Depolymerization of Waste PET with Phosphoric Acid–Modified Silica Gel Under Microwave Irradiation

Chemical recycling of waste poly(ethylene terephthalate) (PET) using phosphoric acid–modified silica gel as a solid catalyst is reported. Advantageously, microwave irradiation was used to progress the depolymerization of PET. In this study, depolymerization of PET with a small amount of water is suggested as a suitable method. The depolymerized product, terephthalic acid was obtained and assigned by ¹H NMR and FT-IR spectroscopy. Finally, over 90 % conversion to terephthalic acid was achieved when waste plastic bottles were treated with the method. This results confirm the importance of the microwave power technique as a promising recycling method for plastic bottles made from PET, resulting in monomer recovery in addition to substantial energy saving.     

Detailed analysis of PCBs and PCDD/Fs impurities in a dielectric oil sample （ASKAREL Nr 1740） from an imported transformer in China

Homolog and congener profiles of polychlori- nated biphenyls （PCBs）, polychlorinated dibenzo-p- dioxins （PCDDs） and polychlorinated dibenzofurans （PCDFs） in commercial PCBs formulations are useful information for the source appointment of PCBs contam- ination as well as the risk assessment caused by potential exposure. Dielectric oil （ASKAREL Nr 1740） in an imported transformer found in China was sampled and analyzed by isotope dilution technology using high resolution gas chromatography-high resolution mass spectrometry （HRGC/HRMS）. The detailed homolog and congener profiles of PCBs obtained were compared with those of known Aroclor formulations. High similarity in the homolog profile between the oil sample and Aroclor 1260was found, with the hexachlorinated and hepta- chlorinated biphenyls accounting for more than 80.2% of the total PCBs concentration. Severn indicator PCBs contribute about 30%, while 12 PCB congeners （i.e., # 153, #143, #168, #180, #149, #165, #138, #170, #190, #187, #174, #181） account for more than 50% of the total PCB concentrations. Total concentration ofPCDDs, PCDFs and dioxin-like PCBs （DL-PCBs） was found to be 740 ng TEQ/g, of which 620 ng TEQ/g came from DL-PCBs. The contribution of PCDDs to the total TEQ was neglectable. The concentration of PCDFs homologs follows the order of OCDF 〉 HxCDFs 〉 HpCDFs 〉 PeCDFs 〉 TeCDFs, which is in consistence with the previous study on Aroclor 1260. Three DL-PCBs congeners （i.e., #118, #156, #157） accounted for 77% of the total concentration of DL-PCBs, also they contribute 72% in the TEQ caused by DL-PCBs.     

苏州河底泥中重金属的烧结无害化研究

采用有氧烧结法和还原烧结法处理苏州河底泥,研究了底泥中重金属的无害化效果.结果表明,有氧烧结温度900℃以上时,对Cu、Pb、Zn、Cd去除率达40%～65%;烧结温度为500～900℃时,尽管对Cu、Pb、Zn、Cd去除效果不明显,但能有效抑制其溶出.有氧烧结法不仅不能实现Cr的去除,而且会增加Cr的溶出,这是由于有氧烧结过程中Cr(III)被转化为Cr(VI),而底泥对Cr(VI)的吸附能力很有限.还原烧结法则能有效防止底泥中Cr(III)向Cr(VI)的转化,从而抑制包括Cr在内的重金属的溶出.     

Important sequence for overexpression of NADH oxidase gene from Thermus thermophilus HB8 in Escherichia coli

Enzymes fixed on the electrode of biosensor are gradually inactivated and the electrode is discarded after using several times. In order to prepare the stable biosensor, we try to use a stable enzyme from extreme thermophilic bacteria, Thermus thermophilus HB8. It is very important that a stable enzyme from T. thermophilus HB8 is overproduced in Escherichia coli, for the purpose of enough supply of enzyme. Thereby, we determined the important sequence for overexpression of NADH oxidase (nox) gene from T. thermophilus HB8 in E. coli. As a result, it is revealed that ten nucleotides sequence, GAAATTAACT, in the upstream of start codon of nox gene was important for its overexpression in E. coli.