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<p>Pesticide contamination in water poses serious environmental and health risks, highlighting the need for efficient adsorbents. Chitosan-based composites are promising due to their biodegradability, functionality and recoverability. In the present investigation, magnetic chitosan grafted with salicylaldehyde (MG-CS-SAL) and magnetic chitosan nanoclay grafted with salicylaldehyde composites (MG-CS-SAL/NCLA) were hydrothermally synthesized and their adsorption efficiencies were evaluated for pesticides (carbofuran, 2,4-dichlorophenyl acetic acid, nitenpyram, cypermethrin, chlorpyrifos, paraquat, glyphosate and atrazine) adsorption. MG-CS-SAL/NCLA showed the highest paraquat removal efficiency, which was and further studied for the optimization of adsorption conditions. The synthesized composites were analyzed using FTIR, SEM-EDX and XRD techniques. The adsorption conditions were optimized using the Taguchi design (OA25) and the point of zero charge (pH<sub>pzc</sub>) was determined to be 6.75. Under adsorption circumstances of pH 7, an adsorbent dosage of 0.01&#xa0;g/50 mL, a contact period of 40&#xa0;min and an initial concentration of 100&#xa0;mg/L at 60&#xa0;°C, a paraquat removal efficiency of 95% was attained (483&#xa0;mg/g). The paraquat adsorption data aligned to a pseudo-second-order kinetic model (R² = 0.99) and a Langmuir isotherm model (R² = 0.97). Thermodynamic study indicated that the adsorption process was spontaneous (ΔG° &lt; 0), endothermic (ΔH° = 0.17&#xa0;kJ/mol) and associated with an increase in entropy (ΔS° = 0.04&#xa0;J/mol·K) at the solid-liquid interface. The synthesized composite showed 95.24% adsorption and 93.33% desorption in the initial cycle of NaOH, which validates the successful recovery of paraquat. Nevertheless, the reusability was limited, as the adsorption decreased to 41.86% in the second run because of loss of active sites, structural degradation and low dosage of the adsorbent (0.01&#xa0;g/50 mL). The optimum conditions were employed to treat paraquat-contaminated wastewater from rice fields and 94.97% removal was observed, which revealed a promising application of the composite for paraquat removal from wastewater. These findings indicate that MG-CS-SAL/NCLA is a highly efficient and promising adsorbent for paraquat removal from contaminated water, with potential applicability for the remediation of other structurally similar pesticides.</p>

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Salicylaldehyde-grafted magnetic chitosan/nanoclay composites for efficient paraquat adsorption

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月23日

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  • Noureen Maryam,
  • Abida Kausar,
  • Sana Ijaz,
  • Kiran Aftab,
  • Shazia Nouren,
  • M. I. Khan,
  • Osama A. Mohammed,
  • Arif Nazir,
  • Atif Islam,
  • Munawar Iqbal

摘要

Pesticide contamination in water poses serious environmental and health risks, highlighting the need for efficient adsorbents. Chitosan-based composites are promising due to their biodegradability, functionality and recoverability. In the present investigation, magnetic chitosan grafted with salicylaldehyde (MG-CS-SAL) and magnetic chitosan nanoclay grafted with salicylaldehyde composites (MG-CS-SAL/NCLA) were hydrothermally synthesized and their adsorption efficiencies were evaluated for pesticides (carbofuran, 2,4-dichlorophenyl acetic acid, nitenpyram, cypermethrin, chlorpyrifos, paraquat, glyphosate and atrazine) adsorption. MG-CS-SAL/NCLA showed the highest paraquat removal efficiency, which was and further studied for the optimization of adsorption conditions. The synthesized composites were analyzed using FTIR, SEM-EDX and XRD techniques. The adsorption conditions were optimized using the Taguchi design (OA25) and the point of zero charge (pHpzc) was determined to be 6.75. Under adsorption circumstances of pH 7, an adsorbent dosage of 0.01 g/50 mL, a contact period of 40 min and an initial concentration of 100 mg/L at 60 °C, a paraquat removal efficiency of 95% was attained (483 mg/g). The paraquat adsorption data aligned to a pseudo-second-order kinetic model (R² = 0.99) and a Langmuir isotherm model (R² = 0.97). Thermodynamic study indicated that the adsorption process was spontaneous (ΔG° < 0), endothermic (ΔH° = 0.17 kJ/mol) and associated with an increase in entropy (ΔS° = 0.04 J/mol·K) at the solid-liquid interface. The synthesized composite showed 95.24% adsorption and 93.33% desorption in the initial cycle of NaOH, which validates the successful recovery of paraquat. Nevertheless, the reusability was limited, as the adsorption decreased to 41.86% in the second run because of loss of active sites, structural degradation and low dosage of the adsorbent (0.01 g/50 mL). The optimum conditions were employed to treat paraquat-contaminated wastewater from rice fields and 94.97% removal was observed, which revealed a promising application of the composite for paraquat removal from wastewater. These findings indicate that MG-CS-SAL/NCLA is a highly efficient and promising adsorbent for paraquat removal from contaminated water, with potential applicability for the remediation of other structurally similar pesticides.