Arsenate Crystals Research Articles

A novel process of immobilizing sodium arsenate crystals as scorodite using Fe(OH)3 as an iron source

Sodium arsenate crystals are a hazardous waste produced from the utilization of arsenic–alkali residue in antimony metallurgy that pose a serious threat to the environment. In this article, to eradicate the damage caused by sodium arsenate and enhance the sustainable development of nonferrous metallurgy, a novel process was proposed to immobilize arsenic as flaky scorodite using Fe(OH)3 as an iron source. Various methods, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and inductively coupled plasma atomic emission spectrometry (ICPAES), were applied to characterize these synthesized products. The whole process is divided into three parts. In the thermodynamic analysis, the stable area of scorodite in the Pourbaix diagram significantly expands at high ionic activity and temperature, which favors the decrease in △rG for scorodite synthesis, and Fe–As coprecipitation is feasible in solution at 0.18 ≤pH≤ 5.30. In the scorodite synthesis, 99.88% of the arsenic was converted to a flaky scorodite with a size of 2–5 µm by optimizing the parameters. In the removal of arsenic, residual arsenic and iron were completely coprecipitated into an iron salt by dropping NaOH solution to a final pH of 5.0. The final products include scorodite and sodium sulfate in this process. Overall, this new approach successfully eliminates the potential arsenic pollution from the utilization of arsenic–alkali residue in antimony metallurgy and can potentially be applied to dispose of other high arsenic-bearing wastes.

Theoretical investigation, of Cochran’s mode frequency, and electrical permittivity of KH2AsO4 (KDA) crystal by using Zuberav’s statistical Green function technique

Potassium dihydrogen arsenate KH2AsO4 crystal is investigated theoretically. It is an order disorder type of ferroelectrics. Another type is displacive like SrTiO3, LiNbO3, etc. The earlier model Hamiltonian (PLCM) is modified by adding some extra terms into it. Applying two time thermal dependent statistical Green function technique employing modified model, formulae for, Cochran’s mode frequency, electrical permittivity, Curie temperature, tangent delta, shift and width, are derived for the potassium dihydrogen arsenate crystal. Model values are fitted for KH2AsO4 crystal to obtain variation with temperature. Results are compared with experimental variations shown by Kaminow et al. [4] for the alkali phosphate potassium dihydrogen arsenate KH2AsO4 crystal.

Theoretical investigation of ferroelectric phase transition, and tangent delta in CsH2AsO4 (CDA) crystal

In this present work, Cesium Dihydrogen Arsenate of ordered dis-ordered type H-bonded crystal is theoretically investigated. Presently modified Pseudo Spin Lattice Coupled Mode (PLCM) model by adding some extra terms, like direct spin–spin terms, third-order and fourth-order phonon anharmonic terms, and extra spin–lattice terms. By using the Green function approach and Dyson’s equation, formulae for various quantities are find out. Thermal variations of Cochran’s mode frequency, electrical permittivity, phase transition, tangent delta, shift, and width are obtained for Cesium Dihydrogen Arsenate crystal. A comparison with theoretical findings has been made with the experimental finding reported by Blinc et al. [8]. A good agreement is seen.

Range-gated active short-wave infrared imaging for rain penetration

A fixed wavelength optical parametric amplifier laser was constructed to create nanosecond pulsed light at 1527 nm for eye-safe range gated active short-wave infrared (SWIR) imaging. The laser pulse is generated using a Nd:YAG operating at 1064 nm to pump a potassium titanyle arsenate crystal in a single-pass geometry, resulting in ≈85 mJ at up to 28 Hz at 1527 nm with a pulse duration of ∼8 ns. The SWIR imager can be gated in as short as a 70-ns window (active time) with time steps as small as 5 ns (e.g., 0 to 70 ns and 5 to 75 ns). This allows for significant weather penetration by reducing the contribution from back-scattered photons reaching the receiver from scattering along the path prior to the imaging target. In addition, by converting to 1527 from 1064 nm, the maximum permissible exposure limit for eye-safety is ≈4 orders of magnitude larger, allowing for higher fluences without risk of injury. NEXRAD weather data along the line-of-sight were utilized to facilitate atmospheric propagation modeling via MODTRAN to retrieve an estimate of the path transmittance during testing. The integrated system herein is shown to extend imaging ranges with improvement factors of ≈2.5–3.1 × during periods of rain. An image of a water tower at a 10-km range was generated with visibilities between 3 and 4 km during testing.

Tunable, few-cycle, CEP-stable mid-IR optical parametric amplifier for strong field applications

We present a robust, three-stage optical parametric amplifier driven by a Ti:Sapphire ultrafast laser system that implements passive carrier-envelope phase stabilization and directly generates five-cycle mid-IR pulses by dispersion compensation. The source is based on potassium titanyl arsenate crystals and exploits intra-pulse difference-frequency seed generation in the mid-IR. This source will be particularly suited for applications in strong-field physics, such as high order harmonic generation and photoelectron spectroscopy.

A new mixed-valent iron arsenate black crystal

Abstract Scorodite (FeAsO4·2H2O) is the most popular phase for arsenic (As) immobilization while the reductive dissolution of Fe(III) to Fe(II) will promote As release. In the present study, an equilibrium between Fe(III) and Fe(II) was achieved in scorodite preparation system by introducing certain alcohol (methanol, ethanol, isopropanol or tert-butanol), and thus a new mixed-valent iron arsenate black crystal formulated as Fe(II)5.2Fe(III)8.8(HAsO4)4(AsO4)8·H2O was prepared. In comparison with scorodite, the black crystal has higher As content (36.4%, mass fraction) and lower crystal water content (0.73%, mass fraction). Additionally, the leaching concentration of As can be lower than the threshold value (5 mg/L) regulated by identification standards for hazardous wastes of China (GB 5080.3–2007). Therefore, this new mixed-valent iron arsenate crystal could be classified as a non-hazardous and promising As-bearing phase in environmental applications.

Effects of anions on calcium arsenate crystalline structure and arsenic stability

Based on the crystallization reaction between calcium and arsenate, three anions, namely, chloride (Cl−), sulfate (SO42−), and carbonate (CO32−), were introduced during the formation of calcium arsenate in this study. The effects of these anions on arsenic stability and calcium arsenate crystalline properties were characterized using TCLP, XRF, XRD, SEM-EDS, TEM and particle size distribution (PSD). The results show that these anions significantly affect the calcium arsenate crystalline structure and arsenic-leachate concentration. The effect of chloride on arsenic stabilization was mainly a result of the formation and growth of calcium arsenate apatite (Ca5(AsO4)3OH and Ca5(AsO4)3Cl) crystal. Sulfate is propitious to improve the formation of Ca4(OH)2(AsO4)2·4H2O crystals and enhance their stability effectively under corresponding sulfate concentration treatments. A small amount of carbonate is beneficial to the formation and growth of Ca4(OH)2(AsO4)2·4H2O crystals. However, when the CO32– concentration was higher than 0.5 mol/L, Ca-As compounds were not precipitated. Instead, CaCO3 and Na3Ca(CO3)2·5H2O were generated successively, inhibiting calcium-arsenate crystallization and thus releasing more arsenic into aqueous solution. The trends of grain size are opposite to that of arsenic-leachate concentration, indicating that larger calcium arsenate crystals are more stable in the TCLP test. The internal structure of different Ca-As compounds can be changed and transformed by adding the three anions within a certain range. In summary, the results of this paper provide some meaningful information for the treatment of arsenic-containing wastewater or arsenic-bearing sludges using lime precipitation.

A compact, self-compression-based sub-3 optical cycle source in the spectral range

We report on the experimental realization of a compact, Ti:sapphire laser-pumped mid-infrared light source, which delivers sub-3 optical cycle pulses in the spectral range. The light source employs difference frequency generation in potassium titanyl arsenate crystal by mixing the signal and idler waves from a commercial near-infrared optical parametric amplifier and subsequent optical parametric amplification in LiIO3 crystal. The amplified sub-100 fs mid-infrared pulses are self-compressed down to sub-3 optical cycles by nonlinear propagation in few mm thick YAG, CaF2 and BaF2 crystals featuring anomalous group velocity dispersion in that spectral range. The self-compression is performed without the onset of self-focusing effects, hence maintaining a homogenous beam profile with energy throughput efficiency of above 90%, yielding the self-compressed pulses with sub- energy. Even larger self-compression factors (down to sub-2 optical cycles) were achieved in the filamentation regime, simultaneously producing an ultrabroadband supercontinuum, extending from the visible to the mid-infrared.

Theoretical Study of Ferroelectric, Dielectric and Loss Tangent Properties of Lead Hydrogen Arsenate Crystal

Theoretical Study of Ferroelectric, Dielectric and Loss Tangent Properties of Lead Hydrogen Arsenate Crystal

Injection-seeded tunable mid-infrared pulses generated by difference frequency mixing

We report on the generation of nanosecond mid-infrared pulses having frequency tunability, a narrow linewidth, and a high pulse energy. These pulses are obtained by frequency mixing between injection-seeded near-infrared pulses in potassium titanyl arsenate crystals. A continuous-wave external cavity laser diode or a Ti:sapphire ring laser is used as a tunable seeding source for the near-infrared pulses. The typical energy of the generated mid-infrared pulses is in the range of 0.4–1 mJ/pulse. The tuning wavelength ranges from 3142 to 4806 nm. A narrow linewidth of 1.4 GHz and good frequency reproducibility of the mid-infrared pulses are confirmed by observing a rovibrational absorption line of gaseous carbon monoxide at 4587 nm.

Effect of ultrasound on sodium arsenate induction time and crystallization property during solution crystallization processes

The effect of ultrasound vibrations on the cooling crystallization of sodium arsenate in supersaturated solutions was investigated. In particular, the effects of ultrasound vibrations on induction time and crystal size distribution were studied using a laser-based apparatus with relative supersaturation ranging from 1.3 to 1.8. The results show that ultrasound vibrations have a significant effect on reducing induction time and crystal size distribution. The application of ultrasound vibrations to the system resulted in a small change in surface tension; however, the induction time and crystal size significantly decreased. The mean size of sodium arsenate crystals decreased from 398.87 ± 3.27 to 168.68 ± 2.07 μm, as the ultrasound power increases from 26 to 130 W. Ultrasound vibrations significantly reduced the induction time in a highly supersaturated solution compared to that in a low supersaturated solution.

Molybdenum arsenate crystal: A highly efficient and recyclable catalyst for hydrolysis of ethylene carbonate

A simple one-step hydrothermal reaction was employed to synthesize the molybdenum arsenate crystallite catalyst, [{Cu(imi)2}3As3Mo3O15]·H2O (1) (imi=imidazole). The catalyst was characterized using X-ray crystallographic analyses, FT-IR, TGA, XRD, ICP-AES, NH3-TPD and BET techniques. Moreover, we performed evaluation on its catalytic activity towards the hydrolysis of ethylene carbonate to produce ethylene glycol. Interestingly, the conversion of this reaction reaches 96.5% and the selectivity is close to 100% at optimum conditions. No polyoxometalate leaching or framework decomposition was observed and the catalyst can be recovered and reused with slight loss of reactivity under identical reaction conditions.

Microscale Investigation of Arsenic Distribution and Species in Cement Product from Cement Kiln Coprocessing Wastes

To improve the understanding of the immobilization mechanism and the leaching risk of Arsenic (As) in the cement product from coprocessing wastes using cement kiln, distribution and species of As in cement product were determined by microscale investigation methods, including electron probe microanalysis (EPMA) and X-ray absorption spectroscopy. In this study, sodium arsenate crystals (Na3AsO412H2O) were mixed with cement production raw materials and calcined to produce cement clinker. Then, clinker was mixed water to prepare cement paste. EPMA results showed that As was generally distributed throughout the cement paste. As content in calcium silicate hydrates gel (C-S-H) was in low level, but higher than that in other cement mineral phases. This means that most of As is expected to form some compounds that disperse on the surfaces of cement mineral phases. Linear combination fitting (LCF) of the X-ray absorption near edge structure spectra revealed that As in the cement paste was predominantly As(V) and mainly existed as Mg3(AsO4)2, Ca3(AsO4)2, and Na2HAsO4.

Band Structure and Optical Characteristics of TDA Crystals

The electronic band structure and related electric and optical properties of the Tris(hydroxymethyl)aminomethane(Dihydrogen)Arsenate crystal (TDA) have been studied within the density functional theory using the ab-initio codes CASTEP, CRYSTAL and ABINIT. On the basis of the dielectric functions obtained ϵ1i (ω) (i = x, y, z), the phase matching angles for second harmonic generation have been calculated, which indicate possibility of this effect in TDA in the photon energy range 0.5–0.75 eV. The dependence of electrical polarization on the crystal unit cell volume has been calculated and the results obtained are discussed in connection with pyroelectric effect in TDA.

Efficient parametric light generators with intracavity pumping by the radiation of a garnet laser with a passive shutter

The characteristics of parametric light generators with intracavity pumping by the radiation of a garnet laser with a passive shutter have been experimentally investigated. The conversion efficiency of laser radiation with a wavelength of λp=1.064μm strongly depends on the characteristics of the phototropic shutter. When a radiation-colored LiF crystal with initial transmittance T0=0.25 is used in a parametric generator based on a potassium titanyl phosphate crystal at a wavelength of λs=1.91μm, a radiation energy of up to 10 mJ and a quantum efficiency of radiation conversion of Hq≈0.6 are achieved. When a YAG:Cr4+ shutter with T0=0.5 was used, the maximum radiation energy of the parametric generator was 5 mJ, while the conversion efficiency was Hq≈0.3–0.4. In a parametric generator based on potassium titanyl arsenate crystal with λs=1.55μm, the radiation energies corresponding to these shutters were about 7.5 and 5 mJ, while Hq≈0.4–0.6 and 0.25–0.4, respectively.

Dielectric properties of betaine arsenate crystal near the phase transition

Dielectric measurements for single crystal of betaine arsenate ( CH 3 ) 3 NCH 2 COO · H 3 AsO 4 connected with the ferroelectric phase transition at 119 K were performed. The temperature dependence of electric permittivity was measured at dc electric fields up to 700 kV/m. The results show significant suppression of the dielectric constant by the application of dc field. Deviation from the classical behavior was observed. The electric permittivity was also measured in the paraelectric phase at constant temperature as a function of electric field intensity up to 700 kV/m. The electric permittivity might be well described by the classical relation with additional term including contribution to permittivity coming from clusters. The fit parameters indicate that the polar-clusters carries polarization P 0 = 0.7 – 4 . 910 - 3 cm 2 with the clusters size of L = 12 –20 nm.

Near infrared optical parametric oscillators

Abstract Optical parametric oscillators are becoming important sources of tunable coherent radiation in the near infrared spectral region. This paper summarizes some of the basic concepts of infrared optical parametric oscillators and presents the results of calculated performance parameters of devices based on arsenate crystals.

Growth, Second Harmonic and Sum Frequency Generation Operations of Potassium Titanyl Arsenate Crystal

Potassium titanyl arsenate (KTiOAsO4, KTA) crystals have been grown with flux method. The infrared absorbing edge of KTA crystal is about 5.3 μm. The electric and other properties of KTA were measured. According to the x-ray orientating, KTA crystal samples were prepared to carry on second harmonic generation (SHG) and sum frequency generation (SFG) experiments. The SHG efficiency of KTA for Nd: YAG is 1.7 times larger than that of KTA. At 20°C, the shortest SHG wavelength is 0.5174 μm, and the shortest SFG wavelength is 0.4994 μm.

Ultrasonic study of deuterated betaine arsenate crystals

Abstract The temperature dependences of velocity and attenuation of longitudinal acoustic waves in deuterated betaine arsenate crystals in the vicinity of low-temperature crystals in the vicinity of low-temperature phase transitions have been measured. Some coefficients in the thermodynamic potential and the relaxation time of the order parameter have been determined.

Rotating-frame NMR relaxation in the dipolar spin glass Rb 1−x(NH 4) xH 2AsO 4

Low-temperature T1ϱ relaxation measurements of a proton pseudo-spin glass system in mixed rubidium-ammonium dihydrogen arsenate crystals are presented. The experimentally observed features of the magnetization decay in the rotating frame are explained with a model which incorporates rotational tunneling of the ammonium ions.