Brine recovery from reverse osmosis effluents using an automatic temperature control system: salt crystallization.

Abstract

The improper brine effluent disposal from the reverse osmosis (RO) process of the industry and mining sites poses various environmental problems including impaired soil ability to produce crops, difficulties for breeding and migrating birds. Various treatment methods reported to provide a short-term solution in which separation of the mixed salt byproducts remains a great challenge. The present study aimed at assessing the performance of locally available automatic temperature control (ATC) system to recover brine from RO effluents through salt crystallization. Laboratory trials via batch experiment containing individual and mixed samples of NaCl·2H₂O, Na₂SO₄·10H₂O, and Na₂CO₃·10H₂O were conducted to evaluate the influence of freezing temperature, concentration, and contact time. The maximum recovery efficiencies of 85.3% (NaCl·2H₂O), 93.3% (Na₂SO₄·10H₂O), and 32.0% (Na₂CO₃·10H₂O) of the individual samples were achieved at 72 h (-26 °C), 96 h (-10 °C), and 2 h (-2 °C), respectively. For mixed samples at -10 °C and 3 h in 50 mL, 29.37 g (65.27%) were recovered with ionic constituents such as Na⁺ (34.1%), Cl^- (1.6%), SO₄^2- (11.3%), CO₃^2- (32.4%), and impurities (20.57%). The findings of this study suggested that ATC could be used as an alternative technology for brine recovery from RO process of industry and mining operation sites.