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Hazardous organic pollutants in industrial wastewaters are becoming a major global challenge that threatens life on earth and particularly poses a serious health risk to human beings. 4-Nitrophenol (4-NP) is a highly hazardous organic contaminant that has been extensively utilized across multiple industries, and their wastewater disposal into water streams leads to a higher accumulation of 4-NP. It is therefore important for both academia and industry to make catalysts that are cheap, very effective, good for the environment, easy to recover, and can be used more than once for reducing 4-NP in normal conditions. This paper reports the synthesis, characterization, and application of Cu/kaolin nanocomposite (NC) as an efficient heterogeneous catalyst for decomposing 4-NP, a model organic molecule. The catalyst was synthesized by incorporating a copper precursor into layered kaolin clay and directly reducing the metal precursor using sodium borohydride (NaBH4). The morphology, structure, surface property, and interaction of the resulting Cu/kaolin NC were characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron spectroscopy/energy-dispersive X-ray spectroscopy, selected area electron diffraction, X-ray diffraction, and N2 adsorption/desorption, and the results clearly demonstrated the growth of copper nanoparticles on the kaolin surface. It was discovered that the Cu nanoparticles (NPs) on the kaolin surface had a crystallite size of about 23.6 nm. The significance of Cu NPs and the high catalytic activity of the synthesized Cu/kaolin NC toward 4-NP reduction by NaBH4 were evaluated by the catalytic reduction experiments. Among the different nanocomposites synthesized, 30-Cu/kaolin showed the highest catalytic activity for 4-NP reduction, with a reduction efficiency of over 99 % within 4 min with a pseudo-first-order rate constant, kapp, of 1.23 min−1. Furthermore, the reusability test indicated that Cu/kaolin NC can be reused for up to six runs efficiently without significant decrease in its catalytic performance, indicating the nanocomposite has excellent stability and great potential applications in industrial and agricultural wastewater treatment.

The biggest challenge of this century is the generation of wastewater which is released to the environment due to industrial expansion. Industrial development has caused the release of various pollutants including heavy metals such as Cd, Pb, and Cr into the environment. In this study, copper diphenylamine metal-organic framework (Cu-DPA MOF) has been synthesized via hydrothermal method and its adsorption capacity toward the removal of heavy metals from wastewater was examined. The removal efficiency of heavy metals by Cu-DPA MOF was tested at optimized adsorption parameters such as optimal adsorbent dosage, pH, initial metals concentration, and adsorption time. The heavy metals concentration in the wastewater before treated with the as-synthesized MOF was determined to be 0.3027, 0.0098, and 0.1021 mg/L for Cr, Cd, and Pb, respectively. The corresponding concentrations of heavy metals in wastewater were reduced to 0.0015, 0.00024, and 0.00016 mg/L when treated with the as-synthesized MOF. As a result, a maximum removal efficiency of 97.6%, 99.5%, and 99.5% was achieved for Cd, Cr, and Pb metals, respectively. This is possibly due to the high porous nature and huge surface area of the as-synthesized MOF. The adsorption data were best fitted with Freundlich isotherm throughout this study. The study sheds light on the design of adsorbents with high removal efficiency of pollutants found in the environment.