Narrow Results

A series of singly and co-doped LiTi₂(PO${}_4{)}_3$:Eu${}^{3+}$, Tb${}^{3+}$ phosphors prepared by solid state metathesis (SSM) was reported the first time. The X-Ray diffraction (XRD) verified that the as-prepared materials exhibit a pure rhombohedral phase with a space group of P2₁/m. Scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDAX) and elemental mapping confirm the morphology and constituents of elements. The LiTi₂(PO${}_4{)}_3$:Eu${}^{3+}$ shows 614nm red emission obtained due to the ⁵D${}_0{\to }^7$L₆ transition under 393nm excitation and the Tb${}^{3+}$ doped sample gives 546nm green emission ascribed to ⁵D${}_4{\to }^7$F₅ for excitation of 376nm. The luminescence properties of Eu${}^{3+}$/Tb${}^{3+}$ doped LiTi₂(PO${}_4{)}_3$ phosphors excited under a UV source were investigated and the relative mechanism was analyzed. Upon excitation by 393nm, the LiTi₂(PO${}_4{)}_3$:Eu_xTb_y phosphor has the capability to generate vivid green, yellow and red emissions, with color tunability achieved through the modulation of dopant ion concentrations. Color chromaticity of LiTi₂(PO${}_4{)}_3$:Eu${}_{0.01}$Tb${}_{0.05}$ gives at $x=0.574$, $y=0.425$ and $\mathrm{\text{CCT}}=1810.04$K. The proposed simple, low-cost, nontoxic and rapid synthesis route of phosphate-based compounds will lead the way to access these LiTi₂(PO${}_4{)}_3$:Eu${}^{3+}$/Tb${}^{3+}$ phosphors for potential applications in w-light-emitting diodes and plasma display panel.

The thermal behavior of Mg and Al layered double hydroxide with interlayer hydrogen phosphate (abb. as Mg/Al-HPO₄-LDH) is investigated below 1273 K by means of XRD, TG-DTA, SEM and FT-IR. The basal spacing of Mg/Al-HPO4-LDH decreases with increasing heating temperature stepwise in two stages; from 1.07 nm at 293 K to 0.85 nm at 333 K in the first stage and to 0.73 nm between 373 K and 443 K in the second one. The LDH becomes amorphous above 443 K until Mg₃ (PO₄)₂, MgO and MgAl₂O₄ (spinel) appear at 1273 K. SEM images of the LDH show plate-like crystallites both before and after heating at 473 K.

In this study, we focused on the investigation of phosphate removal using calcium oxide (CaO) and calcium hydroxide (Ca(OH)₂) which are mainly from the calcined shells as adsorbents. Hydroxylapatite Ca${}_{10}$(PO₄)₆(OH)₂, the component of industrial fertilizer was formed after the adsorption process following the XRD results. The phosphate removal increased from 20% to 97% with the aid of the mixture of flocculants alginic acid (AA), NaHCO₃ and CaCl${}_2\cdot$ 2H₂O in the case of 50 ppm phosphate concentration when the samples were filtered through 2.7 $\mu$m particle retention filter paper which is roughly equivalent to the case of phosphate removal rate of 0.2 $\mu$m membrane filter paper without flocculants (99%). The results suggest that AA, NaHCO₃ and CaCl${}_2\cdot$2H₂O as the flocculants are effective for phosphate removal from 20 to 100 ppm.

Intercalation of hydrogen phosphate (HPO₄) into Mg/Al-Layered Double Hydroxides (LDH) with DodecylBenzeneSulfonate (DBS) was investigated with regard to anion exchange, rehydration and a combination of delamination and anion exchange. HPO₄ could not be intercalated into the interlayer space of LDH with DBS when using either anion exchange or rehydration methods. However, HPO₄ was successfully intercalated into the Mg/Al-LDH using a combination of delamination and anion exchange methods.

The removal of phosphate (PO${}_4^{3-})$ from an aqueous solution by clamshell treated by heat process was investigated through batch experiments. The effects of initial phosphate concentrations, pH value, and contact time on the phosphate removal were carried out. The phosphate adsorption isotherm was described by the Langmuir and Freundlich models. As the result, the adsorption process correlated well to both models, and the theoretical maximum phosphate adsorption capacity was 319.0 mg/g by the Langmuir isotherm model. The influence of pH was investigated from 5 to 10, and the value of pH had no significant effect on phosphate adsorption capacity. This finding indicated the application of calcined clamshell in the large range of pH for phosphate removal. The phosphate adsorption capacity and phosphate removal efficiency were obtained at 209.0 mg/g and 38.7% at the initial phosphate concentration of 540 ppm at 25^∘C for 24 h, respectively. The clamshell modified by heat treatment exhibited its substantial potential for fast and efficient phosphate removal in water and wastewater.

Wide set of experimental results on binding energy of photoelectrons emitted from P 2p, P 2s, and O 1s core levels has been observed for inorganic phosphate crystals and the parameters were compared using energy differences Δ(O 1s - P 2p) and Δ (O 1s - P 2s) as most robust characteristics. Linear dependence of the binding energy difference on mean chemical bond length L(P–O) between phosphorus and oxygen atoms has been found. The functions are of the forms: Δ (O 1s - P 2p) (eV) = 375.54 + 0.146 · L(P–O) (pm) and Δ (O 1s - P 2s) (eV) = 320.77 + 0.129 · L(P–O) (pm). The dependencies are general for inorganic phosphates and may be used in quantitative component analysis of X-ray photoemission spectra of complex oxide compounds including functional groups with different coordination of P and O atoms.

The aggregative state of the Zn(II) tetra-spermine porphyrin derivative, ZnTCPPSpm4, has been investigated in the presence of different buffers at the same pH value: 5K (cacodylate) buffer, phosphate sodium salt buffer, and PBS. The photophysical characterizations (UV-vis, Fluorescence, and RLS) have indicated a precise self-assembly phenomenon depending on the buffered solution used. The porphyrin does not undergo a significant aggregation in 5K buffer, differently from what occurs in phosphate and PBS buffers. Here, the likely specific interaction between the phosphate molecules and spermine pendants leads to spontaneous porphyrin aggregation, as detected by the high fluorescence quenching, enhancement of the RLS signal, and a significant splitting of the porphyrin Soret band. As a result, the current paper aims to highlight the importance of the employed buffer throughout the experimental procedures performed in the presence of porphyrinoids.

Layered double hydroxide (LDH) is a layered hydroxide and exchangeable anion is intercalated in its interlayer. Application of the LDH as a controlled-release material of interlayer anions has become of interest, thus it is important to clarify the elution behavior of interlayer anions. We synthesized hydrogenphosphate-intercalated Mg/Fe and Zn/Fe LDH and elution of phosphate from these LDH were tested in deionized water, sodium chloride solution, sodium sulfate solution, and sodium carbonate solution. For Mg/Fe LDH, the amount of eluted phosphate increased with time and reached to maximum that increased as higher concentrate solution was used. The elution of phosphate from Mg/Fe LDH could be described by the pseudo second-order equation. This elution behavior was explained as ion-exchange reaction of phosphate with sulfate or carbonate in tested solution by means of kinetic simulation using Runge-Kutta method. In the eluted solution, metal ions contained in the LDH were detected and its amount depended on pH of the tested solution, that is, amounts of eluted Mg and Zn ions were small at higher pH (ca. 10) for Mg/Fe and Zn/Fe LDH respectively, but large amount of Zn ion was detected when 2.03 mol·l^-1 carbonate solution (pH = 13) was used. Thus elution of phosphate was caused by two main reactions: ion exchange and decomposition of the LDH.