Synergistic regulation mechanism of Co/CTAB in titanium-based ion sieves and its adsorption extraction lithium performance from post-Li2CO3 precipitation liquor

The post-Li 2 CO 3 precipitation liquor (the residual raffinate after Li 2 CO 3 precipitation with pH of 10–12), referred to as the mother liquor, still contains 20 ∼ 25 % of unrecovered Li + . Efficiently extracting lithium ions from the mother liquor has become one of the key challenges to enterprises. A titanium-based ion sieve precursor (LTO-Co/CTAB) was prepared via simultaneous doping of cobalt (II) acetate tetrahydrate ((CH 3 COO) 2 Co·4H 2 O) and cetyltrimethylammonium bromide (CTAB) by solid-phase synthesis method. After acid washing of LTO-Co/CTAB, the Co/CTAB co-doped titanium-based ion sieve (HTO-Co/CTAB) was characterized by XRD, SEM, XPS, etc. Adsorption isotherms and kinetics of Li + on HTO-Co/CTAB, along with its Li + /Na + and Li + /K + separation selectivity in the mother liquor were investigated. The results showed that the solid-phase Co doping coupled with CTAB-assisted dispersion enabled successful nano-scale refinement and functional modification of HTO-Co/CTAB. The formation of Co-O-Ti bonds, lattice distortions and its short diffusion paths of nanoparticles (100–200 nm) were all beneficial for the diffusion and enrichment of Li + within the channels of HTO-Co/CTAB. The adsorption behavior of Li + on HTO-Co/CTAB was well-described by Langmuir isotherm adsorption model ( R 2  = 0.996) and pseudo-second-order kinetic model ( R 2  = 0.996). An equilibrium uptake capacity of HTO-Co/CTAB for Li + in the mother liquor (initial concentration of Li + , Na + and K + was 1450, 33,800 and 6900 mg/L) could reach 39.78 mg/g, which was 39 % higher than that of HTO, and the equilibrium time was shortened to 5 h compared to HTO (20 h). The separation factors of Li + /Na + and Li + /K + for HTO-Co/CTAB were 677.45 and 284.43, respectively, and it had excellent stability.