Is the Coagulation-Filtration Process with Fe(III) Efficient for As(III) Removal from Groundwaters?

The coagulation–filtration process using Fe(III) salts is the most frequently practiced technology for As(V) removal in full scale water treatment plants. The co-existing As(III) is usually oxidized to As(V) prior to removal. Nonetheless, research studies applying high As(III) initial concentrations showed significant As(III) removal capacities, however, the efficiency of the process for initial As(III) concentrations commonly encountered in drinking water, i.e., 10-100 μg/L is not sufficiently investigated. The experimental results of this study indicated that the coagulation–filtration process using Fe(III) can safely meet the drinking water regulation limit of 10 μg/L, only when the initial As(III) concentration is < 25 μg/L and the Fe(III) dose ≥ 5 mg/L, for experiments performed with NSF challenge water. The limitations for efficient As(III) removal are attributed to the fact that As(III), under circumneutral pH values is mostly present with the uncharged H₃AsO₃ form, which is not efficiently adsorbed onto iron oxy hydroxides (FeOOH), the product of Fe(III) hydrolysis. Adsorption isotherms data were best fitted to BET model, indicating multi-layer adsorption and low affinity of As(III) for Fe(III) hydroxides.     

Di-μ-hydroxy macrocyclic ytterbium(III) complex

The mononuclear [YbracL]Cl₃·2H₂O and dinuclear [Yb₂(OH)₂Cl₂(racL)₂]Cl₂·4CH₃OH·2H₂O complexes of the macrocyclic ligand L derived from trans-1,2-diaminocyclohexane and 2,6-diformylpyridine have been obtained. The formation of the dinuclear species upon addition of hydroxide to the [YbracL]Cl₃·2H₂O or the enantiopure [YbrrrrL(NO₃)₂](NO₃) has been followed using ¹H NMR spectroscopy. The X-ray crystal structure of [Yb₂(OH)₂Cl₂(racL)₂]Cl₂·4CH₃OH·2H₂O complex has been determined. The complex is a dimer consisting of two macrocyclic units. The Yb(III) ion is coordinated by six nitrogen atoms of the macrocyclic ligand, two bridging OH groups and chloride anions. The chiral macrocycle L in this complex exhibits twist-bent conformation of approximate C₂ symmetry.     

Selective Eu(III) Electro‐Reduction and Subsequent Separation of Eu(II) from Rare Earths(III) via HDEHP Impregnated Resin

Abstract

Eu(III) was selectively reduced to Eu(II) at three‐dimensional glassy carbon cathode in 0.01 mol · dm^?3 hydrochloric acid medium. Eu(III) reduction took place after all the dissolved oxygen was reduced and then proceeded steadily. Separation of Eu(II) from trivalent rare earths (La, Ce, Sm, Gd, Er, Yb) was carried out using a novel impregnated resin based on bis(2‐ethylhexy1)phosphoric acid. Eu(II) showed much lower affinity towards the resin than the trivalent rare earths and broke through the column readily. Eu of purity higher than 99.8% was yielded. The back‐oxidation of Eu(II) was observed during the sorption and Eu(III) was absorbed onto the resin. Adsorbed light and middle rare earths could be stripped from the loaded resin by 3M hydrochloric acid. Stripping of heavy rare earths (Er, Yb) was problematic.     

Solid‐Liquid Extraction of Lanthanum(III), Europium(III), and Lutetium(III) by Acyl‐Hydroxypyrazoles Entrapped in Mesostructured Silica

Abstract

The solid‐liquid extraction of lanthanum(III), europium(III), and lutetium(III) by mesostructured silicas doped with 1‐phenyl‐3‐methyl‐4‐stearoyl‐5‐pyrazolone (HPMSP, bearing one chelating site) or with 1,12‐bis(1′‐phenyl‐3′‐methyl‐5′‐hydroxy‐4′‐pyrazolyl)‐dodecane‐1,12‐dione (HL‐10‐LH, bearing two chelating sites) has been studied and compared to the analogous solvent and micellar extractions in terms of the stoichiometry of the extracted complex and of the extraction efficiency. The solid‐liquid extraction order in the lanthanoid series is La<Eu<Lu; it is the usual liquid‐liquid extraction order obtained with acidic extractants. A theoretical model is used to determine the stoichiometries of the extracted complexes and the extraction yield is measured as a function of the pH, of the extractant/metal ratio (S/M) and of the volume ratio of the two phases (φ). For HPMSP, the extracted complexes involve three ligand molecules for one metal. For HL‐10‐LH, the complex stoichiometries are found to be either Ln(L‐10‐L)(L‐10‐LH) (Ln=La, Eu) or Lu₂(L‐10‐L)₃ for S/M=25, or Eu₂(L‐10‐L)₃ for S/M=5. For the first time, the synergistic solid‐liquid extraction is studied after a successful attempt at simultaneously immobilizing both extractants HL‐10‐LH and 2,4,6‐tri(2‐pyridyl)‐1,3,5‐triazine, “TPTZ”, into silica; the complex extracted in this case differs from the one obtained in solvent extraction.     

人工神经网络光度法同时测定水中Fe(II)、Fe(III)

应用径向基函数人工神经网络(RBF)和误差反向传播神经网络(BP),采用磺基水杨酸-邻菲罗啉双显色剂光度法同时分析了水中Fe(II)和Fe(III)。实验证明,RBF算法在所需神经元个数、训练时间、预测准确度等方面均明显优于BP网络算法。该技术和光度法结合有望成为多组分分析的有效选择方法之一。     

Synergistic Extraction of Am(III) and Eu(III) by Tris(2‐pyridylmethyl)Amine with Various Anions in 1,2‐Dichloroethane

The extraction equilibria of Am(III) and Eu(III) by using a tripodal ligand, tris(2‐pyridylmethyl)amine (tpa), with various lipophilic anions have been investigated. The extractability of both Am(III) and Eu(III) was increased by the combination of tpa and counteranions due to a synergistic effect. The separation factors between Am(III) and Eu(III) were also increased from 7.6 to 49 by the combination of counteranions and organic solvents. The extraction equilibria of Am(III) and Eu(III) with tpa in 1,2‐dichloroethane were determined by slope analysis. It was found that three anions and one molecule of the ligand coordinated to Am(III) and Eu(III) was extracted regardless of the anions.     

Lanthanide(III) complexes of a highly efficient actinide(III) extracting agent – 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine

The addition of lanthanide(III) nitrates (Sm–Lu) to the actinide(III) extracting agent – 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (L¹) in a 1:1 ratio results in the crystallisation of complexes containing [Ln(L¹)₃]³⁺ moieties and a variety of anions.     

美国化学文摘(CA)Vol.106(1987)——粘合剂题录(III)

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VISCOMETRIC MEASUREMENT OF CHROMIUM(III)-POLYACRYLAMIDE GELS†

Gelled polymers are being used increasingly to modify the movement of injected fluids in secondary and enhaced oil recovery processes. A common gelation process involves the reduction of Cr(VI) to Cr(III) in the presence of polyacrylamide. The Cr(III) reacts or interacts with the polymer to form a gel network. Although correlations of gelation time with principal process variables have been obtained, viscometric data have not been reported during or after gelation. These data are needed for fluid flow calculations in surface equipment and estimation of flow behaviour in reservoir rocks.

A Weissenberg Rheogoniometer, with cone and plate geometry, was used to obtain viscometric data for the gelation of polyacrylamide and chromium (III). Solutions consisting of polyacrylamide polymer, sodium dichromate-dihydrate and sodium bisulfite were gelled under a steady shear field at constant temperature. The shear stress versus time profile for the galation process was interpreted to define a gelation time and to determine the apparent viscosity of the gelled fluid. The gelation time decreased as the applied shear rate increased up to about 14.25 sec^?1 and was affected by shear rate history. Viscometric properties of the gelled solutions were determined. Apparent viscosity of the gelled solutions decreased as the shear rate under which they were formed increased.

Post gelation studies indicated that gels exhibited a residual stress at zero shear rate and behaved as Bingham plastics under steady shear. Gels formed at low shear rates were more viscous than gels formed at high shear rates. However, the structure of these gels was susceptible to shear degradation.     

Physicochemical Aspects on Fluoride Adsorption for Removal from Water by Synthetic Hydrous Iron(III) – Chromium(III) Mixed Oxide

Fluoride removal with varying different parameters at 303 ± 1.6 K and pH 6.5 ± 0.2 was investigated by hydrous iron(III)-chromium(III) bimetal oxide. The kinetic and equilibrium data fitted with the pseudo-second order and Langmuir isotherm equations very well (R² = 0.99?1.00), respectively. The Langmuir capacity (θ) and free energy (E_DR) of adsorption evaluated were 16.34 (±0.50) mg·g^?1 and 15.81 kJ·mol^?1, respectively. The estimated thermodynamic parameters viz. ΔH⁰, ΔG⁰, and ΔS⁰ indicated that the reaction was endothermic but spontaneous for entropy increase. The small-scale column filtration of high fluoride (C₀ = 7.37 mg·L^?1) water gave encouraging results.     

活性炭负载Fe(III)吸附剂去除饮用水中的As(V)

利用活性炭负载水合铁氧化物制备了复合吸附剂,并用于饮用水中As(V)的去除. 研究了活性炭种类、粒度、溶液pH值、Fe(III)盐浓度和干扰离子等对As(V)去除的影响. 结果表明,煤质活性炭作为基质负载水合铁氧化物比椰壳炭和果壳炭具有更好的除砷效果. 随着炭粒度降低,除砷效率显著增加. 在pH 3~9范围内,活性炭负载水合铁氧化物可有效吸附As(V). F-, Cl-, SO42-的加入对As(V)的去除效率基本无影响,而SiO32-和PO43-则明显抑制As(V)的去除. Langmuir模型比Freundlich模型能更好地描述复合吸附剂对As(V)的吸附平衡. 动力学研究表明,As(V)吸附反应可用二级速率方程描述.     

Binuclear rhodium(III) and iridium(III) monoselenocarboxylates: Synthesis,spectroscopy and structure of an ortho-metallated iridium complex featuring an IrCCC(μ-Se) chelate ring

Monoselenocarboxylate–bridged binuclear complexes of Rh^III and Ir^III, [(Cp1MCl)₂(μ-SeCOAr)₂] (1) (M = Rh or Ir; Cp1 = pentamethylcyclopentadienyl; Ar = Ph, C₆H₄Me–4), have been isolated either by the reaction between [Cp1₂M₂(μ-Cl)₂Cl₂] with KSeCOAr in acetonitrile or by treatment of [Cp1MCl(solvent)₂][PF₆] with KSeCOAr in acetone. The novel binuclear complexes, [Cp1IrCl(μ-SeCOAr)(κ²-SeCOC₆H₃R–)IrCp1] (2) (R = H or Me-4) with ortho-metallation at one of the iridium centres have been isolated following the use of excess AgPF₆. The single crystal structure of [Cp1IrCl(μ-SeCOC₆H₅)(κ²-SeCOC₆H₄–)IrCp1] (2a) exhibits two phenylcarboselenolate moieties situated in syn fashion with respect to the “Ir₂Se₂” plane, one of which leans towards the metal centre in order to undergo ortho-metallation after iridium–chlorine bond dissociation.     

From tetranuclear cluster with single-molecule-magnet behavior to 1D alternating spin-canting chain in a Fe(III)–Mn(III) bimetallic system

A tetranuclear cluster and an alternating zigzag chain were synthesized via rational assembly of the same cyanometalate building blocks with different Mn(III) Schiff bases possessing varying proportions of sterically hindered groups causing steric hindrances. The tetranuclear cluster [(Tp*)Fe(CN)₃]₂[Mn(salen)]₂·H₂O [1; [(Tp*)Fe(CN)₃]⁻ [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl) borate], salen = N,N′-ethylenebis(salicylideneiminato) dianion] was formed with Schiff bases possessing smaller steric hindrances, whereas the one-dimensional alternating zigzag chain {[(Tp*)Fe(CN)₃Mn(salcyen)]·2CH₃OH·H₂O}_n [2; salcyen = N,N′-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion] was formed with Schiff bases possessing larger steric hindrances. Magnetic measurements revealed that 1 exhibits single-molecule-magnet behavior with dominant ferromagnetic interactions, whereas 2 exhibits spin-canting behavior with dominant antiferromagnetic interactions.     

用MnO2 氧化废水中As(III)为As(V)的特性

废水中As(III)的减少速率在开始半小时内较快,半小时后速率较慢,慢反应阶段遵循一级反应动力学方程: ln[As(III)]=-kt+c. MnO2对As(III)的氧化能力随pH的升高而呈上升趋势.温度的升高有利于MnO2对As(III)的氧化.在MnO2氧化As(III)过程中,As(III)扩散到MnO2表面或As(V)从表面扩散到溶液中的反应是整个过程的限速反应.     

Cinetique electrochimique du couple cobalt(III)—cobalt(II) en milieu acide phosphorique concentre

The electrochemical behaviour of the cobalt(III)—cobalt(II) couple in 96.5% and 85 wt% H₃PO₄ have been studied at a stationary gold electrode by using chronopotentiometry and triangular voltamperometry. The results have shown that the Co(III)—Co(II) system is reversible and the electrode reaction involves a single electron. The Co(II) ions' diffusion coefficient in the two phosphoric acid solutions was determined as 4.3 × 10⁻⁸ cm².s⁻ in 96.5% wt % H₃PO₄ and 1.2 × 10⁻⁷ cm².s⁻¹ in 85 wt % H₃PO₄. The stabillity of the Co(III) ion in 96.5 wt % H₃PO₄ media was also investigated.     

基于Fe(III) 和邻苯二胺显色反应快速检测硫化物

本研究系统地比较了不同金属离子对邻苯二胺（OPD）的氧化能力，基于Fe3+ 能直接氧化邻苯二胺(OPD) 产生黄色发荧光的产物，发展了Fe3+-OPD显色体系。硫化物的加入促使Fe3+-OPD显色液的颜色，吸光度和荧光成比例下降，而其他还原性物质及硫醇对硫化物的检测无干扰，基于此发展了选择性检测硫化物的比色法。实验结果表明，向OPD溶液中加入Fe3+，吸光度和荧光随着Fe3+浓度上升成比例增加，溶液从无色变为黄色，在50-1000 μmol/L范围内具有良好的线性关系，检测限为10μmol/L。向Fe3+-OPD显色液加入硫化物，在硫化物浓度1～300 μmol/L 范围内，吸光度和荧光强度成比例下降，溶液的黄色褪去，检测限为0.1μmol/L。在此基础上，将Fe3+-OPD显色体系结合纸芯片，所构建的纸基比色体系蓝色分析色道值即B值与硫化物的浓度在20～150μmol/L浓度范围内呈现良好的线性关系，检测限为 2 μmol/L，可用于定量加标自来水和血清中硫化物含量。