Towards Water, Sodium Chloride and Natural Organic Matter Recovery from Ion Exchange Spent Brine

Abstract

Despite the tremendous success of the application of anion exchange resins (IX) in natural organic matter (NOM) removal over conventional removal methods, the considerable amount of brine spent during its regeneration cycle makes its sustainability questionable. This polluting saline stream can be challenging to manage and costly to discharge. Alternatively, and with the recent shift in perception of resource recovery, the produced spent brine can no longer be seen as a polluting waste but as an unconventional source of water, minerals and nutrients. In this research, for the first time, we evaluated the effectiveness of an integrated monovalent selective electrodialysis (MSED) and direct contact membrane distillation (DCMD) system in IX spent brine desalination and resource recovery. Of particular interest were the effects of operating time on the characteristics of the monovalent permselective ion exchange membranes, the impact of the DCMD stack configuration on minimizing heat loss to the ambient environment and the efficacy of the recovered NaCl in the regenerating cycle of the exhausted IXs. Our findings demonstrated that although the recovered NaCl from the stand-alone MSED can restore nearly 60% ion exchange capacity of the exhausted IXs, coupling MSED with DCMD led to minimizing the consumption of fresh NaCl (in the IX regeneration cycle) significantly, the potential application of NOM in agriculture and diminishing the risk of the IX spent brine disposal. In addition, the initial characteristics of the ion permselective membranes were maintained after 24 h of MSED and the transmembrane flux was increased when the feed/hot compartment (in the DCMD stack) was encapsulated on two outer ends with coolant/permeate compartments as a result of less heat loss to the ambient environment.

Effects of Halides on Organic Compound Degradation during Plasma Treatment of Brines

“…Though the amount of Br – compared to Cl – is relatively consistent in brines (i.e., 0.1–1 mol % Br – , Table S3), the absolute concentrations of halides vary substantially (e.g., 0.007–2 M Cl – , Table S3). ,,,,,,− Therefore, we expanded our experiments to evaluate the effect of halides at different concentrations but at a constant ratio of Br – to Cl – (i.e., 0.1–2 M Cl – with 1 mol % Br – ). The inclusion of halides at concentrations higher than 0.5 M Cl – and 5 mM Br – increased the degradation rate of para -hydroxybenzoate by 2- to 4-fold relative to ClO 4 – at the same ionic strength and conductivity (Figure f).…”

“… ,,− Like Cl – and Br – , additional constituents (i.e., sulfate, SO 4 2– ; nitrate, NO 3 – ; carbonates; organic matter) were added at brine-relevant concentrations (Table S3). ,,,,,,− Some of these constituents have known reactivities with the reactive species of interest (Table S5). ,,,− All salts used in this study contained sodium as the cation.…”

Electrodialysis Processes an Answer to Industrial Sustainability: Toward the Concept of Eco-Circular Economy?—A Review

“…Among them, authors have investigated the treatment of ion exchange resin brine to recover salts (NaCl) and organic matter ( Figure 11 ). Indeed, the ion exchange resins step is major to remove these contaminants from water for aesthetic and operational purposes and also to avoid repercussions for human health [ 183 ]. Nevertheless, the brine produced is complex to discharge and is polluting.…”

“…The use of monovalent ion permselective membranes avoids the formation of fouling and allows the production of an NaCl solution of high purity. Another solution tested was to integrate monovalent selective electrodialysis (MSED) and a direct contact membrane distillation system to improve the process’s eco-efficiency [ 183 ]. The pure NaCl produced was used to regenerate the resins, which decreased the use of fresh NaCl.…”

“…Indeed, the solution produced allowed the recovery of up to 85% of the IEC. Thus, brine was seen as an unconventional source of water, minerals, and nutrients [ 183 ].…”