Polydimethylsiloxane/Nanodiamond Composite Sponge for Enhanced Mechanical or Wettability Performance.

Polydimethylsiloxane (PDMS) is widely utilized in material science, chemical engineering, and environmental science due to its excellent properties. By utilizing fillers, so-called composite materials can be obtained with enhanced mechanical, wettability, or thermal conductivity performance. Here, we present a simple, cost-effective approach to vary either the mechanical properties (Young's modulus) or surface wettability of bulk PDMS and PDMS sponges simply by adding nanodiamond filler with different surface terminations, either oxidized (oND) or hydrogenated (reduced, rND) nanodiamond. Minuscule amounts of oxidized nanodiamond particles as filler showed to benefit the compressive Young's modulus of composite sponges with up to a 52% increase in its value, while the wettability of composite sponges was unaffected. In contrast, adding reduced nanodiamond particles to PDMS yielded inclined water contact angles on the PDMS/nanodiamond composite sponges. Finally, we show that the PDMS/rND composites are readily utilized as an absorbent for oil/water separation problems. This signifies that the surface termination of the ND particle has a crucial effect on the performance of the composite.

Formulation of sludge incineration residue based geopolymer and stabilization performance on potential toxic elements.

Using sludge incineration residue (SIR) to prepare SIR-based geopolymer can realize the minimization and reclamation of urban sludge as well as the stabilization of potential toxic elements. This work has researched the critical factors that influence the formulation of SIR-based geopolymer and the stabilization performance on potential toxic elements. Results showed that the addition amount of SIR had significant influence on the compressive strength of geopolymer, while the modules of sodium silicate and the sodium silicate/metakaolin ratio had little influence thereon. When the addition amount of SIR was 10%, the modules of sodium silicate was 1.3 and the sodium silicate/metakaolin ratio was 0.86, the compressive strength of geopolymer reached the maximum of 95.6 MPa. When the temperature increased from 25 °C to 800 °C, the compressive strength showed a tendency of increasing first and then decreasing. SIR-based geopolymer could significantly reduce the leaching of Zn and Cu from 1264.8 mg/kg and 856.3 mg/kg to 50.8 mg/kg and 30.7 mg/kg respectively, leading to a stabilizing efficiency more than 96%. pH influenced the stabilization of geopolymer on the potential toxic elements, the effective diffusion coefficients De of Zn, Cu, Ni, Pb and Cr at pH = 4 were higher than those at the pH of 7, which were probably due to the physic-chemical characteristics and the corresponding changes in the leaching and species distribution of the potential toxic elements.

Reduction and prediction of N2O emission from an Anoxic/Oxic wastewater treatment plant upon DO control and model simulation.

In order to make a better understanding of the characteristics of N2O emission in A/O wastewater treatment plant, full-scale and pilot-scale experiments were carried out and a back propagation artificial neural network model based on the experimental data was constructed to make a precise prediction of N2O emission. Results showed that, N2O flux from different units followed a descending order: aerated grit tank>oxic zone≫anoxic zone>final clarifier>primary clarifier, but 99.4% of the total emission of N2O (1.60% of N-load) was monitored from the oxic zone due to its big surface area. A proper DO control could reduce N2O emission down to 0.21% of N-load in A/O process, and a two-hidden-layers back propagation model with an optimized structure of 4:3:9:1 could achieve a good simulation of N2O emission, which provided a new method for the prediction of N2O emission during wastewater treatment.

The effects of catalysts on the conversion of organic matter and bio-fuel production in the microwave pyrolysis of sludge at different temperatures.

Adding catalyst could improve the yields and qualities of bio-gas and bio-oil, and realize the oriented production. Results showed that the catalytic gas-production capacities of CaO were higher than those of Fe2O3, and the bio-gas yield at 800°C reached a maximum of 35.1%. Because the polar cracking active sites of CaO reduced the activation energy of the pyrolysis reaction and resulted in high catalytic cracking efficiencies. In addition, the quality of bio-oil produced by CaO was superior to that by Fe2O3, although the bio-oil yield of CaO was relatively weak. The light bio-fuel oriented catalytic pyrolysis could be realized when adding different catalysts. At 800°C, CaO was 45% higher than Fe2O3 in aspect of H2 production while Fe2O3 was 103% higher than CaO in aspect of CH4 production. Therefore, CaO was more suitable for H2 production and Fe2O3 was more suitable for CH4 production.

Preliminary investigation of the microwave pyrolysis mechanism of sludge based on high frequency structure simulator simulation of the electromagnetic field distribution.

Under microwave irradiation, raw sludge was pyrolyzed mainly by evaporation of water, with a weight loss ratio of 84.8% and a maximum temperature not exceeding 200°C. High-temperature pyrolysis of SiC sludge could be realized, with a weight loss ratio of 93.4% and a final pyrolysis temperature of 1131.7°C. Variations between the electric field intensity distribution are the main reason for the differences of pyrolysis efficiencies. HFSS simulation showed that the electric field intensity of the raw sludge gradually decreased from 2.94×104V/m to 0.88×104V/m when pyrolysis ends, while that of SiC sludge decreased from 3.73×104V/m at the beginning to 1.28×104V/m, then increased to 4.03×104V/m. The electromagnetic effect is the main factor (r≥0.91) influencing the temperature increase and weight loss of raw sludge. Both the electromagnetic effect and heat conduction effect influenced temperature rise and weight loss of SiC sludge, but the former's influence was comparatively larger.

A comparative study on the uptake of polycyclic aromatic hydrocarbons by Anodonta californiensis.

Uptake of polycyclic aromatic hydrocarbons (PAHs) by the freshwater bivalve mollusc Anodonta californiensis was examined in the presence and absence of surfactant in order to gain further insight into mixture toxicity and to predict whether certain mixtures have negative and/or positive effects on aquatic organisms. In the presence of surfactant, the uptake of anthracene or chrysene was higher than that of naphthalene, given the same concentration in the solution. In the absence of surfactant, the trend was similar, but the uptakes were increased by approximately 100% compared to those in the presence of surfactant. On the uptake of naphthalene, the presence of anthracene showed only minor influence. The uptake of anthracene was affected by both naphthalene and chrysene. The uptake of chrysene was influenced by neither naphthalene nor anthracene. There was no observable displacement of divalent cations from the surface of the gill membrane by any of the PAHs studied.

Electrophoretic motion of a spherical particle with a symmetric nonuniform surface charge distribution in a nanotube.

The electrophoretic motion of a spherical nanoparticle, subject to an axial electric field in a nanotube filled with an electrolyte solution, has been investigated using a continuum theory, which consists of the Nernst-Planck equations for the ionic concentrations, the Poisson equation for the electric potential in the solution, and the Stokes equation for the hydrodynamic field. In particular, the effects of nonuniform surface charge distributions around the nanoparticle on its axial electrophoretic motion are examined with changes in the bulk electrolyte concentration and the surface charge of the tube's wall. A particle with a nonuniform charge distribution is shown to induce a corresponding complex ionic concentration field, which in turn influences the electric field and the fluid motion surrounding the particle and thus its electrophoretic velocity. As a result, contrary to the relatively simple dynamics of a particle with a uniform surface charge, dominated by the irradiating electrostatic force, that with a nonuniform surface charge distribution shows various intriguing behaviors due to the additional interplay of the nonuniform electro-osmotic effects.