Controlled release formulations of organophosphorus pesticides based on ecofriendly novel and conventional matrices for agro-environmental sustainability

Abstract

Controlled release formulations (CRFs) of the organophosphorus pesticides diazinon and dichlorvos were prepared from a novel cow dung ash (CDA) matrix and the more conventional starch (STA) matrix. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the CRFs. FTIR and XRD spectral data provide evidence for pesticide-matrix interactions fundamental to observed matrix surface binding and pesticide release behaviour in water and soil environments. Properties evaluation of the CRFs reveal similar magnitudes of loading capacity and encapsulation efficiency of CDA- and STA-based CRFs of both pesticides, while the order CDA > STA prevails in matrix porosity and swelling ability. Technical grade (TG) and the CRF-encapsulated pesticides exhibit “burst” release profiles in water; pesticide quantities released at similar lengths of time follow the order TG >> STA-CRF > CDA-CRF, thus revealing the capacity of the CRFs to constrain the active ingredients from free mobility, with CDA-CRF being the more slightly efficacious. The Korsmeyer-Peppas equation reasonably models pesticide release from both CRFs into water, giving n values consistent with both water diffusion into the matrix and matrix relaxation as kinetically important in both matrices. Soil column experiments demonstrate the potential of the CFRs to mitigate ground water pollution. Overall, the results show that CDA- and STA-based CRFs of both pesticides have roughly the same potency for pesticide controlled release and ground water pollution mitigation. Deployment of these CFRs can contribute to the drive for agro-environmental sustainability, while the use of CDA, a waste material, as a matrix in controlled pesticide delivery would resonate with sustainable bioresource utilization.