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 pnitrophenol (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 SO4 center dot- and (OH)-O-center dot were verified to be responsible for the oxidative degradation of PNP. Nevertheless, the contribution of SO4 center dot- to the degradation of PNP was much larger than that of (OH)-O-center dot. Based on the analyses of HPLC-MS data, it could be determined that C6H7 NO, C6H6O2 , and C12H7N3O8 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. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.