Selçuk Şimşek

Investigations for Modification of Polyacrylamide-Bentonite by Phytic Acid and its Usability in Fe3+, Zn2+ and UO22+ Adsorption

Composite of polyacrylamide-bentonite (PAA-B) was prepared by direct polymerisation of PAA in a suspension of bentonite (B). Adsorption and thermodynamic features of phytic acid (Phy) adsorption onto B, PAA and PAA-B, and those of Fe3+, Zn2+, UO22+ adsorption onto PAA-B and its modification by Phy (PAA-B-Phy) have been investigated. The reusability, storagability, ion selectivity and recoverability of sorbed ions with 1 M HCl have also been considered.The chemical and physical structure of adsorbents has been characterised by means of FT-IR and XRD. All adsorption isotherms for Phy and the ions were L-type of the Giles classification except, the one which is S type for adsorption of Phy onto PAA. The maximum adsorption capacities for the ions adsorbed were in order of UO22+ > Fe3+ > Zn2+ for PAA-B and Zn2+ > Fe3+ > UO22+ for PAA-B-Phy. Langmuir equilibrium constants for the adsorption of ions onto PAA-B-Phy were significantly higher than those found for PAA-B; the magnitude of increase for UO22+ was about 100. The thermodynamic parameters indicated that adsorption reactions are spontaneous in terms of adsorption free enthalpy.The chemical structure of PAA-B-Phy was not changed at the end of the studies of reusability and storagability. The composite was selective for UO22+ of the ions of interest.The composite of PAA-B and its modification by Phy have been used for the first time in this investigation. It is proposed that the composites can be practically used in the investigations and applications of adsorption.

Removal of uranyl ions in aquatic mediums by using a new material: Gallocyanine grafted hydrogel

A new material containing gallocyanine (GC) grafted polyacyril amide (PAA) was synthesized and its adsorption ability was examined for the removal of uranyl ions from aqueous media. The new developed adsorbent was characterized by FTIR, SEM, and PZC analysis. Adsorption of UO₂(2+) ions from aqueous solution as a function of ion concentration, pH, ionic strength, temperature, and reusability of adsorbent was investigated in detail. The adsorption data were analyzed by using the Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. The adsorption of UO₂(2+) increased with pH and reached a plateau value in the pH range 5-6. The adsorption of UO₂(2+) ions were not affected by increasing ionic strength. The adsorption mechanism followed an endothermic and spontaneous process with increased disorderliness at adsorbate/adsorbent interface. The adsorption process followed a pseudo-second-order kinetics. The new developed material is a potential adsorbent for effective removal of uranyl ions from aquatic solutions.

Adsorption of UO22+, Tl+, Pb2+, Ra2+ and Ac3+ onto polyacrylamide-bentonite composite

Composite of polyacrylamide-bentonite (PAA-B) was prepared by direct polymerization in a suspension of bentonite (B), the composite was then modified by phytic acid (PAA-B-Phy). The parameters related to adsorption of UO22+ in absence and presence of 0.01M CaCl2 and of natural radionuclides (Tl+, Pb2+, Ra2+ and Ac3+ in a leaching solution) onto PAA-B and PAA-B-Phy, and thermodynamics of the adsorption were investigated. Adsorption isotherms were of L and H types for the adsorption of UO22+ onto PAA-B and PAA-B-Phy, whilst for Tl+, Pb2+, Ra2+ and Ac3+ they were of C type for both adsorbents. Langmuir equilibrium constants for the adsorption of all studied ions onto PAA-B-Phy were significantly higher than those found for PAA-B. The thermodynamic parameters indicated that adsorption reactions are spontaneous in terms of adsorption free enthalpy. The composite of PAA-B and its modification by Phy have been used for the first time in this study. It is concluded that the composites can be practically used for adsorption and applied as adsorbent of radionuclides.

UO22+, Tl+, Pb2+, Ra2+, Bi3+ and Ac3+ adsorption onto polyacrylamide-zeolite composite and its modified composition by phytic acid

The adsorption of naturally occurring radionuclides (UO22+, Tl+, Pb2+, Ra2+, Bi3+ and Ac3+) onto zeolite (Z) and polyacrylamide-zeolite composite (PAA-Z) and its modified composition by phytic acid (Z-Phy and PAA-Z-Phy) were investigated. Adsorption parameters were derived from the Langmuir and Freundlich fits to adsorption isotherms of the ions studied. The adsorption isotherms were of L and H types. The adsorption capacity of Z decreased by PAA inclusion, but the Phy modification of PAA-Z increased the capacity back to that of Z. The Phy modification made the adsorption spontaneity at least ten times better than in the absence of Phy. This investigation showed that the zeolite, as one of the most abundant natural materials and commonly used adsorbent can also be used for the removal of UO22+ and, in the PAA-Z form, of the studied radionuclides. The usage of Z, as PAA-Z and its Phy modification provide research materials which possess adequate practicality and effectiveness in studies of adsorption.

Synthesis and characterization of a composite polymeric material including chelating agent for adsorption of uranyl ions

In this study, a versatile polymeric material was synthesized by grafting Calcon Carboxylic Acid (CCA), which is known as a chelating agent for some metal ions, to polyacrylamide (PAA) structure. Thus, the adsorptive properties of inert PAA polymer were significantly improved owing to this procedure. The obtained new material, CCA-g-PAA, was characterized by point zero charge (PZC), FTIR, SEM, and UV-VIS-NIR analysis. The adsorption properties of new material were investigated comprehensively and experimental variables were optimized such as pH, temperature, time, and concentration. Experimental data were evaluated by using theoretical adsorption models. The maximum adsorption capacity of material was calculated as 0.079molkg-1 by considering Langmuir equation. The constants calculated from Freundlich and DR model were found as 6.98 and 0.441, respectively. Adsorption kinetic was also explained with pseudo second order and intra particular diffusion models. Experimental studies were showed that adsorption was endothermic and occurred spontaneously. The developed material has important advantages such as reusability, cost-effective synthesis procedure, high adsorption capacity, and selectivity.

Investigation of Mechanical and Structural Properties of Blend Lignin-PMMA

This in vitro study investigated the mechanical and structural characteristics of lignin-added PMMA resin composites at concentrations of 1, 3, and 5% by weight. Four sample groups were formed. For the transverse strength test, the specimens were prepared in accordance with ANSI/ADA specification number 12, and for the impact test ASTM D-256 standards were used. With the intent to evaluate the properties of transverse strength, the three-point bending () test instrument (Lloyd NK5, Lloyd Instruments Ltd., Fareham, Hampshire, UK) was used at 5 mm/min. A Dynatup 9250 HV (Instron, UK) device was employed for the impact strength measurements (). All resin samples were tested by using a thermomechanical analyzer (Shimadzu TMA 50, Shimadzu, Japan). Mechanical tests revealed that, although the control group was found to have the value of highest transverse strength, the highest impact strength was observed in the PMMA-L-1 group. Upon examining the thermomechanical analysis data, it could be seen that the value of the control sample was higher than that of all the other samples. Adding lignin powder into PMMA performs plasticizer effect on resin matrix.