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[Display omitted] • A novel method for treatment of red mud and carbide slag has been proposed. • Achieved stepwise separation and recovery of Ti, Al, Ga, Fe, and Sc. • Replacing NaOH with carbide slag to adjust the pH of the leaching solution. • CaCO 3 phase and morphology can be controlled to meet various industrial needs. Red mud and carbide slag, strongly alkaline solid wastes, are produced during the manufacturing of alumina and acetylene gas, respectively. Improper management of these wastes can pose significant environmental hazards. This study proposed a novel method for the collaborative treatment of red mud and carbide slag, enabling the recovery of constituent elements with CO 2 sequestration. During the hydrochloric acid leaching process, Si was reclaimed as Si-rich residue, whereas Ti, Al, Ga, Fe, and Sc were stepwise recovered as Ti-rich product, Al/Ga-rich filtrate, and Fe/Sc-rich product via the subsequent hydrolysis, co-precipitation, and alkali leaching processes, respectively. Utilizing carbide slag to replace the energy-intensive NaOH for pH adjustment in the leaching solution resulted in a Ca2+ concentration of 21,922 mg/L in the filtrate after co-precipitation. Through further mineralization process, CO 2 sequestration was achieved alongside the production of CaCO 3 with the content reaching 98.5 % along with a whiteness of 94.4 %. Furthermore, by adjusting the experimental parameters in the mineralization process, controlled manipulation of the phase and morphology of the CaCO 3 product could be achieved to meet various industry requirements. To summarize, the complete resource recovery of red mud and carbide slag was achieved in this study, demonstrating the promising potential in practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The production of silicon fertilizer while recovering Ga and K has been achieved. • The addition of KOH improved the leaching efficiency of Ga and K. • Ga and Al in the filtrate were recovered during carbonation precipitation. • The regeneration of lye can be achieved through the causticization reaction. Brown corundum fly ash (BCFA) is a fine dust generated during the smelting process of brown corundum. It is rich in gallium and potassium, and improper handling can cause severe environmental damage. This study proposes a cyclic process of calcification leaching, carbonation precipitation, and lye regeneration for the collaborative treatment of BCFA and carbide slag. The leaching efficiencies of gallium and potassium were determined to be 94.02 % and 85.32 %, respectively, under the optimized conditions (120 min, 180 °C, Ca/Si molar ratio 0.9, KOH 10 g/L) of calcification leaching. The contents of effective SiO 2 and CaO in the silicon fertilizer were measured at 34.71 wt% and 33.02 wt%, respectively. During the carbonation precipitation process, gallium and aluminum were extracted from the filtrate and achieved respective contents of 2.1429 wt% and 32.99 wt% in the resulting coprecipitate. The carbonated lye was regenerated through a causticization reaction, and after four cycles, the regenerated lye maintained a consistently high leaching efficiency for gallium and potassium. This method achieves the comprehensive utilization of BCFA and carbide slag without generating any waste residue or wastewater. Additionally, it provides a novel approach for the collaborative treatment of similar solid wastes. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 sequestration and high-value utilization of CSS have been realized. • NH 4 Ac exhibits higher efficacy than NH 4 Cl for Ca2+ extraction. • The CaCO 3 product is high purity vaterite with a whiteness of 95.2%. • The effective SiO 2 of the silica fertilizer is 53.12 wt%, while the pH is 7.34. Calcium-silica slag (CSS) is a highly alkaline residue, rich in calcium, generated during the chemical pre-desilication process of medium- and low-grade bauxite. Mismanagement of CSS can result in detrimental environmental impacts. This study developed a novel method that combines CO 2 sequestration with CSS utilization, thereby achieving simultaneous dual-value enhancement of CSS and eliminating waste discharge. Under optimized Ca2+ leaching and carbonation conditions, a remarkable Ca2+ extraction efficiency of 96.93 % was attained, while the carbonation efficiency reached 99.37 %. Consequently, this process sequestered 301.7 kg of CO 2 per ton of CSS. The leaching process of Ca2+ in NH 4 Ac solution was realized based on the unreacted shrinking core model, which accounts for internal diffusion and chemical reaction as factors influencing leaching. The resulting carbonated product exhibited outstanding characteristics: high-purity vaterite composed of 97.43 wt% CaCO 3 with a whiteness level of 95.2 %. By regulating the carbonation temperature, the crystal particulate size distribution of CaCO 3 was tailored to meet specific requirements for various applications. Furthermore, silicon content was enriched in the leaching residue, increasing the effective SiO 2 content from 25.2 wt% to 53.12 wt% and reducing the pH from 12.23 to 7.34, rendering it a suitable silica fertilizer for agricultural production. [ABSTRACT FROM AUTHOR]