Chitosan (Ch) was entrapped in polyacrylamide (PAA) by direct polymerization of acrylamide in a suspension of Ch. The adsorptive features of PAA-Ch and Ch were then investigated for Pb2+, UO22+, and ...Th4+ in view of dependency on ion concentration, temperature, and kinetics. Additional considerations were also given to their ion selectivity and reusability. Isotherms were L and H type of Giles classification and evaluated with reference to Langmuir, Freundlich, and Dubinin-Radushkevich (DR) models. PAA-Ch had higher adsorption capacity than Ch for all studied ions so that the sequences were Th4+ > Pb2+ > UO22+ concordantly with their affective ionic charges. The affinity of Ch in PAA increased for Pb2+ and UO22+ but did not change for Th4+. The values of enthalpy and entropy changed were positive for all studied ions for both Ch and PAA-Ch. The negative free enthalpy change value indicated that the adsorption process is spontaneous in the sequence of Th4+ > =Pb2+ > UO22+. Free energy values derived from DR model implied that the sorption process is the ion exchange. Well compatibility of adsorption kinetics to the pseudosecond-order model predicate that the rate-controlling step is a chemical sorption. The study for ion selectivity showed that both Ch and PAA-Ch had the highest affinity to Pb2+. The reusability tests for Ch and PAA-Ch for Pb2+ for five uses showed that complete recovery of the ion was possible. The studied features of PAA-Ch suggest that the material should be considered as a new adsorbent. It is envisaged that the use of Ch in PAA will enhance practicality and effectiveness of Ch in separation and removal procedures.
Micro-composite of polyacrylamide (PAA) and apatite (Apt) was prepared by direct polymerization of acrylamide in a suspension of Apt and characterized by means of FT-IR, XRD, SEM and BET analysis. ...The adsorptive features of PAA-Apt and Apt were then investigated for Pb2+, UO22+ and Th4+ in view of dependency on ion concentration, temperature, kinetics, ion selectivity and reusability. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. Apt in PAA-Apt had higher adsorption capacity (0.81, 1.27 and 0.69 mol kg-1) than bare Apt (0.2,0.41 and 1.33 mol kg-1) for Pb2+ and Th4+, but not for UO22+. The affinity to PAA-Apt increased for Pb2+ and UO22+ but not changed for Th4+. The values of enthalpy and entropy changed were positive for all ions for both Apt and PAA-Apt. Free enthalpy change was DeltaG < 0. Well compatibility of adsorption kinetics to the pseudo-second-order model predicated that the rate-controlling step was a chemical sorption. This was consistent with the free energy values derived from DR model. The reusability tests for Pb2+ for five uses proved that the composite was reusable to provide a mean adsorption of 53.2 +/- 0.7% from 4 X 10-3 M Pb2+ solution and complete recovery of the adsorbed ion was possible (98 +/- 1%). The results of this investigation suggested that the use of Apt in the micro-composite form with PAA significantly enhanced the adsorptive features of Apt.
Water-soluble sulfolignin (SL) was grafted onto hydroxyapatite (Hap) by using epichlorohydrin. SLgHap was then entrapped in cross-linked polyacrylamide by in situ polymerizations of acrylamide and N, ...N′-methylenebisacrylamide to obtain the composite of PSLgHap. The composite was characterized by FT-IR, BET- porosity, XRD, EDXRF, SEM-EDX, TGA-DTG, PZC, CEC, and swelling tests. The adsorptive features of PSLgHAP were investigated for Th4+ and BSA in view of its dependence on pH, ionic intensity, concentration, temperature, and time. The results of characterization tests confirmed the formation of PSLgHap. The grafting efficiency concerning sulfur contents of PSLgHap was 96% by EDXRF. The isotherms were best represented by the Sips model, Langmuir adsorption capacities were 369 and 390 mg gSLgHap−1 for BSA and Th4+. The enthalpy and entropy changes were positive whilst Gibbs energy was negative by entropy controlled. The adsorption kinetics of both species was obeyed to pseudo second-order model, whereas it was first-order for BSA and hybrid-order for Th4+ of Langmuir model.
•Sulfolignin grafted hydroxyapatite was entrapped in PAAm by in situ polymerization.•Grafting efficiency was proved to be >95% by EDXRF.•The composite characterized by XRD, SEM-EDX, FTIR, TG/DTG, and swelling features.•Adsorption of Th4+ and BSA was determined by isotherms, kinetics, and thermodynamics.•Monolayer adsorption capacities were 390 mg g−1 for Th4+ and 369 mg g−1 for BSA.
The composites of natural (clinoptilolite) and synthetic zeolite (Z and YZ) with polyacrylamide (PAAm) were synthesized and characterized by FT-IR, TGA, XRD, SEM and PZC analysis. The adsorptive ...features of the minerals and its composites were investigated for Tb analogues to the rare earth elements (REs) by isotopic tracer method, 160Tb was the radiotracer. The composites were the hybrid formations of PAAm and Z or YZ. Tb adsorption capacities of the composites were higher than those of bare Z and YZ. The compatibility of Tb adsorption kinetics to the second order and Weber–Morris models implied that the sorption process was chemical via ion exchange. The values of enthalpy and entropy changes were positive and the negative free enthalpy change was evidence for the spontaneity of adsorption. The reusability tests for the composites for five uses demonstrated that the adsorbents could be reused after complete recovery of the loaded ion. Unlike PAAm–YZ, PAAm–Z was resistant to acidic environment. The overall results eventually suggested that the composite of Z and PAAm was a potential cost effective adsorbent for Tb3+ and REs.
The composite of synthetically produced hydroxyapatite (HAP) and polyacrylamide was prepared (PAAm–HAP) and characterized by BET, FT-IR, TGA, XRD, SEM and PZC analysis. The adsorptive features of HAP ...and PAAm–HAP were compared for UO22+ and Th4+. The entrapment of HAP into PAAm–HAP did not change the structure of HAP. Both structures had high affinity to the studied ions. The adsorption capacity of PAAm–HAP was than that of HAP. The adsorption dependence on pH and ionic intensity provided supportive evidences for the effect of complex formation on adsorption process. The adsorption kinetics was well compatible to pseudo second order model. The values of enthalpy and entropy changes were positive. Th4+ adsorption from the leachate obtained from a regional fluorite rock confirmed the selectivity of PAAm–HAP for this ion. In consequence, PAAm–HAP should be considered amongst favorite adsorbents for especially deposition of nuclear waste containing U and Th, and radionuclide at secular equilibrium with these elements.
SEM images of hydroxyapatite (HAP) and polyacrylamide–hydroxyapatite (PAAm–HAP), and the adsorption isotherms for Uranium and Thorium. Display omitted
► Composite of PAAm–HAP was synthesized from hydroxyapatite and polyacrylamide. ► The materials were characterized by BET, FT-IR, XRD, SEM, TGA and PZC analysis. ► HAP and PAAm–HAP had high sorption capacity and very rapid uptake for UO22+ and Th4+. ► Super porous PAAm was obtained from PAAm–HAP after its removal of HAP content. ► The composite is potential for deposition of U, Th and its associate radionuclides.
The adsorption of naturally occurring radionuclides (
208Tl
+,
212Pb
2+,
226Ra
2+,
212Bi
3+ and
228Ac
3+) onto Polyhydroxyethylmethacrylate–bentonite (PHEMA–B) composite was investigated. ...Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin–Radushkevich (DR) models. The adsorption isotherms were L type of Giles classification proving that PHEMA–B had a high affinity adsorbent for the studied radionuclides. The Langmuir adsorption capacities (
X
L) were in the order of
226Ra (2.8
MBq
kg
−1)>
212Bi (0.4
MBq
kg
−1)>
212Pb (0.3
MBq
kg
−1)>
228Ac and
208Tl (0.2
MBq
kg
−1). The adsorption process was physical via complex formation after proton exchanger for which the adsorption energies obtained from DR model was evidence. The enthalpy and entropy changes were positive and the negative free enthalpy change was proof for the spontaneity of adsorption. The reusability tests for PHEMA–B for five uses demonstrated that the adsorbent could be reused after complete recovery of the loaded radionuclide ions by 1
M HCl. The chemical structure of the composite did not change after the reuses and storage foregoing.
The adsorption of Th4+ ions was studied on composites of polyacrylamide (PAAm) with montmorillonite (Mt), clinoptilolite (Z) and zeolite Y (ZY), and after phytic acid (Phy) modification.
The ...monolayer adsorption capacity was 0.33 and 0.65molkg−1 for PAAm-Mt and PAAm-Mt-Phy, 0.07, 0.21 and 0.60molkg−1 for Z, PAAm-Z and PAAm-Z-Phy, and 0.74, 0.89 and 1.18molkg−1 for ZY, PAAm-ZY and PAAm-ZY-Phy. The enthalpy and entropy changes were positive for all adsorbents. The adsorption kinetics followed the pseudo-second order model indicating that the rate controlling step was chemical adsorption by ion exchange. The reusability tests for five uses proved that the PAAm-Mt and PAAm-Z were reusable and complete recovery of the adsorbed ions was possible. ZY and the composites modified with Phy were not reusable. The presence of foreign metal cations did not influence the Th4+ adsorption. The adsorbed Th4+ onto the columns was effectively recovered with diluted HNO3.
► Montmorillonite (Mt), clinoptilolite (Z) and zeolite Y were encapsulated in PAAm. ► The adsorption of Th4+ on these composites was significant. ► PAAm-Mt/Z were reusable for Th adsorption. ► The Th4+ ions were selectively adsorbed in the presence of foreign metal ions.
Water-soluble sulfolignin (SL) was grafted onto hydroxyapatite (Hap) by using epichlorohydrin. SLgHap was then entrapped in cross-linked polyacrylamide by in situ polymerizations of acrylamide and N, ...N'-methylenebisacrylamide to obtain the composite of PSLgHap. The composite was characterized by FT-IR, BET- porosity, XRD, EDXRF, SEM-EDX, TGA-DTG, PZC, CEC, and swelling tests. The adsorptive features of PSLgHAP were investigated for Th
and BSA in view of its dependence on pH, ionic intensity, concentration, temperature, and time. The results of characterization tests confirmed the formation of PSLgHap. The grafting efficiency concerning sulfur contents of PSLgHap was 96% by EDXRF. The isotherms were best represented by the Sips model, Langmuir adsorption capacities were 369 and 390 mg g
for BSA and Th
. The enthalpy and entropy changes were positive whilst Gibbs energy was negative by entropy controlled. The adsorption kinetics of both species was obeyed to pseudo second-order model, whereas it was first-order for BSA and hybrid-order for Th
of Langmuir model.
