We reveal the critical role of electrolyte pH in efficiency and durability during electrochemical cement clinker precursor production and how to control it.

To extract alumina (Al2O3) from secondary aluminum dross (SAD) with low energy consumption and high efficiency, a novel method is proposed. This method involves the preparation of the precursor of dodecacalcium hepta-aluminate (12CaO·7Al2O3) clinker through the introduction of carbide slag (CS) into SAD during hydrolysis process, followed by calcination at moderate temperatures and subsequent alkaline leaching. During hydrolysis process, tricalcium aluminate hexahydrate (Ca3Al2(OH)12) is formed through reactions between calcium hydroxide (Ca(OH)2) and aluminum hydroxide (Al(OH)3). The removal efficiencies of metallic aluminum (Al) and aluminum nitride (AlN) are thus significantly enhanced, and more valuable ammonia (NH3) gas and hydrogen (H2) can be recovered. Meanwhile, calcium fluoride (CaF2) is generated due to the fixation of fluorine by Ca(OH)2. In addition, a porous clinker with excellent leachability was prepared after calcination at 1050 °C. As a result, an Al2O3 extraction rate of 95% was obtained by leaching the clinker in a sodium carbonate (Na2CO3) solution. Furthermore, the superiority was revealed by evaluations of economic costs and environmental impacts.