The current work focused on the investigation of charge and separation characteristics of nanofiltration (NF) membrane embracing dissociated functional groups under different electrolyte solutions. The electro-kinetic method was carried out to assess the membrane volume charge density (X) with different salt concentrations ranging from 0.1 to 10 mol·m-3 and different electrolyte species, such as type 1–1, type 2–1 and type 3–1. The Donnan steric pore model-dielectric exclusion (DSPM-DE) model was employed to evaluate the separation characteristics of the NF membrane for wide range of electrolyte concentration (from 25.7 to 598.9 mol·m-3). The results indicated that the dissociation of the hydrophilic functional groups and the specific adsorption contributed to charge formation on membrane surface. The former played a dominant role in type 1–1 and type 2–1 electrolytes at dilute aqueous solutions (0.1–0.5 mol·m-3). However, for type 3–1 electrolyte, specific adsorption should contribute to the charge effect to a large extent. Moreover, the correlation between the volume charge density and feed concentration was in accordance with Freundlich isotherm. Furthermore, it was found that the separation characteristic of NF membrane could be evaluated well by DSPM-DE model coupling with electro-kinetic method in a whole concentration range.
The effect of Zr on the catalytic performance of Pd/γ-Al2O3 for the methane combustion was investigated. The results show that the addition of Zr can improve the activity and stability of Pd/γ-Al2O3 catalyst, which, based on the catalyst characterization (N2 adsorption, XRD, CO-Chemisorption, XPS, CH4-TPR and O2-TPO), is ascribed to the interaction between Pd and Zr. The active phase of methane combustion over supported palladium catalyst is the Pd0/Pd2+ mixture. Zr addition inhibits Pd aggregation and enhances the redox properties of active phase Pd0/ Pd2+. H2 reduction could effectively reduce the oxidation degree of Pd species and regenerate the active sites (Pd0/ Pd2+).
Dissolved organic matter (DOM) plays an important role in heavy metal speciation and distribution in the aquatic environment especially for eutrophic lakes which have higher DOM concentration. Taihu Lake is the third largest freshwater and a high eutrophic lake in the downstream of the Yangtze River, China. In the lake, frequent breakout of algae blooms greatly increased the concentration of different organic matters in the lake sediment. In this study, sediment samples were collected from various part of Taihu Lake to explore the spatial difference in the binding potential of DOM with Cu. The titration experiment was adopted to quantitatively characterize the interaction between Cu(II) and DOM extracted from Taihu Lake sediments using ion selective electrode (ISE) and fluorescence quenching technology. The ISE results showed that the exogenous DOM had higher binding ability than endogenous DOM, and DOM derived from aquatic macrophytes had a higher binding ability than that derived from algae. The fluorescence quenching results indicated that humic substances played a key role in the complexation between DOM and Cu(II) in the lake. However, because of the frequent breakout of algae blooms, protein-like matters are also main component like humic matters in Taihu Lake. Therefore, the metals bound by protein-like substances should be caused concern as protein-like substances in DOM were unstable and they will release bound metal when decomposed.
Polyethylenimine (PEI)-modified chitosan was prepared and used to remove clofibric acid (CA) from aqueous solution. PEI was chemically grafted on the porous chitosan through a crosslinking reaction, and the effects of PEI concentration and reaction time in the preparation on the adsorption of clofibric acid were optimized. Scanning electron microscopy (SEM) showed that PEI macromolecules were uniformly grafted on the porous chitosan, and the analysis of pore size distribution indicated that more mesopores were formed due to the crosslinking of PEI molecules in the macropores of chitosan. The PEI-modified chitosan had fast adsorption for CA within the initial 5 h, while this adsorbent exhibited an adsorption capacity of 349 mg·g−1 for CA at pH 5.0 according to the Langmuir fitting, higher than 213 mg·g−1 on the porous chitosan. The CA adsorption on the PEI-modified chitosan was pH-dependent, and the maximum adsorption was achieved at pH 4.0. Based on the surface charge analysis and comparison of different pharmaceuticals adsorption, electrostatic interaction dominated the sorption of CA on the PEI-modified chitosan. The PEI-modified chitosan has a potential application for the removal of some anionic micropollutants from water or wastewater.
In this paper the photolysis half-lives of the model dyes in water solutions and under ultraviolet (UV) radiation were determined by using a continuous-flow spectrophotometric method. A quantitative structure-property relationship (QSPR) study was carried out using 21 descriptors based on different chemometric tools including stepwise multiple linear regression (MLR) and partial least squares (PLS) for the prediction of the photolysis half-life (t1/2) of dyes. For the selection of test set compounds, a K-means clustering technique was used to classify the entire data set, so that all clusters were properly represented in both training and test sets. The QSPR results obtained with these models show that in MLR-derived model, photolysis half-lives of dyes depended strongly on energy of the highest occupied molecular orbital (EHOMO), largest electron density of an atom in the molecule (ED+) and lipophilicity (logP). While in the model derived from PLS, besides aforementioned EHOMO and ED+ descriptors, the molecular surface area (Sm), molecular weight (MW), electronegativity (χ), energy of the second highest occupied molecular orbital (EHOMO-1) and dipole moment (μ) had dominant effects on logt1/2 values of dyes. These were applicable for all classes of studied dyes (including monoazo, disazo, oxazine, sulfonephthaleins and derivatives of fluorescein). The results were also assessed for their consistency with findings from other similar studies.
As low oxygen and high ultraviolet (UV) exposure might significantly affect the microbial existence in plateau, it could lead to a specialized microbial community. To determine the abundance and distribution of ammonia-oxidizing archaea (AOA) in agricultural soil of plateau, seven soil samples were collected respectively from farmlands in Tibet and Yunnan cultivating the wheat, highland-barley, and colza, which are located at altitudes of 3200–3800 m above sea level. Quantitative PCR (q-PCR) and clone library targeting on amoA gene were used to quantify the abundances of AOA and ammonia-oxidizing bacteria (AOB), and characterize the community structures of AOA in the samples. The number of AOA cells (9.34 × 107–2.32 × 108 g-1 soil) was 3.86–21.84 times greater than that of AOB cells (6.91 × 106–1.24 × 108 g-1 soil) in most of the samples, except a soil sample cultivating highland-barley with an AOA/AOB ratio of 0.90. Based Kendall’s correlation coefficient, no remarkable correlation between AOA abundance and the environmental factor was observed. Additionally, the diversities of AOA community were affected by total nitrogen and organic matter concentration in soils, suggesting that AOA was probably sensitive to several environmental factors, and could adjust its community structure to adapt to the environmental variation while maintaining its abundance.
This study compared the growth and lipid accumulation properties of two oleaginous microalgae, namely, Scenedesmus sp. LX1 and Chlorella sp. HQ, under different nutrient conditions. Both algal species obtained the highest biomass, lipid content and lipid yield under low-nutrient conditions (mBG11 medium). The biomass, lipid content and lipid yield of Scenedesmus sp. LX1 were 0.42 g·L–1, 22.5% and 93.8 mg·L–1, respectively. These values were relatively higher than those of Chlorella sp. HQ (0.30 g·L–1, 17.1% and 51.3 mg·L–1, respectively). These algae were then cultivated in an SE medium that contained more nutrients; as a result, the biomass and lipid yield of Scenedesmus sp. LX1 reduced more significantly than those of Chlorella sp. HQ. Opposite results were observed in lipid and triacylglycerols (TAGs) contents. The cell sizes of both algal species under low-nutrient conditions were larger than those under high-nutrient conditions. Chlorella sp. HQ cells did not aggregate, but Scenedesmus sp. LX1 cells flocculated easily, particularly under low-nutrient conditions. In summary, low-nutrient conditions favour the growth and lipid production of both algae, but Scenedesmus sp. LX1 outperforms Chlorella sp. HQ.
Only one bifunctional metal-chelator was used to prepare immunogen and coating antigen in all of the previous researches. However, the antibody-specific recognition to the spacer arm of the bifunctional metal-chelator might lower the specificity of heavy metal ions immunoassay. Two different bifunctional metal-chelators were adopted to prepare the immunogen and coating antigen respectively in our study to avoid this problem. The conjugates of keyhole limpet hemocyanin (KLH) and p-SCN-Bz-DTPA-Pb were used as immunogen, whereas the conjugates of bovine serum albumin (BSA) and p-NH2-Bn-DTPA-Pb were used as coating antigen. Polyclonal antibodies specific to DTPA-Pb chelates were obtained from rabbits. Indirect competitive enzyme-linked immunosorbent assay (ELISA) was adopted to detect Pb2+ ion solutions prepared by Pb2+ standard solution and ultrapure water. In the mixing microplate, DTPA and Pb2+ ions formed chelates and combined with specific antibodies. After incubation, the DTPA-Pb and the antibodies complex were added into the wells of the reaction microplate. The reaction microplate was coated by the conjugates of BSA and p-NH2-DTPA-Pb, which competed for the specific antibodies. The result signals presented a good sigmoid curve when the Pb2+ concentration ranges from 0.01 to 100 mg·L−1. The IC50 of the indirect competitive ELISA is 0.23±0.04 mg·L−1 Pb2+ ion. The cross-reaction with Cd2+, Cu2+, Fe2+, Mn2+, Zn2+, and other divalent ions were less than 5%.
Based on biologic and environmental materials collected from coastal areas of Bohai Bay (China) in April, 2008, three biotic indices (AZTI’s Marine Biotic Index (AMBI), Shannon–Wiener Index and W-statistic) were applied together to evaluate the ecological status of the sampling area. The results showed a clear spatial gradient from a worse ecological status in the near-shore areas (especially around Haihe and Jiyun River Estuaries) to a better status in the offshore areas. While all the three indices could assist decision makers in visualizing spatial changes of organic pollutants in Bohai Bay, two indices, i.e., AMBI and Shannon-Wiener index, were effective in distinguishing sites from Haihe River Estuary, Jiyun River Estuary and other area. However, W-statistic can’t tell the differences between estuaries and other area. It would be explained that organic pollutants and/or other environmental stresses in Bohai Bay were not strong enough to reduce the size of macrozoobenthos, which may cause both of the abundance and biomass curves crossed. To our knowledge, this is the first time that several benthic indices were used to assess the benthic ecological status in Bohai Bay, which gave the similar results. Furthermore, there is indication that the ecological status is related to excess input of wastewater along main rivers and outlets. In a word, AMBI, Shannon–Wiener Index and W-statistic could be able to assess the benthic ecological status of Bohai Bay under the organic pollutants pressure.
Energy for water heating accounts for an increasing part in residential energy demand in China. An extensive survey was conducted to analyze the determinants of household energy choices for water heaters among residents in Nanjing, China. Two sets of variables were examined as potential influences: building features and household socio-economic characteristics. Results suggest that building features such as gas availability and building structures, and household characteristics such as household head’s education degree and energy-conserving sense are crucial determinants in choosing natural gas as water heater energy. Installation permission for solar water heater, building stories, and residential location serve as determining factors in choosing solar water heaters. Based on these, barriers and opportunities are discussed for transitions toward cleaner water heating energies, and suggestions are given for local governments to promote cleaner energy replacement in China.
The water supply network (WSN) system is a critical element of civil infrastructure systems. Its complexity of operation and high number of components mean that all parts of the system cannot be simply assessed. Earthquakes are the most serious natural hazard to a WSN, and seismic risk assessment is essential to identify its vulnerability to different stages of damage and ensure the system safety. In this paper, using a WSN located in the airport area of Tianjin in northern China as a case study, a quantitative vulnerability assessment method was used to assess the damage that the water supply pipelines would suffer in an earthquake, and the finite element software ABAQUS and fuzzy mathematic theory were adopted to construct the assessment method. ABAQUS was applied to simulate the seismic damage to pipe segments and components of the WSN. Membership functions based on fuzzy theory were established to calculate the membership of the components in the system. However, to consider the vulnerability of the whole system, fuzzy cluster analysis was used to distinguish the importance of pipe segments and components. Finally, the vulnerability was quantified by these functions. The proposed methodology aims to assess the performance of WSNs based on pipe vulnerabilities that are simulated and calculated by the model and the mathematical method based on data of damage. In this study, a whole seismic vulnerability assessment method for a WSN was built, and these analyses are expected to provide necessary information for a mitigation plan in an earthquake disaster.
Nitrous oxide (N2O) is a greenhouse gas that can be released during biological nitrogen removal from wastewater. N2O emission from a sequencing batch reactor (SBR) for biological nitrogen and phosphorus removal from wastewater was investigated, and the aims were to examine which process, nitrification or denitrification, would contribute more to N2O emission and to study the effects of heterotrophic activities on N2O emission during nitrification. The results showed that N2O emission was mainly attributed to nitrification rather than to denitrification. N2O emission during denitrification mainly occurred with stored organic carbon as the electron donor. During nitrification, N2O emission was increased with increasing initial ammonium or nitrite concentrations. The ratio of N2O emission to the removed ammonium nitrogen (N2O-N/NH4-N) was 2.5% in the SBR system with high heterotrophic activities, while this ratio was in the range from 0.14% to 1.06% in batch nitrification experiments with limited heterotrophic activities.
Renewable algae biomass, Scenedesmus obliquus, was used as substrate for generating electricity in two chamber microbial fuel cells (MFCs). From polarization test, maximum power density with pretreated algal biomass was 102 mW·m-2 (951 mW·m-3) at current generation of 276 mA·m-2. The individual electrode potential as a function of current generation suggested that anodic oxidation process of algae substrate had limitation for high current generation in MFC. Total chemical oxygen demand (TCOD) reduction of 74% was obtained when initial TCOD concentration was 534 mg·L-1 for 150 h of operation. The main organic compounds of algae oriented biomass were lactate and acetate, which were mainly used for electricity generation. Other by-products such as propionate and butyrate were formed at a negligible amount. Electrochemical Impedance Spectroscopy (EIS) analysis pinpointed the charge transfer resistance (112 ?) of anode electrode, and the exchange current density of anode electrode was 1214 nA·cm-2.
The amount of spent rechargeable lithium batteries (RLBs) is growing rapidly owing to wide application of these batteries in portable electronic devices and electric vehicles, which obliges that spent RLBs should be handled properly. Identification of spent RLBs can supply fundamental information for spent RLBs recycling. This study aimed to determine the differences of physical components and chemical compositions among various spent RLBs. All the samplings of RLBs were rigorously dismantled and measured by an inductive coupled plasma atomic emission spectrometer. The results indicate that the average of total weight of the separator, the anode and the cathode accounted for over 60% of all the RLBs. The weight ratio of valuable metals ranged from 26% to 76%, and approximately 20% of total weight was Cu and Al. Moreover, no significant differences were found among different manufacturers, applications, and electrolyte types. And regarding portable electronic devices, there is also no significant difference in the Co-Li concentration ratios in the leaching liquid of RLBs.
Bed expansion serves an important function in the design and operation of an upflow anaerobic reactor. An analysis of the flow pattern of expanded granular sludge bed (EGSB) reactors shows that most EGSB reactors do not behave as expanded bed reactors, as is widely perceived. Rather, these reactors behave as fluidized bed reactors based on the classic chemical reactor theory. In this paper, four bed expansion modes, divided as static bed, expanded bed, suspended bed, and fluidized bed, for bioreactors are proposed. A high-rate anaerobic suspended granular sludge bed (SGSB) reactor was then developed. The SGSB reactor is an upflow anaerobic reactor, and its expansion degree can be easily controlled within a range to maintain the suspended status of the sludge bed by controlling upflow velocity. The results of the full-scale reactor confirmed that the use of SGSB reactors is advantageous. The full-scale SGSB reactor runs stably and achieves high COD removal efficiency (about 90%) at high loading rates (average 40 kg-COD·m-3·d-1, maximum to 52 kg-COD·m-3·d-1) based on the SGSB theory, and its expansion degree is between 22% and 37%.