Waste cooking oil can be considered as an alternative biodiesel feedstock for replacing edible oils. However, this feedstock can not be directly used since it contains much impurities and high Free Fatty Acid (FFA) content. Thus, pre-treatment process is required to enhance the feedstock quality. Adsorption using activated carbon is one of various methods that can be applied to reduce FFA content which is relatively easy and cheap. Coconut fiber is biomass waste that can be utilized in activated carbon production. This work has successfully synthesized activated carbon from coconut fiber with activator medium of H3PO4 10% weight and carbonization temperature of 600 °C, indicated from yield, water content, ash content, and methylene blue adsorption capacity. The yield of carbonization process developed in this work reached 40% while the yield for water content, ash content, and methylene blue adsorption capacity were 2.5%, 2.3% and 1646.1 mg/g carbon, respectively which complied with SNI 06-3730-1995.  This adsorbent was tested on fixed bed adsorption column with FFA reduction reached up to 93% at waste cooking oil flowrate of 3 ml/min for 45 minutes operation time.

Herein, the adsorption-photocatalytic performance of composite titanium dioxide (TiO2) and Activated Carbon (AC) to decompose methyl orange was investigated systematically. This work demonstrated the synthesis of TiO2/AC composite via the sol-gel method. After getting the composite TiO2/AC under different ratios of AC, the prepared particles were then annealed at 500°C for 2 h. The presence of AC detected by Fourier transform infrared (FTIR) spectra at 1028 nm. Based on Brunauer–Emmett–Teller (BET) analysis, the result showed that the prepared particles specific surface area increased by increasing the AC ratio. The prepared photocatalyst was used to decompose methyl orange under UV light irradiation for 90 minutes. From the photocatalytic performance, the additional AC did not influence the adsorption process significantly under dark conditions. Interestingly, during the irradiation process, methyl orang could be decomposed until 62.5%, which means 15% higher than that of bare TiO2. The present result showed that an additional AC could enhance photocatalytic performance due to its ability as an electron transfer and avoid the recombination process between electrons and holes.

The superhydrophobic composite membrane was successfully manufactured by a sol-gel method by drying the surrounding pressure. Tetraethylorthosilicate (TEOS) was used as a hydrophobic agent, while waterglass was used as a source of silica. The effect of the water to waterglass ratio (noted at 16:1 and 19:1) was evaluated to study the hydrophobic properties of the silica film coated composite membrane surface. By measuring the water contact angle on the film surface, the highest contact angle was found to occur at the ratio of 19:1, which is 143.86°. The stability of the composite membrane was also investigated by immersing the membrane in water until day 6. The results show that the synthesized composite membrane has good stability until day 6. The hydrophobicity of the surface of the silica film membrane was found to be unaffected by immersion time. Furthermore, the hydrophobicity increased after 6 days due to the interaction of alkyl groups with the humidified environment, and the surface was more stable in hydrophobicity (i.e., the contact angle of water is 153.79°). In addition, hydrophobic properties were obtained, confirming that this film has the potential to be applied to the separation of oil-water emulsions.

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