In this study, carbon-silica based acid catalysts derived from rice husks (RH) were successfully synthesized using microwave (MW) technology. The results showed that MW sulphonation produced Sulfur (S) content of 17.2 -18.5 times higher than in raw RH. FTIR showed peak at 1035 cm -1 which corresponded to O=S=O stretching of sulphonic (-SO3H) group. Peak related to silica (788 cm -1 ) remained even after MW pyrolysis and sulphonation. XRD showed sulfonated RH catalysts (SRHCs) have amorphous structure, and through SEM, broadening of the RH voids and also formation of pores is observed. SRHCs were mesoporous with pore diameter ranging from 3.89 nm to 5.41 nm. SRHCs showed high catalytic activity for esterification of oleic acid with methanol with RH600 had the highest initial formation rate (6.33 mmol.L -1 .min -1 ) and yield (97%).The reusability of the catalyst showed gradual dropped in yield for every reused, which might due to leaching of -SO3H. Finally, esterification of oil recovered from Palm Oil Mill Effluent (POME) ©2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/ licenses/by-nc-nd/4.0/ with methanol achieved a conversion of 87.3% free fatty acids (FFA) into fatty acid methyl esters (FAME).

Palm oil mill effluent (POME) is an inevitable by-product of palm oil industry that

IntroductionIn palm oil mill industry, oil losses during the milling process are unavoidable. The main sources of oil losses are through wastewater clarification, sterilizer condensate and hydro-cyclone, which affect the oil extraction rate, % (OER) and the oil extraction efficiency, % (OEE) of the mills [1], [2]. In palm oil milling process, palm oil mill effluent (POME) is the largest waste generated where 2.5 tons of POME are produced from the average in every ton of oil extracted and typical raw POME contains about 1% or range in 4,000 mg/L of oil and grease [3]-[5]. The presence of residual oil in POME may cause serious environmental pollution due to elevation of biological oxygen demand (BOD) and chemical oxygen demand (COD) values, which could detrimental to aquatic organisms and surrounding habitats if untreated [6]. High concentration of BOD and COD values means high presents of organic matter, thus high consumption of oxygen for the microorganisms to decompose the organic matter [7]. Therefore, against the oil layer could reduce the biological activity of conventional biological ponding system since the suspended