Materials Science Forum Vols. 743-744

Abstract: nanosize hydroxyapatite/polyacrylonitrile composite bead was prepared via in-situ synthesis method. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), particle size measurement and X-ray diffraction (XRD) were used to characterize the HAp/PAN composite bead. XRD curve indicates low crystallinity of HAp. Particle size and SEM analysis demonstrates that decreased partical size of synthesized HAp as well as good distribution with the addition of PAN is found. The HAp is well-distributed and the combination between HAp and PAN is well. FTIR showed that there was no shift of characteristic peaks of synthesized HAp in PAN, which proves the physical interaction between PAN and HAp. The approximate HAp content of 28.6% calculated from thermal analysis curves means high conversion ratio of HAp. The adsorption amount of cadmium ions onto composite beads is lower than HAp particles.

Abstract: In order to master the rule of heavy metals migration on the interface of tailings-plants and how matrix physicochemical characteristics change, pot experiment was conducted with/without soil, choosing PAM and EDTA as tailings modifiers, with/ without organic matter. The results showed that: the existence of soil inhibited the absorption of heavy metals, especially for Cu, to which significant inhibition effect has been achieved,join of EDTA and PAM could further restrained the leafy plants to absorb heavy metals. The experimental results also indicated that PAM had a significantly adhesive effect on soil particles than EDTA,improved the soil structure to a certain role,each matrix pH value varies between 7-8, and there are no significant difference between PAM and EDTA processing matrix.

Abstract: A continuous dynamic adsorption in a fixed-bed column was studied by canna edulis ker residue (CEKR) as an adsorbent for the removal of Cr (VI) ions from aqueous solution. The dynamic adsorption process was simulated by some mathematic models, to determine the characteristic parameters of the column. The results indicated that CEKR could effectively absorb Cr (VI) ions from aqueous solution. Breakthrough time reaching saturation increased significantly with the increase of the temperature, while the bed depth increased and the pH value decreased. In comparison, the initial metal concentration is able to slightly affect the adsorption. Some mathematical models could calculate the rate constants, correlation coefficients, the equilibrium adsorption and kinetic parameters, however, they were not suitable for the description the dynamic adsorption of Cr (VI) ions in the fixed-bed column.

Abstract: Fly ash, as a raw materials,is used to prepare micro-nanostructural beads with the surface modified by using silane coupling agent. The coating of micro-nanostructural surface was prepared by using the modified micro-nanostructural beads and silicone rubber adhesive. Then the coating surface was dipped in liquid teflon (PTFE) for hydrophobic modification. Scanning Electronic Microscope (SEM) and JC2000C contact angle tester were used to character the coating surface performance. The results show that the average contact angle and rolling angle of the coating surface are measured as 152.9° and 3.4° respectively which means the prepared coating being of super-hydrophobicity.

Abstract: Aerated concrete is a new type of wall material with beneficial features like light weight, heat insulation, fire prevention and low energy consumption. As a key milestone in wall materials innovation and energy-saving of building system, it has been proven to be an ideal wall material which can replace traditional clay brick through years of application and practice. This study calculated the CO₂ emissions in all the stages of life cycle of aerated concrete production. Compared with clay brick, the life cycle CO₂ intensity of aerated concrete block will be decreased by 67.4% with the same insulation effect. Study on the environmental loads of aerated concrete industry will provide theoretical base for the carry out of energy-saving and emission reduction, the formulation of clean production and the development of recycling economy.

Abstract: With the development of economy, China has become one of the largest cement producers in the world. However, cement industry is a main contributor of global carbon emissions. Substituting calcium carbide sludge for limestone is an effective method for CO₂ emission reduction in cement industry and has developed rapidly in recent years in China. The purpose of this study is to determine the life cycle CO₂ emission of cement clinker produced with calcium carbide sludge as secondary raw material. The results show that compared with general cement clinker, the life cycle CO₂ emission intensity of cement clinker produced with calcium carbide sludge will be decreased by 39.1% when substitution rate is 80%. And the CO₂ emission results from the procedure of cement clinker production accounts for 85.7% of the total emission, in this stage, the CO₂ emission declined by 42.2%.

Abstract: Persimmon tannins (PT) were immobilized on a matrix of collagen fiber by cross-linking of glutaraldehyde. The adsorption behaviours to Cr (VI) on PT were investigated including the effects of initial pH, initial concentration of Cr (VI), temperature, adsorbent dosage, adsorption kinetics and the recycling performance of PT adsorbents. The results showed that pH value had a major influence in adsorption. PT showed a strong adsorbability to Cr (VI) in the pH range of 1.0 to 3.0, whereas the effect of temperature on the adsorption was comparatively weaker. The adsorption equilibrium could be well described by Freundlich equation. PT adsorption efficiency of Cr (VI) reached 98.04% and the maximum equilibrium adsorption capacity of Cr (VI) was up to 49.01 mg/g at 303 K with a pH value of 2.0, 100 mg/L of initial concentration of Cr (VI) and 0.1g of adsorbent dosage. The adsorption data could be well fitted by pseudo-second-order rate model. PT adsorbents were characterized by FTIR and EDS. The analysis indicated that the adsorption mechanism was mainly contributed by redox adsorption.

Abstract: Pollutions of livestock and poultry breeding to the environment have evolved into a serious social problem, while phosphorus is a non-renewable resource. This study aims to not only remove the phosphorus in bovine urine wastewater effectively, but also make it recyclable and reduce the load of the follow-up sewage disposal. Choosing the diatomite as the adsorption material, its adsorption effects and the influence factors of diatomite were investigated by static adsorption method, and the adsorption isothermal curves studied. The results showed that the best adsorption condition was as follows, i.e.,taking 50mL bovine urine wastewater with TP 45.67mg/L, when the diatomite dosage was 3.0g, the pH was 7.0, the adsorption time was at 6.0h with the temperature of 30, TP concentrations could be reduced to 9.86mg/L and total phosphorus removal rate reached at 78.41%. Freundlich equation was better than Langmuir equation in describing the behaviour of adsorption phosphorus on diatomite. It is believed that diatomite is feasible to be used as adsorption agent for phosphorus removal from bovine urine wastewater and this promotes the potential of diatomite being used as sewage treatment materials.

Abstract: In the study, two kinds of hypercrosslinked polymers were prepared by polymerization of dichloromethyl aryl monomer with benzene or itself. The chemical and pore structure of above polymers were characterized by FT-IR and BET. The results showed that these polymers possessed high BET specific surface area (up to 1000 m²/g) and large pore volumes (up to 1.2cm³/g). Two commercial polymer adsorbent (XAD-4, H103) and two new synthesized polymeric adsorbents (BE-XDC, CMB-CMB) have been used for the adsorption of reactive dye methylene blue (MB) from aqueous solution, and the static capacity followed an order as: CMB-CMB(142.77mg/g) > BE-XDC(104.61mg/g) > H103(71.01mg/g) > XAD-4(53.85mg/g). The Equilibrium adsorption data of the four polymeric adsorptions were obtained and fitted very well to Freundlich model. The adsorption equilibrium time of CMB-CMB, BE-XDC resin were less than 200min, which were faster than that of XAD-4, H103. The free energy changes, ΔG for adsorption of MB on the four polymeric adsorbents in the aqueous solution was evaluated. The negative values of ΔG indicated that the overall adsorption processes were spontaneous and thermodynamically favorable.

Abstract: Four kinds of commercial activated carbons were soaked in sodium hydroxide after modification with 10% nitric acid. Nickel adsorption isotherms for modified activated carbons before and after sodium hydroxide treatment were tested. The surface groups were characterized by the Fourier transform infrared spectroscopy and Boehm titration, the adsorption properties were determined by the iodine number and methylene blue number, the pH_IEP were deduced by the Zeta potential analyzer. The results showed that nitric acid blocks the pore, while enhances the content of acid groups, especially carboxyl resulting in the decrease of nickel adsorption capacity. After sodium hydroxide treatment, the nickel capacity of activated carbon from anthracite, long flame coal, lignite and coconut increased by 21.5%, 116%, 78.9%, 89.1% comparing with the virgin activated carbon, respectively. The overall research indicated that nickel ion adsorption capacity of activated carbon can be improved only when the acid groups are transferred into anion, and the modification is more effective on the activated carbon prepared by low metamorphic grade coal.