Sorption of praseodymium(III) ions from aqueous solutions by a natural clinoptilolite-containing tuff

The equilibrium and kinetics of sorption of praseodymium(III) ions from sulfate solutions by a natural clinoptilolite-containing tuff are studied. It is shown that praseodymium is completely extracted from dilute solutions (<0.002 M). The kinetic parameters of the sorption process are determined.     

Thermal behaviour of titanium dioxide nanoparticles prepared by precipitation from aqueous solutions

Thermogravimetry-differential thermal analysis, emanation thermal analysis, mass spectrometry detection, Fourier transform infrared and XRD were used to characterize thermal behaviour of titanium dioxide photocatalyst precursors prepared by precipitation at various conditions from peroxotitanic acid sols. The transmission electron microscopy HRTEM technique was used to characterize the surface microstructure. The sols contained TiO₂ anatase particles of approximately 10 nm in diameter. During heating of the air dried samples, their chemical degradation took place giving rise to anatase. On further heating, the crystallization of anatase and formation of rutile phase was observed. To test the photocatalytic activity of the samples, the decomposition of 4-chlorophenol (4-CP) under ultraviolet and visible irradiation was monitored. It was shown that photocatalytic activities of the samples are comparable to the Degussa P25 photocatalyst reference material.     

Sorption behavior of germanium(IV) on titanium dioxide nanoparticles

Titanium dioxide nanoparticles were employed for the sorption of Ge(IV) ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption process was found to be fast, equilibrium was reached within 3 min. A maximum sorption could be achieved from solution when the pH ranges between 4.0 and 11.0. Sorbed Ge(IV) ions can be completely desorbed with 2 mL of 0.3 mol L⁻¹ K₃PO₄-1.0 mol L⁻¹ H₂SO₄ mixture solution. The kinetic experimental data properly correlate with the second-order kinetic model (k ₂ = 0.88 g mg⁻¹ min⁻¹ (25°C)), Reichenberg equation and Morris-Weber model. The estimated E _a for Ge(IV) adsorption on nano-TiO₂ was 19.66 kJ mol⁻¹. The overall rate process appears to be influenced by intra-particle diffusion. The sorption data could be well interpreted with the Langmuir and Dubinin-Radushkevich (D-R) type sorption isotherms. The D-R parameters were calculated to be K = −0.00321 mol₂ kJ⁻², q _m = 0.59 mmol g⁻¹ and E = 12.48 kJ mol⁻¹ at room temperature. Furthermore, the thermodynamic parameters were also determined, and the ΔH ⁰ and ΔG ⁰ values indicated a spontaneous exothermic behavior.     

Sorption of phosphate ions on iron(III), zirconium(IV), and chromium(III) oxyhydroxides from aqueous electrolyte solutions

The adsorption of phosphate ions from aqueous solutions with an ionic strength of 0.5 on iron(III), zirconium(IV), and chromium(III) oxyhydroxide hydrogels has been studied as influenced by chloride and sulfate ions. Despite the high concentrations of chloride and sulfate ions, they do not inhibit phosphate adsorption on the hydrogels; they only slightly change the isotherm shape. In the range of equilibrium phosphate concentrations equal to 30–50 mmol/l, all isotherms for iron and zirconium oxyhydroxide gels signify the appearance of a second adsorption layer (two-step isotherms). Both steps are satisfactorily fitted by the Langmuir equation. The maximum adsorptions and adsorption constants have been calculated. For chromium oxyhydroxide gels, the intraduction of an electrolyte dramatically decreases the equilibration rate.     

Sorption of uranyl ions on hydrous titanium dioxide

Summary The mechanism of the sorption of U on TiO₂ · x H₂O is investigated in absence and in presence of carbonate as function of pH. Speciation of U in solution and the state of the surface of TiO₂ · x H₂O are taken into account. In the experiments the mole fractions of the U species in presence of carbonate are the same as in seawater. Below pH 5 the sorption of U can be described in absence and in presence of carbonate by ion exchange of UO ₂ ²⁺ or alternatively by sorption of UO₂OH⁺, because hydrolysis and sorption are occurring simultaneously. Above pH 5 in absence of carbonate, first pH-independent sorption of (UO₂)₃(OH) ₇ ^– and then (above the isoelectric point of TiO₂ · x H₂O) pH-dependent sorption of (UO₂)₃(OH) ₇ ^– are observed. In the same pH range, but in presence of carbonate, two species of U are dominating in solution, first UO₂CO₃OH^– and then UO₂(CO₃) ₃ ^4– · UO₂CO₃OH^– is not sorbed in measurable amounts which causes a drastic decrease of the sorption ratio. UO₂(CO₃) ₃ ^4– , which begins to dominate above pH 6 (depending on the carbonate concentration), is sorbed either by formation of TiOUO₂ bonds or (at carbonate concentrations >10^–2 mol/l) via carbonate bridges.

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Sorption von Uranylionen an wasserhaltigem Titandioxid

     

Sorption characteristics and separation of tellurium ions from aqueous solutions using nano-TiO2

Titanium dioxide nanoparticles (nano-TiO₂) were employed for the sorption of Te(IV) ions from aqueous solution. A detailed study of the process was performed by varying the sorption time, pH, and temperature. The sorption was found to be fast, equilibrium was reached within 8 min. When the concentration of Te(IV) was below 40 mg L⁻¹, at least 97% of tellurium was adsorbed by nano-TiO₂ in the pH range of 1-2 and 8-9. The sorbed Te(IV) ions were desorbed with 2.0 mL of 0.5 mol L⁻¹ NaOH. The sorption data could be well interpreted by the Langmuir model with the maximum adsorption capacity of 32.75 mg g⁻¹ (20 ± 0.1 °C) of Te(IV) on nano-TiO₂. The kinetics and thermodynamics of the sorption of Te(IV) onto nano-TiO₂ were also studied. The kinetic experimental data properly correlated with the second-order kinetic model (k₂ = 0.0368 g mg⁻¹ min⁻¹, 293 K). The overall rate process appeared to be influenced by both boundary layer diffusion and intra-particle diffusion. The mean energy of adsorption was calculated to be 17.41 kJ mol⁻¹ from the Dubinin-Radushkevich (D-R) adsorption isotherm at room temperature. Moreover, the thermodynamic parameters for the sorption were estimated, and the ΔH⁰ and ΔG⁰ values indicated the exothermic and spontaneous nature of the sorption process, respectively. Finally, Nano-TiO₂ as sorbent was successfully applied to the separation of Te(IV) from the environmental samples with satisfactory results (recoveries >95%, relative standard deviations was 2.0%).     

Sorption of gold(III) ions from hydrochloric acid solutions by aminated shungite

Sorption of gold ions by aminated shungite from chloride solutions was studied. The effects of the solution pH and process duration on the degree of recovery were considered.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1772–1774.Original Russian Text Copyright © 2004 by Akimbaeva, Ergozhin.     

Sorption of Cu(II) and Eu(III) ions from aqueous solution by olive cake

The sorption of Cu(II) on olive cake, a biomass by-product of olive oil production, has been investigated by potentiometry at pH 6, I=0.1 M NaClO₄, 25 °C and under atmospheric conditions. Numerical analysis of the experimental data supports the formation of surface complexes and allows the evaluation of the corresponding formation constant, which is found to amount log β=5.1±0.4. This value is close to corresponding values given in literature for Cu(II)-humate complexes, indicating that the same type of active sites (e.g. carboxylic and phenolic groups) is responsible for the Cu(II) binding by olive cake. Addition of a competing metal ion (e.g. Eu(III) ion) in the system leads to replacement of the Cu(II) by Eu(III). Evaluation of the potentiometric data obtained from competition experiments indicates on a ionexchange mechanism. The formation constant of the Eu(III) species sorbed on olive cake is found to be log β=5.4±0.9. The results of this study are of particular interest with respect to waste water treatment technologies using biomass products as adsorbent material and environmental impact assessments regarding disposal of biomass by products in the geosphere.     

Sorption investigation on the removal of metal ions from aqueous solutions using chelating terpolymer resin

A novel chelating terpolymer resin has been synthesized from anthranilic acid, phenylhydrazine, and formaldehyde by condensation in glacial acetic acid. The structure of the chelating resin was clearly elucidated by use of a variety of spectral techniques, for example FTIR, and ¹H and ¹³C NMR spectroscopy. The average molecular weight of the terpolymer resin was determined by gel-permeation chromatography. The empirical formula and empirical weight of the resin were determined by elemental analysis. The physicochemical properties of the terpolymer resin were determined. Scanning electron microscopy was used to establish the surface features of the chelating resin. The ion-exchange behaviour of the resin for specific metal ions, viz. Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Pb²⁺, was evaluated by a batch equilibrium method. The study was extended to three variations: evaluation of metal ion uptake in the presence of different electrolytes at different concentrations; evaluation of metal ion uptake at different pH; and evaluation of metal ion uptake at different times. Further, the reusability of the resin was also determined to assess the efficiency of the resin after a few cycles of sorption. From the results it was observed that the resin acts as an effective chelating ion-exchanger.     

Sorption of cesium and strontium ions on hydrous titanium dioxide from chloride medium

Epiboron instrumental neutron activation analysis (EINAA) using flexible boron as thermal neutron filter, has been used to analyze several salt samples obtained from various markets in Ghana for iodine. The method involves the irradiation of samples in boron carbide-lined polyethylene vials at the outer irradiation site of the Ghana Research Reactor-1 (GHARR-1). The samples were then counted directly without any pre-treatment on a Canberra N-type HPGe detector. The qualitative and quantitative analyses were done using the 443 keV photopeak of ¹²⁸I. The precision and accuracy of the method have been evaluated and the detection limits of the various samples were calculated. The values of iodine determined in the iodized salt range between 10.0 and 210 ppm. For non-iodinated salts, iodine levels were below 500 ppb. The values obtained show great variations among the salt samples, sample collection time and from market to market. This results show that the method can be successfully applied in the determination of trace amount of iodine in salt samples without any chemical separation.     

Adsorption of U (VI) ions from aqueous solution using silicon dioxide nanopowder

The adsorption kinetics for removal of uranium (V1) from aqueous solution using silicon dioxide nanopowder (nano-SiO₂) was investigated in batch and continuous techniques. Pseudo-first order and pseudo-second order were used to analyze the kinetics of batch experiments. In continuous technique the important parameters (initial concentration, flow rate and bed height) on the breakthrough curves were studied and the adsorption kinetics was analyzed using Thomas and Yoon and Nelson kinetic models. The comparison between the kinetic models was evaluated by the correlation coefficients (r²). The results indicated that the batch experiments fitted well with pseudo second-order kinetic model. The comparison of the experimental breakthrough curve to the breakthrough profile obtained from Thomas and Yoon and Nelson methods showed a satisfactory fit for silicon dioxide nanopowder.     

Sorption of radiocobalt(II) from aqueous solutions to Na-attapulgite

The sorption of Co(II) on Na-attapulgite as a function of contact time, solid content, pH, ionic strength, foreign ions, fulvic acid (FA) and temperature under ambient conditions was studied. The kinetic of Co(II) sorption on Na-attapulgite was described well by pseudo-second-order model. The sorption of Co(II) on Na-attapulgite was strongly dependent on pH and ionic strength. The sorption of Co(II) was mainly dominated by outer-sphere surface complexation and/or ion exchange at low pH, whereas inner-sphere surface complexation or surface precipitation was the main sorption mechanism at high pH values. The presence of FA did not affect Co(II) sorption obviously at pH <7, and a negative effect was observed at pH >7. The Langmuir and Freundlich models were used to simulate the sorption data at different temperatures, and the results indicated that the Langmuir model simulated the data better than the Freundlich isotherm model. The thermodynamic parameters (∆G°, ∆S°, ∆H°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on Na-attapulgite was an endothermic and spontaneous process. The results suggest that the attapulgite sample is a suitable material in the preconcentration and solidification of radiocobalt from large volumes of aqueous solutions.     

Sorption of strontium ions from aqueous solutions by oxidized multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNTs) oxidized by nitric acid solution were used to investigate the adsorption behavior of strontium from aqueous solutions similar to the nuclear waste media. The physical properties of both as produced and oxidized MWCNTs were studied by Boehm’s titration method and nitrogen adsorption/desorption. The results showed that the surface properties of MWCNTs such as specific surface area, functional groups and the total number of acid sites were improved after oxidation. Furthermore, the effect of solution conditions such as initial concentration of strontium(II), pH, ionic strength, MWCNT concentration and contact time were studied at room temperature. The results of this study showed that the adsorption of strontium(II) was significantly influenced by the pH value and the solution ionic strength. According to the Langmuir model, the maximum adsorption capacities of strontium(II) onto the as produced and oxidized MWCNTs were obtained as 1.62 and 6.62 mg g^?1, respectively. The contact time to reach equilibrium was 100 min. The good adsorption of strontium(II) on oxidized MWCNTs at the lower ionic strength, the relatively high pH and the short equilibrium time indicate that the oxidized MWCNTs have great potential applications in the field of the environmental protection.     

Sorption of cadmium ions from aqueous solutions onto nanoporous modified carbon sorbents

Physicochemical properties of nanoporous modified carbon sorbents and sorption of cadmium ions (0.1–20 mg L^?1) onto them from nitrate solutions at pH 5–7 were studied. The acid-base nature of functional oxygen-containing groups on the carbon surface of the sorbents was determined. The ability to sorb cadmium ions depends on the kind of chemical modification of the sorbent surface.     

Oxidative bromination of olefins catalyzed by thallium(III) and heteropolyacids in aqueous solutions

The system Tl^III+HPA-n, where HPA-n is the heteropolyacid H_3+nPMo_12–nV_nO₄₀ with n=2–8, in the presence of O₂ is found to be a homogeneous catalyst for the oxidative bromination of olefins by Br^– ions in aqueous solutions.

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, Tl^III+HPA-n, HPA-n — H_3+nPMo_12–nV_nO₄₀ n=2–8, O₂ Br^– .

     

Removal of aqueous As(III) and As(V) by hydrous titanium dioxide

Dissolved arsenic in drinking water is a global concern as it causes serious health problems. The purpose of this research was to study the applicability of an industrial intermediate product, a mixture of titanium hydroxide and titanium dioxide for removing aqueous arsenic. The material is common, inexpensive, and non-toxic, making it an attractive choice for drinking water purification. The kinetics and equilibrium of removing both primary inorganic arsenic forms, As(III) and As(V), were studied by separate batch experiments. The tested material functioned well in removing both of these arsenic forms. The apparent values for Langmuir monolayer sorption capacities were 31.8 mg/g for As(III) and 33.4 mg/g for As(V) at pH 4. The studied TiO(2) performed the best in acidic conditions, but also reasonably well in other pH conditions.     

Adsorption of polymethacrylic acid from aqueous solutions on disperse titanium dioxide

The state of macromolecules of polymethacrylic acid adsorbed on the surface of disperse titanium dioxide was assessed using a combination of the differential concentration approach to the determination of adsorption and methods for determining the size of disperse adsorbents by dynamic light scattering and sedimentation analysis in the field of centrifugal forces. Three sections were found on the isotherm of adsorption: in the first, isolated islands of adsorbed macromolecules formed; in the second, layers of macromolecules with a different degree of deformation were observed; in the third, determining the adsorption of macromolecules is complicated by other accompanying processes, and assessing the state of macromolecules in the adsorption layer becomes difficult.     

Sorption of cesium from aqueous solutions using polymer supported bentonite

Polyacrylonitrile supported bentonite (PAN-B) was prepared, characterized and used for adsorption of cesium from aqueous solutions through batch and column techniques. Different techniques were used for characterization of the prepared adsorbent as surface area, swelling properties, FTIR and SEM. The effect of pH, contact time, sorbent dose and the initial cesium concentration on the uptake percent of Cs from aqueous solution were studied. The equilibrium sorption data were described by the Temkin and Flory–Huggins isotherm models and the results could fit more with Temkin model with correlation coefficient 0.997. The effect of temperature on the sorption behavior was studied and the thermodynamic parameters were calculated and showed the exothermic nature of sorption reaction with ΔH_o = ?69.38 kJ/mol. Fixed bed studies were performed, the breakthrough of PAN-B column was studied at different conditions and the breakthrough capacity was calculated.     

Sorption of metal ions from multicomponent aqueous solutions by activated carbons produced from waste

Activated carbons produced by thermal treatment of a mixture of sunflower husks, low-grade coal, and refinery waste were studied as adsorbents of transition ion metals from aqueous solutions of various compositions. The optimal conditions and the mechanism of sorption, as well as the structure of the sorbents, were studied.     

Sorption of thorium(IV) from aqueous solutions by graphene oxide

Graphene oxide (GO) is one of the most important carbon nano-materials. In this paper, GO was synthesized from flake graphite and characterized by transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The sorption of Th(IV) on GO was investigated as a function of contact time, solid-to-liquid ratio, pH, ionic strength, and in the presence of fulvic acid (FA) and humic acid (HA) by batch experiments. The sorption percentage of Th(IV) on GO decreased with increasing ionic strength and decreasing solid-to-liquid ratio. The sorption edge of Th(IV) in the presence of FA/HA is much lower than that in the absence of FA/HA. Furthermore, the sorption processes of Th(IV) can be described by a pseudo-second order rate model. Based on the Langmuir model, the maximum sorption capacities (Cs_max) of Th(IV) were about 5.80 × 10^?4 mol/L. From thermodynamic investigation, sorption of Th(IV) on GO is spontaneous and endothermic in nature. The rapid sorption rate and high sorption capacity suggest that GO is a promising adsorbent for Th(IV).