Agnieszka Gładysz-Płaska

Equilibrium study of selected divalent d-electron metals adsorption on A-type zeolite

The objective of the presented study was to investigate the adsorption of Cu, Co, Mn, Zn, Cd and Mn on A-type zeolite. The isotherms for adsorption of metals from their nitrates were registered. The following adsorption constants K of metals were found: 162,890, 124,260, 69,025, 16,035, 10,254, and 151 [M(-1)] for Cu, Co, Mn, Zn, Cd, and Ni, respectively, for the concentration range 10(-4)-10(-3) M. On the other hand, the investigation of pH influence on the distribution constants of metals showed that the adsorption of metals proceeds essentially through an ion-exchange process, surface hydrolysis, and surface complexation. The supplementary results from DRIFT, scanning electron microscopy, and X-ray diffraction methods confirmed the presumption about the possible connection between the electronic structure of divalent ions and their adsorption behavior, showing that ions with d5 and d10 configurations such as Mn2+, Zn2+, Cd2+, with much weaker hydrolytic properties than Cu2+ and Ni2+, strongly interact with the zeolite framework and therefore their affinity to the zeolite phase is much stronger when compared with that of the Ni2+ ion, but at the same time not as strong as the affinity of the Cu2+ ion, the latter forming a new phase during the interaction with zeolite framework. For Zn2+, during inspection of the correlation between the proton concentration H/Al and zinc concentration Zn/Al on the zeolite surface, the formation of the surface complex [triple bond]S-OZn(OH) was proposed. A correlation between the heterogeneity of proton concentrations H/Al on Me-zeolite surfaces and the hydrolysis constants pKh of Me2+ ions was found.

Silica with immobilized phosphinic acid-derivative for uranium extraction

A novel adsorbent benzoimidazol-2-yl-phenylphosphinic acid/aminosilica adsorbent (BImPhP(O)(OH)/SiO2NH2) was prepared by carbonyldiimidazole-mediated coupling of aminosilica with 1-carboxymethylbenzoimidazol-2-yl-phenylphosphinic acid. It was obtained through direct phosphorylation of 1-cyanomethylbenzoimidazole by phenylphosphonic dichloride followed by basic hydrolysis of the nitrile. The obtained sorbent was well characterized by physicochemical methods, such as differential scanning calorimetry-mass spectrometry (DSC-MS), surface area and pore distribution analysis (ASAP), scanning electron microscopy (SEM), X-ray photoelectron (XPS) and Fourier transform infrared (FTIR) spectroscopies. The adsorption behavior of the sorbent and initial silica gel as well as aminosilica gel with respect to uranium(VI) from the aqueous media has been studied under varying operating conditions of pH, concentration of uranium(VI), contact time, and desorption in different media. The synthesized material was found to show an increase in adsorption activity with respect to uranyl ions in comparison with the initial compounds. In particular, the highest adsorption capacity for the obtained modified silica was found at the neutral pH, where one gram of the adsorbent can extract 176mg of uranium. Under the same conditions the aminosilica extracts 166mg/g, and the silica - 144mg/g of uranium. In the acidic medium, which is common for uranium nuclear wastes, the synthesized adsorbent extracts 27mg/g, the aminosilica - 16mg/g, and the silica - 14mg/g of uranium. It was found that 15% of uranium ions leached from the prepared material in acidic solutions, while 4% of uranium can be removed in a phosphate solution.

Unexpected difference in phenol sorption on PTMA- and BTMA-bentonite

The comparison of phenol sorption on phenyltrimethylammonium (PTMA)- and benzyltrimethylammonium (BTMA)-bentonite shows a clear difference as far as phenol sorption isotherms are concerned. For PTMA-bentonite the sorption isotherm is of a straight-line character which results from simple partitioning of phenol between the aqueous and organic phases sorbed on the bentonite surface. For BTMA-bentonite the isotherm has a convex shape, characteristic of physicochemical sorption. For the first time a three-parametric model, including the dissociation constant of phenol pK(a), distribution constant of phenol Kd(phen) and phenolate anion Kd(phen)(-) between the aqueous phase and the bentonite phases is used for the evaluation of phenol sorption on organoclays with pH change. The model shows that the values of Kd(phen) are higher than those of Kd(phen)(-) for all investigated initial phenol concentrations. The inspection of the FTIR spectrum of BTMA-bentonite loaded with phenol in the regions 1300-1600 and 1620-1680 cm(-1) shows the features of pi-pi electron interaction between the benzene rings of phenol and the BTMA cation together with the phenol-water hydrogen bond strengthened by this interaction.

Adsorption of light lanthanides on the zeolite A surface

Abstract Adsorption studies of light lanthanides on the powdered zeolite type A are presented. It results from the mathematical description of the adsorption isotherms and from complementary scanning electron microscopy (SEM) studies of the adsorbent surface, that heterogeneity of the A type zeolite is most pronounced in the case of lanthanum and cerium, which fact correlates very well with the ability of these lanthanides to hydroxide complexes formation. It was found from the observation of the distribution constants Kd of lanthanides on pH values of the aqueous phase, that lanthanide adsorption proceeds through ion-exchange pathway up to pH 4.9, 4.8, 5.2, 4.0, 4.5 for La, Ce, Pr, Nd and Sm, respectively. For higher pH values surface hydrolysis with evolution of LnpZe3p(OH)q−q seems to be dominant component in the overall adsorption process. The separation of Nd from La, Ce and Pr via adsorption process is recommended.

Scanning electron microscopy and DRIFT study of metal-loaded Y zeolites

Abstract The chemical composition of the ‘surface’ of metal-loaded Y zeolites was investigated by SEM technique. The negative correlation between proton C H/Al and metal C Me/Al local concentrations for Mn, Cu and Zn, resulting from the interaction (ion exchange) of metal ions Me 2+ with ‘surface’ hydroxide bridges ≡Al–OH–Si≡ was found. In turn the positive correlation of C H/Al vs. C Me/Al for Cd was explained as stabilization of CdZe 2 and Cd(OH)Ze complexes in the zeolite structure through the formation of hydrogen bonds with hydroxide bridges. The supplementary Diffusive Reflectance Infrared Study of metal-loaded zeolite showed the sensitivity of framework vibration band T–O–T for Me 2+ ions interaction with negative oxygens of zeolite framework. In connection with this finding two groups of ions were recognized: Mn 2+ , Cd 2+ , Zn 2+ with strong interaction and consequent shift of T–O–T band toward lower frequencies and Co 2+ , Ni 2+ , Cu 2+ ions group with weak interaction with the zeolite framework with consequent position of T–O–T at higher frequencies.

Imidazole-2yl-Phosphonic Acid Derivative Grafted onto Mesoporous Silica Surface as a Novel Highly Effective Sorbent for Uranium(VI) Ion Extraction

A new imidazol-2yl-phosphonic acid/mesoporous silica sorbent (ImP(O)(OH)2/SiO2) was developed and applied for uranium(VI) ion removal from aqueous solutions. The synthesized material was characterized by fast kinetics and an extra-high adsorption capacity with respect to uranium. The highest adsorption efficiency of U(VI) ions was obtained for the reaction system at pH 4 and exceeded 618 mg/g. The uranium(VI) sorption proceeds quickly in the first step within 60 min of the adsorbent sites and ion interactions. Moreover, the equilibrium time was determined to be 120 min. The equilibrium and kinetic characteristics of the uranium(VI) ions uptake by synthesized sorbent was found to follow the Langmuir-Freundlich isotherm model and pseudo-second-order kinetics rather than the Langmuir, Dubinin-Radushkevich, and Temkin models and pseudo-first-order or intraparticle diffusion sorption kinetics. The adsorption mechanism for uranium on the sorbent was clarified basing on the X-ray photoelectron spectroscopy (XPS) analysis. The model of UO22+ binding to surface of the sorbent was proposed according to the results of XPS, i.e., a 1:1 U-to-P ratio in the sorbed complex was established. The regeneration study confirms the ImP(O)(OH)2/SiO2 sorbent can be reused. A total of 45% of uranium ions was determined as originating from the sorbent leaching in the acidic solutions, whereas when the basic solutions were used, the removal efficiency was 12%.

Application of modified clay for removal of phenol and PO43− ions from aqueous solutions

Simultaneous adsorption of phenol and phosphate(V) ions on the surfactant-modified clay from the binary mixture was studied and compared with the single phenol or phosphate(V) sorption. The maximum adsorption capacity of hexadecyltrimethylammonium–bentonite was 18.8 mg/g for phenol and 38.5 mg/g for phosphate(V) at simultaneous adsorption of both of them. The optimal pH values of adsorption on hexadecyltrimethylammonium–bentonite was found to be 7.0 and >7 for phosphate(V) and phenol, respectively. The kinetic studies showed that the adsorption followed a pseudo-second-order reaction for both. The equilibrium data were analyzed using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models.

Study of effect of phosphate and uranium ions on the thermal properties of surfactant-modified natural red clay using TG–FTIR–MS techniques

Products of sorption of uranyl ions on HDTMA-red clay in the presence of phosphates were characterized by thermal analysis. It was established on the basis of DTG curves of the sorption products and FTIR spectra of the gaseous phase of sorption products decomposition that the thermal stability of the mineral increased when P(V) ions were sorbed along with U(VI) ions, i.e., the temperature of defragmentation/oxidation of surfactant increased when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay to P(V)–HDTMA-clay. The DSC curves of the sorption products showed that defragmentation/oxidation was an exothermic process and dehydration and dehydroxylation had an endothermic character. The investigated sorption system has practical importance, since an evident increase in U(VI) sorption over the entire pH range is observed when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay.

Naphthalene sorption on red clay and halloysite modified by quaternary ammonium salts

Sorption of naphthalene on modified red clay and halloysite was carried out successfully. It was established that the process was of pseudo-second-order mechanism. The maximum sorption capacities were 9.23 mg/g and 112.79 mg/g for red clay and halloysite, respectively.