Effect of Operating Parameters on Bromine Extraction from Desalination Plant Discharge

A comprehensive utilization of concentrated seawater is crucial in order to promote the development of the desalination industry as a key solution to global freshwater. Debromination of the desalination plant effluent as well as the bromine product extraction are two parallel goals, which have been the subject of many research studies as well as industrial operations. In this investigation, bromine extraction is investigated experimentally form the effluent of the Konarak desalination plant located in Chabahar bay, Iran. For this purpose, an air blow-out method is used, and the effects of the operating parameters including the temperature, pH, and chlorine gas flow rate are examined in a continuous reactor. The parameters are optimized, and the trend is discussed in details. The bromine concentration of the sample collected from the Pozm Tiyab area, close to the plant discharge point, has been determined to be 1.172 g/L using ion chromatography. A pre-concentration procedure is conducted in order to reach a concentration of 3.100 g/L by evaporation. A reactor with the dimensions of 60 mm × 800 mm is designed and assembled for the experimental studies. In order to investigate the operating parameters, a central composition design (CCD) method is used. Among the factors studied, only the chlorine gas flow rate has a substantial effect on the bromine recovery, and the effects of the other two factors are negligible in the pH range of 2-3 and the temperature range of 50-70 °C. At the three chlorine concentrations of 1, 1.5, and 2 L/min, the bromine production increases almost linearly with the increasing chlorination injection rate. The Br2 gas is recovered with a maximum rate of 93.8% and a bromine loss of 185 mg/L in the mother liquid. The optimum operating parameters to achieve this recovery are a pH of 2.5, a temperature of 60 ˚C, and a chlorine gas flow rate of 1.5 L/min.