Advanced Materials Research Vol. 777

Abstract: Based on the material of EPDM, we develop specialized rubber material for low-temperature multi-effect distillation (LT-MED) conditions. For heat transfer tube and tube sheet connected to the rubber (herein referred as EPDM rubber material) ring are used in the LT-MED desalination equipment, we make regular aging and multivariate synergistic aging test on EPDM. According to the experimental results, we develop an evaluation method applicable to usage of sealing rubber material under LT-MED conditions, and rubber material properties are measured by the changes of mechanical indicators. Finally, we also tested the sealing performance of the sealing rings. The results show that EPDM rubber material can tolerate the LT-MED conditions with the ring boost rate of 0.038kPa/h when the rates of change in Shoer hardness range from-5% to 10%, the rates of change in tensile strength within-20%, the rates of change in elongation at break range from-30% to 10%.

Abstract: Silicone rubber have been aged in air while under 25% compression at temperature up to 250°C. These studies examined the compression set of silicone rubber at accelerated (elevated) temperatures and were then used to make predictions about compression set at room temperature. The data obtained could be amenable to timetemperature superposition and Arrhenius treatment. The results suggest the presence of two degradation processes with activation energies of 71.6 kJ mol^-1 (for temperatures above 165 °C) and 26.08 kJ mol^-1 (for temperatures below 165 °C). Based on the extrapolation of the non-Arrhenius behavior, it was estimated that significant compression set loss would occur after around 67 years at 25 °C.

Abstract: nanohydroxyapatite (nanoHA) powders were prepared by liquid phase precipitation method, using diammonium hydrogen phosphate and calcium nitrate tetrahydrate as raw materials. It was studied that the prepared nanoHA powders not sintered and sintered at 800°C to adsorption of Cu²⁺ and Pb²⁺ in aqueous solutions, respectively. The structure and size of nanoHA powders was investigated by X-ray diffraction (XRD) and the concentrations of Cu²⁺and Pb²⁺ in aqueous solutions were tested by inductively coupled plasma emission spectrometer. The results revealed that the nanoHA powders have obvious absorption function for Cu²⁺ and Pb²⁺ in aqueous solutions. In addition, the absorption ratio was affected by the size of nanoHA.

Abstract: Dried sludge could be used for brick production by firing with shale or clay, which would reduce clay resource exploitation and realize sludge resource utilization. Physical and mechanics parameters of fired shale-sludge brick and clay-sludge brick are tested to examine technical feasibility, and heavy metal leaching concentrations are tested to examine brick safety. The results show that after municipal sludge in Changsha Wastewater Treatment Plant is dried with water content no more than 30%, it can be used for shale-sludge brick and clay-sludge brick firing and qualified produces can be produced. Compressive strength of brick is 10-20 MPa, there is no scum and lime crack on brick body. Under high firing temperature, heavy metal in sludge can be solidified, and leaching concentrations can meet the requirements. By doing so, calorific power of sludge can be utilized and energy saving can be realized.

Abstract: This task studies the impacts and mechanisms of intermittent aeration and movement degree of membrane on the permeate flux in a submerged membrane system. The contents includes: Analysis of the effects of intermittent aeration on the membrane performance, modelling the experimental results and find out the mechanisms; Analysis of the effects of different movement degree of membrane on the permeate flux during the intermittent aeration process, modelling the experimental results and find out the mechanisms; Determination of the optimum membrane running conditions, including the most effective intensity of gas sparging, the most effective intermittent aeration cycle time and the most effective movement degree of membrane, etc. It shows that intermittent aerations between backwashing processes can significantly improve the membrane performance; the change of the movement degree (L/H),which means the ratio of the effective length and the effective vertical height) of membrane can affect the influences of intermittent aeration on the membrane performance significantly; the most effective intensity of gas sparging is 1.5L/h; the most effective intermittent aeration cycle time is 30min; the most effective movement degree of membrane is 1.07.The result of the research is good for the selection of operation condition and determination of running parameters of ultrafiltration membrane water supply process.

Abstract: In this subject, a new spatial structure of the membrane contactor is explored and designed from analysis of mass transfer process, resistance theory and flow type. Under laboratory conditions, the experiment uses several methods including fluid mechanics, mass transfer process and the analysis of the fluid flow to achieve CO₂ absorption function with the new hollow fiber membrane contactor. This new design of device is tested in conditions of two absorption liquids: MEA, DEA; three absorption concentrations: 6L/h, 8L/h, 10L/h; liquid velocity: 1mol/L, 0.5mol/L and air speed: 1L/min, 0.5L/min, to absorb CO₂ from the gas mixture to make sure that if it has good properties. Through these experiments, we could see that the new hollow fiber membrane contactor has an increase in absorption efficiency by 10% on average.

Abstract: Desorption experiments of coconut shell activated carbon (CSAC) saturated with Pb²⁺ had been conducted in presence of dual-frequency and single-frequency (30 kHz,500 kHz,1200 kHz) ultrasound. The desorption efficiency was better at dual-frequency ultrasound than at single-frequency ultrasound. The best of desorption efficiency of Pb²⁺ was 65.5% at 500×500 kHz. The desorption efficiency of Pb²⁺ increased by increasing temperature, but when the temperature was more than 50°C, the desorption efficiency decreased initially. The stability of CSAC was not affected with cavitation effect produced by ultrasound of frequency of 500×500 kHz. The carbon loss was less. The rate of loss was only 0.6%. In conclusion, ultrasound was used as alternative method to regenerate activated carbon adsorbing with heavy metal ion.

Abstract: Expanded graphite is a new porous carbon-based adsorption material with well-developed pore structure and large adsorption capacity for nonpolar molecules pollutants. In this paper, research of the expanded graphite as novel functional carbon material in the fields of environmental remediation of oil pollution and wastewater treatment are reviewed. Based on this, the problems that exist in the current research on expanded graphite in treatment of environmental pollution are analyzed, and the main development trend of research on expanded graphite in the field of water environmental protection is put forward.

Abstract: In this study, TiO₂ nanoparticles composites were prepared by the micro emulsion method, above of all samples were characterized by FT-IR, XRD. Photo activities of Fe-TiO₂, TiO₂ were evaluated by degradation of oil-bearing wastewater. The results show that the photo activity of Fe-TiO₂ was more than that of TiO₂; the best presence of iron ion dopants in TiO₂ was 0.04%. Used stearic acids as the surface modification agent, Fe-TiO₂ were modified by situ surface modification. The results showed that the optimum conditions of stearic acid-Fe - TiO₂ :Temperature (20°C), the modified time (45 min), the ratio modifier dosage tomagnetitemass (4%). Then we did the initial exploration of Fe-TiO₂ Powder that was modified by stearic acid.