Removal assessment of malathion and dichlorodiphenyltrichloroethane pesticides from wastewater using intercalated bentonite clay with mixed aluminum–zinc oxides nanoparticles

Abstract

The presence of agrochemical residues in wastewater resources has raised high concerns owing to their hazardous impacts on the human health and integrity of ecosystems. In this regard, a cost-effective and readily available nanocomposite was designed and assembled via the combination of nano-bentonite (N-Bent), nanoalumina (NAl₂O₃), and nanozinc oxide (NZnO) for the formation of N-Bent-NAl₂O₃-NZnO. This nanocomposite was developed to remove two specific pesticides, namely, malathion and dichlorodiphenyltrichloroethane (DDT), which are frequently detected in surface water from polluted wastewater samples. The characterization of the as-synthesized N-Bent-NAl₂O₃-NZnO nanocomposite was performed using SEM, XRD, HR-TEM, FTIR, BET and TGA techniques. SEM and HR-TEM investigations revealed a favorable degree of homogeneity and surface porosity, with an average particle size of 69.8–86.9 nm. The potential use of this nanocomposite for pesticide pollutant removal was evaluated under diverse conditions via a batch adsorption approach. At pH 3.0, the highest observed removal (R%) rate was 97.42% for malathion and 94.83% for DDT. These results revealed that N-Bent-NAl₂O₃-NZnO exhibited a significantly greater overall removal efficiency for malathion than for DDT. The Langmuir model demonstrated R² = 0.997 and 0.991 for malathion and DDT, respectively. Besides, the pseudo second order model exhibited R² = 0.997 for malathion and 0.995 for DDT, indicating that these were the most suitable isotherm and kinetic model. According to the Langmuir model, the maximum removal capacities were 34.20 mg g⁻¹ for malathion and 28.36 mg g⁻¹ for DDT. Additionally, the effectiveness of N-Bent-NAl₂O₃-NZnO in removing malathion and DDT after five repeated adsorption–desorption cycles was achieved as 84.63% and 81.76%, respectively. These results suggest that N-Bent-NAl₂O₃-NZnO could serve as a viable and effective nanocomposite for treating wastewater generated from agricultural activities.