Abstract
This study aims to valorize hazardous industrial marble machining and shaping waste powder as a precursor to prepare a heterogeneous nano-catalyst (CaO/K(2)CO(3)) employing the wet-impregnation method for producing biodiesel via the transesterification of waste cooking oil (WCO). Surface and morphological characterization of the thus-prepared nano-catalyst has been performed employing various analytical tools, e.g., XRD, BET, CO(2)-TPD, FT-IR, HR-TEM, and FE-SEM & mapping EDX. The impact of calcination treatment on the catalytic performance is investigated together with the weight percentage (wt%) of CaO compared to K(2)CO(3). Response surface methodology (RSM) is used to optimize the parametric independent variables, e.g., catalyst loading level, reaction temperature, and time, as well as methanol to WCO molar ratio (M : WCO) via the central composite design (CCD). The experimentally attained optimal reaction parameters for effective biodiesel production (92%) are: 3.2 wt% catalyst loading, operating at 40 °C for 84 min, along with a 5.8 : 1 M : WCO. The proposed nano-catalyst has been recovered and reused effectively for 5 consecutive cycles, with a slight loss in catalytic activity beginning from the 3(rd) cycle. Additionally, the quality of the obtained biodiesel perfectly fits the American (ASTM D-6751) and the European (EN-14214) standard limits.