Quaternary blend of Carica papaya - Citrus sinesis - Hibiscus sabdariffa - Waste used oil for biodiesel synthesis using CaO-based catalyst derived from binary mix of Lattorina littorea and Mactra coralline shell

Abstract

These studies focuses on synthesizing of an efficient CaO-based-catalyst derived from the binary mixture of Lattorina littorea (periwinkles shell) and Mactra coralline (seashell), and apply it to transesterification of a quaternary mix of Carica papaya - Citrus sinesis- Hibiscus sabdariffa- Waste used. Details characterization of the developed catalyst was carried out using SEM, FTIR, and XRD to establish its catalytic potential. Process parameters optimization for the transesterification process was carried out to determine the optimum yield of biodiesel from oil blend. Lattorina littorea and Mactra coralline were made into powder by milling after drying, the powdered were mixed in the same ratio to obtain a developed catalyst before characterization. Oil was extracted from Carica papaya, Citrus sinesis, Hibiscus sabdariffa seed powder through solvent extraction method, the extracted oil was mixed in quaternary ratio with waste used oil, the properties of the mixed oil was determined before the transesterification with ethanol. Process optimization was carried using response surface methodology (RSM) coupled with central composite design (CCD) by considering four independent variables (reaction time, derived calcined catalyst powder (DCCP) amount, reaction temperature, and EtOH/OMR). The catalyst recyclability test was carried out, and the biodiesel quality was determined through physicochemical properties. The results showed 25:25:25:25 quaternary blend produced oil with low viscous and high volatility. Thermal treatment of a developed catalyst (DP) from Lattorina littorea mix with Mactra coralline, at 900 C for 3 h produced CaO of 99.02 (% wt.) on XRD analysis result. The produced catalyst developed was re-used up to 3ecycles for base transesterification. The maximum experimental yield of 99.95 (% wt.) at a reaction time of 60 min, DCCP amount of 3.0 (g), reaction temperature of 70 C, and EtOH/OMR of 6:1 (ml/ml), was obtained, but the statistical optimization predicted biodiesel yield of 99.8044 (wt. %) at a reaction time of 57.72 min, DCCP amount of 3.0 (g), reaction temperature of 69.54 C, and EtOH/OMR of 6:1 (ml/ml), this yield was validated in triplicate and an average biodiesel yield of 99.7800 (%wt.) was obtained. Analysis of variance and the p-value showed that the selected variable factors were remarkably significant (p-value<0.0001). Based on fit statistics and model comparison statistics, the coefficient of determination (R squared) of 99.84% was obtained with the predicted R2 of 99.06 in reasonable agreement with the adjusted R2 of 99.68. The quality of biodiesel produced was within the specification limits of biodiesel standard.