This study presents the removal of phosphate from aqueous solution using a new silver nanoparticles-loaded tea activated carbon (AgNPs-TAC) material. In order to reduce costs, the tea activated ...carbon was produced from tea residue. Batch adsorption experiments were conducted to evaluate the effects of impregnation ratio of AgNPs and TAC, pH solution, contact time, initial phosphate concentration and dose of AgNPs-AC on removing phosphate from aqueous solution. Results show that the best conditions for phosphate adsorption occurred at the impregnation ratio AgNPs/TAC of 3% w/w, pH 3, and contact time lasting 150 min. The maximum adsorption capacity of phosphate on AgNPs-TAC determined by the Langmuir model was 13.62 mg/g at an initial phosphate concentration of 30 mg/L. The adsorption isotherm of phosphate on AgNPs-TAC fits well with both the Langmuir and Sips models. The adsorption kinetics data were also described well by the pseudo-first-order and pseudo-second-order models with high correlation coefficients of 0.978 and 0.966, respectively. The adsorption process was controlled by chemisorption through complexes and ligand exchange mechanisms. This study suggests that AgNPs-TAC is a promising, low cost adsorbent for phosphate removal from aqueous solution.
Display omitted
•Zn-S catalyst improves DB22 decolonization and mineralization rate by heterogeneous catalytic ozonation.•Zn, Ca constituents in Zn-S improve OH* generation in heterogeneous catalytic ...ozonation of DB22.•DB22′s mineralization by Zn-S catalytic ozonation was highest in alkaline condition.•Mineralization kinetic of DB22 follows pseudo-first order kinetic model.
This study developed a low cost catalyst, namely, zinc slag (Zn-S) for the ozonation process of Direct Black 22 (DB22) from aqueous solutions. Among five different kind of low cost metal slags including Fe-S, Cu-S, Cd-S, Pb-S and Zn-S, the Zn-S slag was selected as an efficient catalyst in this study. Zn-S contained mainly zinc (Zn) and calcium (Ca) discharged from zinc slag waste in Vietnam. It was found that Zn-S could effectively decolonize and mineralize DB22 through heterogeneous catalytic ozonation. The degradation kinetic of DB22 followed the pseudo-first order model. The best removal efficiency of DB22 (Zn-S/O3/H2O2 (76%) > Zn-S/O3 (69%) > O3/H2O2 (66%) > O3 (55% for COD) occurred at pH 11 for heterogeneous catalytic ozonation processes with Zn-S as the catalyst as well as ozone alone and perozone processes due to fast decomposition of O3 in alkaline solution to generate powerful and non-selective OH radicals. An increase in decolonization and mineralization rate was observed when increasing the Zn-S dosage from 0.125 g/L to 0.75 g/L for Zn-S/O3 and 0.125 g/L to 1.0 g/L for Zn-S/O3/H2O2. The K values of the pseudo-first order model followed the same sequence as mineralization rates of DB22 in term of COD removal. Ca and Zn constituents in the Zn-S catalyst contributed to the increase in O3 decomposition and improvement of reaction rate with H2O2. Subsequently, the degradation of DB22 by the ozonation process with Zn-S catalyst was enhanced through the enrichment mechanism of hydroxyl radicals (*OH) and surface adsorption. The degradation mechanism of DB22 by hydroxyl radicals was surely affirmed by tests with the decrease in degradation percentage of DB22 in case of the presence t-butanol, Cl− and CO32−.
Electrokinetic and electroosmotic couplings can play important roles in water and ions transport in charged porous media. Electroosmosis is the phenomena explaining the water movement in a porous ...medium subjected to an electrical field. In this work, a new model is obtained through a new up-scaling procedure, considering the porous medium as a bundle of tortuous capillaries of fractal nature. From the model, the expressions for the electroosmosis pressure coefficient, the relative electroosmosis pressure coefficient, the maximum back pressure, the maximum flow rate, the flow rate-applied back pressure relation and the product of the permeability and formation factor of porous media are also obtained. The sensitivity of the relative electroosmosis pressure coefficient is then analyzed and explained. The model predictions are then successfully compared with published datasets. Additionally, we deduce an expression for the relative streaming potential coefficient and then compare it with a previously published model and experimental data from a dolomite rock sample. We find a good agreement between those models and experimental data, opening up new perspectives to model electroosmotic phenomena in porous media saturated with various fluids.
Dy3+-doped glasses with compositions of (69-x)B2O3 + 10TeO2 + 10Al2O3 + 10Li2O + xDy2O3 (x = 0.1; 0.5; 1.0 and 2.0 mol%) were prepared by a melt–quenching technique. An in-depth Judd-Ofelt analysis ...has been carried out to estimate the influence of the hypersensitive transitions (HST) of Dy3+on the validity of the obtained intensity parameters Ωλ (λ = 2, 4, 6). The thermalization effect of the three-levels system of 6H13/2 (level 0), 4F9/2 (level 1) and 4I15/2 (level 2) was taken into account to evaluate its radiative transition probabilities, life times and energy levels. The obtained results were compared with the experimental data to estimate the validity of the Judd-Ofelt analysis. The Inokuti-Hirayama model was used to analyze the luminescence decay curves. The dipole-dipole interaction was shown to be the dominant mechanism in energy transfer process through cross-relaxation between Dy3+ ions. The possibility to produce the light with chromaticity coordinates in the white-light region by mixing intense blue (484 nm, 4F9/2 → 6H15/2) and yellow (575 nm, 4F9/2 → 6H13/2) emissions of the single Dy3+doped alumino-lithium-telluroborate glass was observed and estimated.
The degradation of MB on TiO2/BNNS NRs glass substrate was detected by Raman spectroscopy under UV irradiation (254 nm) in the time range of 0–50 min.
Display omitted
•Boron nitride nanosheets ...decorated titanium dioxide nanorods were synthesized.•Photo-degradation of methylene blue (MB) was evaluated via Raman spectroscopy.•100% degradation of MB achieved in 50 min under UV light (254 nm, 66 W).
Here, we present a facile synthesis of the boron nitride nanosheets decorated titanium dioxide nanorods (TiO2/BNNS NRs) on glass substrates by hydrothermal method. The photocatalytic performance of TiO2/BNNS NRs is investigated by degrading methylene blue (MB) under UV irradiation (254 nm) and recorded by Raman spectroscopy. The obtained results indicated the photocatalytic performance of TiO2/BNNS NRs was significantly improved than that of TiO2 NRs. The rate of degradation (k) of MB was found to be 0.085 min−1 for TiO2/BNNS NRs and 0.052 min−1 for TiO2 NRs. Besides, TiO2/BNNS NRs hybrid structure exhibits high cycling stability with about 90% after 5 consecutive cycles.
KGdF4:Tb3+, KGdF4:Sm3+ and KGdF4:Tb3+,Sm3+ polycrystalline were synthesized under hydrothermal conditions. The XRD and TEM patterns as well as excitation, luminescence spectra and luminescence decay ...curves of Sm3+, Tb3+ and Gd3+ have been measured at room temperature. For KGdF4:Tb3+(Sm3+), energy transfer processes from Gd3+ ions to Tb3+ (or Sm3+) ions are related to energy migration through Gd3+ ions and energy trapping by Tb3+ (or Sm3+) ions. The energy trapping rate strongly depends on the nature of RE3+ (Tb3+ or Sm3+) ions and it influences to the luminescence efficiency of RE3+ ion. For KGdF4:Tb3+,Sm3+, the characteristic emission bands of Tb3+ ion (blue and green) and Sm3+ ion (orange-red) are obtained simultaneously upon excitation by 375 nm. The chromaticity coordinates and correlated color temperature (CCT) are used to estimate the emission feature of prepared material. The quenching of the luminescence and lifetime of 5D4 (Tb3+) level are relate to the energy transfer process from Tb3+ to Sm3+ ions. It is shown that, by fitting the decay curves of 5D4 (Tb3+) to the Inokuti and Hirayama model, the dominant interaction mechanism between Tb3+ and Sm3+ is dipole-quadrupole interaction. The probability (WET) and the efficiency (ηET) of energy transfer from Tb3+ ions to Sm3+ ions increase with the increase of Sm3+ concentration.
•KGdF4:Tb3+, KGdF4:Sm3+ and GdF4:Tb3+,Sm3+ polycrystalline were synthesized by hydrothermal method.•Energy transfer process from Gd3+ to Tb3+ (or Sm3+) ions in KGdF4:Tb3+(or Sm3+) has been observed and discussed.•The emission feature of KGdF4:Tb3+,Sm3+ has been evaluated by chromaticity coordinates and correlated color temperature.•Energy transfer from Tb3+ to Sm3+ ion in KGdF4:Tb3+,Sm3+ has been analyzed by Inokuti and Hirayama model.
Ag/Au bimetallic nanostructures have received much attention in surface-enhanced Raman scattering (SERS). However, the synthesis of this nanostructure type still remains a challenge. In the present ...research, Ag/Au nanoframes were synthesized
via
a simple room temperature solution phase chemical reduction method using pre-synthesized triangular Ag nanoplates as templates in the presence of appropriate amounts of HAuCl
4
. Controlling experimental parameters was applied for understanding of the growth mechanism. The galvanic exchange reaction resulted in a uniform deposition of the Au shell on the Ag nanoplates and the Ag core was removed which generated triangular hollow nanoframes. It is found that the amount of HAuCl
4
added to the growth solution played a key role in controlling the Ag/Au nanoframes. The resultant silver/gold nanoframes with average size of 50 nm were applied in detecting methyl red (MR) in the solution-phase using an excitation wavelength laser of 532 nm. The SERS signal was greatly enhanced owing to the tunable plasmonic peaks in the visible region (400-650 nm). The limit of detection (LOD) of MR in diluted solution was 10
−6
M. The enhancement factor (EF) was about 8 × 10
4
toward 10
−5
M of MR. Interestingly, the linear dependence between the logarithm of the SERS signal intensity (log
I
) and the logarithm of the MR concentration (log
C
) occurred in the range from 10
−6
to 10
−4
M. Our work promises the application of Ag/Au nanoframes as a chemical sensor in detecting MR molecules at low concentration with high performance.
Ag/Au nanoframes were synthesized
via
room temperature solution phase chemical reduction using pre-synthesized triangular Ag nanoplates as templates in the presence of appropriate amounts of HAuCl
4
, and were applied in detecting methyl red.
This study developed a new adsorbent, specifically activated carbon-loaded silver nanoparticles (AgNPs-AC) by coating the silver nanoparticles (AgNPs) onto activated carbon (AC). The obtained ...AgNPs-AC were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET). The ability of AgNPs-AC to remove methylene blue (MB) was evaluated using different experimental factors, these being pH solution, contact time, adsorbent dose, and initial MB concentration. Results indicated that the highest adsorption capacity of MB onto AgNPs-AC was obtained when the AC was loaded onto AgNPs at the impregnation ratio of 0.5%
w
/
w
for AC and AgNPs. The best conditions in which AgNPs-AC could remove MB were as follows: pH 10, contact time lasting 120 min, and adsorbent dose being 250 mg/25 mL solution. In this scenario, the maximum adsorption capacity of MB onto AgNPs-AC was 172.22 mg/g. The adsorption isothermal equilibrium was well described by the Langmuir, Freundlich and Sips models. The Sips equations had the highest correlation coefficient value (
R
2
= 0.935). The pseudo-first-order and pseudo-second-order kinetic models agree well with the dynamic behavior of the adsorption of dye MB on AgNPs-AC.
It is well-known that Ag-Au bimetallic nanoplates have attracted significant research interest due to their unique plasmonic properties and surface-enhanced Raman scattering (SERS). In recent years, ...there have been many studies on the fabrication of bimetallic nanostructures. However, controlling the shape, size, and structure of bimetallic nanostructures still has many challenges. In this work, we present the results of the synthesis of silver nanoplates (Ag NPls), and Ag-Au bimetallic core/shell and alloy nanostructures, using seed-mediated growth under green LED excitation and a gold salt (HAuCl
4
) as a precursor of gold. The results show that the optical properties and crystal structure strongly depend on the amount of added gold salt. Interestingly, when the amount of gold(
x
) in the sample was less than 0.6 μmol (
x
< 0.6 μmol), the structural nature of Ag-Au was core/shell, in contrast
x
> 0.6 μmol gave the alloy structure. The morphology of the obtained nanostructures was investigated using the field emission scanning electron microscopy (FESEM) technique. The UV-Vis extinction spectra of Ag-Au nanostructures showed localized surface plasmon resonance (LSPR) bands in the spectral range of 402-627 nm which changed from two peaks to one peak as the amount of gold increased. Ag-Au core/shell and alloy nanostructures were utilized as surface enhanced Raman scattering (SERS) substrates to detect methylene blue (MB) (10
−7
M concentration). Our experimental observations indicated that the highest enhancement factor (EF) of about 1.2 × 10
7
was obtained with Ag-Au alloy. Our detailed investigations revealed that the Ag-Au alloy exhibited significant EF compared to pure metal Ag and Ag-Au core/shell nanostructures. Moreover, the analysis of the data revealed a linear dependence between the logarithm of concentration (log
C
) and the logarithm of SERS signal intensity (log
I
) in the range of 10
−7
-10
−4
M with a correlation coefficient (
R
2
) of 0.994. This research helps us understand better the SERS mechanism and the application of Raman spectroscopy on a bimetallic surface.
It is well-known that Ag-Au bimetallic nanoplates have attracted significant research interest due to their unique plasmonic properties and surface-enhanced Raman scattering (SERS).
Herein, we present for the first time a quick, easy, effective, and green method for preparing green nanofluids containing silver nanoparticles. The solution plasma method with a high-voltage DC ...power source and extracts from the
Paramignya trimera
was employed to prepare silver nanoparticles. The obtained results showed that silver nanoparticles were spherical, with a small average size of − 8 nm and fairly uniformly dispersed in solution. Surface plasmon resonance spectra show a strong peak at 410 nm for the prepared samples. The Fourier transform infrared spectra revealed the presence of possible functional groups on the surface of silver nanoparticles. Furthermore, the formation mechanism of silver nanoparticles is also proposed. The effect of the preparation times on the thermal conductivity of nanofluid was also investigated. As a result, the nanofluids prepared with longer preparation times had higher thermal conductivity and the highest improvement of 18.3% was obtained for the nanofluid using 4 min preparation compared to the base fluid. The obtained results indicate promise for a simple, fast, and environmentally friendly method for producing nanofluids containing silver nanoparticles with high thermal conductivity for potential applications.
PDF
