A comparative study on Pb2+, Zn2+ and Cd2+ sorption onto zirconium phosphate supported by a cation exchanger

In the present study, a novel hybrid sorbent ZrP-001 was prepared by loading zirconium phosphate (ZrP) onto a strongly acidic cation exchanger D-001. Sorption behavior of Pb(2+), Zn(2+), and Cd(2+) onto ZrP-001 was experimentally examined by comparing with the host exchanger D-001. ZrP-001 was characterized by scanning electron micrograph (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), pH-titration and pore size distribution analysis. Sorption of the heavy metals onto ZrP-001 was found to be pH-dependent due to the ion exchange mechanism. Compared to D-001, a smaller pore size of ZrP-001 due to the ZrP dispersion consequently resulted in a lower sorption rate. Competitive effect of Ca(2+) on sorption of heavy metals onto ZrP-001 and D-001 was compared to elucidate sorption preference of the hybrid sorbent towards heavy metals. More favorable sorption of ZrP-001 than D-001 was observed for all the three metals and their sorption preference onto ZrP-001 followed the order Pb(2+)>Zn(2+) approximately Cd(2+). Fixed-bed sorption results and its efficient regeneration property further demonstrated that ZrP-001 is a potential candidate for removing heavy metals from contaminated water.     

Diffusion mechanism of Co2+, Cu2+, Cd2+, Cs+, and Pb2+ ions in the particles of polyaniline silicotitanate

ABSTRACT

The kinetic behavior of Co²⁺, Cu²⁺, Cd²⁺, Cs⁺, and Pb²⁺ in the H-form of polyaniline silicotitanate composite as cation exchanger was studied as a function of particle size, concentration of the exchanging ions, reaction temperature, and drying temperature. The exchange rate was controlled by particle diffusion mechanism as a limited batch technique and is confirmed from the straight lines of B versus 1/r² plots. The values of diffusion coefficients, activation energy, and entropy of activation were calculated and their significance was discussed. The data obtained have been compared with that reported for other organic and inorganic exchangers.     

Photo- and thermoluminescence of BaGa2S4:Eu2+ and BaGa2S4:Eu2+,Ce3+ crystals

Data are presented on the photo- and thermoluminescence of polycrystalline BaGa₂S₄:Eu²⁺ and BaGa₂S₄:Eu²⁺, Ce³⁺ at temperatures from 77 to 300 K. The broad photoluminescence band at 505 nm in BaGa₂S₄:Eu²⁺ is shown to be due to the 4f ⁶5d → 4f ⁷ transition. The broad emission bands at 460 and 510 nm in BaGa₂S₄:Ce³⁺ arise from the 5D (² D _3/2) → 4f ²(² F _5/2) and 5D (² D _3/2) → 4f ²(² F _7/2) transitions. Codoping of BaGa₂S₄ with Eu²⁺ and Ce³⁺ increases the luminescence efficiency owing to energy transfer from Ce³⁺ to Eu²⁺. The thermoluminescence data were used to evaluate the energies of the traps involved: 0.26, 0.31, 0.42, 0.57, and 0.64 eV in BaGa₂S₄:Eu²⁺ and 0.28, 0.32, 0.54, 0.61, and 0.65 eV in BaGa₂S₄:Eu²⁺, Ce³⁺. Original Russian Text ? A.N. Georgobiani, B.G. Tagiev, S.A. Abushov, O.B. Tagiev, Zheng Xu, Suling Zhao, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 2, pp. 151–155.     

Removal of Pb2+, Ag+, Cs+ and Sr2+ from aqueous solution by brewery's waste biomass

Heavy metal pollution is becoming a more and more serious environmental problem, posing threat to biota life. Biosorption is an alternative technology for the treatment of wastewater containing metal ions. In this paper, the removal of four metal ions, i.e., Pb2+, Ag+, Sr2+ and Cs+ by waste biomass of brewery was studied. The experimental results showed that metal uptake is a rapid process, which can be described by pseudosecond order kinetic model. The Langmuir adsorption isotherm was applied to correlate the equilibrium data and fitted quite well. The maximum biosorption capacities for four metal ions were 0.413 mmol Pb2+/g, 0.396 mmol Ag+/g, 0.091 mmol Sr2+/g and 0.076 mmol Cs+/g, respectively. The binding of metals was also discussed in term of several factors. The order of accumulated metal ions at equilibrium state on the molar basis was as follows: Pb2+>Ag+>Sr2+>Cs+, which positively correlated with their covalent index and electronegative and reversely correlated with dissociation constant.     

Studies on separation of Cs/Ba and Zn/Cu binary mixtures on zirconium antimonate as ion exchanger

Zirconium antimonate (ZrSb) ion exchanger was prepared. Distribution coefficients of metal ions on ZrSb ion exchanger in solutions of various acids (hydrochloric, nitric, acetic, citric, ascorbic) and salts (sodium chloride and sodium nitrate) were determined to evaluate the ion exchange behavior and selectivity to specific ions. ZrSb, as compared to other inorganic ion exchangers, showed increased thermal and chemical stability. ZrSb is an efficient and promising ion exchanger for preparation of ¹³⁷Cs/^137m Ba and ⁶²Zn/⁶²Cu radioisotope generators.     

Solubility of uranoarsenates MAsUO6·nH2O in water and aqueous HClO4 (M = H+, Li+, Na+, K+, Rb+, Cs+, NH 4 + )

The solubility of poorly soluble uranoarsenates MAsUO₆·H₂O in water and aqueous HClO₄ was determined. The solubility products and Gibbs energies of formation of these compounds were evaluated from the experimental data using the principles of equilibrium thermodynamics. The state of uranoarsenates in aqueous solutions in the range not studied experimentally was estimated.     

Removal of 60Co and 137Cs from simulated NPP bottom residues on the solid phase of K+, Ni2+, and Fe3+ ferrocyanides

The possibility of simultaneous removal of ⁶⁰Co and ¹³⁷Cs from simulated NPP bottom residues by coprecipitation with the solid phase of K, Fe, and Ni ferrocyanides was examined. In coprecipitation of ⁶⁰Co and ¹³⁷Cs with the KFe[Fe(CN)₆] solid phase, the degree of removal of the radionuclides from simulated bottom residue containing 300 g L^?1 NaNO₃ and 3.4 × 10^?5 M EDTA does not exceed 80% for ⁶⁰Co and 99% for ¹³⁷Cs. The scheme based on coprecipitation of the radionuclides with the solid phase of K⁺, Fe³⁺, and Ni²⁺ ferrocyanides, formed by successive addition of K₄[Fe(CN)₆], Fe(NO₃)₃, and Ni(NO₃)₂ to the solution, ensures efficient removal of ⁶⁰Co and ¹³⁷Cs from simulated bottom residue containing simultaneously up to 400 g·L^?1 NaNO₃ and 3.4 × 10^?5 M EDTA. The radionuclides are removed to more than 99%.     

腐植酸树脂对电镀废水中重金属离子的吸附

利用泥炭为原料制备出腐植酸树脂。在动态条件下 ,研究了腐植酸树脂对重金属离子Pb2 +、Cu2 +、Zn2 +、Ni2 +、Cr3+的吸附效果及条件。同时探讨了腐植酸树脂对Pb2 +、Cu2 +、Zn2 +、Ni2 +、Cr3+的吸附与解吸再生机理。含Pb2 +、Cu2 +、Zn2 +、Ni2 +、Cr3+的电镀废水经腐植酸树脂吸附后 ,废水中重金属离子的含量低于国家排放标准     

Synthesis and tunable luminescence of RbCaGd(PO4)2:Ce3+, Mn2+ phosphors

RbCaGd(PO₄)₂ doped with Ce³⁺, Mn²⁺ was synthesized by the sol-gel method. The crystal structure and crystallographic location of Ce³⁺ in RbCaGd(PO₄)₂ were identified by Rietveld refinement. Powder X-ray diffraction (XRD) revealed that the structure of RbCaGd(PO₄)₂:Ce³⁺ compounds is hexagonal structure which is similar to that of hexagonal LnPO₄ with the lattice constant of a = b = 7.005(57) Å, c = 6.352(05) Å, and V (cell volume) = 269.980 Å³. The photoluminescence behavior and emission mechanism were studied systematically by doping activators in the RbCaGd(PO₄)₂ host. The Mn²⁺ incorporated RbCaGd(PO₄)₂:Ce³⁺, Mn²⁺ compounds exhibited blue emission from the parity- and spin-allowed f-d transition of Ce³⁺ and orange-to-red emission from the forbidden ⁴T₁ → ⁶A₁ transition of Mn²⁺. The emission chromaticity coordinates of RbCaGd(PO₄)₂:0.10Ce³⁺, xMn²⁺ (x = 0.16, 0.25) are close to the white region due to an energy transfer process and the energy transfer mechanism from Ce³⁺ to Mn²⁺ in the RbCaGd(PO₄)₂ host was dominated by dipole-dipole interactions.     

Isosteric heats of n-hexane sorption in ion-exchanged NaX containing Co2+, Ni2+, Zn2+, and Cd2+

Sorption—desorption isotherms of n-hexane have been measured at 288 and 298 K in zeolites M_xNa_87-2xX (M = Co, Ni, Zn, Cd) and the corresponding isosteric heats have been obtained. The effect of cations on isosteric heats is highly pronounced at low cowerage, being different for each particular cation. An attempt is made to explain the large differences in those heats in terms of cationic size, charge, electronic configuration, and location in the lattice.     

Ni、Co、Mn、Cu掺杂对K4 Nb6 O17光催化活性的影响

通过高温固相反应合成了铌酸盐K4Nb6O17及Ni2 、Co3 、Mn4 、Cu2 (5.0%mol)掺杂的K4Nb6O17并采用X射线衍射、紫外可见漫反射光谱、扫描电镜、比表面积分析等对其进行了结构和形貌表征.在甲醇为电子给体、Pt为助催化剂的情况下,研究了K4Nb6O17及Ni2 、Co3 、Mn4 、Cu2 掺杂的K4Nb6O17作为催化剂在约400nm紫外辐射下分解水产氢的光催化活性,并讨论了引起催化剂活性差异的原因.     

改性海泡石对电镀废水中Pb2+、Cu2+、Cd2+的吸附

用盐酸溶液对海泡石处理后在 4 5 0℃下灼烧 ,制备出改性海泡石。在动态条件下 ,研究了改性海泡石对重金属离子Pb2 +、Cu2 +、Cd2 +的吸附效果及条件。探讨了改性海泡石对重金属离子Pb2 +、Cu2 +、Cd2 +的吸附机理。含Pb2 +、Cu2 +、Cd2 +的电镀废水经改性海泡石吸附后 ,重金属离子含量显著低于国家排放标准     

Host-sensitized phosphorescence of Mn4+, Pr3+,4+ and Nd3+ in MgAl2Si2O8

Mn⁴⁺ doped and Pr^3+,4+, Nd³⁺ co-doped MgAl₂Si₂O₈-based phosphors were first of all synthesized about 1300 °C. They were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray powder diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM). The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 610–715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the intrinsic d–d transitions of Mn⁴⁺.     

Thermal analysis of a diffusion bonded Er3+,Yb3+:glass/Co2+: MgAl2O4 microchip lasers

The analysis of thermal effects in a diffusion bonded Er³⁺,Yb³⁺:glass/Co²⁺:MgAl₂O₄ microchip laser is presented. The analysis is performed for both wavelengths at 940 nm and at 975 nm as well as for two different sides of pumping, glass side and saturable absorber side. The heat sink effect of Co²⁺:MgAl₂O₄, as well as the impact of the thermal expansion and induced stress on the diffusion bonding are emphasised. The best configurations for reducing the temperature peaks, the Von Mises stresses on the diffusion bonding, and the thermal lensing are determined.     

Synthesis and characterization of Zr4+, La3+ and Ce3+ doped mesoporous TiO2: evaluation of their photocatalytic activity

Sol-gel method was used to synthesize Zr(4+), La(3+) and Ce(3+) doped mesoporous TiO(2) materials with different weight percentage (0.5, 1.0, 2.0 and 3.0 wt%) using triblock copolymer as the structure directing template in ethanol/water medium. Characterization revealed the isomorphic substitution of Zr(4+) ion into the lattice of TiO(2), and surface binding nature of La(3+) and Ce(3+) ions on mesoporous TiO(2). Microscopic examination confirmed the surface adsorption of foreign ion which could alter the particle morphology. The size of the particles was less than 20 nm. Photocatalytic activity of metal ions doped mesoporous TiO(2) was evaluated using aqueous alachlor as a model pollutant. It was found that 1 wt% Ce(3+) doped mesoporous TiO(2) exhibited higher activity than pure and other metal ions doped mesoporous TiO(2). The change of oxidation state of Ce(3+) is suggested to be the cause for enhanced photocatalytic activity.     

Synthesis,characterization and ion exchange properties of zirconium(IV) tungstoiodophosphate,a new cation exchanger

Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L⁻¹ sodium tungstate, potassium iodate and 1 mol L⁻¹ orthophosphoric acid to aqueous solution of 0·1 mol L⁻¹ zirconium(IV) oxychloride. Its ion exchange capacity for Na⁺ and K⁺ was found to be 2·20 and 2·35 meq g⁻¹ dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger at different temperatures has been studied. The analytical importance of the material has been established by quantitative separation of Pb²⁺ from other metal ions.     

Synthesis of Ce4+ ions doped ZnO electrode as a sensor for hydrogen peroxide

Ce⁴⁺ ions doped ZnO nanoparticles were synthesized by the simple chemical precipitation method with different levels of cerium. The synthesized products were analyzed for X-ray diffraction and photoluminescence measurements. The morphology of the optimum level of Ce⁴⁺ doped ZnO was studied by high resolution transmission electron microscopy analysis. To ascertain the sensor activity of Ce⁴⁺ doped ZnO, the electrocatalytic response to the reduction of H₂O₂ was studied with ZnO and ZnO: Ce⁴⁺ electrodes. Fabricated ZnO: Ce⁴⁺ sensor displays excellent performance towards the detection of H₂O₂ than bare ZnO.     

Effect of annealing on the spectroscopy performance of YVO4:Ce3+ single crystals

In this study, 1.0 at.% YVO₄:Ce³⁺ single crystals were grown in the protective atmosphere by using the Czochralski method. The crystals were annealed in Ar and H₂ atmospheres at different temperatures. The absorption and fluorescence spectra of the samples before and after annealing were measured. Results showed that the luminescent efficiency of the crystals was significantly enhanced after annealing in H₂ than after annealing in Ar. This phenomenon can be attributed to the existence of some Ce⁴⁺ ions in the crystal lattice. These Ce⁴⁺ ions can be effectively reduced to Ce³⁺ via annealing in H₂. With a fixed annealing time in H₂, the luminescent intensity significantly increased with increasing annealing temperature. The possibility of the crystal as white light material was also discussed according to the luminescence properties.     

Adsorptive features of polyacrylamide-apatite composite for Pb2+, UO(2)2+ and Th4+

Micro-composite of polyacrylamide (PAA) and apatite (Apt) was prepared by direct polymerization of acrylamide in a suspension of Apt and characterized by means of FT-IR, XRD, SEM and BET analysis. The adsorptive features of PAA-Apt and Apt were then investigated for Pb(2+), UO(2)(2+) and Th(4+) in view of dependency on ion concentration, temperature, kinetics, ion selectivity and reusability. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. Apt in PAA-Apt had higher adsorption capacity (0.81, 1.27 and 0.69 mol kg(-1)) than bare Apt (0.28, 0.41 and 1.33 mol kg(-1)) for Pb(2+) and Th(4+), but not for UO(2)(2+). The affinity to PAA-Apt increased for Pb(2+) and UO(2)(2+) but not changed for Th(4+). The values of enthalpy and entropy changed were positive for all ions for both Apt and PAA-Apt. Free enthalpy change was DeltaG<0. Well compatibility of adsorption kinetics to the pseudo-second-order model predicated that the rate-controlling step was a chemical sorption. This was consistent with the free energy values derived from DR model. The reusability tests for Pb(2+) for five uses proved that the composite was reusable to provide a mean adsorption of 53.2+/-0.7% from 4x10(-3)M Pb(2+) solution and complete recovery of the adsorbed ion was possible (98+/-1%). The results of this investigation suggested that the use of Apt in the micro-composite form with PAA significantly enhanced the adsorptive features of Apt.     

Comparison of laser generation in thermally bonded and unbonded Er3+,Yb3+:glass/Co2+:MgAl2O4 microchip lasers

Pulse laser generation in several Er³⁺,Yb³⁺:glasses thermally bonded with Co²⁺:MgAl₂O₄ was achieved. Peak power in the range of 1.83–7.68 kW with pulse duration between 2.9 and 4.2 ns and energy up to 24 μJ was obtained. The output characteristics for different transmissions of the output couplers were investigated. To show the improvements gained by the thermal bonding procedure, a comparison of thermally bonded and unbonded samples was done in terms of generation efficiency, peak power, beam quality, generated spectra and pulse to pulse jitter.