Scale Deposits from Drinking-Water Pipelines as a Sustainable Heterogeneous Catalyst for Biodiesel Production

Biodiesel has attracted considerable attention as a promising renewable fuel because it burns cleaner than conventional diesel and produces lower pollutant emissions. In this work, a CaO-based heterogeneous catalyst was prepared by calcining drinking water pipeline scale deposits at 900 °C for 2 h. X-ray diffraction (XRD), Fourier transforms infrared (FT-IR) spectroscopy, thermogravimetric analysis (TG-DTA), atomic emission spectrometry ICP-AES, and scanning electron microscopy SEM were used to analyze all the solids. Characterization results revealed that the raw scale deposits mainly consisted of calcite (CaCO3) containing trace amounts of metallic impurities. Catalytic activity was performed on a high-temperature calcined scale material. The effect of catalysts quantities, methanol to oil molar ratios, and reaction periods were researched in order to enhance the biodiesel’s quality. The obtained results showed that at 60 °C, the methyl ester content was 96% under transesterification conditions utilizing a catalyst concentration of 3%, a methanol/oil molar ratio of 12, and a reaction duration of 120 min. The produced biodiesel was also analyzed using FT-IR and NMR. Their properties were recorded according to the ASTM D6751 specifications of biodiesel and were discovered to be within the parameters.