Impurity Shielding in Li/Al-LDH-Based Lithium Recovery from Produced Water via Activated Carbon Pretreatment

Produced water (PW), a complex industrial wastewater byproduct, contains diverse organic contaminants and competing ions that hinder lithium recovery via lithium/aluminum-layered double hydroxide (Li/Al-LDH) adsorption. In this study, an activated carbon (AC)-based pretreatment strategy was developed to improve Li⁺ adsorption efficiency by mitigating impurity-induced interference. Two commercial ACs were screened across three PW sources, with optimal dosage and contact time determined for each. AC pretreatment effectively removed key organic compounds and divalent cations, enhancing the aqueous environment for lithium uptake. More importantly, it preserved the structural integrity of Li/Al-LDH, reducing degradation associated with coadsorbed organics. Adsorption experiments confirmed increased Li⁺ capacity following AC treatment, while adsorption kinetics remained unchanged. Li⁺ selectivity was also modestly improved, particularly over Ca²⁺ and Mg²⁺. Rather than directly enhancing Li⁺ adsorption, AC served as a protective pretreatment, indirectly enabling more efficient and stable lithium recovery. This impurity-shielding approach offers a scalable and environmentally benign pathway for critical mineral recovery from PW, aligning with sustainable water treatment and circular economy principles.