| 1. |
- Maslova, Marina V., et al.
(författare)
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Extended study on the synthesis of amorphous titanium phosphates with tailored sorption properties
- 2012
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093 .- 1873-4812. ; 358:22, s. 2943-2950
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Tidskriftsartikel (refereegranskat)abstract
- The influence of concentrations of both TiO2 and H2SO4 in the syntheses of amorphous titanium phosphates (TiP) is reported. IR, XRD, TGA, BET and NMR techniques were used to characterise the isolated TiP products. The concentration of sulphuric acid in the initial synthesis plays a major role in the structural diversity and sorption properties of the final ionites. In the primary solutions, Ti(IV) is in monomeric, polymeric and colloidal forms. Upon addition of H3PO4 the presence of monomeric titanium ensures formation of the Ti(HPO4)2 phase. The polymeric Ti(IV) is responsible for formation of the titanium hydroxo-phosphate phase, Ti(OH)2(HPO4), whilst the colloidal form of Ti(IV) appears to have a role in coagulation of a minor Ti(OH)4 phase in an amorphous TiP. It is found that TiP ion-exchange capacities gradually increase with an increase of both TiO2 and H2SO4 concentrations and reach a maximum value of 3.8 mg-eq g− 1 when TiO2 is 70–100 g L− 1 and H2SO4 is 480–560 g L− 1. Analyses of compositional, structural and sorption data allowed 3D correlation diagrams to be built that can facilitate fabrication of TiP with tailored sorption properties.
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| 2. |
- Trublet, Mylene, et al.
(författare)
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Mild syntheses and surface characterization of amorphous TiO(OH)(H2PO4)·H2O ion-exchanger
- 2016
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 183, s. 467-475
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Tidskriftsartikel (refereegranskat)abstract
- This work focuses on the synthesis of titanium phosphate (TiP1) ion-exchanger containing solely H2PO4-groups. Based on the elemental analyses, TG, 31P MAS NMR, XRD and Raman data, the formula TiO(OH)(H2PO4)·H2O is assigned to TiP1. The synthesis requires a mild heating at 70–80 °C for a short period of time, followed by filtration and HCl-washing of the TiP1 powder. The layered nature and low crystallinity of this sorbent is confirmed by powder XRD technique. The existence of micro and mesopores in the material is established using BET method. The Na+ capacity of TiP1 is determined to be 6.3 meq g−1 which is the highest value reported for H2PO4-based sorbents. The presence of H2PO4 groups is expected to considerably increase both the pH-working range of the TiP1 sorbent and its exchange capacity towards divalent metal ions. All data for TiP1 are compared to the data for amorphous TiP containing mostly HPO4 groups.
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| 3. |
- Trublet, Mylene, et al.
(författare)
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Sorption performances of TiO(OH)(H2PO4)·H2O in synthetic and mine waters
- 2017
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 7:4, s. 1989-2001
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Tidskriftsartikel (refereegranskat)abstract
- ¨The sorption properties toward Cu2+, Zn2+, Ni2+, Mn2+ and Co2+ ions, in synthetic and industrial waters with pH of 3.9–7.2, and the chemical stability of a titanium phosphate ion-exchanger synthesized at mild conditions and containing solely –H2PO4 groups, TiO(OH)(H2PO4)·H2O (TiP1) are investigated. TiP1 displays the highest Na+ uptake (6.3 meq. g−1) among TiP ion-exchangers and a maximum sorption capacity of ca. 1.55 mmol g−1 (i.e. 3.1 meq. g−1) for the studied ions, which is higher than the ones reported for exchangers composed predominantly of –HPO4 groups. The sorption isotherms were best described by the Temkin model while the Langmuir and the Freundlich models appear to be insufficient in describing all data. TiP1 shows fast kinetics with an equilibrium reached within 10–20 minutes and diffusion processes play a role in the initial period of sorption that is overpowered by chemisorption reactions in the overall rate controlling step. The selectivity order of the metal ions on TiP1 is determined as: Cu2+ > Zn2+ ≫ Mn2+ > Co2+, Ni2+, following the order of stability of MOH+ complexes and the corresponding activation parameters for a water molecule exchange in [M(H2O)6]2+ ions. The surface sorption data are in good correlation with the EDS data for these systems, supporting the idea of chemical sorption with no metal hydroxide precipitation. Additional sorption studies show that the quality of industrial waters after sorption reaches the EU recommendation for drinking water. The faster kinetics and the higher exchange capacity reveal that the presence of –H2PO4 groups strongly enhances the sorption properties of titanium phosphate sorbents.
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