Oily sludge carbon-based materials with gallic acid towards peroxymonosulfate activation for enhancing the degradation of p-nitrophenol

The petroleum sphere’s handling and disposal of oily sludge presents serious obstacles to resource conservation and environmental preservation. Oily sludge (OS) was converted into carbon-based materials through pyrolysis, and their surface structure and crystal formation were investigated. Compared with systems without gallic acid (GA), the GA-assisted system significantly enhanced the degradation efficiency of p-nitrophenol (PNP) by OSC-800-activated peroxymonosulfate (PMS). The optimal catalytic degradation efficiency was observed at a GA concentration of 0.25 mM, achieving an 88.14 % degradation of PNP within 100 min. The observed reaction rate constants (K_obs) increased by 2.42 times, the removal rate of COD improved by 1.65 times, and the utilization rate of potassium peroxymonosulfate rose by 2.90 times. Two key factors were identified that contributed to enhancement mechanism of GA in the OSC-800/GA/PMS system. Firstly, The Fe(II)/Fe(III) redox cycle on the catalyst’s surface was made easier by GA, which improved the production of active groups for PNP degradation. Secondly, GA sped up electron transfer, which increased the reaction rate. The study offers a novel method for employing reductants to improve the activation of permonosulfate by carbon-based materials.