Nitrogen doped graphitic porous carbon from almond shells as an efficient persulfate activator for organic compound degradation

Abstract

Here, we have developed a simple and efficient low-temperature process for doping N into graphitic porous carbon to prepare a catalyst: N-GPC. Almond shell (AS), as bio-sourced material, was used for graphitic porous carbon preparation via a new facile environmentally friendly approach followed by pyrolysis. The resulting powder was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy and BET. The catalytic activity was investigated by using Orange-G (OG) as the target pollutant and N-GPC as the heterogeneous catalyst to activate persulfate (PS). The influence of various parameters such as temperature, PS concentration, catalyst dose, pH and time over the N-GPC/PS system was investigated. OG discoloration of 99% was achieved with a degradation rate of 70% using [N-GPC] = 0.2 g L⁻¹, [OG] = 100 mg L⁻¹ mM, and [PS] = 4 mM at ambient temperature and natural pH. The catalyst N-GPC could be recycled easily for three cycles with good stability. Moreover, quenching experiments and EPR analysis were investigated to elucidate the active radicals participating in the degradation process. The results indicated that ¹O₂ is the most dominant non-radical species in the degradation process of OG. The enhanced activities of the N-GPC/PS system were attributed to the high surface area and generated charges from the surface of the prepared N-GPC. This strategy can lead to the achievement of sufficiently managed biomass waste to pave the way to environmentally friendly catalysis.