ZnO‐Functionalized Silicon Carbide Ceramic Membranes for Removing Impurities From Biodiesel

ABSTRACT This study investigates zinc oxide (ZnO)‐functionalized silicon carbide (SiC) ceramic membranes for biodiesel purification, focusing on phosphorus, sulfur, and metallic impurity removal. Flat‐disc SiC membranes, with ∼37% porosity, were prepared via controlled dip‐coating and characterized by x‐ray diffraction (XRD), SEM, x‐ray fluorescence (XRF), air permeability, and liquid permeation tests (isopropyl alcohol, IPA; on‐spec biodiesel). Air permeation analysis yielded Darcian ( k 1 ) and non‐Darcian ( k 2 ) permeability coefficients of 3.27 ± 0.19 × 10 −15 m 2 and 5.68 ± 0.19 × 10 −12 m, respectively. Crossflow microfiltration of crude and neutralized biodiesel at 3 bar and ∼25°C showed acceptable permeance with IPA (10.7 ± 2.2 L/h m 2 bar) and on‐spec biodiesel (5.63 ± 1.69 L/h m 2 bar). However, severe flux decline occurred with crude biodiesel, indicating fouling. Critically, ZnO–SiC membranes effectively reduced calcium (64.5–16.6 mg/kg), sodium (8.2–0.96 mg/kg), and phosphorus (25.8–8.6 mg/kg) to compliant levels. Sulfur removal was minimal, suggesting ZnO limitation against stable organosulfur compounds under mild conditions. These findings position ZnO‐functionalized SiC membranes as robust polishing systems for selective metal and polar contaminant removal, while highlighting the need for integrated catalytic or hybrid strategies for sulfur reduction.