Nesquehonite and hydromagnesite are hydrated magnesium carbonates (HMCs) that can play important roles in cementitious systems due to their seeding effects and contributions to microstructural development. This study presents a novel CO 2 mineralization strategy for producing high-purity nesquehonite and hydromagnesite using two industrial by-products: reject brine and paper sludge ash (PSA). The developed process involved precipitating magnesium from reject brine using PSA, followed by wet carbonation to form Mg(HCO 3 ) 2 solution and carbonated PSA (CPSA). Nesquehonite and hydromagnesite were produced by drying Mg(HCO 3 ) 2 solution at 50 °C and 105 °C, respectively. Characterization results confirmed the high purity and distinct microstructures of the produced HMCs. Isothermal calorimetry demonstrated that CPSA showed potential as a supplementary cementitious material in Portland cement-based mixes, while HMCs performed as effective seeds in Na 2 CO 3 -activated slag cement. The proposed method achieved 85.5% recovery degree of magnesium; moreover, it offers CO 2 sequestration potential through storage in HMCs while reducing alkali costs compared to conventional methods. Overall, this process provides a feasible route for waste valorization and CO 2 mineralization, while highlighting key scale-up considerations including brine variability, impurity tolerance, and energy demand associated with water removal during drying. • Novel CO 2 mineralization strategy, producing nesquehonite and hydromagnesite from reject brine and paper sludge ash (PSA). • Magnesium from reject brine wet carbonated to form Mg(HCO 3 ) 2 solution and carbonated PSA (CPSA). • CPSA used as SCM in PC-based mixes, while HMCs performed as effective seeds in Na 2 CO 3 -activated slag cement. • Proposed method achieved 85.5% recovery degree of magnesium, providing economic benefits through reduced alkali costs. • Process offers a feasible solution for waste utilization, CO 2 sequestration, and cement performance enhancement.
Du et al. (Sun,) studied this question.