QSAR for Predicting Biodegradation Rates of Polycyclic Aromatic Hydrocarbons in Aqueous Systems

The relationship between chemical structures and biodegradation rates （k b） of 22 polycyclic aromatic hydrocarbons （PAHs） was studied using density functional theory （DFT） and stepwise multiple linear regression analysis （SMLR） method.The equilibrium geometries and vibration frequency have been investigated at the B3LYP/6-31＋G（d,p） level by thinking Solvent effects using a selfconsistent reaction field （SCRF） based on the polarizable continuum model （PCM）.It was concluded that the biodegradation rate was closely related to its molecular structure,and there is one high correlation coefficient between the in-plane bending vibration frequency of the conjugated ring of PAHs （Freq） and k b.By means of regression analysis,the main factors affecting the biodegradation rate were obtained and the equation of quantitative structure-activity relationship （QSAR） was successfully established kb =-0.653＋0.001Freq＋0.068CQ＋0.049N1.Statistical evaluation of the developed QSAR showed that the relationships were statistically significant and the model had good predictive ability.The fact that a bending frequency is more important than the HOMO or LUMO energies in predicting k b suggests that the bending of benzene ring might play an important role in the enzymatic catalysis of the initial oxidation step.

QSBR Study on the Biodegradation Rate Constant of Chloro-phenol Compounds

Structural and thermodynamic parameters of 16 chloro-phenol compounds in water solution were calculated and fully optimized by using Onsager model in self-consistent reaction field（SCRF） based on the B3LYP/6-311G＊＊ level.These quantum chemical parameters were used as theoretical descriptors to correlate with the experimental biodegradation rate constant（Kb） of 16 compounds by stepwise multiple linear regression.As a result,a three-parameter model including molecular average polarizability（α）,entropy（Sθ）,and molar heat capacity at constant volume（CVθ） were established for Kb prediction,which was proposed with correlation coefficient R2 = 0.894.α exhibits the most significant effect on Kb.Variance analysis and standard t-value test were applied to validate the model.As expected,this model exhibits good robustness and prediction ability,which can be used in Kb prediction of analogs.

Degradation Kinetics of Petroleum Contaminants in Soil-Water Systems

On the basis of site investigation and sample collection of petroleum contaminants in the soil-water-crop system in the Shenyang-Fushun sewage irrigation area, the physical-chemical-biological compositions of the unsaturated zone is analyzed systematically in this paper. At the same time, the degradation kinetics of residual and aqueous oils is determined through biodegradation tests. The studies show that dominant microorganisms have been formed in the soils after long-term sewage irrigation. The microorganisms mainly include bacteria, and a few of fungus and actinomycetes. After a 110-days' biodegradation test, the degradation rate of residual oil is 9.74%-10.63%, while the degradation rate of aqueous oil reaches 62.43%. This indicates that the degradation rate of low-carbon aqueous oil is higher than that of high-carbon residual oil. In addition, although microbial degradation of petroleum contaminants in soils is suitable to the first-order kinetics equation, the half-lives of aqueous oil, No. 20 heavy diesel and residual oil in the surface soils (L2-1, S1-1 and X1-1) are 1732 h, 3465 h and 17325 h, respectively.

Biological liquefaction characteristics of Jurassic weak & non-stick coal in Hengshan,North Shaanxi Province

Jurassic weak & non-stick coal in Hengshan of North Shaanxi Province was pretreated by the nitric acid.Then,it was biodegraded by Phanerochaete chrysosporium. The biodegradation role of the white-rot fungus for coal is extremely significant.Orthogo- nal test demonstrate that liquefied time,liquefaction temperature and the amount of fun- gus liquids etc.are the main factors affecting the coal biodegradation rate.The best tech- nical condition of the coal biological liquefaction was got.Comparing the coal sample be- fore biodegradation with that after biodegradation,it is found that the ash of the coal resi- due after biodegradation reduces significantly,H and O contents increase,C and N con- tents decrease.The biodegradation change the coal macromolecular structure.

Application of ultra-sonication, acid precipitation and membrane filtration for co-recovery of protein and humic acid from sewage sludge

A novel method was applied to co-recover proteins and humic acid from the dewatered sewage sludge for liquid fertilizer and animal feed. The proteins in sewage sludge were first extracted using the processes of ultra- sonication and acid precipitation, and then the humic acid was recovered via membrane filtration. The extraction efficiency was 125.9mg humic acid-gWSS volatile suspended solids （VSS） and 123.9 mg proteins-g-1 VSS at the optimal ultrasonic density of 1.5 W·mL-1. FT-IR spectrum results indicated that the recovered proteins and humic acid showed similar chemical characteristic to the natural proteins and humic acid. The acidic solution （pH 2） could be recycled and used more than 10 times during the co-recovery processes. In addition, the dewatered sludge could be easily biodegraded when the humic acid and proteins are extracted, which was essential for further utilization. These findings are of great significance for recovering valuable nutrient fi＇om sewage sludge.

Design of Fe–Mn–Ag Alloys as Potential Candidates for Biodegradable Metals

In this work,a series of biodegradable pure iron,Fe–30Mn and Fe–30Mn–Ag alloys were developed by using a rapid solidification technology.A fine a-Fe dendrite was formed in pure iron,resulting in a high compressive yield strength of above 300 MPa.The Fe–30Mn alloy doped with only 1%Ag exhibited a significant increase in the degradation rate in simulated body fluid due to the precipitation of Ag-rich particles in alloy matrix and the induction of the microgalvanic corrosion.In addition,the novel Fe–30Mn–Ag alloy also exhibited a good magnetic compatibility and offered a closely approaching requirement for biodegradable medical applications.