Degradation of 2,4-dichlorophenol by a novel iron based system and its synergism with Cd(II) immobilization in a contaminated soil

Nowadays, the remediation of heavy metals and organic compounds contaminated soil has been greatly growing attentions. In this paper, the feasibility of a novel biochar-supported zero valent iron (B-nZVI) based system for the degradation of 2,4-Dichlorophenol (2,4-DCP) and immobilization of Cd(II) in contaminated soil was firstly investigated. The most relevant findings revealed that persulfate (PS) could obviously improve the degradation of 2,4-DCP by B-nZVI process. Within 240 min, nearly 91% of 2,4-DCP degradation could be reached at reaction conditions of 40 mg kg⁻¹ 2,4-DCP, 6 mM PS, 3.0 g L⁻¹ B-nZVI and pH 4.51. A much higher performance on the 2,4-DCP degradation was observed at acidic and aerobic conditions. A lower concentration of ethylene diamine tetraacetic acid (EDTA) exhibited a slight improvement of 2,4-DCP degradation, whereas humic acids (HA) exhibited a significant inhibitory effect on that. Radical scavenging tests revealed that SO₄^[rad]− was primarily involved in degradation reaction of 2,4-DCP by B-nZVI/PS process. A total of five intermediate products including 2-chlorohydroquinone, 3,5-dichlorocatechol, phenol, fumaric acid and acetic acid were generated in 2,4-DCP degradation process, whereas two Cd species such as Cd(OH)₂ and CdO were identified in Cd(II) immobilization process. A possible mechanism for the 2,4-DCP degradation and Cd(II) immobilization by B-nZVI/PS process was proposed.