SDS改性沸石对碱性品红的吸附性能研究

通过静态实验探讨了表面活性剂十二烷基硫酸钠（SDS）改性沸石吸附碱性品红的影响因素。实验结果表明在投入量为8 g/L、吸附时间为45 min、p H值为6、温度为25℃时,对初始质量浓度100 mg/L碱性品红溶液的去除率可达到96.16%,吸附量为12.02 mg/g;SDS改性沸石吸附碱性品红的吸附性能符合Langmuir型吸附等温线和一级反应动力学模型的特征;热力学分析结果表明,吸附符合自发吸热过程。     

Adsorption profile of preheated Cr(III)-SCN complexes on polyurethane foam

The accumulation of preheated chromium(III)-thiocyanate complexes onto polyurethane foam (PUF) has been studied. The maximum sorption of Cr(III) (7.01^.10^-5M) is occurred at pH 2 from 1.2M thiocyanate solution in 10 minute agitation time using 7.25 mg/ml PUF. The sorption data have been investigated by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The Freundlich parameters 1/n = 0.31 and of K _F = 9.7^.10^-4 mol^.g^-1, Langmuir constants M = 7.03^.10^-5 mol^.g^-1 and of b = 1.5^.10⁵ l^.mol^-1 and of D-R constants, C _m = 1.91^.10^-4 mol^.g^-1, affinity coefficient b = -0.0023 mol^2.kJ^-2 and sorption energy E = 14.7 kJ^.mol^-1 have been evaluated. Thermodynamic parameters of enthalpy, entropy and Gibbs free energy suggest the endothermic and spontaneous adsorption of Cr(III)-SCN complex onto PUF at higher temperature. The influence of common anions and cations on the accumulation of chromium-thiocyanate on PUF and possible sorption mechanism of [Cr(SCN)₄]^- species on PUF is discussed.     

Adsorption Studies of Cr(III) & Cr(VI) on Lead Sulphide,Copper Sulphide & Zinc Sulphide-Determination Cr(III) in the Presence of Cr(VI)

Abstract

The adsorption studies of Cr(VI) in presence of Cr(III) on the sulphide of Lead, Zinc and Copper has been studied. It has been found that in case of lead sulphide 100% adsorption of Cr(VI) took place at pH 4.0 and of Cr(III) at pH 7.0. While in case of zinc sulphide the 100% adsorption of Cr(VI) took place at pH 4.5 and of Cr(III) at pH 6.5. In case of copper sulphide 100% adsorption of Cr(VI) took place at pH 5.0 and of Cr(III) at pH 7.0. This difference in adsorption at different pH values forms the basis for the determination of these ions. The method is accurate.     

Optimization of the Conditions for the Cr (III) Adsorption on Activated Carbon

In order to understand the patterns of the adsorption equilibrium of Cr (III) on activated carbon, the adsorption process was studied by two different ways: classical batch experiments on commercial Norit and Merck activated carbons and their oxidized forms in a wide range of pHs; and extended time-based tests at the same pH values on the same adsorbents. This approach allowed us to understand the role of texture, chemical carbon surface functionality and experimental conditions (initial pH of the solution, contact time and adsorbate/adsorbent ratio) on the effectiveness of Cr (III) removal. The adsorption process of Cr (III) at (24 ± 1^∘C) on Merck and Norit activated carbons and their oxidized forms were studied at pH values between 1.5 and 5 (either adjusted or buffered). Chromium concentration was fixed at 200 ppm. The carbon loading ranged from 1.2 to 20 g/l. The carbon/Cr (III) solution contact time was varied from 0.5–1 month to 5 months, to ensure that the saturation of the carbon level was reached. According to the data obtained, the presence of carboxylic groups on carbon surface seems to enhance Cr (III) uptake at initial pH of the solution in the range between 2 and 4. Depending on the nature of the adsorbent surface chemistry, the contact time to reach equilibrium may range from 3 to 5 months. There is an optimum carbon loading which limits the Cr (III) uptake/removal at given pH value. In order to understand the adsorption process, an ion exchange, surface complex and surface precipitation were considered. This paper was presented in the 5th Brazilian Meeting on Adsorption, held at Natal, Brazil, 18-21 July, 2004.     

Adsorption of Cr(III) from wastewater by wine processing waste sludge

Wine processing waste sludge has been shown to be an effective adsorbent for the adsorption of Cr(III) from aqueous solution. The sludge has been characterized by scanning electron microscopy (SEM) and energy dispersive X-rays (EDX). The effect of pH, initial concentration of Cr(III), sludge particle size, and temperature on the adsorption studied. The equilibrium data could be described well by the Langmuir and Freundlich isotherm equations. A separation factor was used to judge the favorable adsorption. The calculated thermodynamic parameters, deltaH0 and deltaS0, are 1.95 kJ/mol and 27.16 J/molK, respectively. The deltaG0 values range from -5.98 to -6.79 J/mol, which shows the physical adsorption properties of the sludge. Adsorption dynamics had been successfully studied by the Lagergren model and an intraparticle diffusion model.     

Adsorption Characteristics of Natural Erionite, Clinoptilolite and Mordenite Zeolites from Mexico

Nitrogen sorption properties inherent to some natural zeolites from Mexico, such as erionites, clinoptilolites and mordenites, are determined and compared with corresponding sorption properties of homologous synthetic or acid modified forms. The mineralogies of natural zeolites are determined by X-ray analysis. N₂ low-pressure hysteresis loops are displayed by some substrata while are absent in others; key factors for this phenomenon to occur are the micropore structure and the ion-exchange treatment to which the natural precursors are subjected. Argon sorption at 76 K on selected samples evidence further the strong adsorption and the pore blocking effects at pore necks in the zeolites.     

Adsorption/Desorption Behavior of Bovine Serum Albumin and Porcine Insulin on Chemically Patterned Porous Gel Networks

Adsorption/desorption of proteins onto a biomaterial surface plays a major role on the biocompatibility of the implanted material. By modifying the biomaterial surface with specially designed functional groups one may achieve the most specific behavior of the developed material used in a biological system. Based on that, porous gel matrixes with functionalized surfaces offer unlimited possibilities to control the protein-substrate interaction behavior. In the present work, we have functionalized the surface of porous glass with several chemical groups during the synthesis of the silica matrix. The porous glass matrixes were obtained using tetraethoxysilane (TEOS)/ethanol and functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltriethoxysilane (APTES). In vitro tests of the kinetics of protein adsorption and desorption from the gel matrix were monitored by UV-visible spectroscopy. The bioactivity of the incorporated protein was verified by in vivo experiments with adult male rats, where they presented an acute hypoglycemic peak.     

Sorption and Catalytic Activity of Adsorbent-Catalyst Based on Montmorillonite Modified with Cr(III) and Cu(II) Mixed Oxides

The sorption properties of mixed adsorbent-catalyst based on high-silica zeolite and montmorillonite modified with mixed oxides of Cr(III) and Cu(II) with respect to organic compounds of various classes were studied, and the optimal dynamic conditions of its operation were determined.     

Biotechnology of Cr(VI) transformation into Cr(III) complexes

The dose-dependent formation of Cr(III) complexes and uptake of chromium by Arthrobacter oxydans — a Gram-positive bacterium from contaminated Columbian basalt rocks (USA) — were studied along with the testing under aerobic conditions of two bacterial strains of Arthrobacter genera isolated from the polluted basalts from the Republic of Georgia. Instrumental neutron activation analysis (INAA) was used to track the accumulation of chromium in the bacterial cells. To monitor and identify Cr(III) complexes in these bacteria, electron spin resonance (ESR) spectrometry was employed.     

Fluorimetric Cr(VI) and Cr(III) Speciation With Crystal Violet

Abstract

A simple fluorimetric determination of Cr(VI) in the presence of Cr(III) is described. This determination is based on the fluorescence, produced from the ion-association complex between the Crystal violet cation and the anionic complex, formed between Cr(VI) and excess of I^?. This fluorescence is not observed when Cr(III) is used instead of Cr(VI). The fluorescence intensity is linear over the concentration range of 0–60 μg/1. The method was applied in potable and sea waters.     

Polarographic studies of catalytic reduction of hydrogen in Cr(VI)−As(III) and Cr(III)—As(III) systems

In the presence of traces of Cr(VI) or Cr(III) ions in ammonia or borate buffers containing the As(III) ions a catalytic hydrogen wave arises in the dc polarogram. It was established that the complex Cr(H₂AsO₃)_n^+3?n is formed in the solution, and that its reduced form adsorbed at DME is of catalytic activity. The wave can be employed for the determination of low concentrations (2×10^?8×10^?7M) of Cr(VI) and Cr(III) ions.     

Prediction of Stability Constants for Cr(III) and Cr(II) Complexes

Regression analysis was used to derive equations for estimaing thermodynamic stability constants for complexes of Cr²⁺ (log^° ₁[Cr²⁺L] = 0.53log^° _n [H _n L]) and Cr³⁺ (log^° ₁[Cr³⁺L] = 0.88log^° _n [H _n L]) from the known protonation constants of H _n L ligands and for determining stability constants of Cr²⁺ and Cr³⁺ complexes from the available stability constants of Cu²⁺ complexes (log^° ₁[Cr²⁺L] = 0.76log^° ₁[Cu²⁺L] and log^° ₁[Cr²⁺L] = 0.60log^° ₁[Cr³⁺L], respectively). Parameters of the Panteleon–Ecka equation for calculating stability constants of Cr²⁺ complexes ( = 0.57) and Cr³⁺ complexes ( = 0.69) with two and three bidentate ligands were also determined. The ratio of logarithmic stability constants for complexes with the same metals but with different metal ionic charges was found to be approximately equal to the ratio of charges on the central ions. The stability constant of Cr(II) sulfate complex was calculated.     

Adsorption studies of iron(III) on chitin

Adsorption of ferric ions by chitin was studied by the batch equilibration method. The influence of particle size and dosage of the adsorbant, contact time, initial concentration of the adsorbate and temperature were experimentally verified. The effect of anions like chloride, nitrate and sulphate and also of cations like zinc, chromium and copper on the adsorption of iron(III) was determined. The time dependence of fraction of adsorption,Yt, at varying particle sizes and doses of chitin and the intraparticle diffusion rate constants,k _p , of the adsorption process were calculated. Thermodynamic and equilibrium parameters of the reaction were determined to understand the sorption behaviour of chitin. The results revealed that the adsorption of iron(III) by chitin is spontaneous, endothermic and favourable.     

Cr(III) and Cr(VI) speciation measurements in environmental reference materials

The production of reference materials for quality control of Cr(III) and Cr(VI) speciation in environmental samples is described. It concerns in the first place two lyophilized solutions containing Cr(III) and Cr(VI) at different concentrations, respectively representative for drinking water and filter leaching solutions, and in the second place filters loaded with welding dust. Twenty-four laboratories with experience in the field participated in an intercomparison exercise organized to validate the suitability of the reference materials and to gauge the state-of-the-art of Cr speciation throughout Europe. The outcome of this exercise is discussed.     

Amperometric Determination of Cr(III) and Cr(VI) by Flow Injection Analysis

Speciation of Cr(III) and Cr(VI) can be attained by flow injection analysis with amperometric detection. Cr(VI) is reduced in an acidic medium to Cr(III) with a glassy carbon electrode at —0.1 V vs. Ag/AgCl and the current is recorded. Cr(III) is oxidised on-line to Cr(VI) with alkaline hydrogen peroxide solution. From the difference of the total chromium and Cr(VI), the amount of Cr(III) was obtained. A linear calibration curve for Cr(VI) was obtained for the concentration ranges 0.01-5.0ppm of Cr(VI) and we have calculated the limit of determination to be about 0.5ppb. We have studied the degree of reproducibility obtained using the solid electrodes under various conditions. The influence of flow rate, coil length, interfenences and the extent of reaction were studied.     

Separation of Cr(III) and Cr(VI) using complexation of Cr(III) with 8-hydroxyquinoline and determination of both species in waters by ETA-AAS

Summary A method for the determination of chromium(III) and (VI) species has been studied and applied to mineral water samples. The chromium(III) was chelated with 0.1 mol/l 8-hydroxyquinoline in methyl alcohol, extracted in isobutyl methyl ketone and determined by ETA-AAS. The effects of the pH, extraction and heating time and amounts of the reagents required for the extraction were studied. A method for the determination of total chromium was optimized too, and the chromium(VI) can be calculated. The precision, sensibility, accuracy, graphite furnace program and interferences for both methods were also investigated.