Optimizing The Remediation Of Organophosphorus Pesticide Profenofos From Water Using Activated Date Pits: Mechanistic Studies

Abstract

The aim of the study was to examine the efficiency of date pits as an adsorbent to remove the organophosphate pesticide profenofos from wastewater. Various adsorption isotherms models namely Langmuir isotherm, Freundlich isotherm, Dubinin-Radushkevich isotherm and Temkin isotherm models were examined in order to understand the interactions between the adsorbate (profenofos pesticide) and the prepared adsorbents. In addition, thermodynamic adsorption was carried out to determine the homogeneity and spontaneous of the adsorbents. In the first phase of the study, three types of adsorbents namely roasted date pits, activated date pits and nano-activated date pits were prepared from the date pits collected from different sources. Different physical and chemical characterizations were studied such as scanning electron microscopy (SEM), Fourier transform infrared (FTIR), BET surface area, pore radius and pore volume. The surface area of the nano-activated date pit was the highest 485.441 m2/g. Moreover, the pore volume and pore radius were also the highest for the nano-activated date pits with values 0.338 cm3/g and 17.8 Å, respectively. Therefore, nano-activated date pits have resulted in high removal percentage and removal capacity of profenofos from aqueous solution. Based on adsorption isotherm model, the values of R2 was the highest for the nano-activated date pits. The adsorption maximum capacity (qm) increased with temperature and was maximum for the nano-activated date pit following Langmuir adsorption isotherm model. In the case of roasted date pit and activated date pit, the adsorption fitted the Freundlich model. Thermodynamic parameters showed a negative ΔG for all three adsorbents and the value increased with temperature. The ΔH value was positive for the three adsorbents and was the highest for roasted date pit (23.59 KJmol-1); resulting in an endothermic reaction. Whereas, the value of ΔS was negative for the three adsorbents and was the highest for nano-activated date pits (-83.5 Jmol-1).