Effect of NiFe2O4 on PCDF byproducts formation during thermal degradation of decachlorobiphenyl

Abstract

Relative to the catalyst-free reaction system, the concentration and total toxic equivalent values of 2,3,7,8-PCDFs decreased by 24.1-99.7% and 86-98.4%, respectively, in the NiFe 2 O 4 catalyst system, while initial increases by 744.5% and 426.3%, respectively, followed by reduction up to 81.6% and 90.7%, respectively, were observed in the Fe 2 O 3 catalyst system. Current findings indicate that NiFe 2 O 4 hindered PCDF formation, which was attributed to its chemical structural stability and high activity towards degradation of biphenyl-like constituents in PCBs.

Theoretical insights into the reaction mechanisms between 2,3,7,8-tetrachlorodibenzofuran and the methylidyne radical

“…For example, for the following processes, i.e., (1) P1 / TS17 / P6, (2) P1 / TS29 / P12, (3) P2 / TS9 / P3, (4) P4 / TS30 / P13, (5) P5 / TS21 / P7, (6) P5 / TS22 / P8, (7) P7 / TS20 / P8, and (8) P9 / TS27 / P10, the enthalpy (Gibbs free energy) changes are À18. 16 .96 kcal mol À1 , respectively, where the data in parentheses refer to the results without considering ZPVE corrections. Obviously, only the processes (3), (7), and (8) are feasible due to their low energy barriers kinetically.…”

“…It is well recognized that the major sources of PCDFs are incineration and thermal decomposition of waste materials involving chlorine as well as natural combustion processes (e.g., volcanic activity). Up to now, many studies have been carried out to gain a better understanding of the formation [1][2][3][4][5][6][7][8] and degradation [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] of PCDFs experimentally and theoretically. Especially, for the degradation of PCDFs, many methods have been proposed, such as microbial degradation, photocatalytic decomposition, and high temperature degradation, etc.…”

Theoretical Investigations on the Reactivity of Hydrogen Peroxide toward 2,3,7,8-Tetrachlorodibenzo-p-dioxin

“…Especially, as the most toxic dioxin, 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) has been classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). To understand the formation [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ] and transformation or degradation [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ] mechanisms of PCDDs, many experimental and theoretical investigations have been carried out. Several methods involving microbial degradation [ 9 , 10 , 11 ], photocatalysis [ 12 , 13 , 14 ], incineration and thermal treatment [ 15 , 16 ], have been proposed to degrade PCDDs.…”

Degradation of one-side fully-chlorinated 1,2,3,4-tetrachloronaphthalene over Fe–Al composite oxides and its hypothesized reaction mechanism

“…21 Huang et al compared the decomposition of decachlorobiphenyl over several multi-metal oxides, including NiFe 2 O 4 and Fe 2 O 3 , and found that decachlorobiphenyl were degraded much more efficiently over NiFe 2 O 4 . 22 Based on their excellent physicochemical properties, considerable research efforts have been directed towards the development of highly active composite oxides for the degradation of aromatic chlorohydrocarbons. 23 The composite oxides containing defect spinel structure of g-Al 2 O 3 , endows the surface a certain bonding ability, showing the special chemical activity center.…”