Many countries produced biodiesel from crude vegetable oil. However, current vegetable oil feedstock to produce biodiesel slow the growth of biodiesel blend implementation due to the high cost of feedstock production. As a result, waste cooking oil (WCO) is claimed to be economic and readily available without cultivation and highly potential feedstock for high yield biodiesel. In this study, Fe-exchanged montmorillonite K10 (Fe-MMT K10) was employed as a catalyst in converting WCO to biodiesel. In comparison, Fe-MMT K10 was able to produce 95.26% biodiesel, which is higher than biodiesel produced using unmodified MMT K10 as catalyst and reaction without catalyst (38.39% and 29.50%, respectively). The full process of biodiesel production was carried out by response surface methodology (RSM) in conjunction with the central composite design (CCD) for statistically optimization and modelling. From the ANOVA, it was found that the production of biodiesel achieved an optimum level of 92.74% biodiesel at 134.07 °C, under a specific optimized condition of 6.32 h reaction time, 4.68 wt% of catalyst and 11.77:1 methanol to oil ratio.

The modification of montmorillonite K10 with Fe3+ was investigated to study the optimum ion-exchange occurred in the interlayers of clays. Montmorillonite K10 was modified to be applied as a catalyst in biodiesel production from waste cooking oil (WCO). Three methods to optimize the ion-exchange process were investigated. For method 1 and method 2, respective 14% and 27% by mass of Fe in montmorillonite K10 were stirred in a closed cap system for 7 hours while method 3 applied 20% of Fe stirred with montmorillonite K10 for 24 hours until it became mold and slurry. The ability of ion-exchange was tested using SEM/EDX. It was found that 1.21% Fe composition increased by using method 1 while 2.66% Fe increased using method 2. The highest Fe exchange was detected using method 3 with 5.23% increment. For more accurate result, 20% Fe-MMT K10 from method 3 was characterized using XRF and it was found that the ion exchange occurred with interchangeable Ca2+. In correlation, the effect of Fe increment on acidity was studied by using TPD-NH3. Naturally, montmorillonite K10 possessed 0.232 mmol/g of acidity. The results found that the highest acidity was detected for 20% Fe-MMT K10 (14.261 mmol/g). The application of montmorillonite K10 on biodiesel production increased the yield up to 38.39% compared to the reaction without catalyst (26.80%). With the aid of modified montmorillonite K10, 66.54% and 69.32% biodiesel were produced using catalyst from method 1 and 2 respectively. Amazingly, an outstanding yield was produced by using catalyst from method 3 (84.58%). Therefore, 20% Fe-MMT K10 catalyst was selected for further biodiesel optimization via conventional method. It was found that 96.49% biodiesel was successfully produced with 28.65% acid conversion at 150 °C, 6 h, 12:1 methanol: oil and 4 wt.% mass of catalyst. The investigations on acid conversion and biodiesel yield proved that the modification of montmorillonite K10 with 20% Fe is the optimum and the catalyst can undergo both esterification and transesterification reactions simultaneously to produce optimum biodiesel yield. © 2020, Malaysian Society of Analytical Sciences. All rights reserved.