Ammonia stripping and water recovery in a three-compartment membrane distillation system with in situ lithium carbonate precipitation

Ammonia and lithium recovery are increasingly important in resource management. This study developed a three-compartment membrane distillation (MD) module integrated into an electricity-assisted system for ammonia stripping and lithium precipitation. Key operational parameters (feed concentration, temperature, pH, and applied voltage) were systematically investigated. At 0.5000 mol dm −3 feed concentration, the system achieved 60.20% ammonia removal (1843 mg L −1 ), 1.436 × 10 4  mg L −1 ammonia recovered in the acid compartment, and 2.420 g Li 2 CO 3 precipitated on the feed side. At 75 °C, ammonia removal increased to 92.02% (342.5 mg L −1 ) with 1.389 × 10 4  mg L −1 recovered, 1.63-fold lower than the optimal concentration, and 1.950 g of Li 2 CO 3 recovered. pH exerted the strongest influence: at pH 12, ammonia removal reached 95.40% (163.0 mg L −1 ) with recovery of 1.560 × 10 4  mg L −1 , 5× the initial concentration and the highest among all parameters, though lithium recovery decreased to 1.810 g Li 2 CO 3 , confirming elevated pH's critical role in ammonia volatilisation. Continuous direct current at 2.5 V further enhanced performance, achieving 97.17% ammonia removal (121.8 mg L −1 ) and 1.807 × 10 4  mg L −1 recovery while maintaining 2.420 g Li 2 CO 3 recovery. An XGBoost model accurately predicted key variables across compartments. This study demonstrates the potential for efficient, dual-product recovery from complex aqueous streams.