Preparation of calcium sulfate whiskers from FGD gypsum via hydrothermal crystallization in the H_2SO_4-NaCl-H_2O system

Little attention has thus far been paid to the potential effect of solution composition on the hydrothermal crystallization of calcium sulfate whiskers prepared from flue-gas desulfurization（FGD） gypsum.When purified FGD gypsum was used as raw material,the morphology and phase structure of the hydrothermal products grown in pure water,H2SO4-H2O,NaCl-H2O,and H2SO4-NaCl-H2O solutions as well as the solubility of purified FGD gypsum in these solutions were investigated.The results indicate that calcium sulfate whiskers grow favorably in the H2SO4-NaCl-H2O system.When prepared using 10-70 g NaCl/kg gypsum-0.01 M H2SO4-H2O at 130 ℃ for 60 min,the obtained calcium sulfate whiskers had diameters ranging from 3 to 5 ｜xm and lengths from 200 to 600 ｜xm,and their phase structure was calcium sulfate hemihydrate（HH）.Opposing effects of sulfuric acid and sodium chloride on the solubility of the purified FGD gypsum were observed.With the co-presence of sulfuric acid and sodium chloride in the reaction solution,the concentrations of Ca2＋ and SO42- can be kept relatively stable,which implies that the crystallization of the hydrothermal products can be controlled by changing the concentrations of sulfuric acid and sodium chloride.

Removal of arsenic from acid wastewater via sulfide precipitation and its hydrothermal mineralization stabilization

To achieve a safe treatment of arsenic-containing acid wastewater,a new process was proposed,including arsenic removal via sulfide precipitation and hydrothermal mineralization stabilization.Under optimal conditions of sulfide precipitation,99.65%of arsenic from wastewater was precipitated in the form of amorphous As2S3.The As leaching concentration of amorphous As2S3 in TCLP(toxicity characteristic leaching procedure)test was up to 212.97 mg/L,therefore,hydrothermal mineralization was adopted to improve the stability of amorphous As2S3.The results showed that the As leaching concentration of mineralized As2S3 was only 4.82 mg/L.Furthermore,the amorphous As2S3 could be transformed into crystallized As2S3(orpiment)in the presence of mineralizer Na2SO4.Simultaneously,the As leaching concentration of crystallized As2S3 was further reduced to 3.86 mg/L.Hydrothermal mineralization was an effective method for the stabilization of As2S3.Therefore,this process has a greater application in the treatment of arsenic-containing wastewater.

Hydrothermal Processing,Characterization and Theoretical Calculations of a Copper(Ⅱ) Compound with 1,10-Phenanthroline Derivative Ligand:2-(4-Methoxyphenyl)-1H-imidazo[4,5-f][1,10] Phenanthroline

The metal-organic compound [Cu（MOPIP）2（OH）2] 1（MOPIP = 2-（4-methoxy-phenyl）-1H-imidazo[4,5-f][1,10] phenanthroline） was hydrothermally synthesized and structurally characterized by elemental analysis,Fourier-transformed infrared spectroscopy,thermogravimetric analysis,single-crystal X-ray diffraction and theoretical calculations in Gaussian 03.In the crystal structure,the copper（Cu） atoms are tetra-coordinated with four different nitrogen atoms from two different MOPIP ligands,and the Cu atom is one of the five vertexes of the tetrahedron.Presumably due to the steric bulk of the phenyl ligands,compound 1 adopts a slightly distorted tetrahedral configuration.Moreover,it exhibits a zero-dimensional structure with Cu-MOPIP as the building units.Natural Bond Orbital（NBO） analysis was performed by using the NBO method built in Gaussian 03 Program.The calculation results showed a covalent interaction between the coordinated atoms and Cu（Ⅱ） ion.

Hydrothermal Synthesis, Crystal Structure and Thermal Analyses of Pyrazine-2,3-dicarboxylic Acid Bridged Co(II) Coordination Polymer of _∞~2[Co(phen)(μ-L)_(3/3)]·H_2O (H_2L = Pyrazine-2,3-dicarboxylic Acid)

A novel pyrazine-2,3-dicarboxylic acid bridged Co(II) phen complex 2 ∞ [Co- (phen)(μ-L)3/3]?H2O (H2L = pyrazine-2,3-dicarboxylic acid) has been hydrothermally synthesized, and X-ray single-crystal diffraction analysis shows that it crystallizes in the monoclinic system, space group P21/n with a = 11.480(2), b = 11.885(2), c = 12.939(3) ?, β = 110.55(3)°, V = 1653.1(6) ?3, Mr = 423.25, Dc = 0.425 g/cm3, Z = 4, R = 0.0361 and wR = 0.1011. The title complex consists of 2D 2 ∞ [Co(phen)(μ-L)3/3] layers and crystal water molecules. Each Co atom is octahedrally coordinated by three N atoms and three O atoms to form 2D 2 ∞ [Co(phen)(μ-L)3/3] polymeric layers. Furthermore, such 2D layers are stacked into 3D supramolecular frameworks via Van der Waals’ intermolecular forces, strong and weak hydrogen-bond interactions. The coordination phen and crystal water molecules are resided into cavities of the frameworks.

Hydrothermal Synthesis,Crystal Structure and Fluorescence Spectrum Studies of a Novel Supramolecular Compound {[2-(2-Pyridyl)benzimidazoleH_2]_2·[BiCl_6]·Cl}

A novel supramolecular compound,{[2-（2-pyridyl）benzimidazoleH2]2·[BiCl6]·Cl},was synthesized by the hydrothermal reaction of o-phenylenediamine and α-pyridinecarboxylic acid with BiCl3 in 6.0 mol·L-1 HCl solution,and characterized by elemental analysis,IR,X-ray single-crystal diffraction and photoluminescence spectroscopy.The crystal （C24H22N6Cl7Bi,Mr= 851.61） belongs to the triclinic system,space group P1 with a =7.2887（18）,b =9.548（2）,c= 12.469（3）,α=85.306（4）,β=82.814（4）,γ=71.349（4）°,Z=1,V=814.9（3）3,Dc=1.735 g/cm3,μ（MoKα）=6.007 mm-1,F（000）=410,R=0.0307 and wR=0.0787.The bismuth ion and six chlorine ions construct a distorted octahedral configuration.The three-dimensional supramolecular network is built from electrostatic attractions,hydrogen bonds and π-π interaction between the BiCl6 anion,Cl anion and [2-（2-pyridyl）benzimidazoleH2] cation.The photoluminescence spectroscopy study shows that the title compound has a blue fluorescent emission at 450 nm in the solid state.

Crystallization of calcium silicate at elevated temperatures in highly alkaline system of Na_2O–CaO–SiO_2–H_2O

In Na_2O–CaO–SiO_2–H_2O system,systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumina fly ash(HAFA).The results show that crystal composition and phase may be affected by relatively low concentration of NaOH,and sodium ions are rearranged into the structure to form NaCaHSiO_4 and Na_2Ca_3H_8Si_2O_(12) with different C/S ratio at high concentration of Na OH.In addition,phases in wollastonite group possess the morphology of nano fiber.Formation of nano fiber is attributed to the difference of surface energies between axial and radial direction,and higher temperatures lead to easier growth along radial direction.The preparation of C–S–H with different phases and morphologies can guide for the application of silicate solution with high alkalinity with different purposes.

Hydrothermal Synthesis of WO3 Nanowires in the Presence of Guanidine Sulfate and Its Photocatalytic Activity

WO3 nanowires were fabricated by a hydrothermal method,which proceeded at 170 ℃ for 48 h in a solution containing C2H10N6H2SO4 as a dispersant and Na2WO4 as a starting material.The nanowires exhibit a well crystallized one-dimensional structure with 20 nm in diameter and several microns in length.The physicochemical properties of WO3 were compared using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,energy dispersive X-ray spectroscopy（EDX） and UV-vis spectroscopy（UV-Vis）.The photoactivity of the as-perpared WO3 nanowires was evaluated through the photodegradation of methylene blue（MB） in aqueous solution.The experimental results demonstrate that addition of C2H10N6H2SO4 salt in the WO3 nanowires synthesis process can enhance its photocatalytic activity obviously.

Hydrothermal Synthesis and Characterization of Nd Doped One-dimensional Hexagonal CePO_4 Nanowires

One-dimensional Nd doped CePO4 hexagonal nanowires have been synthesized for the first time at 140 ℃ for 24 hours via a hydrothermal method using P123 surfactant as the template.The products were characterized by X-ray diffraction,transmission electron microscopy,photoluminescence and high-resolution transmission electron microscopy.Compared with CePO4,one-dimensional nanomaterials we have synthesized,Nd doped CePO4 nanomaterials remain their hexagonal one-dimensional morphology and smooth surface.However,their photoluminescence emissions are greatly enhanced at the wavelength of 348 nm.With their novel fluorescence-emission property,the Nd doped CePO4 nanomaterials are potential in many fields such as optics and electronics.

Citrate-Mediated Hydrothermal Route to Synthesis A Large-Scale Y_2O_3∶Eu^(3+) Hexangular Prism

Europium-doped yttrium oxide (Y2O3∶Eu3+) hexangular microprisms were synthesized through a citrate-mediated hydrothermal method followed by subsequent calcination. The as-prepared products were characterized by X-Ray Powder Diffractometer (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and fluorescence spectrometer. The sizes of the Y2O3∶Eu3+ hexangular prisms are about 3 μm in rim and 10 μm in length. The citrate additive was found to be responsible for tailoring the crystal growth dynamically: the concentration of hydroxides in solution is reduced via forming citrate-rare earth ion complexes, giving rise to large crystals with perfect facets; the ratio of growth rate of hydroxides along the c-axis and other crystal facets is suppressed, leading to relatively small aspect ratio. The smooth surface and large size led to the luminescence intensity of hexagonal-prism phosphors higher than that of needle-like bundle products obtained without using trisodium citrate additive.

Effect of Temperature on Anisotropic Crystal Growth of Boehmite under Hydrothermal Condition

Temperature effect （200-400 ℃） on the anisotropic crystal growth of boehmite under hydrothermal conditions with and without octanoic acid was investigated. The crystallinity and the size of particles increased with increasing the treatment temperature. The crystal growth was facilitated greatly above the critical temperature of water. Although several possible factors could affect the crystal growth behavior, the experimental results were discussed in terms of water properties, such as dielectric constant and viscosity The crystallization was enhanced when the viscosity and dielectric constant of water were low. The viscosity reduction at higher temperature may enhance diffusion and crystallization, in particular, without octanoic acid. The enhancement of crystallization at lower dielectric constant implies that the formation of particles, which are less polar than precursor ions, favorably proceeds in such media. The crystal growth along c-axis showed less temperature dependence around the critical temperature in the experiments with octanoic acid, which suggests that the modification reaction on the （001） surface was also facilitated because the modification reaction forms less polar products. This is probably the reason why the aspect ratio （a/c） was considerably higher for the products obtained with the treatments above the critical temperature.

Mild Hydrothermal Synthesis,Crystal Structure and Magnetic Behavior of AgCu(IO_3)_3:a Quasi-one-dimensional S=1/2 Chain Compound

A new complex AgCu（IO3）3 is synthesized by mild hydrothermal method and characterized by single-crystal X-ray diffraction and magnetization measurement.AgCu（IO3）3 is triclinic,space group P1,with a = 7.3081（1）,b = 7.8089（1）,c = 8.2447（1）A,α = 67.159（1）,β = 74.982（1）,γ = 80.982（1）°,and Z = 2.AgCu（IO3）3 is isostructral with Ag Pb（IO3）3.The structure of Ag Cu（IO3）3 consists of CuO6 chain columns parallel to the c axis,formed by corner-sharing Cu（1） and Cu（2） octahedra and flanked by corner-sharing IO3 groups; these CuO6 columns are cross-linked into a three-dimensional framework through I–O and Ag–O bonds.I（1）,I（2） and I（3） are coordinated respectively with 3 oxygens on the same side to form trigonal pyramids confirming the presence of a stereochemically active lone pair of each I^5＋ cation.In the CuO6 chain columns,Cu（1）O6 and Cu（2）O6 octahedra are tetragonally distorted with four shorter bonds in the square planes and two longer apical bonds.Cu（1）O6 octahedra were corner sharing with Cu（2）O6 octahedra with a shorter Cu（1）–O（1） bond in the square planes and a longer apical Cu（2）–O（1） bond,which forms a Cu（1）–Cu（2） magnetic chain along the c direaction.Magnetization measurement shows weak antiferromagnetic property in low temperature range.Ag Cu（IO3）3 provides a new example of a quasi-one-dimensional magnetic system.

Hydrothermal Syntheses and Crystal Structures of Two Complexes with Cyclic Dimer and 2D Network Structures of 3-Nitrophthalate and N-Donor Ligand

Two complexes, [Cd（nphth）（2,2＇-bipy）（H20）]2.2H20 （1） and [Cd（nphth）（4,4＇- bipy）（H20）], （2） （nphth = 3-nitrophthalate, 2,2＇-bipy = 2,2＇-bipyridine, 4,4＇-bipy = 4,4＇-bipyridine）, were synthesized by hydrothermal reactions and structurally characterized. Complex 1 crystallizes in triclinic with space group Pi, a = 0.7599（4）, b = 1.0551（6）, c = 1.2448（6） nm, α = 88.96（2）, β = 75.40（2）, γ= 76.76（2）°, V= 0.9393（9） nm3, Z = 1, Dc = 1.816 Mg/m3, F（000） = 512, μ = 1.217 mm-1, S = 0.946, the final R = 0.0238 and wR = 0.0631, Complex 2 crystallizes in monoclinic, space group P21/c, a = 0.737（5）, b = 2.338（1）, c = 1.0030（6） nm, β = 96：359（9）°, V= 1.803（2） nm3, Z = 4, Dc = 1.826 Mg/m3, F （000） = 984,μ = 1.260 mm-1, S = 1.016, the final R = 0.0455 and wR = 0.1007. Complex 1 exhibits a discrete cyclic binuclear structure and complex 2 possesses a 2D layer structure with cyclic binuclear unit. The fluorescent spectrum study shows that complex 1 exhibits fluorescent emission in the solid state at room temperature.

Preparation, Characterization, and Formation Mechanism of Calcium Sulfate Hemihydrate Whiskers

Calcium sulfate hemihydrate whiskers were synthesized successfully via one-step hydrothermal crystallization method using phosphogypsum at 130 °C for 240 min with an initial slurry mass fraction of 2.5 wt%. The phase compositions, microstructures, thermal properties and molecular structures of asprepared samples were analyzed by XRD, ESEM, EDS, TG-DTA, and FT-IR. The influence of raw materials’ ball-milling time on the morphologies of whiskers was investigated. The effects of impurities on crystallization morphologies and length to diameter ratio(L/D) of calcium sulfate hemihydrate whiskers were studied. The results indicated that the calcium sulfate dihydrate crystalline could be translated directly into fibrous calcium sulfate hemihydrate whiskers. It was beneficial to form fine fiber structure when the ball-milling time of the raw material was 15 min. Aspect ratio of calcium sulfate hemihydrate whiskers decreased with increasing content of impurities. Moreover, the relative growth mechanism of whisker crystals via one-step hydrothermal crystallization method was discussed in detail.

MCM-41 Prepared with Ionic Liquid and Cethytrimethylammonium Bromide as Co-templates

The mesoporous molecular sieves MCM-41 were prepared using room tempera-ture ionic liquid （RTIL） synthesized in laboratory and cethytrimethylammonium bromide （CTAB） as compound templates for the first time. They were prepared under low aging temperature and short aging time. Via characterizing by XRD and nitrogen adsorption instrument, MCM-41 synthesized by this new method exhibited good crystal structure and narrow pore distribution. The following pre-paratory conditions was optimal： the molar ratio of RTIL to CTAB was 1.0∶1.0, aging at 80 ℃, for 40 h and calcined at 540 ℃. It is found that the acidified MCM-41 improves its activity as catalyst over the unmodified ones.

Syntheses and Characterization of ZSM-5 Zeolites Containing Diethylamine and Ethylenediamine

Syntheses of ZSM-5 zeolites from R-SiO2-Al2O3-H2O-HF(R = diethylamine and ethylenediamine, respectively) were investigated by using the hydrothermal crystallization. The large single crystals of ZSM-5 containing diethylamine and ethylenediamine were synthesized. The ZSM-5 precursors were characterized by means of X-ray powder diffraction, scanning electron microscopy, thermal analysis and electron microprobe analysis. The analysis result of aluminium distribution shows that the interior aluminium content of large crystals of ZSM-5 zeolites is rather low.

Synthesis, Crystal Structure and Characterization of the Host-guest Type UOF

A new uranium（Ⅵ）-polycarboxylate framework with honeycomb（6,3） nets {[Zn（phen）_2（H_2O）_2][（UO_2）_2（BDC）_3]·2H_2O}n（1, BDC = benzene-1,4-dicarboxylate） was hydrotherrmally synthesized by the reactions of Zn（NO_3）_2·6H_2O with phenanthroine, UO_2（NO_3）_2·6H_2O and benzene-1,4-dicarboxylate. The complex was structurally characterized by FT-IR spectroscopy, powder XRD and X-ray single-crystal diffraction. Crystal data for 1： monoclinic, space group Cc with M_r = 1522.19, a = 14.9385（10）, b = 20.4922（13）, c = 15.9728（10） ？, β = 100.1240（10）°, V = 4813.5（5） ？~3, Z = 4, D_c = 2.100 g？cm^（–3）, μ = 7.293 mm^（–1）, F（000） = 2872, the final R = 0.0224 and w R= 0.0677 for 6522 observed reflections with I 〉 2σ（I）. Hydrogen bonds and π-π stacking interactions contribute to the structural extension and stabilization. Experimental band gap of about 3.57 e V indicates its broad gap semiconductor nature. UV-Vis spectra and solid-state luminescence were discussed in detail. The compound exhibits photocatalytic activities for the degradation of rhodamine B.

A Metal-organic Framework Containing Octanuclear Zn(Ⅱ) Clusters Constructed by 5-Methoxyisophthalate and Flexible Bis(imidazolyl) Ligand

The hydrothermal reaction of 5-methoxyisophthalic acid（MeO-H2ip）, 1,3-bis（2-methylimidazol-1-yl）propane（bmip） and Zn（NO3）2·6H2O in the presence of NaOCH3 gave rise to a three-dimensional（3-D） metal-organic framework containing octanuclear Zn（II） units, [Zn4（MeO-ip）3（OH）2（bmip）]n. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the triclinic space group P1 with a = 11.348（3）, b = 14.163（4）, c = 15.088（4） , α = 108.537（2）, β = 106.542（2）, γ = 103.106（1）o, V = 2065.4（9） -3, Z = 2, Mr = 334.62, Dc = 1.740 g·cm-（-3）, μ = 2.375 mm-（-1）, S = 1.015, F（000） = 1096, the final R = 0.0272 and w R = 0.0715 for 8929 observed reflections（I 〉 2σ（I））. The complex is thermally stable up to 370 oC, and exhibits photoluminescent emission at 450 nm on 350 nm excitation.

Fluorescence Properties and Crystal Structures of Metal-organic Coordination Complexes Based on the 2,6-Naphthalenedicarboxylic Acid

Two metal-organic coordination complexes, [Zn（2,6-ndc）（1,2-bix）]n（1） and [Zn（2,6-ndc）（1,3-bix）]n（2）（2,6-H2ndc = 2,6-naphthalenedicarboxylic acid, 1,2-bix = 1,2-bis（imidazole-1-ylmethyl）-benzene and 1,3-bix = 1,3-bis（imidazole-1-ylmethyl）-benzene） have been synthesized by the hydrothermal method. Though the two complexes both crystallize in a triclinic system, space group P1 and show similar two-dimensional structures, weak intermolecular interactions（π-π packing interactions） only exist in complex 2. They are characterized by single-crystal X-ray diffraction analysis, fluorescence measurement, IR spectroscopy and TGA. Moreover, the solid-state fluorescence spectra of two complexes show maximal emission peaks at 365（λ（ex） = 329 nm） and 367 nm（λex = 344 nm）, respectively.

Synthesis,Crystal Structure and Fluorescent Properties of Silver and Cadmium Complexes

Two new complexes [Ag（bix）]n·n NAA·n H2O（1） and [Cd（NAA）（phen）2（H2O）]2· 2CH3COO-·H2O（2）（bix = 1,4-bis（imidazol-1-ylmethyl）benzene,HNAA = α-naphthylacetic acid,phen = 1,10-phenanthroline） have been successfully synthesized under hydrothermal conditions.Their structures have been determined by elemental analyses,IR spectroscopy,TG and single-crystal X-ray diffraction analysis.The intermolecular hydrogen bonding or π-π stacking interactions extend the complexes into a 3D supramolecular structure.Moreover,the luminescent properties of complex 2 have been investigated in the solid state.

Syntheses and Structural Characterizations of a Series of Capped Keggin Derivatives

Hydrothermal reactions of Na2MoO2·2H2O and NH4VO3（or V2O5） with appropriate reducing agents such as organic amines, NH2OH·HCl and Mo（CO）6 gave rise to the formation of a series of capped Keggin derivatives, [N（CH3）4]2Na3（NH4）2[（V^VO4）Mo^VI8V^IV4O36（V^IVO）2]·-13H2O（1）, [NH4]7[（V^VO4）Mo^VI8V^IV4O36（V^IVO）2]·7H2O（2）, [HN（CH2CH2）3NH][（PO4）Mo^V3Mo^VI9O36（V^IVO）2]·-3[N（CH2CH2）3N]·（en）·4.5H2O（3） and [HNH2OH][NH4]2[（V^VO4）Mo^VI8V^IV4O36（V^IVO）4]·24H2O（4）. Single-crystal X-ray diffraction analysis revealed that the anions in 1-3 are two-capped Keggin derivatives with characteristic trans vanadium-oxygen caps, whereas the heteropoly anion in 4 is a tetra-capped α-Keggin derivative with characteristic vanadium-oxygen caps on the equatorial plane.