The catalytic ozonation of diazinon using nano-MgO@CNT@Gr as a new heterogenous catalyst: the optimization of effective factors by response surface methodology.

Ghorban Asgari,Ali Esrafili,Abdolmotaleb Seidmohammadi,Javad Faradmal,Maghsoud Jafarinia,Mohammad Noori Sepehr

doi:10.1039/c9ra10095d

Abstract

In this research, the degradation of the insecticide diazinon was studied using a new hybrid catalyst consisting of magnesium oxide nanoparticles (nano-MgO), carbon nanotubes (CNTs), and graphite (Gr), nano-MgO@CNT@Gr, under various experimental conditions. This study shows the optimization of the nano-MgO@CNT@Gr/O3 process for diazinon degradation in aqueous solutions. Box–Behnken experimental design (BBD) and response surface methodology (RSM) were used to assess and optimize the solo effects and interactions of four variables, pH, catalyst loading, reaction time, and initial diazinon concentration, during the nano-MgO@CNT@Gr/O3 process. Analysis of regression revealed an adequate fit of the experimental results with a quadratic model, with R2 > 0.91. Following the collection of analysis of variance (ANOVA) results, pH, catalyst loading, and reaction time were seen to have significant positive effects, whereas the concentration of diazinon had a considerable negative impact on diazinon removal via catalytic ozonation. The four variables for maximum diazinon removal were found to be optimum (82.43%) at the following levels: reaction time, 15 min; pH, 10; catalyst dosage, 1.5 g L−1; and diazinon concentration, 10 mg L−1. The degradation of diazinon gave six kinds of by-products. The mechanism of diazinon decomposition was considered on the basis of the identified by-products. According to these results, the nano-MgO@CNT@Gr/O3 process could be an applicable technique for the treatment of diazinon-containing wastewater.

Highlights

In recent years, the release of insecticides into the environment has become a major concern.[1]
The chemical composition of nano-MgO/carbon nanotubes (CNTs)/graphite was analyzed via X-ray diffraction (XRD) (PW1730 – Philips), scanning over 2q values between 10 and 80
This study investigated the effectiveness of a new hybrid catalyst that combines three materials, nano-MgO, CNTs, and graphite, for diazinon degradation during catalytic ozonation

Summary

Introduction

The release of insecticides into the environment has become a major concern.[1] These toxic compounds have ((CH3)2CHC4N2H(CH3)OPS(OC2H5)2) is a non-selective organophosphorus insecticide. It is widely used on lettuce, turf, citrus fruits, almonds, cotton, alfalfa, and other crops and fruits.[3] The World Health Organization (WHO) has classi ed diazinon as a “moderately hazardous” class II pesticide.[4,5] The toxicity dose associated with diazinon to aquatic organisms and its fetal dose for human is 350 ng LÀ1 and 90–444 mg kgÀ1 respectively.[6]. Diazinon is a non-polar and relatively water-soluble substance, and it shows soil resistance.[7] its presence in surface water and groundwater is worrying. AOPs can involve a combination of chemicals and UV radiation or chemicals and ozone; for example, O3/UV, H2O2/Fe2+ (Fenton's reagent), O3/ H2O2, H2O2/UV, O3/H2O2/UV, and catalytic ozonation systems

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