Efficient production of biodiesel with electric furnace dust impregnated in Na2CO3 solution

Solid catalyst (Na 2 CO 3 @EFD) was prepared by wet impregnation of electric furnace dust (EFD) in aqueous Na 2 CO 3 solution. It had high basicity and acidity of 0.34 and 0.16 mmol/g for biodiesel production. High biodiesel yield of 99.8 wt% from soybean oil was obtained under the optimized reaction conditions (by Central Composite Design) of 71 °C in 111.36 min with 5.4 wt% catalyst and methanol/oil molar ratio of 11.8/1. After 11 cycles, biodiesel yield still maintained at 90.8 wt% with catalyst recovery rate >90 wt% by magnetic separation of catalyst EFD powders (containing Fe 3 O 4 with magnetism of 59.1 Am 2 /kg). Pure Na 2 CO 3 particles presented poorer recyclability with lower biodiesel yield of 89.5 wt% even at the eighth cycle by centrifugal separation . Na 2 CO 3 @EFD catalyst had high activity and recyclability because: (i) EFD as support hosted nanoparticles of Na 2 CO 3 (30.3 nm) as main base site for transesterification ; (ii) porous EFD support provided acidic sites from metal oxides (e.g., ZnO and Al 2 O 3 ) for esterification; (iii) EFD adsorbed active components into its micropores to maintain high recyclability; and (iv) EFD magnetism from magnetic Fe 3 O 4 kept high efficient magnetic separation. Total metals in the blended biodiesel met the National Standard of China and heavy metals were lower than typical petrochemical diesel . The study gave a practical use of industrial solid waste for the green production of biodiesel.