In this study, mesoporous carbonated TiO2 nanoparticles were synthesized by sol-gel route using a complex Ti(OH2)63+·3Cl− and a modifying agent Na2CO3 and used as an adsorbents for Sr(II) removal ...from aqueous medium. The characterization of nanoadsorbents was accomplished using XRD, SEM, EDS, TEM, TG-DTG-DTA, IR, BET, pHPZC analyses. It was found that the sizes of carbonated TiO2 nanoparticles was ~4 nm. The presence of mononuclear bidentate carbonate groups on the titania surface was approved by IR spectroscopy. The kinetic data was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and an intraparticle diffusion models. The adsorption isotherms were fitted by using Langmuir, Freundlich, and Dubinin–Radushkevich models. The fittings show that the pseudo-second-order kinetics and Langmuir isotherm are suitable models for the adsorption process. The sample with 4% (wt.) of carbonate groups showed the best adsorption performance towards Sr(II) cations. The mesoporous carbonated samples demonstrated a higher adsorption capacity for strontium ions than the basic TiO2. The adsorption capacities of modified 2C-TiO2, 4C-TiO2 and 8C-TiO2 samples were 170.4, 204.4, 190.8 mg/g respectively, while it was 70.9 mg/g for the unmodified TiO2 towards Sr(II). Higher removal of Sr(II) was observed in the alkaline medium due to the formation of SrОН+ cations. A mechanism for Sr(II) adsorption was described and the number of chemosorbed ≡Ті(О2СО) groups and active adsorption centers onto unmodified and modified TiO2 surface were calculated. The titania adsorbents have high reusability and retain their adsorption capacity during five adsorption-desorption cycles. The presented results indicated that the mesoporous carbonated adsorbents were appropriate materials for the removal of Sr(II) from aqueous medium.
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•A new mesoporous TiO2 with chemosorbed carbonate groups has been synthesized.•Sr(II) successfully removed using a carbonated mesoporous titania•Sr(II) removal capacity of the 4C-TiO2 is 204.4mg/g at natural pH•Titanocarbonate groups provide the formation of surface acidic centers.
Mesoporous titania samples modified by sodium arsenate to form arsenate functionalities were synthesized using titanium aqua complex Ті(ОН2)63+·3Cl− and salt Na3AsO4 as precursors. The structure, ...morphology, and texture of the samples were characterized using XRD, IR spectroscopy, TG-DTA, TEM, and nitrogen adsorption methods. The adsorption properties of the samples located in the aqueous media were analyzed with respect to Sr(II) removal. The modified titania samples have a large specific surface area (up to 405 m2/g) and appropriate pore volume (up to 0.26 сm3/g) with a major contribution of mesopores. The maximum adsorption capacity of modified titania (with 4% of arsenate groups) towards Sr(II) is 262.9 mg/g. It is much smaller for unmodified titania (92.1 mg/g). The equilibrium adsorption isotherms were fitted using the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The results revealed that the adsorption equilibrium data match with the Langmuir isotherm model (R2 > 0.993) that corresponds to the localized adsorption onto uniform surface. The adsorption kinetics fitted well by the pseudo-second-order kinetic model. A possible adsorption mechanism was analyzed. Sr(II) removal can be attributed to = Ti(О2AsОOН) groups located at a mesopore surface of the adsorbents. The materials demonstrate the stability of the degree of the Sr(II) adsorption during ten cycles. Thus, arsenate-modified mesoporous titania could be considered as an effective adsorbent for Sr(II) removal from wastewater.
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•The mesoporous TiO2 with arsenate groups as surface functionalities was synthesized.•Increase in the arsenate groups amount results in more developed texture of TiO2.•The maximum adsorption capacity of modified titania towards Sr(II) is 262.9 mg/g.•Adsorption mechanism of Sr(II) ions on mesoporous titania is ion exchange.•The synthesized adsorbents can be used for efficient removal of Sr(II) from aqueous solutions.
The adsorption of Sr(II) cations by Boron-doped TiO2 was investigated. The adsorbent samples were obtained by liquid-phase sol-gel method using the aqua complex precursor Ті(ОН2)63+‧3Cl- and ...modifying reagent hydrogen borate Н3ВО3. It was found, that single-phase rutile titanium dioxide or two-phase anatase-rutile oxide materials were formed under the different initial ratios of components. Boron atoms are combined with Oxygen atoms into triangular structural cell ВО3 in the rutile sample 0.5В-ТіО2 and are localized in the surface layer of the nanoparticle material as a grouping =О2ВОН. The introduction of Boron atoms into the structure of the rutile adsorbent causes an increase in its adsorption capacity for the binding of Sr(II) cations in the aqueous electrolyte. The maximal adsorption values for Sr(II) cations by the rutile adsorbent in a neutral electrolyte environment reach 102.3 mg‧g-1, while it is equal to 68.8 mg‧g-1 for the unmodified anatase adsorbent a-TiO2.
The number of acid adsorption centers ≡ТіОНδ+ on the surface of the rutile adsorbent 0.5В-ТіО2 is ~ 50 units on a surface area of 10 nm2, which is twice the number of centers on the surface of the anatase adsorbent a- ТіО2. Anatase-rutile adsorbents 1.0В-ТіО2 and 1.5В-ТіО2 contain, respectively, 70% and 57% of the anatase phase. They are significantly inferior in adsorption ability toward cations of Sr(II) compared with the rutile adsorbent 0.5В-ТіО2. This is because Boron atoms are mainly localized in the anatase phase and with oxygen atoms form tetrahedral groups of ВО4-.
The phase composition and morphology of boron-containing TiO2 nanoparticles obtained by the sol-gel method were investigated. The solution of titanium aqua complex Ti (OH2)63+‧3Cl- was used as a ...precursor. Borate acid Н3ВО3 (promoter of the formation of rutile) was used as a modified reagent. A single-phase rutile TiO2 was obtained at a concentration of borate acid in the reaction mixture, which causes the formation of a 0.5В-TiO2 sample. The particles of 0.5В-TiO2 samples were in the villi-form, with a diameter of 0.8-1.2 nm, and a length of 16-24 nm.
With an increase of the Н3ВО3 concentration in the reaction mixture, synthesized oxide materials (samples of 1.0В-TiO2 and 1.5В-TiO2) contain 70 % and 57% of anatase respectively, in addition to rutile phase. Titanium-borate monodentate molecules Ti(OH)3OB(OH)2‧2Н2О were formed during the synthesis of the 0.5B-TiO2 rutile sample. The interatomic distance of Ti-O in these particles is commensurate with the average length of the Ti-O – bond of TiO6 rutile octahedra. During the polycondensation process, the distance of the Ti-O molecule-promoter was reproduced as a pattern in the following octahedra of rutile crystals.
Two types of titanium-borate molecules are formed in the reaction medium, during the synthesis of 1.0В-TiO2 and 1.5В-TiO2 samples. Molecules with a bidentate mononuclear structure Ті(ОН)2О2ВОН‧2Н2О in which the interatomic distance of Ti-O is commensurate with the average length of the Ti-O –bond in the anatase octahedra was formed. Therefore, titanium-borate molecules of the second type act as a promoter of the formation of the TiO2 anatase phase.
•The adsorption of Sr 2+, Y 3+, and Zr 4+ by Dowex HCR-S / S was investigated•The experimental results fit well with the Elovich and the Lagergren pseudo-first-order kinetic models•The studied ...cations are fixed at adsorption sites and adsorption is limited to the formation of a monolayer•Adsorption values of all three cations are higher in an acidic environment•The separation of Sr 2+, Y 3+, and Zr 4+ under batch conditions can be based on different rates of the cations adsorption by Dowex HCR-S/S
This work is devoted to the study of the adsorption of strontium, yttrium, and zirconium ions by the strong acid cation exchange resin Dowex HCR-s/s. The adsorption of strontium, yttrium, and zirconium ions in batch and dynamic conditions from individual solutions of the studied elements, as well as from their mixture, was studied. It was shown that the dependences of the adsorption of strontium, yttrium, and zirconium ions on agitation time fit well with the pseudo-first-order and Elovich equations. Equilibrium adsorption of all three cations can be described with Langmuir's theory. Column adsorption has shown that Dowex HCR-s/s adsorb all three investigated cations from the acidic medium. The inductively coupled plasma mass spectrometry (ICP-MS) proves that separation of these cations using Dowex HCR-s/s is possible only in highly dilute solutions at a concentration of 10 ng/ml of each element. The basis of separation will be a higher rate of adsorption of tetravalent zirconium, compared with strontium and yttrium. As the concentration of the investigated elements increases to 100 ng/ml, all three cations are adsorbed by the resin in equal amounts and can be separated only using special eluents, such as Ca-EDTA.
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The photocatalytic activity of four titanium dioxide samples (TiO2-P25 Degussa, PC105 Millennium, PC500 Millennium, and Anatase) was studied in the degradation of dyes (Congo Red (CR), Methyl Orange ...(MO), and Direct Red 23 (DR23)) using cost-effective smartphone-based analysis. The obtained kinetic curves are well described by the first-order kinetic model. It was established that the phase composition, the size of the particles, and the specific surface area of the catalyst have a significant effect on the photocatalytic activity of the studied TiO2 samples. It was investigated that the Millennium PC500 sample is the most effective photocatalyst due to a large specific surface area and a small particle size (8 nm). TiO2-P25 Degussa and Anatase also demonstrate a high photocatalytic activity in the degradation of CR and DR23 dyes, which can be explained by the accelerated process of electron transfer between the anatase and rutile phases. For the PC105 sample, a higher CR photodegradation efficiency is observed compared to PC500. It can be concluded that heterogeneous photocatalysis is an effective method for the removal of toxic dyes from wastewater. With the use of smartphone-based analysis, it is possible monitoring the photodegradation kinetics in real-time.
Nanostructured TiO2/AgI photocatalyst under the action of ultraviolet or visible electromagnetic radiation effectively neutralizes organic pollutants in the aqueous environment. It is a nanostructure ...in which micro- and small mesopores of anatase TiO2 are filled with silver iodide in the superionic state. The content of the α-AgI ion-conducting phase in the volume of ТіО2 pores can be ~20 wt %.
To obtain a photocatalyst, titanium dioxide is synthesized by the sol-gel method, using a titanium aquacomplex solution Ti(OH2)63+•3Cl- and a Na2CО3 modifier additive as a precursor. The modifying additive during synthesis ensures the fixation of =О2СО carbonate groups on the surface of oxide material particles. The presence of these groups leads to an increase in both the pore volume and the specific surface area of ТіО2. The specific surface area of carbonized titanium dioxide is 368 m2•g-1, the pore volume is 0.28 cm3•g-1, and their size is 0.9-4.5 nm.
To fill the micro- and small mesopores of TiO2 with the superionic α-AgI phase, Ag+ cations are first adsorbed from the AgNO3 solution on the titanium dioxide surface, and then the oxide material is contacted with the KI solution.
Compared to the Evonik P25-TiO2 photocatalyst, the nanostructured TiO2/AgI photocatalyst demonstrates a significantly higher efficiency of photodegradation of organic dyes Congo Red and Methyl Orange in visible and ultraviolet radiation. The most active ТіО2/40AgI sample achieved complete degradation of the CR dye in 6 minutes of UV irradiation, while the efficiency of commercial Р25-TiO2 over the same time was only 42%.
The oxidative degradation of Rhodamine B dye under ultraviolet irradiation was studied. The degradation rate was measured with using of smartphone camera. Photocatalytic degradation of the Rhodamine ...B dye over the P25-TiO2 catalyst has been found to accelerate substantially in the presence of hydrogen peroxide. The relationship between the photocatalytic degradation rate and H2O2 concentration has been studied. The optimal concentration of H2O2 has been found to in the range of 10-25 mM. The proposed mixture of P25 photocatalyst and H2O2 oxidizer can be used to remove organic pollutions from industrial waste water.
Fe-doped TiO2 (2, 5, 10, 15 and 20% wt. of Fe) photocatalysts have been synthesized by sol-gel method using titanium aquacomplex precursor. The structure and morphology have been characterized by ...XRD, BET, SEM, and EDS analyses, Mossbauer and IR spectroscopies. XRD analysis confirmed the anatase structure. The introduction of ferric ions into the titania structure causes its amorphization. The crystallite sizes of obtained samples are around 3 nm. Fe-doped TiO2 samples possess mesoporous structure and high specific surface area (from 274 m2g-1 for 5Fe-TiO2 to 416.4 m2g-1 for 20Fe-TiO2). Mossbauer spectroscopy data confirms the incorporation of Fe3+ ions in the anatase structure. Photocatalytic degradation of Congo red dye using Fe-doped TiO2 photocatalysts was studied under the UV-A light. Optimized conditions for photocatalytic degradation of CR in the presence of hydrogen peroxide are obtained. It was found that the 2Fe-TiO2 sample in the presence of 20 mM H2O2 solution showed highest efficiency in dye photodegradation (99.4%) under UV-A light. The photodegradation kinetics was analyzed using a smartphone and fits well with first-order kinetics model.
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