Assessing the role of silica gel in the degradation of p-nitrophenol via Zn(0)-activated persulfate

In this study, silica gel (SG) was utilized as an assistant to improve the degradation efficiency of p -nitrophenol (PNP) via persulfate (PS) activated with zero-valent zinc (Zn(0)). The effects of various parameters such as the dosages of SG, PS, Zn(0), and the initial pH on PNP degradation via Zn(0)/SG/PS were investigated through batch experiments. The results demonstrated that SG exhibited a strong synergistic role in the decomposition of PNP via Zn(0)-activated PS due to the dispersion and buffering character of SG. The degradation efficiency of PNP was strongly related to the dosage of SG, PS, or Zn(0). A low pH favored of the degradation of PNP. Nevertheless, PNP could be efficiently removed in a pH range of 3 to 9. The radicals of SO 4 •− and • OH were verified to be responsible for the oxidative degradation of PNP. Nevertheless, the contribution of SO 4 •− to the degradation of PNP was much larger than that of • OH. Based on the analyses of HPLC-MS data, it could be determined that C 6 H 7 NO, C 6 H 6 O 2 , and C 12 H 7 N 3 O 8 were the main intermediates generated from the degradation of PNP via Zn(0)/SG/PS. Furthermore, the possible mechanism and the degradation pathways of PNP via Zn(0)/SG/PS were proposed. PS activated with Zn(0) in the presence of SG could be concluded as a promising approach for the degradation of PNP in aqueous solution.