Direct synthesis of single-phase α-CaSO4·0.5H2O whiskers from waste nitrate solution

Single-phase α-CaSO₄·0.5H₂O whiskers were directly synthesized from waste Ca(NO₃)₂ solution using a hydrothermal method, and HNO₃ was synchronously regenerated. The effects of reaction temperature and Ca²⁺ concentration on the phase composition and morphology of products were determined by X-ray diffraction and optical microscopy. On the basis of the experimental results, the formation diagram of α-CaSO₄·0.5H₂O was plotted within the range of 5-35 g·L^-1 Ca²⁺ and 115℃-150℃. In addition, the conditions of the direct synthesis of α-CaSO₄·0.5H₂O were determined. Well-crystallized, single-phase α-CaSO₄·0.5H₂O whiskers with high aspect ratios (length, 1785 μm; diameter, 10.63 μm; aspect ratio, 168) and HNO₃ (70.25 g·L^-1) were obtained at the optimal conditions of 25 g·L^-1 Ca²⁺ and 125℃.     

Modified iron-molybdate catalysts with various metal oxides by a mechanochemical method: enhanced formaldehyde yield in methanol partial oxidation

A mechanochemical method was employed to prepare modified iron molybdate catalysts with various metal salts as precursors. The physicochemical properties of the iron molybdate catalysts were characterized, and their performances in catalyzing the reaction from methanol to formaldehyde (HCHO) were evaluated. Iron molybdate catalysts doped with Co(NO₃)₂·6H₂O and Al(NO₃)₃·9H₂O resulted in high HCHO yields. Compared with a commercial catalyst, the HCHO yields in the reaction with the modified catalyst at an optimal Co/Mo molar ratio reached 97.37%. According to chemical state analysis, the formation of CoO and the efficient decrease in the MoO₃ sublimation rate could be important factors enhancing the HCHO yield in reactions catalyzed with iron molybdate doped with different Co/Mo mole ratios.     

-15℃下Na+， K+， Mg2+//Cl-， NO3-， SO42——H2O体系相平衡研究

新疆卤水硝酸盐矿主要含有Na⁺、K⁺、Mg²⁺、Cl^-、NO₃^-、SO₄^2-六种离子,属于高元复杂体系,其合理利用和开发需要不同温度下的相平衡研究作为理论支撑。采用等温溶解平衡法,对Na⁺, K⁺, Mg²⁺//Cl^-, NO₃^-, SO₄^2--H₂O体系在-15℃、NaCl·2H₂O饱和条件下的相平衡进行了研究,并构建了相图。相图中有六个零变量点和八个两盐结晶区,只存在一种复盐KCl·MgCl₂·6H₂O。八个两盐结晶区,分别对应于NaCl·2H₂O+Na₂SO₄·10H₂O、NaCl·2H₂O+NaNO₃、NaCl·2H₂O+KCl、NaCl·2H₂O+KNO₃、NaCl·2H₂O+MgSO₄·7H₂O、NaCl·2H₂O+MgCl₂·8H₂O、NaCl·2H₂O+Mg(NO₃)₂·6H₂O和NaCl·2H₂O+KCl·MgCl₂·6H₂O,其中NaCl·2H₂O+Na₂SO₄·10H₂O共晶区最大,在低温时,硫酸钠的溶解度最小,降温过程中较易结晶析出。与该体系在25℃下的相图相比,复盐种类减少5种,零变量点减少19个,相关系得以极大简化。     

Co3O4 with ordered pore structure derived from wood vessels for efficient Hg0 oxidation

Catalytic oxidation of Hgo to Hg^O is an efficient way to remove Hg⁰ from coal-fired flue gas.The catalyst with ordered pore structure can lower mass transfer resistance resulting in higher Hg⁰ oxidation efficiency.Therefore,in the present work,wood vessels were used as sacrificial template to obtain Co₃O₄with ordered pore structure.SEM and BET results show that,when the mass concentrations of Co(NO₃)₂·6H₂O wa...     

Effects of iron precursors on the structure and catalytic performance of iron molybdate prepared by mechanochemical route for methanol to formaldehyde

Mechanochemical synthesis has been applied for many novel material preparations and gained more and more attention due to green and high-efficiency recently. In order to explore the influences of iron precursors on structure and performance of iron molybdate catalyst prepared by mechanochemical route, three typical and cheap iron precursors have been used in preparation of iron molybdate catalyst. Many characterization methods have been employed to obtain the physical and chemical properties of iron molybdate catalyst. Results indicate that iron precursors have the significant impact on the phase composition, crystal morphology and catalytic performance in the conversion of methanol to formaldehyde. It is hard to regulate the phase composition by changing Mo/Fe mole ratios for Fe_2(SO_4)_3 as iron precursor. In addition, as for Fe_2(SO_4)_3, the formaldehyde yield is lower than that from iron molybdate catalyst prepared with Fe(NO_3)_3·9H_2O due to the reduction in Fe_2(MoO_4)_3 phase as active phase. Based on mechanochemical and coprecipitation method, the solvent water could be a key factor for the formation of MoO_3 and Fe_2(MoO_4) for FeCl_3·6H_2O and Fe_2(SO_4)_3 as precursors. Iron molybdate catalyst prepared with Fe(NO_3)_3·9H_2O by mechanochemical route, shows the best methanol conversion and formaldehyde yield in this reaction.     

Study on phase equilibrium of system Na+, K+, Mg2+//Cl-, NO3-, SO42--H2O at -15℃

Xinjiang brine nitrate mine mainly contains six kinds of ions: Na⁺, K⁺, Mg²⁺, Cl^-, NO₃^-, and SO₄^2-, belonging to a high-element complex system, and its rational utilization and development require phase equilibrium studies at different temperatures as theoretical support. The phase equilibrium of the system Na⁺, K⁺, Mg²⁺//Cl^-, NO₃^-, SO₄^2--H₂O saturated with NaCl·2H₂O at -15℃ was investigated using the isothermal solution equilibrium method. According to the measured data, the phase diagrams were constructed. Only one double salt KCl·MgCl₂·6H₂O was found in the system. There are six invariant points and eight two-salt crystallization fields corresponding to NaCl·2H₂O+Na₂SO₄·10H₂O, NaCl·2H₂O+NaNO₃, NaCl·2H₂O+KCl, NaCl·2H₂O+KNO₃, NaCl·2H₂O+MgSO₄·7H₂O, NaCl·2H₂O+MgCl₂·8H₂O, NaCl·2H₂O + Mg(NO₃)₂·6H₂O and NaCl·2H₂O+KCl·MgCl₂·6H₂O. The crystallization area of NaCl·2H₂O+Na₂SO₄·10H₂O occupies the largest part because of its low solubility, and they will crystallize out easily from the mixed solution in the cooling process. Compared with the phase diagram of the system at 25℃, there are 5 types of double salts reduced, 19 zero variable points reduced, and the phase relationship is greatly simplified.     

Self-assembly of metal-cholesterol oxidase hybrid nanostructures and application in bioconversion of steroids derivatives

A cholesterol oxidase (COD) was hybridized with Ca²⁺, Zn²⁺, Al³⁺, Fe²⁺ and Mn²⁺. After precipitation with PO₄^3– at 4 °C for 72 h, the resulting pellets were freeze-dried. In scanning electron microscopy assays, the metal-COD complexes revealed flower-like or granular structures after hybridization. Fourier transform infrared spectroscopy assay revealed the characteristic peaks of both the enzyme and metal materials. X-ray diffraction analysis indicated that COD was encapsulated in CaHPO₄·2H₂O-, Zn₃(PO₄)₂·4H₂O-, AlPO₄-, FeP₄- and Mn₃(PO₄)₂·3H₂O-based nanostructures, respectively. Differential scanning calorimetry assay indicated significant increases in thermo-denaturation temperatures from 60.5 °C to 167.02 °C, 167.02 °C, 137.70 °C, 172.85 °C and 160.99 °C, respectively. Using steroid derivatives as substrates, this enzyme could convert cholesterol, pregnenolone, dehydroepiandrosterone, ergosterol, b-sitosterol and stigmasterol to related single products. Hybridization in metal-based nanostructures could significantly enhance the initial conversion ratio and reaction stability of the enzyme. In addition, substrate selectivity could be affected by various metal materials. Briefly, using Ca²⁺, Zn²⁺, Al³⁺, Fe²⁺ and Mn²⁺ as hybrid raw materials could help to encapsulate COD in related metal-enzyme nanostructures, and could help to promote the stability and tolerant properties of the enzyme, while also enhancing its catalytic characteristics.     

水合硝酸镁热解过程研究

水合硝酸镁是红土镍矿硝酸湿法冶金工艺中产生的副产品,其资源化利用是决定湿法冶金工艺绿色化工艺链条贯通的关键环节之一。水合硝酸镁热解生产氧化镁是其资源化利用最具潜力的发展方向。为此,以稳定的硝酸镁水合物——六水硝酸镁为实验物料,采用热重分析（TG-DTG）、红外光谱（FT-IR）、X射线衍射（XRD）和差示扫描量热分析（DSC）等技术手段研究了其热解基本过程,旨在为水合硝酸镁资源化工艺参数的确定提供理论支撑。研究结果表明,水合硝酸镁热解过程可以分为脱水和分解两个阶段：脱水阶段,六水硝酸镁在68~170 ℃失去4个结晶水生成二水硝酸镁,二水硝酸镁在170~389 ℃失去2个结晶水生成无水硝酸镁;分解阶段,无水硝酸镁在389~510 ℃分解生成氧化镁、二氧化氮和氧气。六水硝酸镁热解过程是一个吸热反应,其反应热约为940.50 J/g。     

Porous structures constructed from [SiMo12O40] and [SiW12O40] Keggin units

Three compounds, K₂(H₂O)₄H₂SiMo₁₂O₄₀ · 7H₂O (1), K₂Na₂(H₂O)₄SiW₁₂O₄₀ · 4H₂O (2), and Na₄(H₂O)₈SiMo₁₂O₄₀ · 6H₂O (3) have been synthesized and structurally characterized by single-crystal X-ray analysis, IR, and thermogravimetry. Compounds 1 and 2 both show the high symmetry trigonal space group P3₂21 and a novel 3D network structure. The Keggin anions [SiM₁₂O₄₀]⁴⁻(M = Mo, W) are linked by potassium or sodium cations to generate hexagon-shaped channels along the c-axis, in which water molecules are accommodated. Compound 3 is tetragonal, space group P4/mnc constructed from [SiMo₁₂O₄₀]⁴⁻ anions and Na ions.     

利用磷酸镁水泥固化富集型重金属铜和镍研究

利用磷酸镁水泥对富集型重金属铜和镍进行固化研究。对掺入硝酸铜和硝酸镍水泥的抗压强度、铜镍离子浸出质量浓度、水化产物组成等进行测定,观测水泥表面的微观形貌,分析铜镍离子在水泥中的化学态及赋存状态。研究表明：硝酸铜掺量为0~3%（质量分数）时,水泥的抗压强度随着铜离子掺量的增加呈现先增大后减小的趋势,当硝酸铜掺量为1%时,水泥7 d抗压强度达到最大值46.05 MPa;硝酸镍掺量为0~3%（质量分数）时,水泥的抗压强度随着镍离子掺量的增加而逐渐减小,当硝酸镍掺量由0增加到3%时,水泥7 d的抗压强度降低了约29%。水泥的密实度与铜镍离子的固化效果直接相关。在硝酸铜和硝酸镍掺量都为3%时,水泥1 d铜离子浸出质量浓度最高为1.95 mg/L、镍离子浸出质量浓度最高为0.97 mg/L,均远低于相关国家标准。铜主要以+2价态的Mg_0.95Cu_0.05O形式存在,镍主要以+2价态的Ni（OH）₂无定形沉淀形式存在。     

The effect of oxygen concentration on the reduction of NO with propylene over CuO/γ-Al2O3

The effect of oxygen concentration on the pulse and steady-state selective catalytic reduction (SCR) of NO with C₃H₆ over CuO/γ-Al₂O₃ has been studied by infrared spectroscopy (IR) coupled with mass spectroscopy studies. IR studies revealed that the pulse SCR occurred via (i) the oxidation of Cu⁰/Cu⁺ to Cu²⁺ by NO and O₂, (ii) the co-adsorption of NO/NO₂/O₂ to produce Cu²⁺(NO₃⁻)₂, and (iii) the reaction of Cu²⁺(NO₃⁻)₂ with C₃H₆ to produce N₂, CO₂, and H₂O. Increasing the O₂/NO ratio from 25.0 to 83.4 promotes the formation of NO₂ from gas phase oxidation of NO, resulting in a reactant mixture of NO/NO₂/O₂. This reactant mixture allows the formation of Cu²⁺(NO₃⁻)₂ and its reaction with the C₃H₆ to occur at a higher rate with a higher selectivity toward N₂ than the low O₂/NO flow. Both the high and low O₂/NO steady-state SCR reactions follow the same pathway, proceeding via adsorbed C₃H₇---NO₂, C₃H₇---ONO, CH₃COO⁻, Cu⁰---CN, and Cu⁺---NCO intermediates toward N₂, CO₂, and H₂O products. High O₂ concentration in the high O₂/NO SCR accelerates both the formation and destruction of adsorbates, resulting in their intensities similar to the low O₂/NO SCR at 523–698 K. High O₂ concentration in the reactant mixture resulted in a higher rate of destruction of the intermediates than low O₂ concentration at temperatures above 723 K.     

氯化铬和氯化镍浓度及其存在形式对ChCl-EG低共熔溶剂电导率的影响

研究了氯化铬(CrCl₃·6H₂O)和氯化镍(NiCl₂·6H₂O)浓度和存在形式对氯化胆碱-乙二醇(ChCl-EG)低共熔溶剂的黏度和电导率的影响。电喷雾质谱(ESI-MS)分析结果表明,在溶解有CrCl₃?6H₂O和NiCl₂?6H₂O 的ChCl-EG(ChCl-EG-NiCl₂·6H₂O-CrCl₃·6H₂O)溶液中出现了配阴离子[Cr(H₂O)₂Cl₄]^–和[Ni(H₂O)₂Cl₄]^2-。由此可以推断,Cr³⁺(或Ni²⁺)的两个d轨道、4s 和4p轨道发生d²sp³杂化,形成6个等同的杂化轨道,接受6个配体(Cl^-和H₂O)形成阴离子配合物。该溶液的电导率随温度的升高而增大,随总金属离子浓度的增大而减小。此外,溶液黏度随温度和总金属离子浓度的变化趋势与电导率相反。这主要是由于镍和铬配离子的形成改变了溶液中的离子组成。     

多组分氯盐体系镁锂分离规律初探

以Na₂CO₃为沉淀剂,初步研究了多组分氯盐混合体系（0.6 mol MgCl₂+1.1 mol LiCl+3.2 mol NaCl）中选择性沉镁的工艺规律。结果表明：在25~80 ℃,总C与总Mg物质的量比[n（C_T）/n（Mg_T）]为 0.8~1.1时,25 ℃形成针状MgCO₃·3H₂O,40 ℃以上形成Mg₅（CO₃）₄（OH）₂·4H₂O不规则片状团聚微球,其中40~50 ℃形成的片状物较为分散且粒径较小,导致固液分离困难。40 ℃时沉镁率最低。温度越高,Li₂CO₃越易形成,沉锂率越大。n（C_T）/n（Mg_T）越大沉镁率和沉锂率越高。室温（25 ℃）、n（C_T）/n（Mg_T）=1.0时,沉镁率达98%以上,且沉锂率<0.1%,镁锂分离效果最好。     

Effect of codoping LiNbo3:Eu3 crystal with Mg2 ions on the Eu3 optical absorption spectrum

In this work the optical absorption spectra of Eu³⁺ doped LiNbO₃ measured as a function of Li/Nb ratio are presented. Two Eu³⁺ sites, dealing with the Nb⁺⁵ and Li⁺ lattice sites, have been characterized by their corresponding ⁷F_o -⁵D₂ optical transitions. A doubly doped sample (LiNbo³: Mg, Eu) has been used to study the influence of Mg²⁺ ions on the Eu³⁺ optical absorption spectrum. The main effect is a shifting of the relative occupation of the two Eu³⁺ sites.     

High-quality, oriented and mesostructured organosilica monolith as a potential UV sensor

We synthesized high-quality and oriented periodic mesoporous organosilica (PMO) monoliths through a solvent evaporation process using a wide range of mole ratios of the components: 0.17–0.56 1,2-bis(triethoxysilyl)ethane (BTSE): 0.2 cetyltrimethylammonium chloride (CTACl): 0–1.8 × 10⁻³ HCl: 0–80 EtOH: 5–400 H₂O. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images indicated that the mesoporous channels within the monolith samples were oriented parallel to the flat external surface of the PMO monolith and possessed a hexagonal symmetry lattice (p6mm). The PMO monolith synthesized from a reactant composition of 0.35 BTSE: 0.2 CTACl: 1.8 × 10⁻⁶ HCl: 10 EtOH: 10 H₂O had a pore diameter, pore volume, and surface area – obtained from an N₂ sorption isotherm – of 25.0 Å, 0.96 cm³ g⁻¹ and 1231 m² g⁻¹, respectively. After calcination at 280 °C for 2 h in N₂ flow, the PMO monolith retained monolith-shape and mesostructure. Pore diameter and surface area of the calcined PMO monolith sample were 19.8 Å, 0.53 cm³ g⁻¹ and 1368 m² g⁻¹, respectively. We performed ²⁹Si and ¹³C CP MAS NMR spectroscopy experiments to confirm the presence of Si–C bonding within the framework of the PMO monoliths. We investigated the thermal stability of the PMO monoliths through thermogravimetric analysis (TGA). In addition, rare-earth ions (Eu³⁺, Tb³⁺ and Tm³⁺) were doped into the monoliths. Optical properties of those Eu³⁺, Tb³⁺ and Tm³⁺-doped PMO monoliths were investigated by photoluminescence (PL) spectra to evaluate their potential applicability as UV sensors.     

In-situ growth of needlelike LaAl11O18 for reinforcement of alumina composites

In situ growth of needlelike LaAl₁₁O₁₈ grains reinforcing Al₂O₃ composites can be fabricated by a coprecipitation method using La(NO₃)₃√6H₂O and Al(NO₃)₃√9H₂O as starting materials. The new two-step process involved firstly preparing needlelike LaAl₁₁O₁₈ grains distributed homogeneously in Al₂O₃ powder and then pressureless sintering the composite powders. The Al₂O₃/25 vol.%LaAl₁₁O₁₈ samples pressureless sintered at 1550°C for 4 h achieve relative density up to 96.5% and exhibit a bending strength of 420±30 MPa and a fracture toughness of 4.3±0.4 MPa m^1/2.     

Hydrothermal synthesis of Ba(Ti, Sn)O3 fine powders and dielectric properties of the corresponding ceramics

Fine powders of submicron-sized crystallites of BaTiO₃ were prepared at 85–130°C by the hydrothermal method, starting from TiO₂.ξH₂O gel and Ba(OH)₂ solution. The products obtained below 110°C incorporated considerable amounts of H₂O and OH⁻ in the lattice. As-prepared BaTiO₃ is cubic and converts to the tetragonal phase after heat treatment at 1200°C, accompanied by the loss of residual OH⁻ ions. Hydrothermal reaction of SnO₂.ξH₂O gel with Ba(OH)₂ at 150–260°C gives rise to the hydrated phase, BaSn(OH)₆.3H₂O, due to the amphoteric nature of SnO₂.ξH₂O which stabilises Sn(OH)₆²⁻ anions in basic media. On heating in air or releasing the pressure in situ at 260°C, BaSn(OH)₆.3H₂O converts to BaSnO₃ through an intermediate, BaSnO(OH)₄. Solid solutions of Ba(Ti,Sn)O₃ are directly formed from (TiO₂ + SnO₂)..ξH₂O gel up to 35 mol% SnO₂. At higher Sn contents, the hydrothermal products are mixtures of BaSn(OH)₆.3H₂O and BaTiO₃, which on annealing at 1000°C result in monophasic Ba(Ti,Sn)O₃. The sintering characteristics and the dielectric properties of the ceramics prepared out of these fine powders are presented. The dielectric properties of fine-grained Ba(Ti,Sn)O₃ ceramics are explained on the basis of the prevailing diffuse phase transition behaviour.     

Carbon oxidation with platinum supported catalysts

The effect of the support oxide, Pt precursor and reactant gas composition on the catalysis of soot oxidation was investigated using carbon black as a model soot and simulated exhaust gases. The Pt precursors used were Pt(NH₃)₄(OH)₂, H₂PtCl₆·6H₂O, Pt(NH₃)₄(NO₃)₂, and Pt(NH₃)₄Cl₂. The support metal oxides used were SiO₂, Al₂O₃, and ZrO₂. Pt/SiO₂ prepared from Pt(NH₃)₄(OH)₂ showed the highest carbon oxidation activity. It had much higher activity in the condition of N₂+O₂+H₂O+NO+SO₂ than without NO and SO₂.     

Synthesis of NiO–ZrO2 powders for solid oxide fuel cells

With NH₃·H₂O, NH₃·H₂O-NH₄HCO₃ buffer solution and NaOH solution as coprecipitation agents, NiO–ZrO₂, anode powder of solid oxide fuel cell, was synthesized by coprecipitation methods. Composition accuracy was analyzed by comparing the original composition with the mass of the eventually obtained powder. It was shown that cubic NiO and cubic YSZ with a cascade powder distribution were obtained after the powder was calcined for 1h at different temperatures. Composition analysis of the powder synthesized with NH₃·H₂O as coprecipitation agent showed that NiO–YSZ powder greatly deviated from the original composition due to the loss of Ni²⁺ in the form of [Ni(NH₃)₄]²⁺. When NH₃·H₂O–NH₄HCO₃ buffer solution was used, productive output of nickel was increased. The loss of nickel can be totally avoided and better control of the powder composition could be realized when NaOH was used as coprecipitation agent.     

Decomposition of nitrous oxide over supported rhodium catalysts and dependency on feed gas composition

The catalytic decomposition of nitrous oxide to nitrogen and oxygen was studied overRh/ZnO, Rh/CeO₂, Rh/ZSM-5, CuZSM-5 and CoAlCO₃HT (hydrotalcite). The effects of metal loading and calcination conditions upon the catalytic performance were examined on Rh/ZnO. A 0.5 wt.% Rh/ZnO catalyst was found to be the most active catalyst, whose reaction rate was 4.0 × 10⁴ μmol(N₂O) · g⁻¹ · h⁻¹ under the conditions of 950 ppm N₂O and 5% O₂ at 300°C. The oxidized Rh/ZnO showed a higher activity than that calcined in a reducing atmosphere. The TEM and EDX observations revealed the formation of particles of ca. 50Åin diameter. They consisted of rhodium and zinc oxides as major and minor components, respectively. The activities of all these catalysts decreased when NO₂ and H₂O were added to the feed.