(174br) Efficient Degradation of Imidacloprid through Biochar Activated Sodium Percarbonate

Metal-free carbonaceous materials have been evaluated for the very first time to activate sodium percarbonate (SPC) for the degradation of insecticides. Palm empty fruit bunch biochar (PEFBB) was produced using pyrolyzation process. During this research work, a relatively low-cost carbonaceous material under limited oxygen supply for the activation of SPC to degrade imidacloprid was studied. The pyrolysis temperature was found to be a key parameter for the activation of SPC through biochar in the successive batch experiments. The degradation efficiency of imidacloprid considerably improved from 5.2 to 81.9 % when pyrolysis temperature increased from 250-850 ^oC. The degradation efficiency in the imidacloprid contaminated tap and ground water was 73.4 and 59.8% respectively. The elimination of excessive oxygen functional groups of biochar was found due to its higher temperatures, producing more defect structures with possible transformation and modulation of sp³ carbons, thus enhancing the activation potential of biochar towards SPC. In addition, three intermediate products were identified and two different pathways were proposed as the major imidacloprid degradation. The reactive oxygen species (ROS) were studied using radical scavengers and electron spin resonance (ESR) to verify the dominant generation of hydroxyl radicals (OH^●) in the biochar/SPC system. Fourier transform infrared (FTIR), Raman analysis and ESR combined X-ray photoelectron spectroscopy (XPS) elucidated the generation of OH^● as well as superoxide (O₂^{●–}) free radicals due to the biochar defect structure. In conclusion, biochar activated SPC process is promising technique for the imidacloprid degradation that significantly enhance its application in the imidacloprid contaminated sites.