Adsorption isotherms for removal of iron, copper, phosphorus and oxidation products from crude palm oil using natural and acid-activated clays

A study was carried out on acid activated clay (W) and non-acid activated clays W and A). Trace metal components and phosphorus compounds were monitored. The Langmuir isotherm was more applicable than the Freundlich isotherm for the adsorption of trace metals, copper and iron. Both the non-acid activated clays were better adsorbents of iron from degummed and bleached palm oil than the acid-activated clay, indicating that neutral and natural adsorbents (clays P and A) could be better for removal of iron in crude palm oil than the acid activated clay in spite of having lower surface areas. Clay P was the best adsorbent for most of the analysed components among the three tested clays. The degummed palm oil bleached with clay P had the lowest concentrations of phosphorus and copper. The removal of primary and secondary oxidation products did not follow the Freudlich and Langmuir equations, probably due to changing values effected by the adsorbent rather than by just mere adsorption. The study shows that careful selection of clays for specific functions is very important for bleaching efficiency where minor impurities in palm oil are removed.