BACKGROUND: Nafion ® membranes have found several applications in chemical processes, one of which is 'salt splitting', where a salt is split to produce acid and/or alkali. So, the determination of the behaviour of this membrane in the electrolysis of certain salts is an important issue. The aim of this study is to investigate the performance of Nafion ® 424 membrane in a two-compartment membrane cell for the membrane electrolysis of lithium sulphate (Li 2 SO 4 ), where lithium hydroxide (LiOH) is the target product. RESULTS: Regression analysis was performed between conductivity and concentration to predict instantaneous electrolyteconcentration. The effects of catholyte concentration (4-8% LiOH), current density (4-16 A dm −2 ) and temperature (30-60 ∘ C) were investigated. 45-70% current efficiency; 6.1-14.6 kWh kg −1 LiOH power consumption and 140-900 g LiOH m −2 membrane h −1 production rate were obtained. A cost estimation revealed that 60 ∘ C, 8% LiOH and 4 A dm −2 are the optimum parameters within the studied range. CONCLUSION: Concentration can be successfully predicted for lithium sulphate and lithium hydroxide with the help of conductivity-concentration regression equations. Current efficiency is affected primarily by LiOH concentration with a direct proportion. Power consumption increases with the increase of current density and the decrease of temperature. Based on production cost estimation, optimum working parameters can be recommended.

This study aims to measure the solubility and binary eutectic point parameters (temperatures, densities, and compositions) of H 3 BO 3 −H 2 O, Na 2 B 4 O 7 −H 2 O, and NaBO 2 −H 2 O solid−liquid equilibrium systems. Eutectic temperatures were determined using multichannel thermometers equipped with high-precision Pt25 (±0.004 °C) sensors, whereas densities of the eutectic points were measured using a density meter equipped with an oscillating high-precision U-tube (±0.00005 g/cm 3 ) sensor. Chemical compositions of the binary eutectic point samples were analyzed using an ICP-OES instrument. Eutectic parameters, that is, temperature, density, and composition of the H 3 BO 3 −H 2 O binary system were determined to be −0.61 ± 0.01 °C, 1.0114 ± 0.0005 g/cm 3 , and 2.37 ± 0.07 wt% respectively. Similarly, the same eutectic parameters were measured as −0.30 ± 0.01 °C, 1.0116 ± 0.0004 g/cm 3 , and 1.05 ± 0.06 wt% for the binary system of Na 2 B 4 O 7 −H 2 O, whereas eutectic parameters of the NaBO 2 −H 2 O binary system were found to be −6.11 ± 0.01 °C, 1.1823 ± 0.0004 g/cm 3 , and 13.40 ± 0.09 wt%.