Synthesizing LiFePO by phosphate & iron recovered from sludge-incinerated ash and Li extracted from concentrated brines.

Phosphorus (P) recovered from sludge-incinerated ash (SIA) could be applied to synthesize highly added-value products (FePO and LiFePO) with in situ Fe in SIA. Indeed, LiFePO is a future of rechargeable batteries, which makes lithium (Li) highly needed. Alternatively, Li could also be extracted from concentrated brines to face a potential crisis of Li depletion on lands. Based on HPO and Fe co-extracted from the acidic leachate of SIA by tributyl phosphate (TBP), FePO (31.2 wt% Fe, 17.6 wt% P and the molar ratio of Fe/P = 0.98) was easily formed only adjusting pH of the stripping solution to 1.6. Interestingly, the organic phase from the first-stage co-extraction process of Fe and HPO could be utilized for Li-extraction from salt-lake brine, based on the TBP-FeCl-kerosene system, and a good performance (78.7%) of Li-extraction and separation factors (β) (186.0-217.4) were obtained. Furthermore, the compounds with Li-extraction are complex, possibly LiFeCl∙2TBP, in which Li could be stripped to form LiCO by 4.0 M HCl (with a stripping rate up to 83%). Besides, LiCO could also be obtained from desalinated brine by adsorption with manganese oxide ion sieve (HMO) and desorption with HCl. In the two cases, almost pure LiCO products were obtained, up to 99.7 and 99.5 wt% LiCO respectively, after further purification and concentration. Finally, recovered FePO and extracted LiCO were synthesized for producing LiFePO that had a similar electrochemical property (69.5 and 77.8 mAh/g of the initial discharge capacity) to those synthesized from commercial raw materials.