The magnetic mesoporous hydrogel-based nanoadsornet was prepared by adding the ex situ prepared Fe3O4 magnetic nanoparticles (MNPs) and bentonite clay into the three-dimentional (3D) cross-linked pectin hydrogel substrate for the adsorption of organophosphorus chlorpyrifos (CPF) pesticide and crystal violet (CV) organic dye. Different analytical methods were utilized to confirm the structural features. Based on the obtained data, the zeta potential of the nanoadsorbent in deionized water with a pH of 7 was − 34.1 mV, and the surface area was measured to be 68.90 m2/g. The prepared hydrogel nanoadsorbent novelty owes to possessing a reactive functional group containing a heteroatom, a porous and cross-linked structure that aids convenient contaminants molecules diffusion and interactions between the nanoadsorbent and contaminants, viz., CPF and CV. The main driving forces in the adsorption by the Pectin hydrogel@Fe3O4-bentonite adsorbent are electrostatic and hydrogen-bond interactions, which resulted in a great adsorption capacity. To determine optimum adsorption conditions, effective factors on the adsorption capacity of the CV and CPF, including solution pH, adsorbent dosage, contact time, and initial concentration of pollutants, have been experimentally investigated. Thus, in optimum conditions, i.e., contact time (20 and 15 min), pH 7 and 8, adsorbent dosage (0.005 g), initial concentration (50 mg/L), T (298 K) for CPF and CV, respectively, the CPF and CV adsorption capacity were 833.333 mg/g and 909.091 mg/g. The prepared pectin hydrogel@Fe3O4-bentonite magnetic nanoadsorbent presented high porosity, enhanced surface area, and numerous reactive sites and was prepared using inexpensive and available materials. Moreover, the Freundlich isotherm has described the adsorption procedure, and the pseudo-second-order model explained the adsorption kinetics. The prepared novel nanoadsorbent was magnetically isolated and reused for three successive adsorption–desorption runs without a specific reduction in the adsorption efficiency. Therefore, the pectin hydrogel@Fe3O4-bentonite magnetic nanoadsorbent is a promising adsorption system for eliminating organophosphorus pesticides and organic dyes due to its remarkable adsorption capacity amounts.

This study aimed to synthesize Fe3O4 nanoparticles and Pectin/Fe3O4/Bentonite nanocomposite hydrogel. Then this nano adsorbent was used to remove heavy metals (Pb2+, Cu2+, and Ca2+) from aqueous solutions. The percentage of adsorption efficiency for Pb2+, Cu2+, and Cd2+ by 30 mg of adsorbent during 60 minutes and concentration of 200 ppm was 91.5%, 89.5%, and 85%, respectively. At the concentration of 250 ppm, it is 87.2%, 86%, and 80.4%, respectively, and in the concentration of 300ppm, it is 78.66%, 77.33%, and 69%, respectively. In the continuation of the experiment, the optimal conditions for removing heavy metals with nanocomposite under laboratory conditions, pH = 7, contact time of 60 minutes, the concentration of 250 ppm, and adsorbent mass of 0.03 g were carried out. Because the concentration of 250 ppm was considered the average of the other two concentrations. The results of the adsorption isotherm studies exhibit a good fit of the data with the Langmuir adsorption isotherm compared to Freundlich and Temkin models. The collected kinetic and thermodynamics data illustrated that the pseudo-second-order equations, the spontaneous process and endothermic, control the adsorption process.

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