By combining the structures of P227 and Cyanex 272, a nonsymmetric dialkylphosphinic acid USTB-1 was synthesized. Its structure was confirmed by 31 P NMR, 1 H NMR, MS and IR. Its pK a and purity were determined through potentiometric titration method. Its extraction and separation performance for RE(III) were studied. The purity of USTB-1 was 97.6%. Its pK a was 5.73, which was very close to that of P227 and Cyanex 272. Its solubility in deionized water was 34.7 mg/L. Its extraction ability was equal to that of P227 and Cyanex 272. It can reach extraction equilibrium as fast as Cyanex 272. Its complex with Lu(III) has larger solubility in n -octane than that of Cyanex 272, which indicated that USTB-1 has higher extraction capacity than Cyanex 272. The Lu(III) loaded in USTB-1 solution can be stripped by HCl as easily as the Lu(III) loaded in P227 and Cyanex 272 solutions. USTB-1 has good separation performance for RE(III), especially for heavy RE(III). Its average separation factor of adjacent heavy RE(III) from Ho to Lu was 2.21, superior to Cyanex 272 ( β N + 1 / N ‾ from Ho to Lu: 2.08).
Jing-Nan Jin,Jun Yao,Qing-Ye Zhang,Chan Yu,Peng Chen,Wen-Juan Liu,Dan-Ning Peng,Martin M.F. Choi
Naphthalene dioxygenase (NDO) is the initial enzyme catalyzing the biodegradation of aromatic compounds, and it plays a key role in microbial remediation of polluting sites. In this study, Rhodococcus sp. ustb-1 derived from crude oil was selected to investigate the biodegradation characters and dihydroxylation mechanism of pyrene by an integrated approach of bioassay and molecular docking. The biodegradation experiment proved that the strain ustb-1 shows high effective biodegradability to pyrene with a 70.8% degradation on the 28th day and the metabolite pyrene cis-4,5-dihydrodiol was found. The results of molecular docking indicated that the regions surrounding pyrene are defined by hydrophobic amino acids which are favorable for the binding of dioxygen molecule at C4 and C5 positions of pyrene in a side-on mode. The binding positions of dioxygen are in agreement with the mass spectral analysis of the metabolite pyrene cis-4,5-dihydrodiol. In summary, this study provides a promising explanation for the possible binding behavior between pyrene and active site of NDO.
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