STRUCTURE BASED TOXICITY ANALYSIS OF PESTICIDAL POPs & EFFICIENT ADSORPTIVE REMOVAL FROM WATER USING ZIF-8

Abstract

Persistent Organic Pollutants (POPs) are a class of highly persistent and bioaccumulative chemicals that pose serious negative impacts on the ecosystem and human health. This POPs family comprises certain pesticides i.e., organochlorine (OCPs), organophosphate pesticides (OPPs), and carbamates (CMs). The use of these organic pesticides (OPs) in the agricultural sector offers significant benefits, however, their use is regulated and banned in many countries owing to their devastating impacts on the off-target environments. Water pollution by such persistent chemicals is a global concern making agriculture both a cause and victim of water pollution. The toxicity analysis of pesticidal POPs through DFT methods at the electronic level, and a comparison between various classes of these POPs, monitoring their fate and adsorption on the surface of ZIF8, has not been explored yet. This research work aims at structure-based toxicity assessment of various pesticidal classes belonging to the POPs family by employing a dual methodology approach i.e., through monitoring these pollutants in the environment and computing their electronic & molecular behavior for assessing their distribution, bioaccumulation, and aquatic toxicity and exploring active sites responsible for molecular interactions which contribute to their toxicity. Herein, environmental fate of these pesticidal POPs is monitored by calculating their bioconcentration factor (log BCF), biodegradation probability (BIOWIN 3), Henry’s law constant (HLC), soil adsorption coefficient (Koc), octanol-water partition coefficient (log Kow), and water solubility (WS) using Estimation Program Interface (EPI) Suite. Moreover, DFT calculations are performed to explore & compare their chemical reactivity and toxicity through double zeta (DZ) basis set, GGA and BLYP functional. Furthermore, this research extends to address the effectiveness of the zeolitic imidazole framework i.e., ZIF-8 in the removal of these hazardous compounds from the aqueous environment by elucidating adsorption mechanisms and adsorption energies through Monte Carlo based simulations. Environmental fate monitoring reveals that aldrin has the lowest water solubility (0.0024 mg/L) and paraquat dichloride is the most watersoluble pesticide (6.082x105 mg/L). According to DFT analysis, paraquat dichloride has highest reactivity owing to energy gap of 0.2721 eV, while acephate possesses the highest stability having energy gap of 4.5586 eV. The obtained pore limiting diameter (PLD) of ZIF-8 through Zeo++ is 3.5 Å, indicating adsorption of all POPs to be physisorption in nature. Through Monte Carlo (MC) simulations, the highest adsorption energy of -48.06 Kcal/mol is observed for the dieldrin-ZIF-8 complex, thus highlighting the effectiveness of selected MOF in removal of OCPs.