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Electrically driven separation (EDS) technology with a high voltage (HV) alternating current source (AC) was used to remove glycerol and other contaminants from biodiesel in order to meet the ASTM D6751 and EN 14214 standards. Biodiesel was produced from a transesterification of refined palm oil and methanol using sodium methylate as a homogeneous catalyst. The effects of an Iron (Fe) electrode, including types of electrode configurations, vertical distance between electrodes, applied voltage, and separation time, were studied. Furthermore, the effects of the remaining catalyst and soap content in biodiesel phase were also investigated to improve the separating performance using the EDS technique. The EDS using HVAC and low amperage with a point-to-point electrode configuration showed the highest separation efficiency of 99.8%. The optimum vertical distance between electrodes was 3 cm, while the optimum applied voltage was 3 kV. The separation time of 240 s yielded the best separating performance, completely eliminating the unreacted catalyst, and the lowest of the normalized remaining soap value content was obtained. Considering all of this, the EDS technique had higher efficiency to remove glycerol and other contaminants than a conventional separation of gravitation settling. The final biodiesel product was produced with the high purity of 98.0 wt% after purification and met all standard specifications.

Electrocoagulation with AC electrical current at low voltage was implemented to remove crude glycerol from biodiesel which was produced via transesterification reaction of refined palm oil (RPO) as feedstock with methanol in the presence of sodium hydroxide derivative-catalyst at 60°C for 2 hr using the conventional heating in the water bath. Effects of point-to-point electrode configuration, electrode materials, inter-electrode distances, optimized AC low voltages, molar ratios of glycerol and biodiesel product mixture on the separation time and the separation efficiency were studied. Electrocoagulation process with applied AC at 96 V and using Al point-to-point electrodes at the inter-electrode distance of 0.1 cm could efficiently remove free glycerol more than the gravitation settling for the separation time of 120 s. The separation efficiency was over 99.99%. Even though the clear interface between biodiesel and glycerol was firstly observed after applying the electrocoagulation for 30 s, the separation time had to proceed for additional 90 s to eliminate unreacted catalyst. The methyl ester content of 98.56±0.47 wt% was obtained after purification with 2 times of water-washing. This process can be achieved by shortening the separation time and could significantly reduce the water consumption during the purification process.

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This work is focused on the preliminary development of purification process using electrocoagulation technique for biodiesel produced via homogeneous catalyzed transesterification process of refined palm oil (RPO) to shorten the separation process and reduce the water consumption during the final purification with water-washing process. Biodiesel as Fatty acid methyl esters (FAMEs) were produced via transesterification reaction of RPO as feedstock with methanol in the presence of sodium hydroxide derivative-catalyst at the optimal condition using conventional heating. Electrocoagulation separation process was in-house designed to investigate the effects of electrode configurations such as shapes, distances between electrodes and suitable applied AC high voltages (ranging from 1 to 9 kV) on the separation efficiency of glycerol and biodiesel. Results revealed that with the electrocoagulation process at room temperature using AC electrical current at high voltage of 3 kV (and low amperage) with a point to point electrode configuration and the vertical-distance between electrodes of 3 cm was very efficient and achieved higher free glycerol removal than using the conventional separation of the gravitational settling. Furthermore, the separation time was significantly shortened from typically > 24 h with the gravitational settling to 240 s (4 min) and the number of water-washing was reduced from 5 to 3 times during the final purification process. The final purity of biodiesel was 98.89%±0.25% with high quality according to standards of EN 14214 and ASTM D6751.