Energy Harvesting by Waste Acid/Base Neutralization via Bipolar Membrane Reverse Electrodialysis

Abstract

Bipolar Membrane Reverse Electrodialysis (BMRED) can be used to produce electricity exploiting acid-base neutralization, thus representing a valuable route in reusing waste streams. The present work investigates the performance of a lab-scale BMRED module under several operating conditions. By feeding the stack with 1 M HCl and NaOH streams, a maximum power density of ~17 W m−2 was obtained at 100 A m−2 with a 10-triplet stack with a flow velocity of 1 cm s−1, while an energy density of ~10 kWh m−3 acid could be extracted by a complete neutralization. Parasitic currents along feed and drain manifolds significantly affected the performance of the stack when equipped with a higher number of triplets. The apparent permselectivity at 1 M acid and base decreased from 93% with the five-triplet stack to 54% with the 38-triplet stack, which exhibited lower values (~35% less) of power density. An important role may be played also by the presence of NaCl in the acidic and alkaline solutions. With a low number of triplets, the added salt had almost negligible effects. However, with a higher number of triplets it led to a reduction of 23.4–45.7% in power density. The risk of membrane delamination is another aspect that can limit the process performance. However, overall, the present results highlight the high potential of BMRED systems as a productive way of neutralizing waste solutions for energy harvesting.

The Acid–Base Flow Battery: Sustainable Energy Storage via Reversible Water Dissociation with Bipolar Membranes

“…Moreover, the development of bipolar membranes specifically tailored for the ABFB application (i.e., able to withstand high current densities under forward bias without delaminating) will allow to operate the ABFB at higher discharge current densities, and hence to increase the power density. Power density of 17 W/m 2 total membrane area has already been achieved at the lab scale [ 36 ], and simulations by our model predict power densities up to 30 W/m 2 ( Section 3.1 ). Taking into consideration that the development of new membranes with lower resistance will decrease the internal resistance of the battery stack in the future, power densities in the range of 30–40 W/m 2 (100 W/m 2 triplet assumed for the cost calculations) could be realistically achieved.…”

“…This aspect was highlighted by Culcasi et al, who modeled ABFB systems predicting a loss in round-trip efficiency in the range of 25–35% due to parasitic currents [ 35 ]. More recently, Zaffora et al investigated the ABFB under different conditions of acid–base concentration (focusing on the discharge phase, similarly to Pretz and Staude [ 27 ]), and reported a maximum power density of 17 W/m 2 , and energy density of 10 kWh/m 3 (1 M HCl-NaOH, at 100 A/m 2 current density during discharge) [ 36 ].…”

Chemical and Energy Recovery Alternatives in SWRO Desalination through Electro-Membrane Technologies

“…R-EDBM, at its current low TRL, is able to produce high energy densities (considering concentrations of 1.0 M of acid and base) approximately one order of magnitude than the ones reported for mixing salt and freshwater [72]. Most of the research works in literature to date [32,[72][73][74][75][76][77][78][79][80] use HCl as the acidic solution and NaOH as the alkaline solution, both with concentrations up to 1.0 M. Even if 1.0 M concentrations are the standard maximum so far, higher concentrations could enhance the performance of R-EDBM [72], due to higher pH gradients. Aside from HCl and NaOH, R-EDBM could recover energy from acidic and alkaline byproduct or waste streams, achieving by its integration improvements in the environmental performance of the processes.…”

“…Aside from HCl and NaOH, R-EDBM could recover energy from acidic and alkaline byproduct or waste streams, achieving by its integration improvements in the environmental performance of the processes. Among the mentioned studies, Xia et al [76] and Zaffora et al [79] are those that report higher power densities, with~15 W•m −2 (stack of 20 membrane triplets) and~17 W•m −2 (stack of 10 membrane triplets), respectively, for current densities of 100 A•m −2 .…”

Recovery of Acid and Base from Sodium Sulfate Containing Lithium Carbonate Using Bipolar Membrane Electrodialysis

“…The anion and cation membranes are bonded by an intermediate catalytic layer. When a current is applied to the bipolar membrane, water was split into hydrogen ions and hydroxide ions in the interfacial layer of the bipolar membrane [ 13 , 14 , 15 ]. Electrodialysis (ED) technology is an electromembrane separation process in which anions and cations migrate to opposite electrodes under the action of a direct current electric field, thereby achieving ion separation, concentration, and purification [ 16 , 17 , 18 ].…”