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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] 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] 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] 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] Lead's uptake on magnetite has been quantitatively evaluated by equilibrium adsorption isotherms at 200 oC and pH of 8.5 for 2 hours contact time with [Pb2+] ranging from 5-175 ppm. The adsorption data has been fitted to Langmuir and Freundlich models. The maximum adsorption capacity of magnetite as an adsorbent for lead according to Langmuir and Freundlich models were 89.28 and 4.44 mg/g respectively. The regression correlation coefficients (R2) were higher for Freundlich isotherm (0.97) than Langmuir isotherm (0.90). A pH independent Pb2+ sorption on magnetite was observed that suggests Pb2+ sorption is due to permanent charges through weak electrostatic, non-specific attraction where cations are sorbed on the cation exchange sites rather than pH dependent sorption through surface hydroxyl/surface complexation. Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-AES), Fourier Transformed Infrared Spectrophotometry (FTIR), and X-ray diffraction (XRD) techniques were used to study mechanism of Pb2+ adsorption on magnetite. XRD results indicate a monotonic increase in the lattice parameter of Pb2+ containing magnetite with [Pb2+] increase in solution from 5-175 ppm suggesting incorporation of Pb2+ into magnetite structure. (author)