Residual oil and suspended solid removal using natural adsorbents chitosan, bentonite and activated carbon: A comparative study

Palm oil mill effluent (POME), which contains about 4000 mg/l of residual oil, has been chosen to remove its residual oil using three types of adsorbents. Jar-test method has been used to identify the best adsorbent to remove the residual oil from POME. Chitosan was compared to activated carbon and bentonite as a potential residual oil remover. Chitosan showed the best removal compared to the other adsorbents for all the parameters studied. Chitosan could successfully remove 99% of residual oil and minimize the suspended solid content to a value of 25 mg/l from POME at a dosage of 0.5 g and employing a mixing time of 30 min, a mixing rate of 100 rpm, sedimentation for 30 min and a pH value of ranging from 4.0 to 5.0. For activated carbon and bentonite, the optimum dosages were 8.0 g and 10.0 g/l, respectively, 30 min of mixing time at 150 rpm, 80 and 60 min of settling time, respectively, and pH of 4.0-5.0 to obtain the same percentage of removal as performed by chitosan. Activated carbon and bentonite can only reduce the suspended solid values up to 35 and 70 mg/l, respectively, at the optimized conditions.