Enhanced Adsorptive Removal of Chlorpyrifos and Malathion by Functionalized Mesoporous Silica: A Detailed Insight Into Kinetics, Isotherm, and Statistical Surface Modeling

Chlorpyrifos and malathion are both widely used pesticides that pose significant hazards to the environment. Siliceous MCM-48 functionalized with 3-Aminopropyltriethoxysilane modification (AMCM-48) was employed as a highly efficient adsorbent, achieving removal capacities of 957 and 540 mg g –1 for chlorpyrifos and malathion, respectively. The presence of characteristic XRD patterns in the range 2θ = 2–5°, along with BET surface areas of 787 and 593 m 2 g –1, ascertained the retention of the mesoporous structure during functionalization. A subsequent drop in the surface area to 197 and 191 m 2 g –1 indicates that chlorpyrifos and malathion are, respectively, adsorbed onto the internal pores of AMCM-48. FTIR and EDX characterization confirmed the uptake of pesticide molecules by AMCM-48. The maximum removal efficiency of CP (90.02%) was obtained within 27 min, when 90 mg L –1 of CP was contacted with 40 mg of AMCM-48, at 31 °C. MTH uptake was 86.24% when 12 mg L –1 was contacted with 35 mg of adsorbent at 41 °C, optimized by RSM-CCD. The adsorption parametric studies fitted well into the Langmuir model and pseudo-second order kinetics. The thermodynamic parameters (Δ G °, Δ H °, and Δ S °) indicated the exothermic and spontaneous nature of adsorption. The above analyses indicated that the adsorption was primarily driven by high surface area, hydrogen bonding, dipole–dipole interactions, and electrostatic forces. Desorption at higher pH achieved approximately 85% recovery, reflecting reversible physical interactions. AMCM-48 demonstrated excellent reusability, maintaining significant adsorption capacities for both pesticides over seven consecutive cycles. Overall, AMCM-48 is a simple and sustainable adsorbent for efficient pesticide removal.