Exploring hydrogen production for self-energy generation in electroremediation: A proof of concept

Abstract

Highlights• Self-produced H2 from electrodialytic treatment of environmental matrices collected • Collected H2 average purity (% mol/mol) of ≈ 98%• A fuel cell used to produce electricity from the self-produced H2 (~1 V)• Experimental self-generated energy promotes savings on electroremediation (≈ 7%) AbstractElectrodialytic technologies are clean-up processes based on the application of a low-level electrical current to produce electrolysis reactions and the consequent electrochemically-induced transport of contaminants. These treatments inherently produce electrolytic hydrogen, an energy carrier, at the cathode compartment, in addition to other cathode reactions. However, exploring this by-product for self-energy generation in electroremediation has never been researched. In this work we present the study of hydrogen production during the electrodialytic treatment of three different environmental matrices (briny water, effluent and mine tailings), at two current intensities (50 and 100 mA). In all cases, hydrogen gas was produced with purities between 73% to 98%, decreasing the electrical costs of the electrodialytic treatment up to ≈ 7%. A protonexchange membrane fuel cell was used to evaluate the possibility to generate electrical energy from the hydrogen production at the cathode, showing a stable output (~1 V) and demonstrating the proof of concept of the process.

Electrodialytic Hydrogen Production and Critical Raw Materials Recovery from Secondary Resources

“…Six electrodialytic experiments were carried out with three matrices and two current intensities (50 and 100 mA), in duplicate: Sewage sludge, mining residues with effluent, and mining residues with sewage sludge. The data from these experiments was compared with the effluent and mining residues data from [17], and ten electrodialytic experiments were evaluated ( Sewage sludge tests were performed adding 200 mL of sample to the central compartment. Suspensions with effluent or sewage sludge and mining residues were prepared at the same L/S (9), adding 22.2 g of solid sample to 200 mL of liquid sample.…”

“…Six electrodialytic experiments were carried out with three matrices and two current intensities (50 and 100 mA), in duplicate: Sewage sludge, mining residues with effluent, and mining residues with sewage sludge. The data from these experiments was compared with the effluent and mining residues data from [17], and ten electrodialytic experiments were evaluated ( Table 1).…”

“…Despite of promising results in substances removal and separation from a wide range of solid and liquid environmental matrices, energy requirements for electro-based technologies operation are still one of the main operational drawbacks of these treatments. Regarding current low-carbon economy principles [16], this topic was addressed in a proof-of-concept work presented by Magro et al, 2019 [17]. The use of hydrogen produced during the electrodialytic process due to water electrolysis reactions was studied.…”

“…Water was reduced to hydrogen gas, with purity levels up to 97% (mol/mol) and promoting the generation of ≈1 V electrical energy throughout the course of wastewater treatment. However, many factors may decrease hydrogen cleanliness, namely the typology of the process, the experimental matrix, and the presence of contaminants, involving competitive redox reactions at the electrodes (e.g., chlorine gas, metals deposition) [17].…”

Applying Chemometrics to Evaluate Tungsten Mining Residues Potential As Partial Cement Replacement

“…Electroremediation [8] and natural deep eutectic solvents (NADES) [9] are clean-up strategies deeply addressed for metals removal and critical raw materials recovery from solid matrices. However, electroremediation is now being shaped to address current sustainable priorities [10]. The potential to remove contaminants from secondary resources and eventual enhancement in pozzolanic reactivity of secondary mining resources, through electrochemical phenomena generated inside the reactor, may also contribute to improve the technological maturity and the feasibility for different purposes [11].…”