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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 catalysts were prepared by wet impregnation of blast furnace dust (BFD) in Na 2 CO 3 ·H 2 O, Na 2 CO 3 ·10H 2 O, NaHCO 3 and Na 2 CrO 4 solution and subsequent calcination at 300–600 °C. At low temperature of 65 °C for 2 h with methanol/oil molar ratio of 15/1, high biodiesel yield of 100 wt% was obtained with for both Na 2 CO 3 ·H 2 O@BFD 300 and Na 2 CO 3 ·H 2 O@BFD 400 catalyst (impregnating with Na 2 CO 3 ·H 2 O solution and calcining at 300 and 400 °C) at 7 wt% for the first use. Na 2 CO 3 ·H 2 O@BFD 300 catalyst exhibited outstanding stability and recyclability with biodiesel yield of 100 wt% at the fifth use (93 wt% at the twelfth use) owing to the formation of stable and active nanocomponents of NaFeO 2 (32.42 nm) and magnetic nanocomponent of Fe 3 O 4 (size of 3.14 nm and magnetization of 6.16 Am2/kg). This study finds a solution to use solid waste for the green production of biodiesel. [Display omitted] • NaFeO 2 -Fe 3 O 4 composites were prepared by wet impregnating and calcination. • High biodiesel yield of 100.00 wt% (Na 2 CO 3 ·H 2 O@BFD 300) was obtained at 65 °C. • Efficient biodiesel production can be achieved for 12 reuses with 92.56 wt% yield. • Na 2 CO 3 ·H 2 O@BFD 300 exhibited outstanding recyclability due to nano NaFeO 2 (32.42 nm). • Efficient magnetic separation form nano Fe 3 O 4 (6.16 Am2/kg) ensured continuous production. [ABSTRACT FROM AUTHOR]

This study focuses on evaluating the carbonation potential of argon oxygen decarburization (AOD) slag and analyzing influence mechanism of carbonation on chromium leachability. Static thin-film accelerated carbonation and sequential leaching tests were carried out. Results show that the liquid to solid (L/S) ratio was the most influencing factor for AOD slag's carbonation, and the maximum carbonation ratio of AOD slag was 50–52% (L/S = 0.4 mL/g, P CO2 = 7.5 bar, and t > 6 h). Dicalcium silicate's carbonation resulted in the generation of amorphous calcium carbonate, crystalline calcite and silica gel. AOD slag's smooth surface could be eroded by these products gradually with carbonation furthered. The mineral phase evolution clearly influenced the mineral phase hydrolysis and physical encapsulation, and thus affected the hydrolysis behavior of the primary phase and the generation behavior of the secondary phase in the carbonated slags. Chromium leachability (20 days) declined to its lowest value (1.7 mg/kg) as the carbonation ratio growing to 23% and then increased to its highest value (7.9 mg/kg) with the carbonation ratio increasing to 52%. Chromium leachability varies with the carbonation ratio. The optimal carbonation ratio that resulting in minimum chromium leaching risk must be taken full in mind before using AOD slag in carbonation-related production activities. Image 1 • Static thin-film carbonation tests conducted on AOD Stainless Steel Slag. • Maximum carbonation ratio is 50–52% (L/S of 0.4 mL/g, P CO2 of 7.5 bar and time>6 h) • 23% carbonated AOD slag holds minimum Cr leachability. • 52% carbonated AOD slag holds a higher Cr leachability than original AOD slag. • Carbonation affects Cr leachability mainly by mineral phase hydrolysis and physical encapsulation. [ABSTRACT FROM AUTHOR]

Direct production of biodiesel by both esterification and transesterification of renewable oils with acid value (AV) of 9.6–28.9 mg KOH/g using calcined blast furnace dust is studied. Blast furnace dust calcined at 600–700 °C obviously promotes efficient biodiesel production because of the crystal form transformation from lead sulfate particles in dust into active lead oxide, lead sulfide, and lead particles. It is found for the first time that lead oxide, lead sulfide and lead particles can resist saponification from fatty acids to catalyze raw renewable oils to biodiesel with catalytic activity order as follows: lead oxide > lead > lead sulfide > lead sulfate. Biodiesel production process is optimized according to an orthogonal design with biodiesel yield of 92 wt% obtained at AV of 9.6 mg KOH/g (82 wt% after 5 cycles). Biodiesel yield of 84 wt% is achieved at AV of 28.9 mg KOH/g with acidity of 0.18 mmol/g. Calcined blast furnace dust presents potential applications in the production of biodiesel from renewable oils with high AVs. [Display omitted] • Renewable Jatropha biodiesel is produced by calcined blast furnace dust. • Main components PbO, Pb, PbS, PbSO 4 resist saponification of free fatty acids. • Catalytic activity sequenced as PbO > Pb > PbS > PbSO4 at acid value (AV) 9.6 mg KOH/g. • Jatropha biodiesel yield is 92 and 84 wt% at AV of 9.6 and 28.9. • Calcined blast furnace dust is cycled 5 times with biodiesel yield of 82 wt%. [ABSTRACT FROM AUTHOR]

Electric furnace slag was highly productive and rich in elements, which can be used as a nutrient source for microalgae growth. The regulation of growth and lipid synthesis of Chlorella pyrenoidosa (C. pyrenoidosa) in electric arc furnace slag leaching solution with or without citric acid was investigated to develop efficient lipid production method with low cost. High lipid content of 45.89 wt% from C. pyrenoidosa with adding electric arc furnace slag leaching solution ≤40% into BG11 was obtained due to C. pyrenoidosa increasing lipid accumulation to resist oxidative stress caused by heavy metals in electric arc furnace slag (Ca of 5.13 mg/L, Fe of 0.05 mg/L, Mn of 0.12 mg/L and Cr of 0.01 mg/L). Exogenous citric acid can improve the ability of C. pyrenoidosa to resist heavy metal toxicity with high biomass content (0.44 g/L) achieved. The cooperation of multiple metal ions in electric arc furnace slag shortened the biomass accumulation stage and prolonged and speeded up the lipid synthesis stage of C. pyrenoidosa by modulating PEPC, ACC and ME activities. This study provided guidance for the industrialization of low-cost lipid-rich microalgae and metallurgical solid waste treatment. [Display omitted] • High lipid content (45.89 wt%) was obtained by adding EAFS leaching solution into BG11. • High biomass content (0.44 g/L) was achieved by citric acid assisting EAFS leaching. • The cooperation of elements in EAFS assisted overexpression of ACC and ME in algae cells. • Biomass production was promoted by regulating PEPC in algae cells. • Exogenous citric acid can improve the ability of microalgae to resist heavy metal toxicity. [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]

Metallurgical slag as a by-product of the metallurgical industry not only has huge storage capacity and low price, but also causes serious damage to the environment and threatens the safety of human life by heavy metal in metallurgical slag leaching. The approach of metallurgical slag used to remove pollutants in wastewater is considered to achieve the purpose of "using waste to treat waste". This review focuses on three pretreatment methods of metallurgical slag including acid/alkali pretreatment, mixed pretreatment, and core-shell structure pretreatment, and their structural properties and performance optimization after pretreatment. The removal mechanism of typical pollutants, catalytic performance, reaction conditions, and recyclability of metallurgical slag such as steel slag, blast furnace slag, red mud, copper slag, and manganese slag are summarized and compared. [Display omitted] • Application of metallurgical slag in the wastewater treatment is summarized. • Three pretreatment methods of metallurgical slag are introduced. • Structure and performance of pretreated metallurgical slag are compared. • The removal mechanisms and influencing factors are introduced. • Sustainable utilization of metallurgical slag is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Blast furnace dust (BFD) was impregnated and calcined as heterogeneous catalysts. • Biodiesel yield of 100 wt% (Na-BFD) and 98.3 wt% (Ca-BFD) was achieved at 65 °C. • Na-BFD 500 achieved 95.8 wt% yield for 16 cycles by nano-components NaFeO 2 & Ca 2 Fe 2 O 5. • Ca-BFD 600 reached 94.1 wt% yield for 7 cycles by nano-components CaO & Ca 2 Fe 2 O 5. • Fe 2 O 3 and CaCO 3 in BFD were converted to magnetic and active components. In this study, nanocatalysts for biodiesel production were prepared via wet impregnation of blast furnace dust (BFD) in Na 2 CO 3 (Na-BFD) and CaCO 3 (Ca-BFD) suspension solutions and calcination at 500 and 600 °C, respectively. Biodiesel yields of 100.0 wt% (Na-BFD 500) and 98.3 wt% (Ca-BFD 600) were achieved at 65 °C. Synthesized catalysts showed outstanding activity and recyclability, due to the transition of CaCO 3 , Na 2 CO 3 and Fe 2 O 3 to nanocrystals of NaFeO 2 (29.9 nm), Ca 2 Fe 2 O 5 (10.5 nm), CaO (100.1 nm) and Ca 2 Fe 2 O 5 (50.0 nm). Na-BFD 500 achieved 95.8 wt% biodiesel yield with 16 cycles, whereas Ca-BFD 600 reached 94.1 wt% biodiesel yield with 7 cycles via magnetic separation. BFD containing convertible magnetic and active components (Fe 2 O 3 and CaCO 3) was an ideal raw material to synthesize catalyst for biodiesel production with high catalytic efficiency and easy separation. The study provided a practical utilization of industrial solid waste for biodiesel production. [ABSTRACT FROM AUTHOR]