Advanced Materials Research Vols. 955-959

Abstract: Nano-Fe₂O₃/goldmine complex was obtained by chemical coprecipitation on the surface of goldmine waste-solid. And its application as the heterogeneous catalyst in Fenton-like advanced oxidation processes (AOPs) was discussed for the degradation of dyeing wastewater. It was found that advanced oxidation processes play an important role to the removal of dyeing wastewater. And the best removal rate of 15400mg/L dyeing wastewater reached up to 63.1% with the presence of 50g/L dosage of nano-Fe₂O₃/goldmine complex and 50mL/L concentration of H₂O₂ at 50°C with pH=3.

Abstract: The aerobic granular sludge (AGS) was used to remove pollutants (COD, NH₃-N, TN and TP) in wastewater under different salinity in a sequencing batch reactor (SBR). The results show that: the salinity has a significant impact on the removal of COD and TN, and the removal rate declines to 60% and 56% respectively when the water salinity rises from 5g/L to15g/L. The NH₃-N removal is not much affected by the salinity, and the average removal rate is 75%. TP removal rate changes little at low-salted environment (the salinity less than 10g/L), however, the rate declines heavily when the salinity gets more than 10g/L, 70% in 10g/L and 57% in 15g/L.

Abstract: The ion-absorbed rare earth deposit occurred in the South of China is unique all over the world. Since the 1970s, rare earth in Longnan, South China has begun to be mined with leaching methods using oxalates and ammonium sulfate. Although this kind of methods is simple and economic, its presence in the environmental causes a growing environmental problems, especially changes in regional hydrochemical environment. In this paper typical ion-absorbed rare earth deposit——the Longnan rare earth mine, Jiangxi Provence, South China was selected as the study object, where the surface water and groundwater samples were collected. Analytic results show that the mining activities have affected the regional hydrochemical environment, which are expressed in the decreased pH（pH 3-4）, the enrichment of REE and heavy metal Pb in water with the maximum of 44760.1 μgL^-1 and 1550 μgL^-1 respectively, and the sulfate（214-1121 mgL^-1）, ammonium（33.7-268 mgL^-1） and nitrate ions（90-468 mgL^-1） far beyond the background value. The impaction of the mining area surface hydrochemical environment is severest, then around the mining area, and the main rivers and groundwater in the study area have not been affected yet.

Abstract: With many natural and anthropogenic factors, rare earth (RE) compounds in the environment are increasing. It affects not only plant growth but also ecosystem. So an experiment was conducted to investigate the effects of elevating rare earth element La concentration singly treatments [La-0(CK), La-50(50mg·L^-1), La-100(100 mg·L^-1) and La-150(150 mg·L^-1)] on the changes of lipid peroxidation extent,ROS production rate,content and anti-oxidative enzymes activities in soybean (Glycine max) roots. The results showed that during the whole growth stage the elevated La concentration at 100mg·L^-1 induced a decrease on the content of malondialdehyde (MDA),superoxide anion (O₂) production rate,hydrogen peroxide (H₂O₂) content, which were lower than the other treatments, however, an increase on the activities of superoxide dismutase (SOD),catalase (CAT),peroxidase (POD),which were higher than the elevated La concentration at 50mg·L^-1, 150mg·L^-1 and CK. The results demonstrated that with the increase of La concentration, metabolism rates of reactive oxygen species (ROS) are restrained with the protective ability of anti-oxidative system strengthened. However, when the La concentration is higher than some concentration which is around 100 mg·L^-1, the activities of anti-oxidative enzymes drop and reactive oxygen species accumulate, thus increasing membrane lipid peroxidation, which represents injured effects on soybean.

Abstract: This study examined the effects of nitrogen enrichment and clonal integration on the growth and expansion process from terrestrial to aquatic habitats of the amphibious and invasive plant Alternanthera philoxeroides. The clonal fragments of A. philoxeroides were subjected to three nitrogen levels of 10/3, 10 and 30 mg/l N with the stolon connections either severed or left connected. The results suggested that nitrogen enrichment increased the clonal growth and expansion of A. philoxeroides in aquatic habitats. Clonal integration supports the expansion of A. philoxeroides from terrestrial to aquatic environments. And A. philoxeroides will be more invasive in nitrogen enriched waters due to the synergistic effects of nitrogen enrichment and clonal integration.

Abstract: Warm water discharge from nuclear power plant will elevate the temperature of seawater and may subsequently have influences on important marine aquiculture bivalves. In present study, the effects of temperature elevation caused by warm water discharge on the filtration behavior, calcification rate, and ammonia excretion of a major local bivalve species, razor clam, were investigated via laboratory simulation. The results showed that the filtration rates of razor clam increased significantly with an increased temperature, which were 0.46±0.06, 0.62±0.09, and 0.85±0.08L/g·h for 28 °C, 30 °C, and 32 °C, respectively. Under the experimental temperature gradient, the pattern of calcification rates of razor clam was shown to be bell-shaped, with the highest calcification rate 2.85±0.28μmol/FWg·h at 30 °C. The ammonia excretion rates were shown to increase slightly with increased temperature, which were 0.31±0.03, 0.32±0.09, and 0.34±0.06mg/ g·h for 28 °C, 30 °C, and 32 °C, respectively. The results suggest that razor clam will increase its energy intake and metabolic rate to maintain a relatively constant growth rate under thermal stress within 4 oC range even during the summer season.

Abstract: To explore purification approach of anaerobic-digested-slurry from cattle dung, this study translated a technology in inorganic coagulation. Under the same condition, a coagulation experiment was carried out by three kinds inorganic coagulants such as polyaluminium chloride (PAC), aluminum sulfate and ferric chloride, respectively, then measured indicators of pH value, BOD₅ value, CODc_r value, ammonia nitrogen value, turbidity value. Results showed that there was a varying degree of purification effect, and the removal rate of the above indicators increased as the coagulant dosage increasing, the ferric chloride with the dosage of 960mg/L was the best one in purifying effect among the three coagulants. It is feasible that coagulation technology was used to pretreatment biogas slurry from cattle dung, and most of the indicators reached Chinese national standard basically (GB 18596-2001).

Abstract: The objective of this research is to enhance the degrading ability of zero-valent iron (ZVI) on trichloroethylene (TCE) by using electrochemical technique. ZVI has been shown to effectively degrade TCE by reductive dechlorination, a process in which the ZVI, acting as a reducing agent, causes the chlorine to separate from TCE sequentially. The efficiency of this technique could be enhanced by lowering the redox potential of ZVI using electrochemical methods. In this research the lowering of redox potential was achieved by filling granular ZVI into a cathode compartment in a reactor. The ZVI was mixed with granular graphite to increase the overall electrical conductivity before being filled into the cathode. The anode and cathode compartments were separated with a Nafion membrane. The loss of TCE due to adsorption by the granular graphite during the experiments was evaluated by conducting batch adsorption tests. The electrochemical experiments were conducted by applying a direct current using a potentiostat. The TCE concentration as well as possible degradation products was analyzed with gas chromatography equipped with a mass detector. Chloride concentration was measured with ion chromatography. The results of adsorption tests of TCE by granular graphite fits a linear isotherm with a K_d value of 2.3 L/kg, which is comparable to values reported in the literature. Results from the TCE degradation experiments leads to two major conclusions: (1) degradation of TCE was facilitated by the applied current even when the cathode was filled with only granular graphite and (2) degradation rate of TCE by ZVI was increased by the applied current. The degradation rate of TCE could be fitted with a pseudo-first-order kinetics; the reaction rate constant, k_h, increases from 0.017 at no current to 0.064 h^-1 at a current of 100 mA. No degradation product was observed in the liquid phase. In the gaseous phase, however, cis-1,2-dichloroethylene was observed. The applied current also caused the increasing rate of pH to decrease. The pH of the solution after 8h of processing time increased from 5.7 to 8.6 at no current, whereas it increased from 5.7 to 5.9 with the same processing time. This suggests the applied current caused the decrease of the corrosion rate of ZVI. The results of this study show the electrochemical technique not only increased the TCE degradation rate by ZVI but also decreased the consumption of ZVI by corrosion. Thus, the technique can be applied to prolong the life of ZVI installed in the field for TCE degradation.

Abstract: Vacuum distillation (VD) by NaOH was used for treatment of petroleum refinery wastewater, and the optimal experimental conditions including operation vacuum degree, initial pH, feeding process were also investigated. Chemical oxygen demand (COD), conductivity and pH value were utilized to estimate the removal efficiency for treatment of refinery wastewater. Based on experimental results, it can be concluded that NaOH displays higher efficiency for the treatment of refinery wastewater, the pellucid effluents with satisfied COD removal efficiency (99%) and low salinity were obtained in fully batch process at operation vacuum degree of-0.085 MPa, operation time of 50 min, initial pH of 11, and the corresponding pH values of effluents varied from 7 to 9. Thus, in view of fine COD and mineralization removal efficiency, the VD technology is an effective approach to treat petroleum refinery wastewater.

Abstract: Aerobic denitrification process is attracted more attention to enhance nitrogen removal technology. Aerobic denitrifying bacteria present excelled abilities with fast growth rate and denitrifying speed, though they are not dominant in most practical processes. A high-efficiency strain was enriched in SBR from aerobic activated sludge by the way of intermittent aeration and continuous aeration combination. The strain was determined to Pseudomonas stutzeri T13 with ability of TN removal 90% and nitrate removal 97%. The limiting factors for aerobic denitrifying efficiency were optimized to temperature=31°C,pH=7.11 and DO=2.5 mg/L using response surface methodology. A total of 32 genes are related to nitrogen removal in strain T13. And 10 related to nitrate reductase, especially including 3 genes encoding the periplasmic nitrate reductase, playing important role to aerobic denitrification. It gave good understanding to supply effective technological supports for aerobic denitrification process.