Technological breakthroughs

Compiled by Bao Hien

A research team at the University of Palermo (Italy) has published the latest results in a years-long research program on bipolar membrane electrodialysis (EDBM) — a technology that allows caustic soda (NaOH) and acid to be produced directly from waste brine streams, rather than discharging them into the environment as is conventional practice. The latest study, published in the journal Desalination, focuses on improving the system's capacity to handle concentrated brine at semi-industrial pilot scale.

The Problem to Solve: Waste Brine and the Process's Fresh Water Demand

Seawater desalination plants, along with many other industries (non-ferrous metallurgy, high-salinity industrial wastewater treatment), generate large volumes of concentrated brine that must be managed. As discharge regulations continue to tighten, the "Minimum Liquid Discharge" (MLD) model is drawing growing interest as a way to both comply with regulations and recover valuable resources from these waste streams.

EDBM technology uses an electric field to split a salt solution into its corresponding acid and base — for instance, sodium chloride (table salt) can be used to simultaneously produce hydrochloric acid (HCl) and caustic soda (NaOH). However, according to the research team, one of the technology's key limitations is that the process requires large amounts of fresh water to dilute the acid and base compartments within the system — a requirement that runs counter to the very goal of treating and utilizing saline wastewater, particularly in water-scarce regions.

A New Configuration: "Water Salt Backflip" to Cut Fresh Water Consumption

In the study published in 2026, the research team — Giovanni Virruso, Calogero Cassaro, Alessandro Tamburini, Andrea Cipollina, and Giorgio Micale of the Department of Engineering, University of Palermo — tested a new operating configuration called "Water Salt Backflip" (WS-BF), in which, instead of using only fresh water to dilute the acid or base compartments, concentrated brine is fed directly into these chemical-producing compartments.

Test results showed that feeding brine into the alkaline compartments did not affect the system's energy performance, while still achieving up to a 50% reduction in fresh water consumption — a significant improvement in the process's sustainability. The team observed similar behavior when brine was fed into only the acid compartment or only the base compartment alone, and testing with two different commercial membrane sets (from suppliers Fumatech and SUEZ) showed productivity differences ranging from 9% to 40% between the two — indicating that the choice of membrane supplier is also a significant factor affecting overall system performance.

Results from Earlier Trials: Effective with Real Brine, Not Just Synthetic Solutions

This latest study is part of an ongoing series of work by the same Palermo-based research team, carried out on the same semi-industrial-scale EDBM pilot system. In an earlier study published in 2023 in the journal ACS Sustainable Chemistry & Engineering, the team tested the system under both continuous and batch operating modes at varying current densities (200-500 A/m²). Results showed that at low current density (200 A/m²), closed-loop operation achieved the lowest specific energy consumption (1.4 kWh/kg) with high current efficiency (80%); while at higher current densities (300-500 A/m²), the "feed and bleed" mode proved more suitable, thanks to its low specific energy consumption (1.9-2.6 kWh/kg) and high specific production rate (0.82-1.3 tonnes/year/m²).

Another study by the same group, published in late 2024, tested the system not only with synthetic salt solutions but also with real waste brine taken from a seawater desalination plant — finding that switching from synthetic salt solution to real brine actually improved the efficiency of base (alkali) production. The technology has also been successfully tested with high-salinity brine generated by the non-ferrous metallurgy industry — a study published in early 2026 in the journal Water, Air, & Soil Pollution recorded H2SO4 and NaOH concentrations of 0.539-0.563 and 1.270-1.313 mol/L respectively during on-site pilot operation.

Implications for the Basic Chemicals Industry

Taken together, this body of research shows EDBM technology gradually maturing from laboratory-scale experiments to semi-industrial pilot scale, with demonstrated effectiveness across a range of real-world saline waste streams — from seawater and desalination reject brine to metallurgical wastewater. For the basic chemicals industry — producers of caustic soda and inorganic acids — this represents a noteworthy direction: rather than relying solely on the conventional chlor-alkali electrolysis process, which requires purified salt as feedstock, EDBM technology opens up the possibility of harnessing waste brine streams — previously regarded purely as an environmental treatment cost — to generate an additional source of basic chemicals, while also easing the burden of saline wastewater treatment for related industries.