Purification Capacity of a Modified Montmorillonite on the Post-Consumption Vegetable Oil Recycling Process

Among the naturally abundant clays in the Earth’s crust, montmorillonite (MMT), a member of the smectite group, stands out for its versatility. Its interesting properties can be further improved by chemical processing with inorganic acids and reaction temperatures close to boiling. In this study, a Brazilian polycationic MMT was treated with a low-concentration (2M) aqueous solution of hydrochloric acid at 60 and 70 °C for 5 h. The resulting modified clay was then employed in the purification of post-consumption oil (PCO), specifically soybean oil. The effect of the modification variables of the clay and also the purification parameters (time and temperature) were investigated, comparing the adsorptive and purification capacities of the modified MMT with those of the natural and a commercial clay sample. The characterization of the MMT (raw and modified) was carried out by bulk density, moisture content, plasticity limit, BET, SEM/EDS, XRD, and FTIR, whereas the characterization of the PCO, as-received and after purification, involved the analyses of apparent density, relative flow time, UV-Vis spectrophotometry, and acid value. The results show that light acid activation, especially at 70 °C, promoted a significant increase in the surface area up to 96% and the adsorption capacity of the clay. The oil purification showed good results in all tests, with the best condition being 70 °C for 24 h with the C70 clay. Thus, the satisfactory results represent an economy of time and energy.