Integration of monopolar and bipolar electrodialysis for valorization of seawater reverse osmosis desalination brines: Production of strong acid and base

Abstract

Water scarcity in the Mediterranean basin has been solved by using seawater desalination reverse osmosis technology (SWD-RO). This technology produces brine which is discharged back into the sea resulting in an environmental impact on marine ecosystems. Under the circular economy approach, the aim of this work is to recover resources from NaCl-rich brine (~60-70 g/L), e.g. in the form of NaOH and HCl, by integration of two ion exchange-based membrane technologies and quantify the electrical energy consumption. Electrodialysis (ED) incorporating monovalent selective cation exchange membranes as divalent ions purification and concentration of the NaCl present in the SWD-RO brine, was integrated with bipolar membrane ED (EDBM) to produce NaOH and HCl. Current densities of 0.30–0.40 kA/m2 at two temperature ranges simulating different seawater temperature regimes (15-18 ºC and 22-28ºC) were tested and a pure NaCl solution was used as starting concentrate stream. NaCl-rich brines with 100 or 200 gNaCl/L were obtained by ED and then introduced in the EDBM stack producing HCl and NaOH up to 2 M, depending on the initial concentrations. A minimum energy consumption of 1.7 kWh/kgNaOH was calculated when working by EDBM with initial concentrations of 104 g NaCl/L and 0.24 M HCl and NaOH.Peer ReviewedPostprint (author's final draft

Integrated Valorization of Desalination Brine through NaOH Recovery: Opportunities and Challenges

“…[7,9] 2. [12][13][14] Each of the pretreatment methods provides ad istinct way of valorizing the SWRO brine (Table 1). [10,11] To produce NaOH and HCl, the SWROb rine can first be pretreated through nanofiltration (NF), selective electrodialysis (SED), or electrodialysis (ED); and, subsequently,i tc an be processed by electrodialysis with bipolar membranes (BMED) into the products of interest ( Figure 1).…”

“…[13] By increasing the NaCl concentration prior to BMED treatment, the higher concentration can enhance the performance of the BMED process owing to ah igher ionic conductivity,h ence lower ohmic losses.H owever,o ne key inefficiencyo fE Dt hat requires further attention is the removal of multivalent ions from the SWROb rine.A ss tated before,S WROb rine contains other ions in addition to Na + and Cl À ;t he presence of divalent ions such as Ca 2+ and Mg 2+ can deteriorate the performance of BMED membranes.I no rder to prevent membrane scaling from calcium and magnesium ions,s ome researchers have proposed the use of monovalent-selective membranes in ED,i nw hich the CEMs are coated with ap olymer (e.g.,p olyaniline) that rejects divalent cations. NF and SED both remove multivalent ions,b ut they do not concentrate the brine stream, so the resulting monovalent-rich stream is less able to produce concentrated acids and bases.C onversely, since ED pretreatment can concentrate NaCl up to 200 gL À1 , the BMED system can produce NaOH and HCl at higher concentrations (approximately 2 m).…”

“…[10,11] To produce NaOH and HCl, the SWROb rine can first be pretreated through nanofiltration (NF), selective electrodialysis (SED), or electrodialysis (ED); and, subsequently,i tc an be processed by electrodialysis with bipolar membranes (BMED) into the products of interest (Figure 1). [12][13][14] Each of the pretreatment methods provides ad istinct way of valorizing the SWRO brine (Table 1). NF can purify the concentrated brine such that the brine mainly contains monovalent ions.…”

Potential of nanofiltration and reverse osmosis processes for the recovery of high‐concentrated furfural streams

“…Separation methods with membrane process technology have attracted great attention owing to their unique ability to separate and purify process streams . Several studies have been intensively investigating the removal, recovery and purification of inhibitors such as furfural from biomass by using membrane process technology .…”

“…Separation methods with membrane process technology have attracted great attention owing to their unique ability to separate and purify process streams. [28][29][30][31][32][33] Several studies have been intensively investigating the removal, recovery and purification of inhibitors such as furfural from biomass by using membrane process technology. [34][35][36][37][38][39][40][41] For instance, Sagehashi et al 40 used a reverse osmosis (RO) membrane (NTR-759HR) to separate phenols and furfural from pyrolysis of biomass with superheated steam aqueous solution and observed that furfural was recovered (maximum 70%) by the RO membrane.…”