Recovery of Ca²⁺ and SO₄ ²- from Bittern Wastewater using Electrodialysis Method

Abstract

The recovery of bittern is expected to obtain the added value products and minimize untreated wastewater disposal generated from the salt industry. Bittern is a waste stream resulted from the crystallization of the salt production process, consisting of a concentrated mineral in liquid form, known as the mother liquor of salt. The dominant minerals that can be recovered in bittern are calcium (Ca2+) and sulfate (SO4 2-), and salts such as calcium chloride, potassium sulfate, sodium chloride, and calcium sulfate, which are commonly found in bittern wastewater. In this study, mineral recovery of bittern was conducted by applying cylindrical membrane electrodialysis technology, due to the high demineralization rate and the applicability on fluctuating composition of the feed. This study determined differences in applied electrical current, temperature conditioning, recirculation flow rate, and specific energy requirements based on the optimum process. This research was conducted in the applied current of 5A, 7.5A, and 10A. Then, the temperature conditioning in the feed tank with a range of 25°C – 35°C, 36°C – 45°C, and without conditioning. The applied flow rate recirculation was 30 L/h and 36 L/h for 5 hours electrodialysis time. The highest removal efficiency was 31.57% and 35.03%. This result was achieved at 30 L/hour of flow rate recirculation, 10 A, and 40°C for Ca2+ and SO4 2-. Furthermore, the recovery efficiency of the ionic products was 30.17% and 27.62% for Ca2+ and SO4 2-, respectively.