For both the waste treatment of large quantities of blast furnace (BF) slag and carbon dioxide (CO₂) that are discharged in ironworks, mineral carbonation by BF slag was proposed in this decade. However, it has not been widely used due to its high energy consumption and low production efficiency. In this study, a microwave roasting method was employed to mineralize CO₂ with BF slag, and the process parameters for the sulfation and energy consumption were investigated. A mixture of BF slag and recyclable ammonium sulfate [(NH₄)₂SO₄] (mass ratio, 1 : 2) was roasted in a microwave tube furnace, and then leached with distilled water at a solid : liquid ratio of 1 : 3 (g mL^-1). Under the optimized experiment conditions (T = 340 °C, holding time = 2 min), the best sulfation ratios of calcium (Ca), magnesium (Mg), aluminum (Al), and titanium (Ti) were 93.3%, 98.3%, 97.5%, and 80.4%, respectively. Compared with traditional roasting, the production efficiency of this process was more than 10 times higher, and the energy consumption for mineralizing 1 kg of CO₂ could be reduced by 40.2% after simulation with Aspen Plus v8.8. Moreover, 236.1 kg of CO₂ could be mineralized by one ton of BF slag, and a series of by-products with economic value could also be obtained. The proposed process offers an energy-efficient method with high productivity and good economy for industrial waste treatment and CO₂ storage.

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To improve the boron-removal efficiency of metallurgical-grade silicon by increasing the reaction rate, a combined method with the 30 mol pct CaO-23.3 mol pct SiO2-46.7 mol pct CaCl2 slag treatment and ammonia injection at 1723 K to 1823 K was proposed. For 1 hour and at 1823 K, the maximum removal efficiency of boron was 98 pct, and the final boron concentration in silicon decreased to 1.5 ppmw by the present method without the introduction of the iron catalyst. A kinetic model was also established to clarify the reaction mechanism and rate-limiting steps of this complicated boron-removal process. In this model, the rate-limiting step is the mass transfer of boron oxide at the interface between the slag and silicon phase.@en

Solar energy has received considerable attention over the past few decades, due to its importance as a green and renewable energy. Low-cost solar-grade silicon production is critical for the widespread use of solar cells. Conventional routes (e.g., modified Siemens process: chlorosilane and hot filament) have still dominated the production of solar-grade silicon. The metallurgical route offers benefits in the productivity and cost, but efficient removal of boron is one of the most daunting challenges in front of us. This paper reviews thermodynamic and kinetic properties (solubility, diffusivity, diffusion coefficients, mass transfer rate, and activity coefficient) of boron and recent research topics (slag treatment, solvent refining, gas injection, plasma treatment, and acid leaching) for boron removal.

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