Thermal dechlorination of heavily PCB-contaminated soils from a sealed site of PCB-containing electrical equipment

Abstract

A large amount of soils are contaminated by leakage of polychlorinated biphenyls (PCBs) from sealed-up PCB-containing electrical equipment in China. Thermal dechlorination of soils contaminated with PCBs at a level of 108 mg g(-1) and PCB77 (3,3',4,4'-tetrachlorobiphenyl) as a model isomer in conjunction with calcium oxide was investigated in this study. The PCB dechlorination rate improved with increased temperature and time. The highest dechlorination rate was 85.3 %, and temperature was the main influencing factor. Pentachlorobiphenyl and tetrachlorobiphenyl in soils decreased or disappeared in response to treatment at 350 and 400 °C for 4 h, while monochlorinated biphenyl and biphenyl were detected after the reaction, indicating the presence of a dechlorination/hydrogenation pathway. Discrepancy in chlorine balance was observed after low-temperature thermal dechlorination. The species of dechlorination products were identified as amorphous carbon containing a crystalline graphite plane structure and a carbonyl group-containing polymerized product, demonstrating the existence of a dechlorination/polymerization pathway. The yield of amorphous carbon and high-molecular-weight intermediates increased with heating time. The results showed that the discrepancy in chlorine balance was because of the generation of polymerized products and undetected intermediates.

High-yield synthesis of Ce modified Fe–Mn composite oxides benefitting from catalytic destruction of chlorobenzene

“…Among them, chlorinated aromatic compounds have been always considered as the most harmful contaminants. [1][2][3][4] The widespread emissions of chlorinated aromatic compounds not only cause the pollution of the ecological environment but also damage human health due to their acute toxicity and strong bioaccumulation potential. 5,6 Thus, the elimination of chlorinated aromatic compounds has received more and more attention.…”

Carboxylated Multiwalled Carbon Nanotubes as Dispersive Solid-Phase Extraction Sorbent to Determine Eighteen Polychlorinated Biphenyls in Vegetable Samples by Gas Chromatography-Mass Spectrometry

“…PCBs have physicochemical properties that are industrially useful, including nonflammability, chemical stability, high boiling point, and electrical insulating properties, which has led to their mass production and widespread use in electrical transformers, capacitors, regulators, hydraulic fluids, plasticizers, and lubricants [2]. Despite the limited production or the ban of PCBs since the late 1970s due to their toxic, bioaccumulative, and carcinogenic behavior, some industrial equipment containing PCBs has remained in operation [3, 4]. Large amounts of PCBs have been released into the environment, and congeners are still frequently detected in environmental media including soil [5], sediment [6], water [7], and air [8].…”