Valorization of aluminum dross into calcium-aluminum composite for efficient chloride removal from saline wastewater

Calcium-aluminate composite (Ca/Al composite) exhibits a promising structural fixation capacity for removing chloride ions (Cl − ) from saline wastewater, but its application is hindered by the dependence on expensive commercial alumina (Al 2 O 3 ). This study represents the first attempt to valorize industrial aluminum dross (Al dross) as a low-cost alternative Al source, establishing a new route for converting solid waste into functional sorption materials. Pretreated Al dross was combined with CaO at a Ca: Al molar ratio of 1:1 and sintered at 1100 °C via a solid-phase reaction to prepare the Ca/Al composite. The Cl − removal performance and mechanism were systematically investigated. The findings are as follows: (1) Ca/Al composite could efficiently remove Cl − in saline wastewater, in which tricalcium aluminate was identified as the primary component responsible for Cl − uptake, and the Cl − removal efficiency exceeded 90 %, with a maximum sorption capacity of 85.01 mg/g (2) The sorption mechanism was dominated by chemisorption with synergistic physisorption, accompanied by mineral phase transformation. (3) This method offers a low-cost and sustainable route for Cl − removal, with an estimated cost of 4.91 USD/kg of Cl − removed, which is about one-third lower than commercial Al 2 O 3 . Overall, this study established a novel, cost-effective valorization pathway for Al dross and provided new insights into the structure-reactivity relationship of calcium-aluminate-based adsorbents, enabling efficient Cl − removal from saline wastewater while advancing environmental sustainability and resource recovery.