Effect of water soluble PVA on the microstructure characteristics of C-S-H formed in Na<Subscript>2</Subscript>SiO<Subscript>3</Subscript>-Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> solution system

The structure characteristics of hydrated calcium silicate synthesized by solution reaction method with the existing of water soluble polymer polyvinyl alcohol(PVA)are investigated.Using Na 2 SO 3 and Ca(NO 3 ) 2 as the main raw materials,in the condition of 2%(in weight)addition of PVA and the water to solid ratio of 20,hydrated calcium silicate samples(Ca/Si=1.0 and 1.5)were prepared with 60℃water bath.IR,BET,XRD and SEM methods were used to study the microstructure of the hydration products.The results s...     

Hydrothermal synthesis of zeolites-calcium silicate hydrate composite from coal fly ash with co-activation of Ca(OH)2-NaOH for aqueous heavy metals removalOA

Coal fly ash is a typical secondary aluminum/silicon resource. The preparation of zeolite-type absorbent is a potential way for its value-added utilization, while the purity and adsorption property of zeolite are limited due to the occurrence of side reactions in the synthesis process. In this study, a designated composite consisted of crystalline zeolites and amorphous calcium silicate hydrate was selected, which was direct synthesized from fly ash under conditions of a Ca/Si molar ratio of 0.8...     

Removal of fluoride from aqueous solution onto Zr-loaded garlic peel （Zr-GP） particles

Garlic peel, as the raw material, was modified by loading with zirconium(IV), exhibiting quite good uptaking behaviour for fluoride anion. The adsorption experiments were carried out in batch shaking vessels, and the process was strongly dependent on the pH value. The adsorption fits Langmuir model well, and the maximum adsorption capacities at equilibrium pH 2 and 6 are evaluated to be 1.10 and 0.89 mol(fluoride)/kg of Zr-loaded garlic peel gel, respectively. The evaluation of effects of coexisting anions such as nitrate, sulfate and phosphate shows that nitrate and sulfate have no negative effect on the adsorption of fluoride, while phosphate has a little effect. Adsorption kinetics of fluoride is well described by pseudo-second-order rate equation, and the corresponding adsorption rate constant is calculated to be 3.25×10⁻³ g/(mg·min).     

Dehydration Characteristics of C-S-H with Ca/Si Ratio 1.0 Prepared Via Precipitation

Calcium silicate hydrate(C-S-H) with Ca/Si ratio 1.0 was prepared via precipitation in solution and heated at various temperatures to investigate its dehydration behavior. The dehydration, structural collapse and recrystallization characteristics of C-S-H and its microstructural change during heating process were investigated by XRD, SEM, Raman and TG-DSC techniques. C-S-H gradually lost non-evaporable water upon heating, about 50% and 80% non-evaporable water was removed below 200 and 400 ℃, respectively, and the rest was removed up to about 1 000 ℃. At 400 ℃, dehydrated C-S-H exhibited the increasing disordering of calcium/silicon environment and the decreasing symmetrical bending vibration of Si-O-Si of Q~2 silicate chains. At 650 ℃ non-bridging oxygen atoms(O_(non)) attached to silicon were almost removed, and significant structural change occurred, and at 815 ℃ C-S-H dehydrated to wollastonite.     

Influence of coal fly ash particle size on structure and adsorption properties of forming adsorbents for Cr<Superscript>6+</Superscript>

Forming adsorbents FFA-R, FFA-A and FFA-B were prepared from different particle size coal fly ashes FA-R, FA-A and FA-B, their average particle sizes (d ₅₀) were 15.75, 3.61 and 1.73 μm respectively. The structure and adsorption properties for Cr⁶⁺ of forming adsorbents from aqueous solution were studied. The results show that forming adsorbent prepared from the coal fly ash with smaller particle size exhibits higher specific surface area, higher pore volume and better adsorption properties for Cr⁶⁺.The adsorption kinetics of Cr⁶⁺ on FFA-R, FFA-A and FFA-B fitts the second order kinetic model and the second adsorption rate constants are 7.523, 3.197 and 2.187 mg·g^-1· min^-1/2, respectively. The adsorption of Cr⁶⁺ on FFA-R, FFA-A and FFA-B can be described in terms of Langmuir isotherms better, and the adsorption processes are spontaneous and exothermic.     

Alkaline treatment kinetics of calcium phosphate by piezoelectric quartz crystal impedance

Calcium phosphate film was prepared by electrochemical deposition technology. Subsequently, the alkaline treatment process of calcium phosphate film in 0.1 mol/L NaOH solution was monitored on real time by the piezoelectric quartz crystal impedance (PQCI) technique. The variations of morphology and composition for the alkaline treatment products were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray diffraction (XRD), respectively. The dynamic variations of calcium phosphate can be characterized by the change of equivalent circuit parameters. The results show that the forming process of hydroxyapatite (HA) is composed of three stages: (1) acidic calcium phosphate dissolution; (2) phase transformation; and (3) HA formation. Furthermore, the correlative kinetic equations and parameters are obtained by fitting the static capacitance (C _s)—time curves. Foundation item: Project(2005CB623901) supported by the Major State Basic Research and Development Program of China     

Preparation and Properties of Pillared Montmorillonite by Polyhydroxyl-aluminum-manganese Cations

Al-Mn-pillared montmoriUonite ( AMPM ) was prepared by using the artificial Na-montmoril-lonite from the Qingfengshan bentonite mine as starting materials mixed with Al-Mn pillaring solutions at different Al / Mn molar ratios ( R ). The basal spacing and specific surface area of the materials were increased significantly compared with untreated c/ays. When R=0.5, the d(001) value and specific surface area of pillared montmoril-lonite were 1.8987 nm and 146.01 m^2 g^-1, respectively. The thermal stability was determined using calcined tests,X-ray diffraction( XRD ) analysis, thermal gravimetry and differential thermal analysis( TG- DTA ). The formed at initial R = 0. 5 exhibited a high stability, the basal interlayer spacing was stabilized at 1. 7859 nm after calcined for 2 h at 300℃. The adsorption behavior of the materials wets studied by adsorption experi-ments. The results show the AMPM and calcined AI-Mn-pilloTed montmoriUonite (CAMPM) exhibit a strong ca-pacity of adsorbing the Zn ( Ⅱ ) in aqueous solution at pH 10.0.     

Pore structure of new composite adsorbent SiO<Subscript>2</Subscript>·<Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O· <Emphasis Type="Italic">y</Emphasis>CaCl<Subscript>2</Subscript> with high uptake of water from air

A new composite adsorbent SiO₂·xH₂O·yCaCl₂ which is composed of macro-porous silica gel and calcium chloride is introduced. In order to analyze its adsorption theory, adsorption and desorption isotherms, BET surface areas, pore volumes and average pore diameters of macro-porous silica gel and four composite adsorbent samples with different CaCl₂ content are measured using SEM and Asap2010 apparatus. From the adsorption isotherms, desorption isotherms and lag loops, it can be deduced that the main pore structure in macro-porous silica gel and the new composite adsorbent have two shapes: taper with one top open and taper or hyperbolic taper with both ends open. Based on the analysis of pore diameter distribution and lag loop, a sketch map showing calcium chloride filled in pore of macro-porous silica gel is presented. The adsorption isotherms at 25°C are measured. Experimental results show that the new composite adsorbent can adsorb more water than common adsorbents (macro-porous silica gel, micro-porous silica gel and synthetic zeolite 13X). In the light of the results of pore structure, adsorption isotherms and lyolysis phenomenon are analyzed.     

Structural characteristics and photocatalytic activity of ambient pressure dried SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> aerogel composites by one-step solvent exchange/surface modification

An ambient pressure synthesis of SiO₂/TiO₂ binary aerogel was prepared through the low-cost precursors of titanium tetrachloride (TiCl₄) and sodium silicate (Na₂O·nSiO₂). After gelation, solvent exchange and surface modification were performed simultaneously and the modified gel was finally dried under ambient pressure. Microstructural analyses by transmission electron microscope (TEM) indicate that fabricated SiO₂/TiO₂ aerogel composite shows similar sponge-like nanostructure as silica aerogel, and the Brunauer–Emmett–Teller (BET) analysis shows that the specific surface area of the composite reaches 605 m²/g, and the average pore size is 9.7 nm. Such binary aerogel exhibits significant photocatalytic performance in this paper for treating model pollutant of methyl orange (MO), and the decolorizing efficiency of MO is detected as 84.9% after 210 mins exposure to UV light irradiation. Degraded gel suspends in the water so as to separate from solution for reuse, and after 4 times recycling, 70% degradation efficiency can be easily reached when composite catalyzed system is exposed for 210 mins under UV irradiation.     

Adsorption of methylene blue from aqueous solution onto hydrochloric acid-modified rectorite

H+-rectorite clay,which was prepared by modifying the raw rectorite with 10% hydrochloric acid at 60 °C for 24 h,was used as an absorbent for removal of methyl blue (MB) from aqueous solutions.The morphology and the structure and crystallinity of the pristine rectorite and the H+-rectorite were characterized by scanning electron microscopy (SEM) technique and X-ray diffraction (XRD) technique,respectively.The results showed that the H+-rectorite exhibited high adsorption ability than the raw rectorite,and it was found that the removal percentage of MB increased with increasing in adsorbents dose,whereas the adsorption amount qe (mg/g) decreased.The equilibrium was attained within 30 min in adsorption process,and the maximum adsorption capacity of H+-rectorite for methylene blue reached as high as 37 mg/g.Besides,the effect of temperature on the adsorption of MB with H+-rectorite was investigated and the equilibrium data were well fitted to Freundlich equations.The H+-rectorite absorbent saturated with MB can be regenerated by calcinating at 400 °C for 2 h and the regenerated absorbent still showed higher percentage removal of MB.     

Preparation and adsorption property of hydrophobic SiO<Subscript>2</Subscript> aerogels modified by methyl triethoxysilane

The hydrophobic SiO2 aerogels were prepared by in-situ polymerization sol-gel method and supercritical drying of ethanol method with tetraethylorthosilicate(TEOS) as silica source, methyl triethoxysilane (MTMS) as modifier, ethanol as solvent. Moreover, the structure and adsorption property of SiO2 aerogels were also studied. As results, the surface area of SiO2 aerogels was 863.59 m2/g, the pore volume was 3.57 cm3/g, and the contact angle was 150 °. Adsorption intensity of silica aerogels for organic liquid (alkanes, benzene compounds, and nitro-compounds) is bigger than that of activated carbon. The mass of the liquid absorbed increased linearly with the surface tension of the liquid. The lower surface tension and boiling point are, the shorter desorption time is. After regenerating 10 times, nitromethane regeneration rate remain the same, and almost more than 94%. So SiO2 aerogels have good absorption and regeneration property.     

Dynamic Characteristics of Double-Helical Planetary Gear Sets Under Time-Varying Mesh Stiffness

Internal and external meshes are two of primary excitation sources which induce vibration while double-helical planetary gear sets are in transmission. Based on the analysis of tooth movement principle,three cases of mesh stiffness are derived via investigating the length of action lines,and catalogued in terms of β β0,β = β0and β β_0. The simulation demonstrates mesh stiffness between gear pairs performs as a trapezoid waveform( TW) and changes along with the line of action simultaneously,total mesh stiffness comes from the superposition of each engaged gear. While governing equations of motion contained 16 DOFs( degree of freedom) are constructed and effectively solved through the combination of numerical approaches. Comparing with sinusoidal waveform mesh stiffness( SW),the results show that dynamical factors and perturbation under the excitation of TW( β β_0) are greater and remarkable than that from SW,with respect to the mean dynamic factors about 1. 51 and 1. 28,respectively. The fluctuation response between ring- planet( R- P) is stronger than sun-planet( S-P) which is also validated by both approach studies,frequency spectra analyses identifies larger distinct rotational resonance and more frequencies under TW excitation.     

Process optimization of reaction of acid leaching residue of asbestos tailing and sodium hydroxide aqueous solution

Silica is the major component of the acid leaching residue of asbestos tailing. The waterglass solution can be prepared by the reaction of the residue with sodium hydroxide aqueous solution. Compared to the high temperature reaction method, this process is environmental friendly and low cost. In this paper, the reaction process of the residue and the sodium hydroxide aqueous solution is optimized. The optimum reaction process parameters are as follows: the usage of sodium hydroxide is 26.4 g/100 g acid leaching residue, the reaction temperature is 90℃, the reaction time is 1 h, and the ratio of the liquid/solid is 2.0. The significance sequence of the process parameters to the alkali leaching reaction effect is the usage of sodium hydroxide > the ratio of the liquid/solid > the reaction time > the reaction temperature. The significance sequence to the leaching ratio of SiO2 is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. The significance sequence to the modulus of the sodium silicate is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. Under the optimum conditions, the leaching ratio of the SiO2 is 77.5%, and the modulus of the sodium silicate is 3.15. The XRD analysis result indicates that the major components of the alkali leaching residue are serpentine, talc, quartz and some albite.     

Influence of silicate anions structure on desilication in silicate-bearing sodium aluminate solution

The structural changes of silicate anions in the desilication process with the addition of calcium hydrate alumino-carbonate were studied by measuring Raman spectra, infrared spectra and corresponding second derivative spectra. The results show that the desilication ratio in the solution prepared by the addition of sodium silicate(solution-SS) is much greater than that in the solution by the addition of green liquor(solution-GL), and low alumina concentration in the sodium aluminate solutions facilitates the desilication process. It is also shown that alumino-silicate anions in the solution-GL, and Q~3 polymeric silicate anions in solution-SS are predominant, respectively. In addition, increasing the concentration of silica favors respectively the formation of the alumino-silicate or the Q~3 silicate anions in the solution-GL or the solution-SS. Therefore, it can be inferred that the low desilication ratio in the silicate-bearing aluminate solution is mainly attributed to the existence of alumino-silicate anions.     

Preparation of Chelating Polymer Grafted Magnetic Adsorbent and Its Application for Removal of Pb(Ⅱ) Ions

A novel magnetic chelating adsorbent (CPMS) with iminodiacetate functionality was prepared by polymerization of glycidyl methacrylate-iminodiacetic acid (GMA-IDA) monomer with N, N-methylenebisacrylamide as crosslinker in the presence of monodisperse magnetic silica microspheres (MS). CPMS was characterized by IR, SEM, VSM and TGA. The experimental results revealed that MS was embedded in the gel polymer, but the morphology of CPMS was irregular. The saturation magnetization for CPMS was found to be 28.4 emu/g, and the percentage of GMA-IDA polymer grafted on MS was about 46.5%. CPMS were shown to be efficient for the removal of Pb(II) ions at pH 3.0 - 6.0, and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 54.4 mg?g?1 at pH 5.0. Moreover, the adsorption rate of CPMS was fast and it took about 5 minutes to achieve adsorption equilibrium in aqueous solution of lower lead ions concentration.     

JP-10在不同硅源合成的HZSM-5上的催化裂解

分别以硅溶胶、硅胶、硅溶胶和硅酸钠混合物、硅胶和硅酸钠混合物为硅源,采用直接法(不含有机模板剂)合成出高结晶度NaZSM-5分子筛,用1 mol/L盐酸溶液离子交换3次后得HZSM-5催化剂,采用X射线衍射（XRD）、低温氮吸附法及氨-程序升温脱附（NH3-TPD）等方法对催化剂的结构和酸性位进行表征,评价了这些催化剂对JP-10裂解的催化活性.结果表明,用硅溶胶为硅源合成的ZSM-5分子筛比用硅胶为硅源合成的ZSM-5分子筛具有更高的相对结晶度、酸性中心和裂解催化活性.当用硅溶胶和硅酸钠组成的双硅源代替单一的硅溶胶为硅源时,所得ZSM-5分子筛的相对结晶度和裂解催化活性均略有下降;相反,当用硅胶和硅酸钠组成的双硅源代替单一的硅胶为硅源时,可提高所得ZSM-5分子筛的相对结晶度和裂解催化活性.     

Effects of functionalized silica nanoparticles on characteristics of nanocomposites PES cation exchange membranes

Nanocomposite cation exchange membranes(CEMs) were prepared by adding various loadings of functionalized silica nanoparticles to the sulfonated polyethersulfone(s PES) polymeric matrix. The silica nanoparticles were functionalized by mercaptopropyl(F_1, IEC=0), propylsulfonic acid(F_2, IEC= 2.71), and sulfonic acid(F_3, IEC=2.84). The properties of prepared membranes were investigated by varying the loadings of functionalized silica nanoparticles. Applying functionalized nanoparticles provides additional ion exchange groups and enhances water contents as well as conductivities and permselectivities of the membranes. The maximum IEC of 1.9 meq.g~(-1) was obtained for the membrane having 3 wt% F_3 nanoparticles and the maximum conductivity of 0.237 S·cm~(-1) was achieved for the membrane having 2 wt% F_3 nanoparticles, which were 19.6% and 64% higher than the corresponding values for s PES membrane, respectively. The excellent properties of the nanocomposite cation-exchange membranes make them appropriate candidates for electrodialysis and desalination processes.     

功能化Fe_3O_4对水中亚甲基蓝染料的吸附性能研究

通过共沉淀法制备了磁性Fe_3O_4纳米粒子,并将其表面包覆二氧化硅外壳,制备了性质稳定,脱色性能较好,同时易于固液分离的功能化磁性纳米粒子.以模拟印染废水的脱色为目标,研究了pH、温度、吸附时间等因素对脱色效果的影响.研究结果表明,磁性吸附剂制备成本低,对亚甲基蓝溶液的脱色效率显著.     

Effects of different conditions on Pb2+ adsorption from soil by irrigation of sewage in South China

Pb²⁺ adsorption onto a soil by irrigation of sewage in the Pearl River Delta of South China was examined as a function of the reaction time, solution pH, initial lead concentration, organic matter (humic acid) and competitive ions (Cu²⁺). The adsorption of Pb²⁺ onto the soil was investigated on batch equilibrium adsorption experiments. Results show that the Pb²⁺ adsorption on the soil is relatively rapid in the first 30 min and reaches equilibrium at 2 h, and the kinetics of the adsorption process on the soil is well characterized by the pseudo-second order reaction rate. Langmuir, Freundlich and Temkin isothermal models are fit for the adsorption of Pb²⁺ onto the soil, and the maximum amount of Pb²⁺ adsorption (Q _m) is 7.47 mg/g. The amount of Pb²⁺ adsorption increases with increasing the pH at the range of 1.2–4.5 and reaches a plateau at the range of 4.5–12. The presence of humic acid in soil decreases the adsorption of Pb²⁺ onto the soil at solution pH of 8 since the negatively charged humic acid with Pb²⁺ is difficult to be adsorbed on the negatively charged soil surface. The adsorption of Pb²⁺ onto the soil also decreases in the presence of Cu²⁺ due to the competition adsorption between Pb²⁺ and Cu²⁺.     

Functionalization of semi-terminated silica nanotubes

The semi-terminated silica nanotubes with 80–100 nm porous diameter were prepared with Al/Al₂O₃ (AAO) template by the sol-gel method, and then were functionalized by 3-aminopropyltriethoxysilane (APTES). The functionalized silica nanotubes were characterized by transmission electron microscope (TEM), fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (¹H-NMR and ²⁹Si-NMR). The results indicated that APTES was successfully functionalized onto the internal surface and the mouth of the silica nanotubes. It would provide the material base for silica nanotubes corking and delivery drug.