Degradation of p-Aminobenzoic Acid by Zero-Valent Iron Activated Persulfate System

Abstract

Persulfate (PS) activated by zero-valent iron (ZVI) for the degradation of p-aminobenzoic acid (PABA) was investigated in this study. Compared with the removal of PABA, the degradation of PABA−CAP (in the presence of chloramphenicol) was not obviously affected in the ZVI/PS system. The removal of PABA (.5 mM) and PABA−CAP (.5 mM) were nearly 1% after 5 min. Moreover, the effective degradation of PABA and PABA−CAP were observed at a brand range of pH from 3. to 8.5, and the higher degradation efficiencies of PABA and PABA−CAP were obtained under acidic and neutral conditions. With the increase of Cl- and Suwannee River humic acid (SRHA) dosage, the degradation rate of PABA decreased continuously. However, the degradation of CAP−PABA (in the presence of PABA) was significantly inhibited by the addition of PABA in the ZVI/PS system. The results of scavenging tests suggested that the sulfate radical (SO4•−) predominated the PABA and PABA−CAP degradation, while the hydroxyl radical (HO•) contributing to the CAP−PABA removal approximated to SO4•− by the ZVI/PS system. Major intermediate products were identified during PABA−CAP and CAP−PABA degradation processes. A primary reaction pathway of PABA−CAP and CAP−PABA degradation was proposed in the ZVI/PS system.