible (UV-Vis) spectrophotometry. The conditions involving citric acid at 1.0 mol/L for 45 minutes were further investigated using a scanning electron microscope (SEM) to analyze the clay before and after activation. Results indicated that the surface of the unmodified clay was smoother with fewer visible pores, whereas the activated clay displayed a more porous structure, with noticeable pores and cracks. The activated clay's average pore diameter was found to be larger, reflecting a 32.19% increase in pore size compared to the unmodified clay. Additionally, a considerable enhancement in pore area was observed, with the average pore size increasing from 1.614 μm to 2.077 μm, suggesting improved adsorption performance followingactivation. Fourier transform infrared spectroscopy (FTIR) was utilized to characterize and compare the recovered oil, revealing that activated clay treated with citric acid at 1.0 mol/L for 45 minutes was superior in eliminating most remaining contaminants, such as soot, water, fuel residues, carbonyl groups, discoloration, and other impurities compared to its pre-activated state.