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1
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EN
A new method to determine the effective diffusion coefficient of sorbate in sorbent granule based on the analytical solution of the shrinking core model (SCM) has been proposed. The experimental data presented by Lewandowski and Roe1 concerning the sorption of copper ions by alginate granules have been applied to compare the analytical and numerical methods. The results obtained by both methods are very close.
EN
The sorption capacity of three weak base ion exchangers based on acrylic copolymers functionalized with ethylenediamine, triethylenetetramine and N, N- dimethylamino propylamine for Ag(I) ions was evaluated. Adsorption experiments were carried out by batch method. The effect of pH, crosslinking degree of copolymers, amount of sorbent, initial ion concentration, contact time and temperature was studied. The parameters which characterize the retention process were estimated using Langmuir and Freundlich isotherm models, the best fitting being for the first model. Kinetic data were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion models. Experimental data were in good agreement with the pseudo second order. [...]
3
Content available remote Epoxy resin modified with amine as an effective complexing agent of metal cations
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EN
A simple synthesis of a material capable of metal cation removal is proposed. The material was a derivative of epoxy resin containing amine groups. It is insoluble in water and in this study it was characterized by elemental analysis and infrared spectroscopy. The sorbent obtained was tested for its ability to remove coper(II), cadmium(II) and lead(II) from water solutions. The tests were performed for different concentrations of metal ions (10–200 mg L−1) and at different pH (2.0–9.0). The effects of temperature and stirring time, as well as reusability of the sorbent were also studied in batch experiments. In the optimum conditions, the decrease in the cation concentration in aqueous solutions was observed in the order Cu>Pb>Cd but for each ion the decrease was at least 50% of the initial concentration. The sorbent has demonstrated high effectiveness in cation sorption and after regeneration it can be applied repeatedly in the process described. [...]
EN
The layers of mixed copper chalcogenides, CuxS-CuyTe, were formed on the surface of polyamide using solutions of potassium and sodium telluropentathionates, K2TeS4O6 and Na2TeS4O6, respectively, and of telluropentathionic acid, H2TeS4O6, as precursors of chalcogens. The concentration of sorbed chalcogens increased with the increasing time of the treatment, concentration and temperature of precursor solution. CuxS-CuyTe layers are formed on the surface of polyamide after the treatment of chalcogenized polymer with Cu(II/I) salt solution. The concentration of copper in the layer increases with the increase of chalcogenization duration, concentration and the temperature of chalcogenization solution. In the surface of CuxS-CuyTe layers various copper, sulfur, tellurium and oxygen compounds (Cu2S, CuS, S8, CuxS, CuyTe, Cu(OH)2 and TeO2) were present. Chalcogenides were the major components in the layer. Chalcogenide phases - digenite, Cu1.8S, djurleite, Cu1.9375S, anilite, Cu7S4, geerite, CuS2, chalcocite, Cu2S, tetragonal Cu3.18Te2, Cu2.72Te, hexagonal Cu2Te, Cu4Te3, Cu1.80Te, Cu1.85Te2, and orthorhombic vulcanite, CuTe were identified in the layers by X-ray diffraction. Electrical sheet resistance of CuxS-CuyTe layers vary from ∼ 1.0 kW cm−2 to 4×103 kΩ cm−2. It is concluded that the formation of chalcogenide layers proceeds in the form of islands which grow into larger agglomerates. Use of the gathered data enables design and formation of the CuxS-CuyTe layers with desired conductivities. [...]
EN
The sorptive potential of some lignocellulosic agro-industrial wastes (sunflower seed shells and corn cob) for Basic Blue 9 cationic dye removal from aqueous solutions was examined using the batch technique. The Freundlich, Langmuir, and Dubinin-Radushkevich isotherm models were used in order to determine the quantitative parameters of sorption. The Langmuir isotherm model indicated a maximum sorption capacity for these materials in the range of 40–50 mg dye per g (25°C), slightly higher for corn cob than for sunflower seed shells. The values of the thermodynamic parameters showed that the retention of cationic dye is a spontaneous and endothermic process. The application of pseudo-first order and pseudo-second order intraparticle diffusion models, and a Boyd - Reichenberg model for kinetic data interpretation suggested that sorption of Basic Blue 9 dye onto the studied materials is a process where both surface sorption and intraparticle diffusion contributed to the rate-limiting step. These lignocellulosic wastes can be used with good efficiency for dye removal from aqueous effluents. [...]
EN
A cheap and efficient fibrous hydrolyzed polyacrylonitrile (HPAN) sorbent was obtained by alkaline hydrolysis of Romanian polyacrylonitrile fibres. Scanning electronic microscopy and infrared spectroscopy were used to characterize the hydrolyzed product and to confirm its functionalization. The adsorptive potential of the proposed sorbent for reactive dye Brilliant Red HE-3B removal from aqueous solutions of pH=2 was examined by the batch technique as a function of dye concentration, temperature solution and contact time. The Freundlich, Langmuir and Dubinin-Radushkevich adsorption models were applied to describe equilibrium sorption data and to determine the corresponding isotherm constants. The thermodynamic parameters ΔG, ΔH and ΔS were also determined; the values obtained show that sorption of reactive dye on HPAN fibres is a spontaneous, endothermic and entropy-driven process. The kinetics of sorption of the reactive dye were analyzed using pseudo-first order and pseudo-second order kinetic models. The kinetic data fitted well to pseudo-second order kinetics, indicating the chemisorption of reactive dye onto the fibrous sorbent. The sorption mechanism of the dye onto hydrolyzed fibres was confirmed by FTIR spectroscopy. The dye-loaded HPAN sorbent can be regenerated by treatment with 0.1M NaOH and the regenerated sorbent may be reused in several adsorption-desorption cycles. The results of this study provided evidence that the HPAN fibres are effective for removing reactive dye Brilliant Red HE-3B from aqueous effluents. [...]
EN
In this study, the use of the weakly basic anion exchange resins of phenol-formaldehyde (Amberlyst A 23), polyacrylate (Amberlite IRA 67) and polystyrene (Lewatit MonoPlus MP 62) matrices for removal of the reactive dye Remazol Black B (RBB) from aqueous solution and wastewater were investigated. RBB sorption on the anion exchangers was a time dependent process. Color reduction percentiles of 75.2, 33.9 and 25.1% in wastewater treatment were found after 216 h of phase contact time with Lewatit MonoPlus MP 62, Amberlyst A 23 and Amberlite IRA 67, respectively. Inorganic salts and anionic surfactant action influenced RBB uptake by the anion exchangers. The amounts of dye retained by the anion exchangers increased with a rise in temperature. The maximum sorption capacities calculated from the Langmuir model were 66.4, 282.1 and 796.1 mg g−1 for Amberlite IRA 67, Amberlyst A 23 and Lewatit MonoPlus MP 62, respectively. Regeneration of phenol-formaldehyde and polystyrene resins were possible using 1 M NaOH, 2 M KSCN, 1M KSCN in 40–60% methanol as well as 1 M NaOH in 60% methanol. [...]
8
Content available remote Use of peat-based sorbents for removal of arsenic compounds
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EN
It is important to apply sorbent materials for purification of water from arsenic contamination due to serious arsenic pollution worldwide. We have developed new sorbents based on natural materials that provide a cheap and environmentally friendly alternative. For the first time, peat modified with iron compounds and iron humates were tested for sorption of arsenic compounds. The highest sorption capacity was found in peat modified with iron compounds. We have found that sorption of different arsenic speciation forms was strongly dependent on solution pH, reaction time and temperature. Calculations of the sorption process using thermodynamic parameters indicate the spontaneity of sorption process and its endothermic nature. Sorption kinetics showed that most arsenates are removed within 2 hours, and the kinetics of arsenate sorption on modified peat can be described by the pseudo-second order mechanism. [...]
9
Content available remote Equilibrium isotherm analysis of the sorption of congo red by palm kernel coat
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EN
The ability of Palm Kernel Coat (PKC), a waste agricultural product, in the abstraction of Congo Red (CR), an anionic dye, from aqueous solution was studied. The effects of sorbent dose and temperature were studied using batch sorption system. Isotherm experiments were conducted and the data obtained were fitted with different equilibrium isotherm equations namely, Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Harkins-Jura and Halsey isotherm equations. The Langmuir isotherm equation gave the best description of the sorption process and the maximum saturated monolayer sorption capacity of the PKC for CR was 79.37 mg g−1. Harkins-Jura isotherm equation gave the poorest description of the sorption process. The linear form of the Langmuir equation was used to analyze the data obtained when the sorbent dosage was optimized by method of continuous variation. The results obtained showed that the equilibrium monolayer sorption capacity, qm, of the PKC for CR decreased (79.37–17.07 mg g−1) with an increase in sorbent dosage. The relationship between the dimensionless parameter, KR, and initial concentration, Co, showed that the sorption of CR was favored at higher initial dye concentration and PKC dosages than the lower ones. The thermodynamic parameters, such as change in the free energy, the enthalpy and the entropy, were also evaluated. The thermodynamic analysis showed that the sorption is spontaneous and exothermic. [...]
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