Evaluation of phillipsite as cation exchanger in lead removal from water

Synthesis, characterization and sorption properties of silica modified with some derivatives of β-cyclodextrin

Nanoporous β-cyclodextrin-containing silicas which differ by functional substituents of wide edge of attached cyclic oligosaccharide molecules (alcohol, bromoacetyl, thiosemicarbazidoacetyl groups) have been synthesized. The structure and chemical composition of the surface, porosity of obtained materials, their chemical and thermal stability have been characterized by scanning electron microscopy, IR spectroscopy, thermogravimetry, nitrogen ad-desorption, elemental and chemical analyses of solid surface. Sorption of trace amounts of cadmium (II) in the presence of ten- and hundred-fold excess of hardness salts by synthesized organosilicas has been studied. It has been demonstrated that the sorption equilibrium is reached after 30 min. The sorption of trace amounts of cadmium (II) from multi-component solutions does not decrease, but even increases in the presence of hardness salts, simulating soft and hard water. Coefficients of distribution and selectivity as well as the sorption parameters of Langmuir and Freundlich equations have been calculated. It was found that the driving force of cadmium (II) sorption on the surface of functional β-cyclodextrin-containing silicas is the formation of inclusion complexes "β-cyclodextrin-nitrate-anion". It has been proved the formation of supramolecular structures on the surface of synthesized organosilicas as a result of cadmium (II) sorption. Chemical composition of supermolecules depends on the structure of surface active centers.

Removal of Mn from aqueous solution using fly ash and its hydrothermal synthetic zeolite

A number of water purification processes have been developed in recent years based on the utilisation of low-cost materials with high pollutant removal efficiency. Among these materials, fly ash and zeolite synthesised from fly ash are two examples of high-efficiency adsorbents. Column absorption tests were performed in order to compare the manganese sorption behaviour of an Italian coal fly ash and zeolite synthesised from it. Different masses of both materials (10-60 g) were exposed to solutions containing a total metal concentration of 10 mg/L. Batch adsorption studies were also conducted to determine the effect of time on the removal on Mn sequestration. The results indicate that both materials are effective for the removal of Mn from aqueous solution by precipitation due to the high pH of the solid/liquid mixtures. However, the leaching tests reveal that the amount of Mn removed from the fly ash was greater than that leached from the zeolite, thereby indicating that the metal is partially sequestrated by zeolite.

Preparation, characterization and adsorption properties of a novel 3-aminopropyltriethoxysilane functionalized sodium alginate porous membrane adsorbent for Cr(III) ions

In this study, we prepared 3-aminopropyl-triethoxysilane (APTEOS) functionalized sodium alginate (SA) porous membrane adsorbent (APTEOS/SA) and tested its adsorption performance for removing of Cr(III) ions. The physico-chemical properties of the pristine and Cr(III) ions loaded APTEOS/SA were investigated by FT-IR, SEM-EDX, TG, AFM, and contact angle goniometer methods. To investigate the adsorption kinetics of Cr(III) ions onto this newly developed APTEOS/SA, we performed a batch of experiments under different adsorption conditions: solution pH, adsorbent dose, initial Cr(III) ion concentration, adsorption temperature, and contact time. The APTEOS/SA exhibited an encouraging uptake capacity of 90.0mg/g under suitable adsorption conditions. To study the mechanism of adsorption process, we examined the Lagergren pseudo-first-order and pseudo-second-order kinetic model, the intra-particular diffusion model, and the Crank model. Kinetics experiments indicated that the pseudo-first-order model displayed the best correlation with adsorption kinetics data. The Crank model showed that the intra-particle solute diffusion was the main rate-controlling step. Furthermore, our adsorption equilibrium data could be better described by the Freundlich equation. We also carried out consecutive adsorption-desorption experiments eight times to show that the APTEOS/SA has encouraging adsorption-desorption efficiencies. The results indicates that the prepared adsorbent is promising for using as an effective and economical adsorbent for Cr(III) ions removal.

Removal of humic substances from water by means of calcium-ion-enriched natural zeolites

The ability of the natural zeolited Neapolitan Yellow Tuff (NYT) enriched with calcium ions to remove humic acids from water was evaluated by batch adsorption equilibrium tests and dynamic experiments carried out by percolating humic acid solutions through a small NYT column (breakthrough curves). Under the experimental condition explored, the sorption capacity increases with the ionic strength and has the highest value at pH 7.4. The partition coefficient for a low concentration of humic acid ([humic acid] --> 0), at pH 7.4 in 0.01 M sodium chloride, was approximately 1000 L/kg, versus the value of approximately 100 L/kg in the absence of the alkaline metal salt. Therefore, after humic acids have been adsorbed in a column filled with the calcium-ion-enriched tuff, a reduction of the salt concentration in the ongoing solution enhances the release of the adsorbed material. These findings show that NYT can be used for the removal of humic acids from water.

Comparison of isotherms for the ion exchange of Pb(II) from aqueous solution onto homoionic clinoptilolite

The ion exchange equilibrium of Pb(II) on clinoptilolite modified with NH(4)Cl and NaCl can be represented by two types of isotherms. The first one is the ion exchange isotherm based upon the constant of thermodynamic equilibrium for the ion exchange reaction; however, the fitting procedure for this isotherm can be very tedious due to all the calculations involved and additional thermodynamic data. The second one is the Langmuir isotherm. The use of the Langmuir isotherm to represent ion exchange equilibrium has increased in recent last years since it adequately fits the equilibrium data and, furthermore, its calculation is much simpler. A comparison between the two isotherms showed that they fitted the experimental data reasonably well, but the Langmuir isotherm is much simpler and easier to use.

Selective removal of the heavy metal ions from waters and industrial wastewaters by ion-exchange method

By ion exchange undesirable ions are replaced by others which don't contribute to contamination of the environment. The method is technologically simple and enables efficient removal of even traces of impurities from solutions. Examples of selective removal of heavy metal ions by ion-exchange are presented. They include removal of Pb(II), Hg(II), Cd(II), Ni(II), V(IV,V), Cr(III,VI), Cu(II) and Zn(II) from water and industrial wastewaters by means various modern types of ion exchangers.