Catalytic reduction of nitrophenols and dyes by HKUST-1/hydrogel composite.

The effective removal of nitrophenols from wastewater is crucial due to their high carcinogenic risk. This research presents the development of a copper-based metal-organic framework (HKUST-1) integrated into a chitosan--poly(acrylic acid) hydrogel. The hydrogel composite was evaluated as a catalyst for reducing nitrophenols and dyes using sodium borohydride (NaBH) as a reducing agent. Various conditions were investigated for the reduction of 4-nitrophenol (4-NP) to the less harmful 4-aminophenol (4-AP), including catalyst dosage, NaBH concentration, initial 4-NP concentration, temperature, and pH. The catalyst was able to completely reduce 4-NP within 25 minutes at a dosage of 3 g L and a NaBH concentration of 300 mM. The reduction rate increased with higher temperatures, with an Arrhenius activation energy of 54.4 kJ mol. Common anions found in surface water, such as Cl, NO , SO , and HCO , had a slight impact on the reduction rate of 4-NP. When tested in real water environments, the reduction rate decreased, but complete conversion was still achieved. Additionally, the composite successfully reduced 100% of 2-nitrophenol, 100% of methyl orange, and 69% of Congo red. Overall, the hydrogel composite has shown significant potential as a catalyst for reducing various organic pollutants with high efficiency and easy separation through filtration.