Recycling solvent and managing impurities: Screening industrial wastes for cyclic operation in indirect mineral carbonation

Indirect mineral carbonation converts CO 2 into precipitated calcium carbonate (PCC) while neutralizing alkaline industrial waste. The process relies on a solvent to extract calcium before precipitation, making efficient solvent recycling essential for technical, environmental and economic feasibility—yet this remains largely unexplored. This study evaluates the recyclability of aqueous ammonium nitrate using three different industrial residues: basic oxygen furnace slag (BOFS), cement kiln bypass dust (CKBD), and municipal waste incineration bottom ash (MWBA). Continuous experiments were conducted over 18 h, representing 24 solvent recycling cycles and a cyclic steady model was developed and validated against experimental datato support predictive process design. Ammonium nitrate proved recyclableunder effective control of ammonia volatilization. BOFS enabled stable operation and consistently produced high-purity PCC (>99 %), meeting specifications for high-value applications. Conversely, CKBD and MWBA suffered impurity-driven performance losses. CKBD released highly soluble alkaline impurities that inhibited calcium extraction, progressively reducing PCC production by over 60 %. PCC purity decreased from 98 % in single-cycle experiments to 95 % for MWBA and to 90 % for CKBD due to sulfates, copper, and accumulated alkali metal chlorides. Pre-washing CKBD with water removed soluble alkali impurities, stabilizing PCC production and significantly improving purity. The polymorphic composition remained stable throughout the process, yielding predominantly vaterite with some calcite. While ammonium nitrate is recyclable, these findings highlight the need for impurity management strategies to maintain process stability and product quality, with potential for co-recovery of valuable elements such as potash or trace metals. • Solvent recycling tested over 24 cycles for steel slag and two types of incineration ash. • Stable performance upon ammonium nitrate recycling using impurity-poor feedstocks. • Impurity accumulation reduced PCC purity and lowered process performance up to 60%. • Pre-washing solids removed alkali impurities, increasing PCC purity from 90% to 97%. • Cyclic-steady-state model captured impurity effects and solvent degradation.