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Metallurgical slag such as solid waste generated in the steel industry carries environmental pollution risks, but it is rich in nutrients required by microalgae. Metallurgical slag used for carbon capture and biomass energy conversion has multiple benefits: (i) reduction and harmless treatment of metallurgical solid waste, (ii) assisting in carbon neutrality by efficient carbon fixation, and (iii) production of biodiesel from CO2. In this study, AOD, BOF, BFS, HVS, and VTS slag were applied to culture Chlorella pyrenoidosa (C. pyrenoidosa) with the regulation of growth, carbon fixation, and lipid synthesis. An excellent fixed amount of CO2 with 94.59 mg is obtained from C. pyrenoidosa biomass at BOF slag added (mass ratio of CO2 captured/microalgae/slag with 1.99/1.00/10.53) since high Ca/Mg mass ratio of 419 (8.38 mg/L Ca and 0.02 mg/L Mg), no Cr and low concentration of Al (0.04 mg/L) contribute to regulating antioxidant enzyme activity (SOD and POD) to resist ROS and improving PEPC activity to reduce carbon flux toward lipid to promote biomass synthesis. Both metal concentrations from Ca (5.86 mg/L), Mg (0.05 mg/L), Al (0.42 mg/L), and Cr (0.006 mg/L) and suitable pH (10.53) in AOD leaching solution at solid/liquid ratio of 0.5 g/L change carbon flow toward efficient lipid synthesis (47.07 wt%) by continuously providing raw materials and energy by regulating ACC, ME, and PEPC activities. High value‐added biodiesel with high concentrations of C16 and C18 methyl esters from lipid of C. pyrenoidosa is achieved, following other ecological and economic benefits including 197 mg CO2 captured and 2198 mg AOD applied with harmless. In this study, C. pyrenoidosa is cultured with elements from metallurgical slag solid waste, which promotes C. pyrenoidosa efficient carbon fixation to assist in carbon neutrality, and provides guidance for CO2 conversion to high‐value‐added products with low cost. [ABSTRACT FROM AUTHOR]

As a by-product from the metallurgical industry, steel slag contains a large amount of metal elements. In many developing countries, the output of steel slag is huge and the comprehensive utilization rate is low, hence the development of a novel application method for steel slag is of great significance to increase its utilization rate to improve the environment. This paper reviewed the dissolution behavior of Fe, P, Ca and silicate of steel slag under seawater and acidic solutions as an application in the cultivation of different microalgae, such as diatoms, spirulina, and chlorella. This review clarifies that proper pre-treatment of steel slag can effectively increase the dissolved elements of steel slag in the solution and provide more nutrients for the growth of microalgae. Microalgae cultivated with steel slag as a nutrient can be used to produce biodiesel which has a very broad application prospects for cleaner production and environmental protection. [ABSTRACT FROM AUTHOR]

Resistance of biodiesel industrial production came from high energy consumption and feedstock costs. To solve it, Na 2 CO 3 @BFD catalyst was prepared from blast furnace dust and used to catalyze biodiesel production at low temperature. Biodiesel yield of 99.04 wt% was obtained under conditions optimized by response surface methodology of methanol/oil molar ratio 13.72/1, catalyst dosage 9.77 wt % and 74.86 °C for 1.62 h. The order of influence of the four factors was temperature (245.9) > time (109.8) > methanol/oil molar ratio (23.83) > catalyst dosage (1.19). Back propagation neural network model (BPNN) was optimized using genetic algorithm (GA) and sparrow search algorithm (SSA) to predict biodiesel yield. The evaluation indexes of mean absolute error, mean square error, root mean square error and mean absolute percentage error of SSA-BPNN were 0.9236, 2.0184, 1.4207 and 1.0247 (vs. 2.4329, 9.1037, 3.0172 and 3.5000 for GA-BPNN and 4.3291, 43.4693, 6.5931 and 6.9227 for BPNN), indicating that SSA-BPNN model had excellent prediction ability to effectively reduce experimental costs and resource consumption. The reaction kinetics of Na 2 CO 3 @BFD for transesterification process showed that its activation energy was 65.73 kJ/mol, lower than that of reported solid base catalyst, indicating that it had significant potential in biomass conversion. [Display omitted] [ABSTRACT FROM AUTHOR]

Highly stable heterogeneous catalysts were prepared by impregnating carbonates suspension solutions onto electric furnace dust (EFD) and being calcined at high-temperature for the production of biodiesel from soybean oil. Process of impregnating with CaCO 3 , BaCO 3 , SrCO 3 and CdCO 3 suspension solutions and being calcined at high-temperature did not promote improvement of catalytic activity of EFD powder, while the single impregnating with K 2 CO 3 suspension solution can only improve its catalytic activity in the first use. Na 2 CO 3 @EFD catalyst synthesized by impregnating with only Na 2 CO 3 suspension solution owned considerable catalytic activity from nano Na 2 CO 3 (37.0 nm) and good recyclability from nano Fe 3 O 4 (size of 30.0 nm & Ms of 26.77 Am2/kg) with biodiesel yield of 99.13 wt% at 65 °C in 2 h with 15/1 methanol/oil molar ratio and 7 wt% catalyst dosage in the first use (93.50 wt% in the eleventh use). The kinetic study with Na 2 CO 3 @EFD was carried out, and it was found that the activation energy was 32.81 kJ/mol and the frequency factor was 3760.85 /min, lower than reported solid base catalysts, which suggested synthesized Na 2 CO 3 @EFD catalyst owned remarkable potential for industrial application in biomass energy conversion. Highly stable heterogeneous catalysts were prepared with carbonates suspension solutions impregnating onto electric furnace dust to catalyze the production of biodiesel from soybean oil with biodiesel yield of 99.13 wt% in the first use (93.50 wt% in the eleventh use). [Display omitted] • Highly stable catalysts were prepared by impregnating with carbonates onto EFD. • High biodiesel yield of 99.13 wt% was obtained at 65 °C within 2 h. • Good recyclability from Na 2 CO 3 for transesterification and Fe 3 O 4 for separation. [ABSTRACT FROM AUTHOR]

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 Am2/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. [Display omitted] • Nanocatalyst was synthesized by impregnating electric furnace dust in Na 2 CO 3 solution. • It was bifunctional with high basicity and acidity of 0.34 and 0.16 mmol/g. • High biodiesel yield of 99.79 wt% was obtained at 71 °C. • 90.84 wt% biodiesel yield was still achieved after 11 cycles. • Metals in biodiesel met National Standard, lower than that petrochemical diesel. [ABSTRACT FROM AUTHOR]