Removal of Oil from Concentrated Wastewater by Attapulgite and Coagulant

Abstract The removal of oil from wastewater by adsorption on pulverized attapulgite and coagulation was investigated. It was found that raw clay is better for the removal of floating oil than clay-calcined products. Raw clay, however, was not quite so effective for the removal of emulsified oil. The percentage removal is a function of both the amount of attapulgite added and the initial oil concentration. The relationship between the amount added and the remaining oil concentration has a form similar to the Freundlich model, though equilibrium is not achieved. As for the removal of the emulsified oil, the use of coagulant and attapulgite implies a synergistic enhancement. The adsorption time is very important. A linear relationship is observed between the logarithm of adsorption time and the percentage removal. Over 90% removal of the floating oil is obtained by using 1% attapulgite for 1 h at 30°C and 1 ppm PAM when the initial oil concentration is about 500 mg/L. This is superior to that of bentonite. Over 99% removal of emulsified oil is achieved by using 2.5% attapulgite for 15 min and 800 ppm aluminum sulphate when the initial concentration is 126,000 mg/L. The used clay could be regenerated.