Abstract
The nitrogen and sulphur oxide (NOx and SO2) emissions are causing a serious threat to the existence of life on earth, requiring their effective removal for a sustainable future. Among various approaches, catalytic or electrochemical reduction of air pollutants (NOx) has gained much attention due to its high efficiency and the possibility of converting these gases into valuable products. However, the required catalysts are generally synthesized from lab-grade chemicals, which may not be a sustainable approach. Herein, a sustainable approach is presented to synthesize an efficient iron-based catalyst directly from industrial/lake wastewater (WW) for NOx-reduction. According to the theoretical calculations and experimental results, Fe-ions could be readily recovered from wastewater because it has the best adsorption efficiency among all other co-existing metals (Ni2+, Cd2+, Co2+, Cu2+, and Cr6+). The subsequent experimental investigations confirmed the preferential Fe adsorption from different WW streams to develop Fe3O4@EDTA-Fe composite, whereby Fe3O4 could be used due to its high recycling ability, and ethylenediaminetetraacetic acid (EDTA) acted as a chelating agent to adsorb Fe-metal from effluents. The Fe3O4@EDTA-Fe exhibited high efficiency (≥87%) for NOx reduction even in the presence of high-degree oxygen contents (10–12%). Moreover, Fe3O4-EDTA-Fe showed excellent long-term stability for 24 h and maintained more than 80% NOx reduction. The fabricated catalyst has a great potential for executing a dual role simultaneously for Fe-recovery and NOx removal, promoting the circular economy concept and providing a potentially sustainable remediation approach for large-scale applications.
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•Wastewater effluents are utilized as alternative Fe source for sustainable catalyst synthesis.•Etched Fe3O4-L-Fe has best selectivity for Fe recovery by theoretical and experimental results.•Characterization tools confirmed synthesis of Fe3O4-L-Fe with abundant active sites.•Etched Fe3O4-L-Fe outperformed other composites (e.g., Fe3O4-L-M) in NOx removal.•Etched Fe3O4-L-Fe showed good stability and maintained >80% NOx removal after 24 h.