Microwave-assisted hydrothermal preparation of magnetic hydrochar for the removal of organophosphorus insecticides from aqueous solutions

Hydrochar-loaded iron nanoparticles (HC-FeNPs) were effectively synthesized through a microwave-assisted hydrothermal approach, characterized and examined for removing three noxious organophosphorus insecticides, namely Ethoprophos (ETH), Terbufos (TER), and Diazinon (DIA), from aqueous solutions. The effect of different factors, including adsorbent dosage (40-90 mg), initial concentration of insecticides (0.25-3 mg/L), incubation time (20-240 min), and pH (4-10) on the adsorption efficiency, was analyzed using batch adsorption experiments. According to kinetic data, the removal adequately fits the pseudo-second-order and intraparticle diffusion kinetic models. The analysis of adsorption data of ETH, TER, and DIA by Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin isotherms revealed that experimental data were best fitted by the Langmuir isotherm with maximum adsorption capacity (qmax) of 3.19, 3.07, and 3.19 mg/g, respectively. Additionally, thermodynamic studies demonstrated the adsorption process was chemisorption, spontaneous, and endothermic. Under the optimized conditions, HC-FeNPs were successfully employed to eliminate insecticides from environmental water samples. Regeneration and reusability tests showed that HC-FeNPs composite had outstanding recoverability and significant recycling potential. The proposed composite is an effective, economical, and ecological adsorbent with high adsorption affinity toward the organophosphorus insecticides, making the adsorption process a viable and efficient process for treating water containing such contaminants.