Advanced Materials Research Vols. 518-523

Abstract: A series of crosslinked cationic starches with different degree of substitution(DS) are used to adsorb Acid Orange 7. Some factors, such as pH, adsorption time, adsorption temperature, initial concentration of dye, dose of cationic starch and DS of cationic group are investigated. The results show that the adsorption quickly establish equilibrium within 15 min. The adsorption capacity of the dye increases with the increasing of DS of the crosslinked cationic starches.The initial pH of 2-10 is reasonable. The adsorption of the dye on the crosslinked cationic starch is well described with the pseudo-second-order model and the Langmuir isotherm.

Abstract: Degradation of aqueous 3, 4-dichloroaniline (3, 4-DCA) by wire-cylinder dielectric barrier discharge reactor was carried out in the present paper. Generation of reactive species was analyzed, changes of aqueous ozone concentration and solution pH values were examined; meanwhile, the effect of input power and initial pH value on the degradation efficiency of 3, 4-DCA were investigated. The results showed that the degradation efficiency of 3, 4-DCA increased with increasing input power when the input power was increased from 70 W to 90 W, while it decreased with increasing input power when the input power was increased from 90 W to 110 W; and the same changing trend was observed in the change of aqueous ozone concentration. At alkaline conditions and acidic conditions, 3, 4-DCA degradation rate was significantly higher than that of neutrality conditions. In addition, there was a remarkable decline of the solution pH values during 3, 4-DCA degradation.

Abstract: Sewage sludge (SS) contains deleterious constituents that strongly inhibited seed germination. Pretreatment methods of composting, leaching and carbonizing were thus evaluated to alleviate the phytotoxicity. All the pretreatments improved germination rate, root length and germination index of radish seeds. The best performances were presented by composting pretreatment and the pretreatment of carbonizing plus leaching. Composting greatly alleviated phytotoxicity of SS and improved seed germination, however, it also showed stunted root length and germination index compared with the soil control. The adverse effects of composted SS on seed germination were completely eliminated by leaching, while carbonizing had little effect on reversing the stunt. These results indicated that the most effective pretreatment method to alleviate phytotoxicity of SS were composting plus leaching.

Abstract: Nitrobenzene is an important contaminant existed in water and wastewater widely. Because of its toxicity to organisms, it is hardly biodegradable. A new structural Fe(II): Ferrous Hydroxy Complex (FHC) was prepared with ferrous sulfate to investigate the reduction of nitrobenzene by structural ferrous iron. This study focused on the effects of inorganic anions on the reactivity of FHC towards nitrobenzene. It was found that soluble Fe(II) could hardly reduce any nitrobenzene within 2h while FHC could reduce nitrobenzene to aniline rapidly within 0.5h. Various anions such as CO32-, PO43-, SiO32-, S2- might have significant impact on the reactivity of structural Fe(II) in nitrobenzene reduction. These anions would slow down the rate of the reaction. Among these anions, SiO32- and PO43- had a greater effect on the reduction of nitrobenzene than CO32- and S2-. Structural ferrous iron (SFI) was prepared by two ways: (i) Aqueous Fe2+ was directly added to wastewater, then adjusted the pH value of water to 8-9; (ii) FHC prepared in advance was added to wastewater, SFI(II). Results indicated that the effect of anions on reactivity of SFI(I) was greater than that of SFI(II). When the initial concentration of nitrobenzene was 60mg/L and ferrous iron dosage was 240mg/L, NO3- with the concentration of 4mM had little effect on the reduction of nitrobenzene by both forms of Fe(II); NO2- had greater effect on reactivity of SFI(I) than that of SFI(II).

Abstract: Effect of water-retaining agent on growth and development of three local legumes were studied, in order to provide science basis for revegetation of lead-zinc tailings in Lanping. Testing survival numbers and moisture and proline content in plants, aim at revealing effect of water-retaining agent on plants under drought stress. The results show that water-retaining agent can prolong survival time of plants and keep stability of moisture and proline content in plants under drought stress. Survival numbers and moisture content of plants leafs decrease with prolonging drought stress time, and proline content of plants leafs increase with prolonging drought stress time. There was no significant difference of survival numbers and moisture and proline content in plants on tailings soil with 0.3% and 0.4% water-retaining agent, so 0.3% water-retaining agent was best dosage in tailings soil for revegetation of lead-zinc tailings in Lanping.

Abstract: The basic mechanical problem facing of environmental geotechnical engineering in cold regions is the physical and mechanical properties of rocks under freeze-thaw conditions. The freeze-thaw cycling experiment was conducted first for two types of rock which are red sandstone and shale, then the splitting tensile experiment on different freeze-thaw cycles. The damage deterioration and breaking behavior under freeze-thaw conditions was investigated, and the influence of lithology and freeze-thaw cycle on anti-tensile characteristics of rock was studied. It is shown that three freeze-thaw damage deterioration modes of two kinds of rock are spalling mode, fracture mode and crack mode. The freeze-thaw cycle leads to irreversible deterioration on physical and mechanical properties for rock, but the damage of red sandstone is more serious than that of shale by the number of freeze-thaw cycles. The regularity of freeze-thaw effects of compression and tensile characteristics for two rocks are identical, but the tensile characteristic is more sensitive to freeze-thaw cycle.

Abstract: We have succeeded in preparing micro/nanostructured α-Fe2O3 spheres (MNFSs). The resulted MNFSs have an average diameter of about 5 µm, and are constructed by subunits of interlinked and elongated particles with a diameter of 20~60 nm. MNFSs show an obviously structural enhanced Cr(VI) removal capacity (5.88 mg/g) compared with nanoscaled (0.81 mg/g) and microscaled α-Fe2O3 (0.1 mg/g) due to its high specific surface area together with the special porous structure. Moreover, MNFSs show good availability of reusing to remove Cr(VI) ions.

Abstract: Polycyclic aromatic hydrocarbons are the component of the exhaust gases, from which some are characterized by carcinogenic and mutagenic properties. The most considerable sources of polycyclic aromatic hydrocarbons are combustion engines, thermal plants, production and distribution of products as pesticides, detergents, conservation matters, refuse inciferating plants, pyrolysis processes, coke production, cigarette gas, coal gasification. In consequence those matters from the atmosphere are accordied to earth, where they are cumulated, thereat bold increasing of aromatic hydrocarbons concentration is chronicled. The most dangerous from them is benzo(a)phyrene. If the polycyclic aromatic hydrocarbons are get into live organisms, reagents with their structure at formation epoxides and thiolepoxides. These matters liaise to DNA, corrupted their structure and this fact induces cancer formation. The sorption possibility of natural zeolite – clinoptilolite, also its modified forms was observed in regard to some species of polycyclic aromatic hydrocarbons.

Abstract: The drying of sludge can reduce its mass and the volume and consequently the cost of storage, handling and transport. In this paper, a one-dimensional model is established for the sludge drying process and hot water from the solar energy is applied as a discontinuous heat source (periodic heating). Based on the simplified physical model, the thermal behavior of the sludge drying process is investigated by numerical method. The effects of the sludge depth, mixing time and heat transfer coefficient are analyzed. The simulation results show that the most important effecting factor is the mixing time. One hour mixing cycle can increase heat transfer rate to 430%, 130% than that of without mixing and two hours mixing cycle, respectively. On the other side, both the sludge thickness and the heat transfer coefficient have some effects. For the cases studied the 40cm thick sludge with 1 hour mixing time is an optimal option.

Abstract: The grid “freezing” method in computational fluid dynamics (CFD) was used to deal with the moving boundary in this study, which can make the dynamic boundary into the fixed boundary and qualitatively describe the particle deposition morphology on the surface of the fibrous media. Meanwhile, the filtration efficiencies of the fibrous media with different deposition particle numbers and particle deposition morphologies were calculated using numerical simulation method. The results show that particle deposition on the surface of the fibrous media can help to improve the filtration performance, and in the steady-state, the effect is not obvious, but in the unsteady-stage, the particle deposition can improve the filtration efficiency greatly. In addition, the disposition morphology that has greater contact area with the oncoming particles is conductive to fibrous media capturing particles.