Multi-stage thermally assisted alkali activation for simultaneous self-solidification of multiple heavy metals in lithium slag

• • Mechanical strength of solidified lithium slag reached 3.48–8.25 MPa under full slag conditions; optimized composite activator and multi-stage thermal assistance increased strength by 137.07%, enabling structural applications without cement addition. • • Average heavy metal immobilization rate improved from 97.26% to 99.77%, with leachate concentrations below regulatory limits in acidic (pH 3), neutral (pH 6.5), alkaline (pH 10), high-salt (0.1 M NaCl), acid rain, and leachate simulations, ensuring environmental safety. • • The process promotes formation of Si-O-Al skeletal structures, reducing structural defects and enhancing durability; this mechanism underpins both mechanical performance and long-term metal retention. • • Solidification cost is 185–200 CNY per ton of slag, significantly lower than conventional cement-based methods, with low energy consumption and no high-temperature calcination, offering a scalable and economically viable solution for lithium slag management.