1. The similar Li(I) and Mn(II) concentrations before and after adsorption (Fig. 4a) indicates their negligible uptakes by HPCA@SiO 2 @Fe 3 O 4 . The molar Q e of Co(II) is 10 times higher than Mn(II) and 100 times than Li(I), confirming Co(II) preference of HPCA@SiO 2 @Fe 3 O 4 . The K D values (Fig. 4b) also indicate that Co(II) prefers the HPCA@SiO 2 @Fe 3 O 4 phase over the feed with K D = 1880 mL g -1 vs. Li(I) and Mn(II) with K D < 50 mL g -1 . Their CF values also suggest that Co(II) can be concentrated 970 times by HPCA@SiO 2 @Fe 3 O 4 relative to the feed vs. Li(I) and Mn(II) with lower CF < 34. Thus, HPCA@SiO 2 @Fe 3 O 4 is ? =166 more selective towards Co(II) vs. Li(I) and ? = 55 vs. Mn(II) (Fig. 4c). Unfortunately, the lack of studies on Co(II) selectivities limits the comparison to one reported adsorbent 2-hydroxy benzaldehyde/magnetite-silica;( Co;HPCA@SiO 2 @Fe 3 O 4 was evaluated using simulated LIB liquid waste with Co(II)
2. The binding sites of HPCA are borderline "hard" pyridine (aromatic -N=) and "hard" -COOH groups [73] and their combination resulted in a moderately "hard" ligand that is most compatible with moderately "hard" Co(II) with ?G 0 f,Co(II) = -13.0 kcal mol -1 vs;These findings demonstrate the suitability of HPCA for preferential Co(II) binding over Li(I) and Mn
3. Cobalt in lithium-ion batteries;M Li;Science,2020
4. Cobalt-base high-temperature alloys;J Sato;Science,2006