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The purpose of this study was to the synthesis of Fe₃O₄@SiO₂ nanocomposites and using it as an adsorbent for removal of diazinon from aqueous solutions. Structural characteristics of the synthesized magnetic nanocomposite were described by Fourier transform infrared spectroscopy and scanning electron microscopy.

The effects of different parameters including pH (2-10), contact time (1-180 min), adsorbent dosage (100-2000 mg L⁻¹) and initial diazinon concentration (0.5–20 mg L⁻¹) on the removal processes were studied. Finally, isotherm and kinetic and of adsorption process of diazinon onto Fe₃O₄@SiO₂ nanocomposites were investigated.

The maximum removal efficiency of diazinon (96%) was found at 180 min with 1000 mg L⁻¹ adsorbent dosage using 0.5 mg L⁻¹ diazinon concentration at pH = 7. The experimental results revealed that data were best fit with the pseudo-second-order kinetic model (R² = 0.971) and the adsorption capacity was 10.90 mg g⁻¹. The adsorption isotherm was accordant to Langmuir isotherm.

In the present study, the magnetic nanocomposites were synthesized and used as an absorbent for the removal of diazinon. The developed method had advantages such as the good ability of Fe₃O₄@SiO₂ nanocomposites to remove diazinon from aqueous solution and the magnetic separation of this absorbent that make it recoverable nanocomposite. The other advantages of these nanocomposites are rapidity, simplicity and relatively low cost.

This paper aims to study the application of high-tolerance and flexible indigenous bacteria and fungi, along with the co-metabolism in recycled paper and cardboard mill (RPCM) wastewater treatment (WWT).

The molecular characterization of isolated indigenous bacteria and fungi was performed by 16S rRNA and 18S rRNA gene sequencing, respectively. Glucose was used as a cometabolic substrate to enhance the bioremediation process.

The highest removal efficiency was achieved for both chemical oxygen demand (COD) and color [78% COD and 45% color removal by Pseudomonas aeruginosa RW-2 (MZ603673), as well as approximately 70% COD and 48% color removal by Geotrichum candidum RW-4 (ON024394)]. The corresponding percentages were higher in comparison with the efficiency obtained from the oxidation ditch unit in the full-scale RPCM WWT plant.

Indigenous P. aeruginosa RW-2 and G. candidum RW-4 demonstrated effective capability in RPCM WWT despite the highly toxic and low biodegradable nature, especially with the assistance of glucose.