A novel lithium phosphate production method by stripping of lithium from the lithium enolate in kerosene using orthophosphoric acid

Abstract

A novel orthophosphoric acid stripping (OpaS) system has been developed for the stripping and crystallization of lithium from the synergistically produced organolithium compound consisting of lithium enolate in kerosene. In order to determine regression models and optimum conditions, a D-optimal experimental plan was constituted. Reduced quadratic, cubic and quartic models were selected for lithium and non‑lithium metal stripping responses. Accordingly, the linear terms of A and B (A: Organic/aqueous phase ratio [O/A], B: [H3PO4]) were determined as a major factor for all lithium responses while the only two-factor interaction (2FI) of AB was determined for all responses. In optimization, the non‑lithium responses were minimized while the lithium responses were maximized. The O/A was determined as 8.2 when the upper limit of 1.0 M was targeted for [H3PO4]. The optimum validated lithium stripping yield and mass fraction of lithium crystallized were predicted as 94.1% and 0.77, respectively. Based on the lithium strip McCabe Thiele diagram, two theoretical stages are required with a 1.0 M H3PO4 strip solution at an O/A ratio of 8.2. At the validated optimum equilibrium pH (pH[eq]) of 7.44, the Li3PO4 crystals of 92.2% purity of were obtained. As a result, the OpaS system has been proven to be a novel method for stripping and crystallization of lithium as Li3PO4 from the lithium enolate organic system without any requirement of thermal and extra chemical processes.