Removal of residual palm oil-based biodiesel catalyst using membrane ultra-filtration technique: An optimization study

In this research work, residual potassium hydroxide catalyst was removed from palm oil-based alkyl esters (biodiesel) using membrane separative technique, with the aim of achieving high-quality biodiesel that meets international standard specifications. Further, Central Composite Design (CCD) coupled with Response Surface Methodology (RSM) was employed to study the effects of the system variables such as flow rate, temperature and transmembrane pressure (TMP) on the retention of potassium. At the optimum conditions, the coefficient of retention (%R) of the catalyst was 93.642, and the content of the potassium was reduced from 8.328 mg/L to 0.312 mg/L; a value well below the one specified by both EN 14214 and ASTM D6751 standards. In addition, the comparison between predicted and experimental values for the catalyst retention offers a reasonable percentage error of 0.081%. Therefore, this study has proven that membrane technique can be used to post treat crude biodiesel; in order to achieve high-quality biodiesel fuel that can be efficiently used on diesel engines.