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[en] A new amine-functionalized graphene oxide (GO-NH_2) nanosheet was prepared via covalently grafting reaction. The removal of U(VI) from aqueous solution with GO and GO-NH_2 was compared using batch method. The adsorption of uranium ions could be well-described by the Langmuir isotherm and pseudo-second kinetic model. The adsorption capacities of GO and GO-NH_2 were found to be 97.3 and 215.2 mg g"-"1 at 298.15 K, respectively. Results showed that adsorption capacity of GO was significantly improved by amine functionalization. (author)
[en] Highlights: • Poly(N-2-aminoethylacrylamide) was grafted magnetite nanoparticles via ATRP. • Removal of Cu(II) cations was investigated by differential pulse voltammetry (DPV). • Kinetics, thermodynamics and adsorption isotherm models were studied. • The re-usability of the prepared magnetic sorbent was investigated.
[en] The equilibrium sorption of a local Ayous (Triplochiton scleroxylon) wood sawdust was examined as substitute adsorbent for removal of paraquat from water. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (DRK) isotherms were used to compare the equilibrium sorption data obtained. The separation factor revealed a constructive sorption experiment since the maximum monolayer coverage (Q0) from Langmuir isotherm model was found out to be 41.66 µmol/g. In addition, the correlation value of Langmuir isotherm model was the maximum among the four adsorption isotherms. From Freundlich isotherm model, the sorption intensity (n) that denotes favorable sorption and the correlation value are 2.402 and 0.929, respectively. Temkin isotherm model was used to calculate the heat of sorption process which corresponds to 18.39 J/mol, and the mean free energy was estimated from DRK isotherm model to be 0.091 kJ/mol which vividly proved that the adsorption experiment was obeyed to a physical process. The results indicate that this local wood sawdust could be employed as an economical material for reducing paraquat from industrial wastewater.
[en] Vapor pressure isotherms of 3He on Cs are reported which show that, in contrast to 4He, 3He wets Cs for 1.26 K < T < 2K. Although the isotherms are distinctly different from those taken on strong binding substrates, the authors have observed no evidence for a first order prewetting transition. The data suggest that the prewetting critical point is substantially below T = 1.26 K
[en] An expression for describing the contribution of insoluble crystalline particles to the proton relaxation in water is obtained by applying the Langmuir adsorption isotherm formula. It is found that the expression can also be utilized for determining the number of grams adsorbed per gram of adsorbent
[en] This patent describes a method of determining an adsorption isotherm of a thin film using a piezoelectric substrate having a surface. It comprises coating the thin film on the surface of the substrate; applying an adsorbate to the film; generating a surface acoustic wave along the coated surface, the acoustic wavelength of the surface acoustic wave, being greater than the thickness of the film; measuring the change in frequency of the surface acoustic wave to determine the adsorption/desorption isotherm of the adsorbate on the film; and determining the mass/surface area of the film by applying the BET model to the isotherm
[en] Multiwall carbon nanotubes (MWCNTs) were modified by nitric acid solution and then used to study the adsorption of cesium from aqueous solution using a batch technique under ambient conditions. As produced and oxidized MWCNTs were characterized by nitrogen adsorption/desorption, Boehm's titration method and Fourier transform infrared spectroscopy. The physical properties of MWCNTs such as functional groups, total number of acid sites and specific surface area were greatly improved after oxidation, and these were responsible for more sorption of cesium from aqueous solution and made them more dispersible in water. The adsorption of cesium ions as a function of contact time, initial concentration of cesium, pH, ionic strength and oxidized MWCNT concentrations was also investigated. The results showed that cesium adsorption percentage strongly depended on the pH value, oxidized MWCNT content and on the solution ionic strength. Kinetic data indicated that the adsorption process achieved equilibrium within 80 min. Equilibrium data for as produced and oxidized MWCNTs was well described by both Freundlich and Langmuir isotherms. The dominant mechanism of cesium adsorption on oxidized MWCNTs may be mainly attributed to ion exchange. This study suggests that oxidized MWCNTs can be a promising candidate for the removal of cesium from nuclear waste solution. (author)
[en] The sorption of uranium from acidic aqueous solutions (pH 4.5, Cinit = 10 to 1000 mg U/L) by Saccharomyces cerevisiae, Debaryomyces hansenii, Kluyveromyces marxianus and Candida colliculosa was investigated using a batch technique. The U-sorption onto Saccharomyces cerevisiae and Debaryomyces hansenii followed a Langmuir, while that onto Kluyveromyces marxianus and Candida colliculosa a Freundlich isotherm. The results demonstrated that all investigated biomasses could effectively remove uranium from acidic aqueous solutions. From all sorbents, Saccharomyces cerevisiae appeared to be the most effective with a maximum sorption capacity of 127.7 mg U/g dry biomass. (author)
[en] The influence of initial uranium concentration, solution pH, contact time and adsorbent mass was investigated for removal of uranium from aqueous solutions by pine wood powder and wheat straw using a batch technique. The maximum removal efficiency of uranium achieved at pH 8 and 7 for pine wood powder and wheat straw, respectively. Langmuir and Freundlich adsorption isotherms and three kinetic models of adsorption including; Elovich, Lagergren pseudo-first and Lagergren pseudo-second order were used to describe the adsorption mechanisms. The uranium sorption onto wood and wheat straw powders followed a Freundlich isotherm. The kinetic studies showed that the data fitted very well to the pseudo-second order model in the studied concentration range of uranium for both adsorbents. Uranium desorption from loaded adsorbents also studied using batch techniques as a function of desorptive reagent, desorption time and desorptive reagent concentration. The results of the experiment indicated that the optimum desorption efficiency of uranium for wood powder and wheat straw occurred in 5 min shaking time, using 1.5 M HNO3 and 2 M Na2CO3 solutions, respectively. (author)
[en] In this study, natural biofilm matrices formed on stones have been used for the adsorption of Alcian blue dye. Alcian blue is a member of polyvalent basic dyes that largely used from laboratory until industrial dying purposes. The adsorption of the dye onto the biofilm matrix has been carried out at different experimental conditions such as adsorption isotherm and kinetic of adsorption. The electric charge properties of biofilm matrix and its changes related to the adsorption of Alcian blue have been also investigated. Moreover, the results of Alcian blue adsorption to the biofilm were compared to those onto the acidic and neutral resin. The kinetics of adsorption result showed that the adsorption of the Alcian blue dye reached to a maximum adsorption amount within 60 minutes. The adsorption amount of Alcian blue to biofilm increased monotonously, and the maximum adsorption amount was greater compared to the resins. On the contrary, Alcian blue did not attach to the neutral resin having no electric charge. It seems that Alcian blue attached to the acidic resins due to electrostatic attractive force, and the same seems to be the case for adsorption of Alcian blue to biofilm. The adsorption of Alcian blue to the biofilm and acidic resins fitted to Langmuir type indicates that the binding of Alcian blue to the biofilm and acidic resins occurred in a monolayer like form. The maximum adsorption amount of Alcian blue on the biofilm (0.24 mmol/dry-g) was greater than those of acidic resin (0.025 mmol/dry-g). This indicates that the biofilm has many more sites for Alcian blue attachment than acidic resins. According to the result of this study, the biofilm matrix can be a good adsorbent for dye such as Alcian blue or other dyes that causing hazards in nature. (paper)