New Insights into the Fate of Electrode in Flow Electrode Capacitive Desalination of Industrial RO Reject

Reverse osmosis technique is a globally adopted process for producing quality water, regardless of the area of application. Yet, low water recovery and reject disposal are critical concerns still left unsolved. The feasibility of desalinating industrial RO reject with flow electrode capacitive deionization (FCDI) is attempted, keeping a future goal of coupling FCDI with RO process for industrial water treatment applications. Saline activated carbon flow electrodes are the most economical and environment friendly choice to enhance the efficiency of FCDI technique. Along with the performance metrics of FCDI in treating RO reject, the impact of salinity to the flow electrode sustainability is assessed. With saline-activated charcoal (AC), 63% of total dissolved solids (TDS) removal was achieved on desalinating second stage RO reject of concentration 39,480 mg/L, whereas with non-saline AC it was 34%. On prolonged desalination, carbon oxidation is observed even in the absence of saline electrolyte. The same is identified as slightly enhanced, in saline condition. Corrosion rate compared between the unspent carbon and spent carbons at non-saline and saline conditions were 7.3, 13.5, and 16.5 mm/year, respectively, implying that the impact specific to saline condition is relatively less.

Automated summary

This study investigates the feasibility of desalinating industrial reverse osmosis reject using flow electrode capacitive deionization (FCDI) and assesses the impact of salinity on flow electrode sustainability. The results show that using saline-activated carbon can achieve a higher removal rate of total dissolved solids in the reject.