In this work, residual potassium hydroxide catalyst was removed from palm oil-based methyl esters using an adsorption technique. The produced biodiesel was initially purified through a water washing process. To produce better quality biodiesel, as well as to meet standard specifications (EN 14214 and ASTM D6751), batch adsorption on palm shell activated carbon was used for further catalyst removal. The central composite design (CCD) of the response surface methodology (RSM) was used to study the influence of adsorbent amount, time and temperature on the adsorption of potassium species. The maximum catalyst removal was achieved at 40 °C using 0.9 g activated carbon for 20 h adsorption time. The results from the Response Surface Methodology were in good agreement with the measured values. The absolute error in prediction at the optimum conditions was 3.7%, which is reasonably accurate. This study proves that adsorption post-treatment techniques can be successfully employed to improve the quality of biodiesel fuel for its effective use on diesel engines and to minimize the usage of water.
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