Advanced Materials Research Vols. 518-523

Abstract: Oxidation of gas phase elemental mercury (Hg⁰) in the simulated flue gas by DBD plasma under atmospheric pressure and ambient temperature (298 K) was conducted. Experimental results indicated that the oxidative efficiency of Hg⁰ increased with O₂ content, the residence time of flue gas in reactor and the applied voltage. The oxidation efficiency of Hg⁰ reached over 96% under the applied voltage of 11 kV and the residence time of 0.24 s when the O₂ content in flue gas was 20%, and the corresponding energy efficiency was at about 14.1 μg kJ^-1. It was noted that the oxidation efficiency of Hg⁰ could still reach 80% when the O₂ content in flue gas was only 4% (near the actual O₂ content in flue gas of coal-fired boilers). The experimental results indicated that DBD plasma was one of the efficient technologies for purification of Hg⁰ vapor industrial flue gas.

Abstract: A pilot-scale test was conducted with an up-flow anaerobic sludge blanket (UASB) treating pharmaceutical wastewater containing berberine. The aim of this study was to investigate the performance of UASB in the condition of a high chemical oxygen demand (COD) loading rate from 4.64 to 8.68 kg/m³d and a wide berberine concentration from 254 to 536 mg/L, in order to provide a reference for treating the similar pharmaceutical wastewater containing berberine. The results demonstrated that the UASB average percentage reduction in COD and berberine 68.14% and 57.39%, respectively. Granular sludge was formed during this process. In addition, a model, built on the back propagation neural network (BPNN) theory and linear regression techniques was developed for the simulation of the UASB system performance in the biodegradation of pharmaceutical wastewater containing berberine. The average errors of COD and berberine were -0.55% and 0.24%, respectively. The results indicated that this model built on the BPNN theory was well-fitted to the detected data, and was able to simulate and predict the removal of COD and berberine by UASB reactor.

Abstract: The body of knowledge on the performance of tidal flow constructed wetlands treating strong wastewaters like livestock wastewater is insufficient. Experiments on three laboratory-scale tidal flow constructed wetlands with different operational strategies were carried out to investigate the performance, regarding the removal of organic matter, nitrogen and phosphorus in livestock wastewater. Results demonstrated that the removal of total organic carbon averaged about 70% under varying influent concentration. The findings demonstrated a change from 290 mg/L to 1500 mg/L in three wetlands with flood drain ratios of 1 h:3 h, 3 h:3 h, 6 h:6 h, respectively. There was no significant difference in TOC removal between the experimental phases with different organic load and flood drain ratio. The removal of ammonium was particularly impactful to the flood drain ratio with results that achieved 59% (flood drain ratio 1 h:3 h), 65% (3 h:3 h) and 71% (6 h:6 h), respectively. The presence of nitrate (180 mg/L) in the effluent indicated enhanced nitrification process in tidal wetland due to its high capacity of oxygen transfer. The removal of phosphorus was exhibited to be 35% which was mainly adsorbed to the matrix.

Abstract: Simulated runoff was conducted on self-designed soil bins to compare the effectiveness of 6m treating systems consisting of contrast system(bear soil),soil-tall fescue system and soil-alfalfa system in reducing SS, NO3--N,NH4+-N,TDP and PP. The concentration reductions were greater in soil-plant system compared with contrast. Vegetation type (Tall fescue and alfalfa) had somewhat affection on contaminant removal. The mean concentration reductions of SS, NO3--N,NH4+-N,TDP and PP reached 86.61%,25.83%,52.03%,26.53%and 76.59% under tall fescue, which were slightly higher than Alfalfa. However, the load reductions of alfalfa neared to that of tall fescue due to more water detained, which made Alfalfa show the same potential in runoff clarification as tall fescue. The removal efficiency of NO3--N and NH4+-N decreased significantly with increasing concentration, while the changes of SS ,PP and TDP were much smaller, which meant the conditions of vegetation and soil in this study were not enough to deal with NO3--N and NH4+-N increasing, and the ground roughness could bear SS and PP increasing. Most SS and PP were trapped in first 2m and it was ineffective to increase the runoff distance beyond 4m for removal. The reduction of resolved compound occurred uniformly along the runoff and it related with runoff extension distance linearly.

Abstract: The photocatalytic degradation of 2,4,5–Trichlorophenol(2,4,5–TCP) in TiO2/UV/ H2O2 photocatalytic system was examined using absorption spectroscopy and GC-MS. It was found that 2,4,5–TCP could be degraded almost completely within 100 min under the conditions of initial pH 3, C(H2O2) = 0.08 mol/L and C(TiO2) = 0.5 g/L. The effects of pH and the concentration of hydrogen peroxide on the degradation of 2,4,5–TCP were also studied. Besides, the degradation mechanism was concluded accorrding to convertional analysis method too.

Abstract: Photodegradation of dimethyl phthalate (DMP) in aqueous solutions by Fe(III)-pyruvate complex system was preliminarily investigated. The influences such as light sources, initial pH value, initial concentration of Fe(III), pyruvate and DMP on photodegradation efficiency of DMP were discussed in detail. The result indicates that DMP could be decomposed efficiently in Fe(III)-pyruvate system. The degradation efficiency of DMP are dependent on initial pH value, Fe (III) initial concentration and pyruvate initial concentration. The optimum pH for photodegration of DMP is 3.0. The degradation efficiency of DMP increases with increase of the initial concentrations of Fe(III) or pyruvate, whereas decreases with increase of the initial concentrations of DMP. Various light sources including metal halide lamps, daylight lamps, UV disinfection lamps and sunlight can be adopted in the system.

Abstract: Photolytic and photocatalytic degradation of phenols in aqueous solution were investigated under the UV irradiation of 254 nm light and VUV irradiation of 254 nm and 185 nm light. The decomposition and mineralization of 4-CP in UV/TiO2 process were both faster than in UV process. VUV irradiation led to the most efficient degradation of 4-CP. The initial concentration of 4-CP had little effect on the decomposition rate in UV and UV/TiO2 processes while in VUV and VUV/TiO2 processes the pseudo first-order rate constants decreased with the increase of the initial concentration. In UV/TiO2 process gas bubbling and liquid circulation could enhance the formation of oxidative species (HO2•) and mass transfer efficiency. The optimal air flow rate and liquid circulation flow rate were 300 mL/min and 1200 mL/min respectively in our reactor. Photocatalytic decomposition and mineralization of 4-CP were highly dependent on the nature of the organic substrate treated. Adding salt into aqueous solution could enhance photocatalytic degradation of phenols but after long operation with aqueous solution containing salt TiO2 catalyst would lose activity.

Abstract: Pot experiments under controlled conditions were conducted to study the physiological response of influence of ryegrass (Lolium perenne) to petroleum pollution and to evaluate the removal efficiency of hydrocarbon pollutants. The morphological and physiological characteristics such as height, root length, weight, chlorophyll content, activities of superoxide dismutase (SOD), and peroxidase (POD) were investigated. Our results indicated that, due to crude oil pollution stress, the growth and antioxidant enzymes were inhibited more or less with increased crude oil concentrations, but ryegrass also showed resistance to crude oil pollutants and good potential in crude oil bioremoval. This study lays a preliminary foundation on phytoremediation of crude oil pollution in soil.

Abstract: The Pollution characteristics of heavy metals in sediment of Chongqing urban section of Three Gorges Reservoir after impoundment were investigated and analyzed by assessing the geoaccumulation index and the potential ecological risk of actural measurement of eight monitoring stations(Lijiatuo,Egongyan,Huangshaxi,Shanhuba,Dafosi(Cuntan),Huanghuayuan,Hualongqiao,Ciqikou).The results showed that the average contents of Cd and Pb in the sediment of Chongqing urban section are 1.83mg/Kg and 98.14mg/Kg in Yangtze River and 1.28mg/Kg and 28.80mg/Kg in Jialing River respectively, which all surpass the soil background value of Chongqing. The enrichment degree of heavy mental was Cd>Pb. According to the evaluation based on the soil background value of Chongqing, the pollution of Pb in all monitoring stations was low; the pollution of Cd in Lijiatuo、Egongyan、Huangshaxi and Shanhuba was moderate and the rest was low.

Abstract: In the present study, geometrical optimization and electrostatic potential calculations have been performed at the HF/6-31G* level of theory for 25 investigated persistent organic pollutants (POPs), including ten polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), nine polychlorinated biphenyls (PCBs), four polycyclic aromatic hydrocarbons (PAHs) and two polybrominated diphenyl ethers (PBDEs). A number of statistically-based parameters have been obtained. Linear relationships between soot–water partition coefficients (log K_SC) of POPs and the structural descriptors have been established by multiple linear regression method. The result shows that the quantities derived from electrostatic potential, together with molecular surface area (A_S) and the energy of the highest occupied molecular orbital (E_HOMO) can be well used to express the quantitative relationships between structure and soot–water partition coefficients of POPs. Predictive capability of the model has been demonstrated by leave-one-out cross-validation with the cross-validated correlation coefficient (R_CV) of 0.9797. Furthermore, the predictive power of this model was further examined for the external test set. The QSPR model established may provide a new powerful method for predicting soot–water partition coefficients (K_SC) of persistent organic pollutants.