Ordered mesoporous silica to the rescue: A potential anti-contamination ally for pesticide capture in soil

Abstract

Pesticides capture and slow-release pesticide formulations (SRPF) in soils are technologies aimed at reducing the adverse environmental effects of agricultural pesticides as well as enhancing and prolonging their biological efficacies. Thus, they are techno-economically and environmentally friendly. In this study, amine and tripolyphosphate functionalized mesoporous silica SBA-15 (SBA-A and SBA-T, respectively) were studied as sorbents for the capture of pentachlorophenol (PCP) in a Nigerian soil (Monguno soil- MG) exhibiting low PCP sorption with low hysteresis. Results revealed that PCP sorption was higher (≥345 %) in both SBA-A and SBA-T than in the pristine SBA-15. Adsorptive pore-filling and electrostatic interactions were implicated in the removal of PCP from solution, and the processes were controlled by two mechanisms: intra-particle and equilibrium diffusion. Electrostatic interaction (within and outside SBA-15 mesopores) led to ≥ 75 % increase in sorption upon functionalization. SBA-15 expressed low desorption hysteresis (high release) unlike both SBA-A and SBA-T with very high hysteresis (slow release). The MG soil amendment using 1.0 % SBA-A or SBA-T caused ≥ 465 % PCP sorption and higher hysteresis (slow release) than in pure MG soil. Analysis of this study data demonstrated the feasibility of using mesoporous silica functionalized with amine or tripolyphosphate as adsorbents in the design of SRPF and capture adsorbents that can lessen the adverse environmental consequences of continuous agricultural pesticide application on soils.