Highly Efficient and Rapid Removal of Malathion Using Crosslinked Chitosan-Alginate Nanocomposites and Optimization of Parameters by Box-Behnken Design: Isotherms and Kinetic Studies

The accumulation of organophosphorus pesticide residues in aqueous media due to their highly recalcitrant nature is causing increasing human health and ecosystem concerns. In this study, sponge composites were fabricated with five different ratios of chitosan (CS) and sodium alginate (SA) for the removal of malathion from aqueous media. The structural and morphological features of these nanocomposites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller. The CS-SA with a ratio of 1:1.5% was selected as the best adsorbent. The process optimization was performed using the response surface methodology based on Box-Behnken design as a function of the pH (4-10), malathion concentration (5-15 mg L-1), contact time (10-20 min), and adsorbent dosage (0.1-0.2 g). The maximum removal was obtained at 97.56% under the optimum conditions of 7, 15 min, 10 mg L-1, and 0.15 g for the pH, contact time, malathion concentration, and adsorbent dosage, respectively. Langmuir and Freundlich adsorption isotherm models were surveyed and the data were fitted well with the Langmuir isotherm model (R-2 = 0.9993). The maximum adsorption capacity (q(max)) was found to be 52.08 mg g(-1), indicating good potential of CS-SA in the adsorption of malathion. The adsorption kinetics was investigated with the pseudo-first-order and pseudo-second-order (PSO) models. The PSO with R-2 = 0.9999 showed the best fit to the experimental data. The implementation of this study reveals that CS-SA is a potential adsorbent for application in the removal of pesticides from aqueous solutions.

Automated summary

Sponge composites with different ratios of chitosan (CS) and sodium alginate (SA) were fabricated for the removal of malathion from aqueous media. The CS-SA with a ratio of 1:1.5% was selected as the best adsorbent. Response surface methodology based on Box-Behnken design was used for process optimization, and the maximum removal was achieved at 97.56% under the optimized conditions. Langmuir isotherm model showed good fitting to the data, with a maximum adsorption capacity of 52.08 mg g(-1). Pseudo-second-order model exhibited the best fit for the adsorption kinetics. The study demonstrates the potential of CS-SA as an adsorbent for pesticide removal from aqueous solutions.