Investigation on the recovery of used engine oil using a single contactor and South African clays

Abstract

In this study, used engine oil has undergone treatment by means of adsorption using three different naturally occurring South African clays. These were activated using sulphuric acid to enhance the removal of heavy metals. Adsorption is an effective and economic method for removing heavy metal constituents from used engine oils. Different types of low-cost adsorbents have been developed and tested to remove heavy metal ions. However, the adsorption efficiency is dependent on the type of adsorbents. Clay porous structure and the high surface area provide benefits in the treatment of liquids such as used oil and the adsorption of heavy metals. The effect of various parameters affecting adsorption behavior, i.e. contact time, pH, clay dosage, and initial metal ion concentration have been investigated. The three types of clays have been characterized by X-ray diffraction (XRD) to determine crystalline structure, the components in the clay material using X-ray fluorescence (XRF), and the thermal analysis to detect the structural changes that are accompanied by the thermal treatment. The metallic components found in the oil were determined using an atomic emission spectrometer (AES). Furthermore, the experimental adsorption data have been modelled by means of Langmuir and Freundlich’s isotherms. In addition, adsorption kinetics psuedo first and second order used to describe the mechanism of zinc and lead adsorption. Physio-chemical analysis of the treated and untreated used oil showed the presence of iron (Fe), lead (Pb), zinc (Zn), and copper (Cu), in the investigated clays. In conclusion, the Attapulgite clay has the most removal efficiency when compared to the Bentonite and Kaolin clay. Hence, this is observed for both the elemental analysis and the fluid properties before and after treatment.