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Abstract  

The sorption of copper on synthetic hydroxyapatite was investigated using a batch method and radiotracer technique. The hydroxyapatite sample prepared by a wet precipitation process was of high crystallinity with Ca/P ratio of 1.688. The sorption of copper on hydroxyapatite was pH independent ranging from 4 to 6 as a result of buffering properties of hydroxyapatite. The adsorption of copper was rapid and the percentage of Cu sorption was >98% during the first 15–30 min of the contact time. The experimental data for sorption of copper have been interpreted in the term of Langmuir isotherm. The sorption of Cu2+ ions was performed by ion-exchange with Ca2+ cations on the crystal surface of hydroxyapatite under experimental conditions. The competition effect of Zn2+, Fe2+ and Pb2+ towards Cu2+ sorption was stronger than that of Co2+, Ni2+ and Ca2+ ions. The ability of the bivalent cations to depress the sorption of copper on hydroxyapatite was in the following order Pb2+ > Fe2+ > Zn2+ > Co2+ ≈ Ni2+.

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Abstract  

The sorption of strontium on synthetic hydroxyapatite was investigated using batch method and radiotracer technique. The hydroxyapatite samples were prepared by a wet precipitation process followed by calcination of calcium phosphate that precipitated from aqueous solution. Also, commercial hydroxyapatites were used. The sorption of strontium on hydroxyapatite depended on the method of preparation and it was pH independent ranging from 4 to 9 as a result of buffering properties of hydroxyapatite. The distribution coefficient K d was significantly decreased with increasing concentration of Sr2+ and Ca2+ ions in solution with concentration above 1 × 10−3 mol dm−3. The percentage strontium sorption for commercial and by wet method prepared hydroxyapatite was in the range of 83–96%, while calcined hydroxyapatite was ranging from 10 to 30%. The experimental data for sorption of strontium have been interpreted in the term of Langmuir isotherm. The sorption of Sr2+ ions was performed by ion-exchange with Ca2+ cations on the crystal surface of hydroxyapatite. Although calcined hydroxyapatite is successfully used as biomaterial for hard tissues repair, it is not used for the treatment of liquid wastes.

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fit curve of C / θ against C when plotted expresses the Langmuir isotherm model is obeyed with the adsorption of the extracts onto the metal surface. 3 Results and discussion 3.1 Chemical composition of the alloy sample The chemical composition

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Journal of Thermal Analysis and Calorimetry
Authors: Eunice F. S. Vieira, Antonio R. Cestari, Wagner A. Carvalho, Cíntia dos S. Oliveira, and Renata A. Chagas

scales, Q int = Q r − Q w , were calculated with both Q r and Q w normalised for 1 g of material. Adsorption results were analyzed in terms of the Langmuir isotherm model [ 25 ]. The following linearized form equations were used for this purpose

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), K L = k ads /k d is the Langmuir constant and T is the temperature (K). Δ H and Δ S values can be obtained from the slope and intercept, respectively, of Van't Hoff plots of ln K L (from the Langmuir isotherm) versus 1/ T

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Abstract  

Biosorption of uranyl ions from aqueous solution by Saccharomyces cerevisiae was studied in a batch system. The influence of contact time, initial pH, temperature and initial concentration was investigated. The optimal conditions were found to be 3.5 h of contact time and pH = 4.5. Temperature had no significant effect on adsorption. The uptake of uranyl ions was relatively fast and 85 % of the sorption was completed within 10 min. The experimental data were well fitted with Langmuir isotherm model and pseudo-second order kinetic model. According to this kinetic model, the sorption capacity and the rate constant were 0.455 mmol UO2 2+/g dry biomass and 1.89 g mmol−1 min−1, respectively. The Langmuir isotherm indicated high affinity and capacity of the adsorbent for uranyl biosorption with the maximum loading of 0.477 mmol UO2 2+/g dry weight.

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Abstract  

The ability of the back-fill and the host rock materials to take up radioisotopes like 241Am, 85,89Sr and 137Cs has been examined as a function of contact time, pH, amount of sorbent, sorbate concentration, and the presence of complementary cations. A batch technique using actual borehole water from the granite formation has been utilized. In general, the uptake of nuclides by bentonite is much higher than that with granite. The sorption order of nuclides on bentonite is Am>Cs>Sr. The presence of complementary cations, Na+, K+, Ca2+ and Mg2+ depresses the sorption of Cs and Sr on bentonite. The sorption data have been interpreted in terms of Freundlich and Langmuir isotherm equations. Utilizing the Langmuir isotherm equation, the monolayer capacity, V m ,and the binding constant, K, have been evaluated. The change in free energy for the sorption of nuclides on bentonite has also been calculated.

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Abstract  

137Cs and134Ba were removed from synthetic aqueous solutions by means of natural zeolites of Slovakian origin. The equilibrium sorption behavior of Cs and Ba ions onto clinoptilolite and mordenite were studied under static as well as dynamic experimental conditions. Both Freundlich and Langmuir isotherms describe satisfactory by Cs and Ba adsorption on the zeolites studied. The elution of Cs and Ba ions from zeolite columns after the loading cycle was undertaken additionaly, in order to compare column operating runs of various exchanged zeolite forms.

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Abstract  

The model of "ideal" binary ion exchange based upon the competitive sorption of two different cations onto elementary anionic units of dissociated ion-exchanger was developed. The explanation of several phenomena, which are considered to be incompatible with the conception of "ideal" ion exchange, has been suggested, in the frame of this model. General equation of sorption isotherm has been derived and conditions, under which it turns to Langmuir's isotherm, were specified. This work is oriented rather to inorganic ion-exchangers than to those classical organic ones.

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Abstract  

The adsorption of uranium from crude phosphoric acid has been investigated using conventional activated carbons. It was found that treatment with nitric acid oxidized the surface of activated carbon and significantly increased the adsorption capacity for uranium in acidic solutions. The parameters that affect the uranium(VI) adsorption, such as contact time, solution pH, initial uranium(VI) concentration, and temperature, have been investigated. Equilibrium data were fitted to a simplified Langmuir and Freundlich isotherms for the oxidized samples which indicate that the uranium adsorption onto the activated carbon fitted well with Langmuir isotherm than Freundlich isotherm. Equilibrium studies evaluate the theoretical capacity of activated carbon to be 45.24 g kg−1.

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