From rock waste to reactive surfaces: Natural gabbro rocks for solar remediation of gaseous and aqueous contaminants

- This study investigates the structural, optical, and catalytic properties of mafic rock grains derived from Gabbro collected in the United Arab Emirates are to evaluate their potential as alternative catalysts for environmental applications. Nitrogen adsorption and desorption analysis revealed mesoporous and macroporous structures with low specific surface area (0.56–4.96 m2/g). UV–Vis spectroscopy showed that the analyzed gabbroic rocks have band gap energies that are suitable for photocatalytic activity under illumination with visible light. The results of the photocatalytic experiments carried out under simulated sunlight showed the superior ability of the invested gabbro rock to oxidise 4-nitrophenol dissolved in water with a degradation extent of up to 65.4 %. The photodegradation of 2-propanol in air under simulated sunlight was also successful with acetone as the only formed intermediate. Thermocatalytic tests showed a significant NO2 reduction activity of the investigated gabbroic rocks at temperatures above 125 °C with the highest NO2 reduction rate of 17.5 %. The implementation of light radiation enabled the reduction of NO2 by the studied gabbroic rock at temperatures below 120 °C. CO adsorption and its photoconversion to CO2 was observed in the analyzed samples. Most of the CO2 formed from CO is not released into air, as it is captured on the surface of the rocks in the form of carbonates. The high catalytic activity and CO and CO2 adsorption ability can be correlated to the properties of the rocks’ surface. The results underline the potential of gabbroic rocks as efficient and sustainable catalysts for pollutant degradation and NO2 reduction in environmental remediation processes. These results are not only environmentally relevant for air and water quality in the various regions where gabbroic rocks occur but also pave the way for their use as commercial photocatalysts.