BiOI/melamine foam as an extremely efficient and highly recyclable catalyst for the treatment of continuous flow organic pollutants

The use of nano-catalysts to reduce nitroaromatic compounds is a promising wastewater treatment strategy. In this study, melamine foam (MF) is employed as the substrate, and sheet-like bismuth oxide iodide (BiOI) was grown on its surface through a cross-impregnation process involving Bi(NO₃)₃ and KI solution. As a catalyst, bismuth oxide iodide/melamine foam composite (BiOI/MF) exhibits remarkable catalytic activity and excellent durability in the treatment of continuous flow 4-nitrophenol (4-NP) solutions. The loading capacity of BiOI on a 2 × 2 × 2 cm³ MF substrate is notably low at just 0.13 g, yet it can completely reduce 50 mL 4-NP solution (0.37 mmol L^-1) within 32 minutes. After six consecutive cycles, the catalyst maintained a conversion efficiency of over 90%, with the total treatment amount for 4-NP reaching 1.49 × 10^-2 mmol. Furthermore, BiOI/MF also exhibited high catalytic reduction activity towards other organic pollutants, such as methylene blue and methyl orange solutions. In this study, we propose an efficient and cost-effective composite catalyst that offers technical guidance for the practical treatment of wastewater and sewage.