Electrochemical methods show promise for wastewater treatment by removing pollutants, recovering nutrients, and generating hydrogen. To scale this technology, durable and affordable electrode materials are needed. This study evaluates aluminum 6061-T6, titanium grade II, ductile iron, and magnesium to understand their performance in promoting precipitation, gas production, and treating wastewater under several conditions. Electrodes were tested with ammonia-, magnesium-, and phosphate-spiked wastewater samples with induced precipitation at concentrations of 0.033 mol/L and 0.0033 mol/L; the liquid, gas, and precipitation phases were characterized. The results showed up to 35% reduction in ammonia, total phosphate recovery, and up to 70% reduction in magnesium. The cell generates hydrogen with purity levels of 95.6%, 96.1%, 87.9%, and 93.5% when utilizing iron, aluminum, titanium, and magnesium electrodes, respectively. The analyses of precipitants showed formation of vivianite crystals from iron, struvite precipitation from magnesium, and berlinite from aluminum. Overall, these results hold substantial promise for hydrogen generation from wastewater and potential for nutrient recovery and treatment.

Thermodynamic methods such as exergy analysis enable the evaluation of environmental load (environmental impacts) by quantifying entropy generation and exergy destruction associated with using renewable and non-renewable resources throughout a production system. Based on the principle that environmental impacts occur when exergy is dissipated into the environment, this study applies exergy analysis as a tool for assessing the sustainability of gold mining in Colombia. Two extraction technologies—open-pit and alluvial mining—are evaluated by calculating exergy efficiencies, cumulative exergy demand (CExD), and associated environmental impacts. The results reveal significant differences between the two methods: open-pit mining is heavily dependent on fossil fuels (53% of input exergy), with 99.62% of total exergy destroyed, resulting in an exergy efficiency of just 0.37% and a sustainability index (SI) of 1.00. In contrast, alluvial mining relies predominantly on water (94%), with 69% of input exergy destroyed, an exergy efficiency of 31%, and an SI of 1.46. Four strategies are proposed to reduce environmental burdens: improving efficiency, minimizing exergy losses, integrating renewable energy, and adopting circular economy principles. This study presents the first application of exergy analysis to comprehensively assess the exergy cost of gold production, from extraction through refining, casting, and molding, highlighting critical exergy hotspots and offering a thermodynamic foundation for optimizing resource use in mineral processing.