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Abstract
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Water desalination plants produce huge amounts of reject brine, which are usually sent back to the sea. These wastewaters can in the long run, result in detrimental effects on the aquatic life as well as the quality of the seawater in the area. In this research, an approach for the management of saline water and the production of solid sodium bicarbonate, has been investigated. This process does not involves the use of ammonia. Instead, it is the chemical reaction between the sodium chloride salt present in the abalone with carbon dioxide in the presence of calcium hydroxide. In this study, the effect of various process parameters such as reaction temperature, sodium chloride salt concentration and calcium hydroxide concentration on the 4-hour reaction time for the modified Solvay process based on calcium oxide, was investigated by using response surface methodology and central composite design. The results were well fitted by the quadratic polynomial model (R2 = 0.94). Optimal conditions when using synthetic sodium chloride solution for maximum sodium removal efficiency up to 51.53%, temperature 10 °C, calcium hydroxide to sodium chloride salt concentration ratio 0.36 and gas flow 800 ml/min for this process, determined. Subsequently, the optimum extraction rate of sodium up to 43%, was obtained by testing the actual desalination reject brain with a salinity concentration of 63 g/l. In order to study the kinetics of sodium removal during the process, three models of zero, first and second order kinetics models were used. During this study, when using synthetic salin, R2 was set to 0.9101, 0.915 and 0.9141 for the zero, first and second degree kinetic models, respectively. Whereas, when using real salin for the kinetic models R2 obtained 0.9115, 0.9324 and 0.9532, respectively. Therefore, the removal of sodium in real salin follows the quadratic kinetic model.
The results showed that the modified Solvay process based on calcium oxide has a high potential for reducti
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