科研成果

Municipal sewage sludge is abundant and rich in phosphorus, making it a promising alternative phosphorus reserve. A good knowledge of the phosphorus transformation during pyrolysis will underlie the industrial phosphorus recycling and reclamation of sewage sludge. This work first advanced a novel calcium oxide (CaO)-enhancement phosphorus-recycling technique based on pyrolysis of sewage sludge, by regulating the transformation of phosphorus in sewage sludge during pyrolysis through the CaO addition. The obtained results indicated that CaO addition promoted the formation of hydroxylapatite, which is a desirable phosphorus species for plant growth. The factors of pyrolysis temperature and inherent composition of sewage sludge both influenced the fraction of hydroxylapatite during pyrolysis. An increase in pyrolysis temperature and a sludge with a high content of ash and a low content of volatile matters potentially promoted the transformation of P from organic phosphorus to the inorganic species during pyrolysis with the addition of CaO, particularly for the formation of hydroxylapatite. Increasing CaO addition significantly increased the fraction of hydroxylapatite in the obtained char, and the maximum content of 25 wt % hydroxylapatite over total phosphorus was attained. This enhanced transformation of hydroxylapatite may be potentially attributed to the interaction between CaO and the polyphosphate with the aid of the inherent minerals that appeared to benefit the immobilization of phosphorus during sludge pyrolysis. As the formation of hydroxylapatite was enhanced, this facile technology of CaO-enhancement sewage sludge pyrolysis could be used for the direct recycling of P as well as the disposal of sewage sludge. © Copyright 2018 American Chemical Society.

Capacitive deionization (CDI) can remove ionic contaminants from water. However, concentrations of background ions in water are usually much higher than target contaminants, and existing CDI electrodes have no designed selectivity toward specific contaminants. In this study, we demonstrate a selective CDI process tailored for removal of SO42- using activated carbon electrodes modified with a thin, quaternary amine functionalized poly(vinyl alcohol) (QPVA) coating containing submicron sized sulfate selective ion exchange resin particles. The resin/QPVA coating exhibited strong selectivity for SO42- at Cl- : SO42- concentration ratios up to 20:1 by enabling preferential transport of SO42- through the coating, but had no negative impact on the electrosorption kinetics when the coating thickness was small. The cationic nature of the coating also significantly improved the charge efficiency and consequently the total salt adsorption capacity of the electrode by 42%. The resin/QPVA coated CDI system was stable, showing highly reproducible performance in more than 50 adsorption and desorption cycles. This work suggests that addition of selective ion exchange resins on the surface of a carbon electrode could be a generally applicable approach to achieve selective removal of target ions in a CDI process.

This paper proposes a new constitutive model for geotechnical materials that consists two basic constitutive functions, the free energy function and the dissipation rate function, within the framework of hyperplastic theory. This free energy function is capable of describing the pressure-dependent elastic behavior of soils. The new constructed dissipation rate function accounts for the frictional mechanism of energy dissipation. Based on this dissipation rate function, the non-associated flow rule can be obtained. Furthermore, the convexity of the yield surface that is derived from the dissipation rate function is proved. Predictions of the behavior of a soil sample using this new constitutive model agree well with triaxial test data under drained and undrained conditions.

This paper proposes a new constitutive model for geotechnical materials that consists two basic constitutive functions, the free energy function and the dissipation rate function, within the framework of hyperplastic theory. This free energy function is capable of describing the pressure-dependent elastic behavior of soils. The new constructed dissipation rate function accounts for the frictional mechanism of energy dissipation. Based on this dissipation rate function, the non-associated flow rule can be obtained. Furthermore, the convexity of the yield surface that is derived from the dissipation rate function is proved. Predictions of the behavior of a soil sample using this new constitutive model agree well with triaxial test data under drained and undrained conditions.

This paper proposes a new constitutive model for geotechnical materials that consists two basic constitutive functions, the free energy function and the dissipation rate function, within the framework of hyperplastic theory. This free energy function is capable of describing the pressure-dependent elastic behavior of soils. The new constructed dissipation rate function accounts for the frictional mechanism of energy dissipation. Based on this dissipation rate function, the non-associated flow rule can be obtained. Furthermore, the convexity of the yield surface that is derived from the dissipation rate function is proved. Predictions of the behavior of a soil sample using this new constitutive model agree well with triaxial test data under drained and undrained conditions.

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous air pollutants associated with negative impacts on growth, development and behavior in children. Source-specific biological markers of PAH exposure are needed for targeting interventions to protect children. Nitro-derivatives of PAH can act as markers of exposure to diesel exhaust, gasoline exhaust, or general combustion sources. Using a novel HPLC-APCI-MS/MS detection method, we examined four hemoglobin (Hb) adducts of nitro-PAH metabolites and the Hb adduct of a benzo[a]pyrene (BaP) metabolite in 22 umbilical cord blood samples. The samples were collected from a birth cohort with comprehensive data on prenatal PAH exposure, including prenatal personal air monitoring and DNA adducts in maternal and umbilical cord blood. Using non-parametric analyses, heat maps, and principal component analysis (PCA), we analyzed the relationship between the five Hb adducts and previous PAH measurements, with each measurement representing a different duration of exposure. We found that Hb adducts derived from several diesel-related nitro-PAHs (2-nitrofluorene and 1-nitropyrene) were significantly correlated (r = 0.77, p

To satisfy the increasingly high demands in many applications of microfluidics, the size of the droplet needs accurate control. In this paper, a level-set method provides a useful method for studying the physical mechanism and potential mechanism of two-phase flow. A detailed three-dimensional numerical simulation of microfluidics was carried out to systematically study the generation of micro-droplets and the effective diameter of droplets with different control parameters such as the flow rate ratio, the continuous phase viscosity, the interfacial tension, and the contact angle. The effect of altering the pressure at the x coordinate of the main channel during the droplet formation was analysed. As the simulation results show, the above control parameters have a great influence on the formation of droplets and the size of the droplet. The effective droplet diameter increases when the flow rate ratio and the interfacial tension increase. It decreases when the continuous phase viscosity and the contact angle increase.

Antibiotic resistance genes (ARGs) are regarded as emerging contaminants related with human activities. Aquatic environments of an urban city are apt for the persistence and prevalence of ARGs. In this study, we investigated the occurrence and distribution of ARGs and integrase genes in the sediment samples collected from drinking water sources, urban rivers, and coastal areas of Zhuhai, China, in the dry and wet seasons of 2016. The results show that sulfonamide resistance gene of sulII was present at the highest detection frequency (85.71%); and its average concentrations were also the highest in both dry and wet seasons (3.78×107 and 9.04×107 copies/g sediment, respectively), followed by tetC, tetO, tetA, ermB, dfrA1, and blaPSE-1. Temporally, the concentrations of total ARGs in the wet season were likely higher than those in the dry season; and spatially, the concentrations of total ARGs in the drinking water sources were substantially lower than those in the urban rivers and nearby coastal areas, indicating the different degrees of anthropogenic impact and consequent health risks. Positive correlations were found between intI1 and each quantitative ARG in all wet season samples rather than dry season samples, which suggested higher temperature and more rain in summer might have positive influences on ARG dissemination, especially that mediated by intI1 gene and class I integrons.

This paper presents two scalable resonator-based transducers (RBTs) at terahertz (THz) frequency range to realise THz spectroscopy for dielectric sensing. First, the design of 0.24 THz RBT is described by scaled a 0.12 THz sensing structures which utilises a wavelength-long closed-ring resonator to place inside of the Coplanar stripline (CPS) to make a high-selective bandpass response and combines with short-ended strips to create the bandstop behavior. Its scattering parameter can have a very large magnitude change and resonance frequency shift for the loaded samples. Next, a ring structure is also presented to implement 0.48 THz sensing by scaled a low frequency RBT, which employs ring resonator with an asymmetrically loaded stubs to perform a high analytic sensitivity and selectivity for loaded samples. Both presented scalable transducers, possessing the high integration capability of silicon circuits, are proved to be the promising employments in THz spectroscopy.