Feroxyhyte - from synthesis and characterization to application.

Feroxyhyte (δ-FeOOH) was synthesized and characterized using X-ray diffractometry (XRD), simultaneous thermal analysis (STA), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), and low-temperature nitrogen adsorption-desorption measurements. Its potential application as adsorbent of an anionic and cationic dyes such as C.I. Acid Violet 1 (AV1) and C.I. Basic Blue 3 (BB3) was investigated by determining the adsorption capacities based on the Langmuir (36.6 mg/g for AV1 and 187 mg/g for BB3), Freundlich and Dubinin-Radushkevich isotherm models. Adsorption of AV1 and BB3 by δ-FeOOH drops with the presence of additives such as cationic and anionic surfactants (CTAB, SDS) and ionic polymers (PAA, PEI). The surface and electrokinetic properties of examined suspensions were also described. They include determination of the solid surface charge density and the zeta potential, as well as values of point of zero charge and isoelectric point of feroxyhyte particles without and with adsorbed layers of organic substances. Their analysis made possible to propose the most probable structure of electrical double layer formed at the iron mineral/aqueous solution interface.

Fly Ash-Based Na-X Zeolite Application in Separation Process of Bovine Serum Albumin from Aqueous Solution in the Presence of Organic Substances with Anionic Character.

The main purpose of the investigations was to explore the protein adsorption on porous materials, as well as to identify the mechanisms of protein attachment without and with other common environmental contaminants, such as drugs, polymers or surfactants. This study applied the Na-X zeolite for the adsorption of bovine serum albumin (BSA) from solutions with various pH values. Electrophoretic mobility measurements and potentiometric titrations were conducted in systems containing both protein and/or PAA (poly(acrylic acid) polymer/DCF (diclofenac) drug/SDS (sodium dodecyl sulfate) surfactant to investigate the protein binding mechanisms in the complex adsorbate systems. In addition, aggregate size and stability measurements were performed in the investigated systems. Based on the research results, it was possible to conclude that the protein adsorbed most preferably on the zeolite surface at a pH value close to its isoelectric point (pI) (102.15 mg/g), and protein adsorption was the lowest in the solutions with strongly alkaline (29.61 mg/g) or acidic (77.45 mg/g) pH values. Thus, the examined zeolitic material can be considered an effective adsorbent for protein removal from an aqueous solution.

C.I. Basic Red 46 Removal from Sewage by Carbon and Silica Based Composite: Equilibrium, Kinetic and Electrokinetic Studies.

The worldwide production of colored products and intermediates is increasing year on year. The consequence of this is an increase in the number of liquid effluents containing toxic dyes entering the aquatic environment. Therefore, it is extremely important to dispose of them. One of the techniques for the elimination of environmentally harmful dyes is adsorption. The main purpose of this study was to explore the possibility of using a carbon and silica (C/SiO2)-based composite for the removal of the azo dye C.I. Basic Red 46 (BR46). The adsorption capacity of C/SiO2 was found to be temperature dependent and increased from 41.90 mg/g to 176.10 mg/g with a temperature rise from 293 K to 333 K in accordance with the endothermic process. The Langmuir isotherm model seems to be the better one for the description of experimental data rather than Freundlich or Dubinin-Radushkevich. The free energy (ΔGo) confirmed the spontaneous nature of BR46 adsorption by C/SiO2. Kinetic parameters revealed that BR46 uptake followed the pseudo-second-order equation; however, the external diffusion plays a significant role. Surfactants of cationic, anionic and non-ionic type influenced BR46 retention by C/SiO2. The electrokinetic results (solid surface charge density and zeta potential) indicated that the adsorption of cationic dye and surfactant influences the structure of the electrical double layer formed at the solid-liquid interface.

Investigations of chromium(III) oxide removal from the aqueous suspension using the mixed flocculant composed of anionic and cationic polyacrylamides.

The main purpose of experiments was determination of the adsorption mechanism of two forms of ionic polyacrylamide (PAM) on the surface of chromium(III) oxide dispersed in the aqueous medium. This was performed in relation to anionic polyacrylamide (AN PAM) and cationic one (CT PAM) in the simple systems (containing only one selected polymer) and in the mixed systems (containing both ionic forms of PAM). The turbidimetry was applied to determine the stability of examined suspensions. To explain the obtained changes in suspension stability after the polymer addition, polyacrylamide adsorbed amount, surface charge density and zeta potential of solid particles were determined. It was found that the solution pH, order of both adsorbates addition as well as the time interval between the AN and CT PAM addition have considerable influence on the structure of polymeric adsorption layer formed on the Cr2O3 surface. It was also proved that changes in the PAM adsorbed amount in the systems containing mixed adsorbates result from formation of AN PAM - CT PAM complexes. They are bounded at the interface in the formed multilayer. As a result, the dual-polymer flocculation occurs more effectively than the destabilization process in the suspensions containing only one type of adsorbate.

Impact of anionic polyacrylamide on stability and surface properties of the Al2O3-polymer solution system at different temperatures.

The stability mechanism and thermal properties of the system alumina-anionic polyacrylamide (PAM) was studied. The polymer's adsorption properties in dependence on the following parameters solution pH (in the range 3-9), temperature (in the range 15-35 °C), and carboxyl groups' content in the PAM chains (in the range 5-30 %) were examined. The turbidimetry method was applied for determination of the suspension stability of alumina in the presence of PAM. The obtained results indicate that the polymer addition improves significantly Al2O3 suspension stability at pH 6 and 9 (in the whole examined temperature range). PAM containing a larger number of carboxyl groups stabilizes solid particles more effectively (due to greater contribution of electrosteric interactions). Moreover, the polymer adsorption on the alumina surface causes changes in the thermal stability of the examined systems. In dependence on temperature, the higher the content of carboxyl groups in the PAM molecules, the greater the total mass loss. This is due to increased adsorption of polyacrylamide whose chains contain numerous -COOH groups.

Investigation of the polyvinyl alcohol stabilization mechanism and adsorption properties on the surface of ternary mixed nanooxide AST 50 (Al2O3-SiO2-TiO2).

A new adsorbent consisting of fumed, mixed alumina, silica, and titania in various proportions (AST 50) was investigated. The studied material was prepared by chemical vapor deposition method. The diameter of AST 50 primary particles was equal to about 51 nm which denotes that it can be classified as a nanomaterial. In the presented paper, the adsorption properties of polyvinyl alcohol on the ternary oxide were investigated. The polymer macromolecules were characterized by two different molecular weights and degree of hydrolysis. The polymer adsorption reaches the maximum at pH 3 and decreases with the solution pH rise. The reduction of the adsorbed PVA macromolecules is related to the electrostatic repulsion forces occurring in the studied system. The AST 50 point of zero charge (pHpzc) obtained from the potentiometric titration is equal to 4.7. Due to the nonionic character of the analyzed macromolecular compound, the polymer attendance has an insignificant effect on the AST 50 surface charge density. In the case of the adsorbent particles zeta potential, the obtained dependencies are different in the absence and presence of PVA. The shift of the slipping plane and displacement of the counter-ions from Stern layer by the adsorbed polymer chains have the greatest effect on the ζ potential value. The stability measurements indicate that the AST 50 suspensions in the presence of the background electrolyte at pH 3 and 6 are unstable. In turn, in an alkaline medium the mixed oxide suspensions exhibit the highest durability, which is a result of a large number of the negative charges on the AST 50 surface. The addition of PVA 100 significantly improves the suspension stability at pH 3 and 6; at higher pH value, the polymer presence does not influence the system durability. It is related to the steric and electrosteric stabilization of the colloidal particles by the adsorbed polyvinyl alcohol macromolecules.

Impact of polyacrylamide with different contents of carboxyl groups on the chromium (III) oxide adsorption properties in aqueous solution.

The main goal of experiments was determination of solution pH and contents of anionic groups in polyacrylamide (PAM) macromolecules on the stability mechanism of chromium (III) oxide suspension. The spectrophotometry, potentiometric titration, microelectrophoresis, viscosimetry and turbidimetry were applied. They enabled determination of polymer adsorbed amount, surface and diffusion charges of solid particles with and without PAM, thickness of polymer adsorption layer, macromolecule dimensions in the solution and stability of the Cr2O3 - polymer systems, respectively. It was found that adsorption of anionic PAM decreases and thickness of polymeric adsorption layer increases with the increasing pH. Slightly higher adsorption was obtained for the PAM samples containing a greater number of carboxyl groups. At pH 3 and 9 insignificant deterioration of stability conditions of Cr2O3 particle covered with polyacrylamide was observed (neutralization of solid positive charge by the adsorbed polymeric chains (pH 3) and single polymeric bridges formation (pH 9)). The electrosteric repulsion between the solid particles covered with PAM layers at pH 6, is the main reason for significant improvement of Cr2O3 suspension stability in the polymer presence.

Competitive adsorption of Ca2+ and Zn(II) ions at monodispersed SiO2/electrolyte solution interface.

A study of competitive adsorption of Ca(2+) and Zn(II) ions at the monodispersed SiO(2)/electrolyte solution interface is presented. Influence of ionic strength, pH, and presence of other ions on adsorption of Ca(2+) and Zn(II) in the mentioned system are investigated. zeta potential, surface charge density, adsorption density, pH(50%), and DeltapH(10-90%) parameters for different concentrations of carrying electrolyte and adsorbed ions are also presented. A high concentration of zinc ions shifts the adsorption edge of Ca(2+) ions adsorbed from solutions with a low initial concentration at the SiO(2)/NaClO(4) solution interface to the higher pH values. This effect disappears with a concentration increase of calcium ions. The presence of Ca(2+) ions in the system slightly affects the adsorption of zinc ions on SiO(2), shifting the adsorption edge toward lower pH values and thereby increasing the adsorption slope.