Guangjun Mei

Anaerobic biodegradation of ethylthionocarbamate by the mixed bacteria under various electron acceptor conditions.

Biodegradation behavior and kinetics of ethylthionocarbamate under nitrate, sulfate and ferric reducing conditions by mixed cultures enriched from the anaerobic digester sludge was investigated. The results showed that ethylthionocarbamate could be degraded independently by the mixed cultures coupled to nitrate, sulfate, and ferric reduction, and meanwhile, nitrite, sulfide, and ferrous were accumulated as a result of nitrate, sulfate and ferric reduction, respectively. Ferric was a more favorable terminal electron acceptor compared to nitrate and sulfate. The order of the electron acceptors with decreasing biodegradation rates of the ethylthionocarbamate was: ferric>nitrate>sulfate, and the corresponding maximum biodegradation rate was 7.240, 6.267, and 4.602 mg/(L·d), respectively. The anaerobic biodegradation of ethylthionocarbamate under various electron acceptor conditions can be accurately described by first order exponential decay kinetics.

Integrated assessment for aerobic biodegradability of sulfide mineral flotation collectors

ABSTRACT The biodegradability of flotation collectors has the most important impact on mine environment. Understanding the flotation collectors’ biodegradability is a crucial element in developing an informed strategy for analysing and managing the mine environment. Integrated assessment method including three biodegradability tests namely, BOD5/CODCr ratio test, Static-flasks test and OECD 301B have been established to evaluate the aerobic biodegradability of the sulfide mineral flotation collectors. Consistent conclusions have been obtained through these three biodegradability tests: the aerobic biodegradation of the different sulfide mineral flotation collectors is different, namely, sodium diethyldithiocarbamate is a readily biodegradable collector, and ammonium butyl-dithiophosphate is partially biodegradable. However, n-butyl xanthate and ethylthionocarbamate are considered as poorly biodegradable. Besides, the order of aerobic biodegradability of these collectors is: sodium diethyldithiocarbamate >...

Study on Biodegradation of Alkyl Xanthate Collectors

The biodegradation extent of several alkyl xanthate collectors has been determined according to ISO 7827 and the kinetic model of biodegradation has been discussed. Meanwhile, the impact of molecular structure on biodegradability has been studied. The results indicated that the biodegradation extent of ethyl xanthate, n-butyl xanthate, n-amyl xanthate, isopropyl xanthate and iso-butyl xanthate can attain 96.36%, 81.76%, 73.74%, 63.37% and 60.30%, respectively in 8d. The rate constants (k) follows the order of: kethyl>kn-butyl>kn-amyl>kisopropyl>kisobutyl. And their aerobic biodegradation follows the first order reaction kinetics equation. The biodegradation of the xanthates decreases with the DT-90 and half-life time increase with an increase in the length of hydrocarbon chain and number of alkyl lateral chains. Comparing to the hydrocarbon chain length, the branched structure has a more significant effect on the degradability of alkyl xanthates. Through the preliminary study of the biodegradation mechanism of xanthates, it was found that CS2 and monothiocarbonate are the main products of biodegradation of xanthates and a small amount of oil-like dixanthogen droplets are also produced.

Recovery of Red (Y2O3:Eu³+), Blue(Sr,Ca,Ba)10(PO4)6Cl2:Eu²+ and Green(LaPO4:Tb³+,Ce³+) Rare Earth Phosphors from Waste Phosphor Sludge by Liquid/Liquid Extraction

A new method for recovery of red (Y₂O₃:Eu³⁺), blue (Sr,Ca,Ba)₁₀(PO₄)₆Cl₂:Eu²⁺ and green (LaPO₄:Tb³⁺,Ce³⁺) rare earth phosphors from waste phosphor sludge by liquid/liquid extraction is proposed in this paper. At first ,the recommended pretreatment process is effective to remove the adhesive binder such as Al₂O₃ and the other impurities from the spent florescent powder complex, which including treatment by nitric acid solution of pH 2 for 1-5 minutes, by sodium hydroxide solution of pH 12.5 for 12 minutes and rinsing by 99.5% ethanol and distilled water. The subsequent separation for dried florescent powder was carried out in the heptane/ DMF (N, N-Dimethylformamide) system in presence of DAA (laurylamine) surfactant. Through two steps extraction process with different DAA concentration. Satisfactory separation results have been achieved; the grade and recovery of recovered red, blue and green product reach 86.0% and 80.3%, 74.8% and 95.6%, 81.2% and 79.5%, respectively. This invention provides a new possibility for the recycling of valuable rare earth phosphor from spent fluorescent lamps in the future.

Experimental Study on Aerobic Co-Metabolism Biodegradation of Xanthate

In order to improve the biodegradability of xanthate, the biodegradation process of butyl xanthate as the sole source of carbon and energy was compared to that with an external carbon source added. The experimental results showed that the degradation rate of xanthate was significantly increased in the co-metabolism process. The biodegradation rate of butyl xanthate was 65.2% after shaking culture for 72 hours under the following conditions: constant temperature of 25 ℃, external glucose as growth substrate with a concentration of 0.20g/L. While using butyl xanthate as the sole source of carbon and energy, its biodegradation rate was only 43.1%, and there was a 22.1% increase of the degradation rate. So the co-metabolism may be one of the effective ways to improve the biodegradability of butyl xanthate.