The concentration of ammonia nitrogen in a slaughterhouse wastewater sample was determined using Nessler's reagent spectrophotometry with four different pretreatment approaches. Comparison of the results shows that the concentrations increased in the following order: coagulation sedimentation < boric acid absorption < filtration < acidifying filtration. Boric acid absorption method is more favorable, and standard curve method (SCM) should be considered superior to standard addition method (SAM) in the present research.
The quantitative structure property relationship (QSPR) study was performed in this work to develop models to predict the normalized reaction rate constants for the reductive debromination of polybrominated diphenyl ethers (PBDEs) by zero-valent iron (ZVI). In order to consider the solvent effect, conductor-like polarizable continuum model (CPCM) was applied to optimize the geometries and obtain the molecular descriptors using the pseudopotential basis set. The prediction results with the inclusion of solvent effect are slightly better than that of the corresponding gas-phase calculations. The artificial neural network (ANN) model could be more satisfactory to predict the rate constants than the partial least squares regression (PLSR) and principal component analysis-multiple linear regression analysis (PCA-MLR) models.
Neutral PBDEs congeners and their corresponding radical anions were studied with the pseudopotential method of stuttgart group (SDD) effective-core potentials basis set for the bromine atoms and the all-electron basis set for all other atoms. The pseudopotential method can be used for compounds containing heavy elements with relativistic effects and can reduce the computational time. The quantitative structure property relationship (QSPR) study was also performed in this work to develop models to predict the normolized reaction rate constants for the reductive debromination of polybrominated diphenyl ethers (PBDEs) by zero-valent iron (ZVI). The partial least squares regression (PLSR), principal component analysis-multiple linear regression analysis (PCA-MLR), and back propagation artificial neural network (BP-ANN) approaches were employed for the QSPR study between the molecular descriptors and the logarithm of normalized reaction rate constants of fourteen selected BDE congeners. The results show that the ANN models could be more satisfactorily to predict the rate constants than the PLSR and PCA-MLR models.
The modified Tessier method was used in the present study to analyze the antimony (Sb) speciation in suspended solids in mining wastewater from Ban-po Antimony Mine in Guizhou province. It was found that the residual fraction and the soluble fraction are the highest and the lowest in the five Sb fractions, accounting for 62.5% and 3% of the total respectively. The order of the five Sb fractions is: the residual fraction > the reduced fraction > the oxidation fraction > the acid-extractable fraction > the soluble fraction. The antimony soluble form in aqueous solution is mainly Sb (V), about 90% of the total. The results from the analysis by X-ray diffraction and scanning electron microscopy showed that the major crystalline forms of suspended solids are K-Mg-Fe-Al-Si-O-H2O, Cu3SbS4, 3CaO·2Sb2O5·8H2O, SiO2 and the content of antimony element is approximately 2.55%.
This paper reports a study on vertical distribution characteristics of phosphorus speciation in samples collected at four sites from Baihua Lake, based on the Standards, Measurements and Testing (SMT) programme. In this study, the total phosphorus (TP) concentrations of these sediments samples varied from 944.86 to 2591.56 mg/kg and inorganic phosphorus (IP) was the main phosphorus fraction. For this heavily contaminated sediment, the IP mainly consisted of the Fe/Al-P. The vertical variation of the phosphorus had a tendency to decrease with the depth at sites JYS and YPZ. Since the concentrations of the TP in sediments were high and the phosphorus release potential and bioavailability were significant, the lake is still facing an ecological risk.
The zero-valent iron (ZVI) particles were synthesized by the aqueous phase reduction, and the tapping mode image of atomic force microscope (AFM) showed that the diameter of the ZVI particles was in the range of 90 nm - 400 nm. By comparison of the debromination of BDE-47 by sunlight, ZVI, ZVI impregnated activated carbon (ZVI/AC) and ZVI impregnated ion exchange resin (ZVI/IER), the debromination effect was found to descend in the following order: ZVI/IER > ZVI/AC > ZVI > sunlight. Second order and first order kinetic models were used for the fitting of the debromination data of BDE-47. Results show that the debromination data of BDE-47 by the sunlight, ZVI, ZVI/AC and ZVI/IER in the current study are generally best described by the pseudo first order equation. Meanwhile, the debromination data of BDE-47 by the ZVI and ZVI/IER can also be described by the pseudo second order equation.
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