Insecticide imidacloprid degradation with solar light catalyzed by Al-doped ZnO and pristine particles supported on different solids
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Date
2020-08-27
Authors
سدر, دعاء فاروق ياسر
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Publisher
An-Najah National University
Abstract
ZnO nanoparticles were widely used as semiconductors for treatment of water from organic pollutants. Commercial and prepared ZnO nanoparticles were used in this work. ZnO nanoparticles were modified by doping with Al in different atomic percentages and supported on activated carbon (AC), Montmorillonite (MONT) and Glass. The photocatalytic activities of different systems were studied against imidacloprid insecticide which is highly used by agriculture sector in Palestine. The results indicate that Al doping and support have nearly no effect on ZnO band gap (3.2 - 3.3 eV) which has been measured by UV-Vis absorption and luminescence emission spectroscopy. From XRD results all systems show hexagonal wurtzite structure with no additional peaks in case of Al doping. However, in MONT supported system, MONT signals appeared. The particle sizes were increased by increasing Al atomic % and decreased by support. The morphology of pristine and Al-doped ZnO are regular spherical shaped where for ZnO@MONT spherical ZnO particles are distributed at plate-like MONT surface as SEM image show. Point of zero charge (PZC) for doped and supported systems were higher than pristine ZnO. The photocatalytic activity of commercial ZnO was better than the prepared one. Factors affecting degradation process like imidacloprid concentration, catalyst loading, time of irradiation, pH and light intensity were determined, as 0.2 g catalyst per 100 ml of 20 ppm imidacloprid at pH 5.6 under light intensity similar to solar light intensity were the optimum parameters. For Al doping effect, the increase in Al content shows depression effect on photocatalytic activity, which reaches zero percentage at 10% of Al. The depression in activity was explained by catalyst surface charge, band gap and surface area. For supported systems no degradation occurred in MONT and glass, while high activity was shown with AC. ZnO stability decreased with increasing Al percent. AC support stabilized the system whereas MONT did not. The catalysts were also studied under visible light radiation and showed lower activity which indicates sensitization effect of some impurities in the solution. The results show that using pristine ZnO nanoparticles is advantageous over the Al-doped in photodegradation of imidacloprid insecticide in contaminated water. Using AC as supporting system for ZnO showed highest tendency to remove the contaminant.