Akiko Ido

Practical method for PCB degradation using Pd/C–H2–Mg system

Polychlorinated biphenyls (PCBs) were mainly used as lubricants and coolants in electrical equipment. However, their chemical stabilities as well as hydrophobic properties caused persistent environmental pollution and damage to human health based on their bioaccumulative property. PCBs are currently targeted for worldwide elimination and should be disposed by 2028 based on the Stockholm Convention on Persistent Organic Pollutants. The conventional PCB degradation methods require high-heat, high-pressure or/and strongly basic conditions. The development of a safer and more practical method, therefore, is desired. We have reported a catalytic degradation method of PCBs based on a palladium on carbon (Pd/C)-catalyzed dechlorination in the presence of Et(3)N under ambient hydrogen pressure and temperature. In this study, we demonstrate a more practical system using magnesium metal instead of Et(3)N for the dechlorination of a variety of aromatic chlorides. The method was applicable for the complete degradation of a variety of PCB mixtures, such as Aroclor 1242, 1248, 1254 and PCBs removed from a capacitor to produce only biphenyl and magnesium chloride as the maritime component, both of which are less toxic and easily separable. Moreover, the Pd/C could be recovered and reused at least five times without any loss of catalytic activity. The present Pd/C-Mg-H(2) system is a simple, safe, inexpensive, and environmentally-benign degradation method of PCBs.

Pd/C-catalyzed dechlorination of polychlorinated biphenyls under hydrogen gas-free conditions.

The simultaneous use of catalytic amount of palladium on carbon (Pd/C) and Mg metal (1.5-2.0 equiv vs. Cl numbers of the substrates) in MeOH achieved the complete dechlorination of a variety of aryl chlorides at room temperature under a nitrogen atmosphere in the absence of hydrogen gas. The present method could be successfully used for the detoxification of PCBs based on the dechlorination reaction. Both virgin PCBs, such as Aroclors 1242, 1248 and 1254, and used PCBs as a high-tension capacitor oil, were smoothly dechlorinated into harmless biphenyl without any byproducts within 2h at rt. The distinctive features of this method are convenience and safety due to no needs for the pretreatment of catalyst and Mg and complete degradation of PCBs under mild conditions without hydrogen gas.

Occurrence of fibrates and their metabolites in source and drinking water in Shanghai and Zhejiang, China

Fibrates, which are widely used lipidaemic-modulating drugs, are emerging environmental pollutants. However, fibrate concentrations in the environment have not been thoroughly surveyed. Here, we determined concentrations of the most commonly used fibrates and their metabolites in source water and drinking water samples from ten drinking water treatment plants in Shanghai and Zhejiang, China, using solid-phase extraction and liquid chromatography–tandem mass spectrometry. All the target compounds were detected in at least some of the source water samples, at concentrations ranging from 0.04 ng/L (fenofibrate) to 1.53 ng/L (gemfibrozil). All the compounds except fenofibrate were also detected in at least some of the drinking water samples, at recoveries ranging from 35.5% to 91.7%, suggesting that these compounds are poorly removed by typical drinking water treatment processes. In a peroxisome proliferator-activated receptor α agonistic activity assay, the target compounds showed no significant activity at nanogram per litre concentrations; therefore, our results suggest that the fibrate concentrations in drinking water in Shanghai and Zhejiang, China do not significantly affect human health. However, because of the increasing westernization of the Chinese diet, fibrate use may increase, and thus monitoring fibrate concentrations in aquatic environments and drinking water in China will become increasingly important.