Waste snail shell derived heterogeneous catalyst for biodiesel production by the transesterification of soybean oil

A waste snail shell (<i>Pila spp.</i>) derived catalyst was used to produce biodiesel from soybean oil at room temperature for the first time. The snail shell was calcined at different temperatures of 400-1000 °C. The synthesized catalysts underwent XRD, SEM, TEM, EDS, FTIR, XRF, TG/DTA and N₂ adsorption-desorption isotherm (BET) analysis. The major component CaO was determined at a calcination temperature of 900 °C as depicted in the XRD results. 100% conversion of soybean oil to methyl ester biodiesel was obtained, as confirmed by ¹H NMR. A biodiesel yield of 98% was achieved under optimized reaction conditions such as a calcination temperature of 900 °C, a catalyst loading of 3 wt%, a reaction time of 7 h and a methanol to oil ratio of 6 : 1, and biodiesel conversion was confirmed by FT-NMR and IR spectroscopies. A total of 9 fatty acid methyl esters (FAMEs) were identified in the synthesized biodiesel by the retention time and fragmentation pattern data of GC-MS analysis. The catalyst was recycled 8 times without appreciable loss in its catalytic activity. A high biodiesel yield of 98% was obtained under these optimised conditions. The catalyst has the advantage of being a waste material, therefore it is easily prepared, cost free, highly efficient, biogenic, labor effective and environmentally friendly, making it a potential candidate as a green catalyst for low cost production of biodiesel at an industrial scale.