Accelerated low-temperature, low-fouling brine concentration through evaporative ion exchange mediated by the effect of functional groups

Achieving brine concentration by membrane distillation or the various humidification–dehumidification processes that are currently available always requires a thermal energy input and an elevated temperature. In this study, we developed a brine concentration process mediated by the unique osmotic and evaporation properties of high-capacity ion exchange resins. The evaporative ion exchange process consists of two steps. First, when a concentrated salt solution is brought into contact with a relatively dry, high-capacity polymeric ion exchanger, water selectively permeates into the ion exchanger phase through osmosis and the resin swells. In the second step, water evaporates when the swollen ion exchanger is brought into contact with air with low relative humidity and the resin shrinks. Here we show that, with hypersaline produced water from Marcellus gas shale, this evaporative ion exchange process attained total dissolved solids greater than 400,000 mg l−1, leading to the precipitation/crystallization of barium and sodium chloride at ambient temperature without causing any fouling of the ion exchange resins. The evaporative ion exchange process developed in this study achieves brine concentration at ambient temperature without fouling, providing a non-thermal brine concentration technology towards zero liquid discharge.