Bench Scale Production of Sodium Hydroxide from Solar Salt in Ghana

Abstract

Currently, sodium hydroxide as well as other chlor-alkali products used in Ghana and the entire ECOWAS sub-region is imported in spite of the huge salt potential as raw material available in Ghana. This study sought to produce sodium hydroxide (NaOH) from solar salt in Ghana using the membrane cell process. Sodium stearate solution was used as alternative brine purification for calcium and magnesium impurities present in the salt. Sulphate impurities were also precipitated with calcium chloride. The electrolytic membrane cell consisted of carbon and stainless-steel electrodes separated by Nafion 117 membrane. Titration methods were then used to analyse the electrolytic products and it was established that the impure solar salt contained 6030 ppm, 1920 ppm, 1030 ppm and 0.43 ppm of sulphate, calcium, magnesium and iodine impurities respectively. It was also realised that for each batch of purification, an optimal sodium stearate solution per 1 litre of brine solution required was 200g. Five brine concentrations i.e. 27 wt%, 28 wt%, 29 wt%, 30 wt% and 31wt% were prepared and used for the electrolysis. However, the 29 wt% brine concentrations produced the highest amount of sodium hydroxide of 6.1g at the fifth hour at a current efficiency of 44.92%.This study concludes that solar salt mined in Ghana is suitable for the production of sodium hydroxide using the membrane cell process