Study of the direct production of lithium phosphate with pure synthetic solutions and membrane electrolysis

[Display omitted] •Production of Li3PO4 was studied with synthetic solutions and membrane electrolysis.•New process was proposed for natural alkalisation of the catholyte to produce Li3PO4.•Results revealed that the optimal operating conditions were 25 °C and 7.3 mA/cm2.•Temperature negatively affects the efficiency of the membrane and Li3PO4 recovery.•X–ray diffractograms indicates that the proposed process produces high purity Li3PO4. This work studies a membrane electrolytic process, where a diluted lithium chloride brine solution is concentrated, while simultaneously producing lithium phosphate. This innovative process takes advantage of the alkaline pH generated in the cathodic section, allowing added phosphoric acid to be precipitated as lithium phosphate. The influence of the operation variables, such as temperature and current density, was evaluated to optimise the precipitation process. Some key findings were observed: a) the optimal conditions for the precipitation of lithium phosphate were 25 °C and 7.3 mA/cm2, as the chemical equilibrium was reached in a shorter time period (15 min) under these operating conditions; b) the efficiency and stability of the cationic membrane was favoured at 25 °C; c) it was possible to concentrate the lithium chloride brine solutions to precipitate lithium phosphate, while neutralising the alkaline pH of the cathodic section; and d) the experimental results could be explained using fundamental thermodynamics.