Ultrasound-assisted Impregnation Research Articles

Comparison of potassium catalysts on zeolite sodium A and X in transesterification of palm oil and active species specification

Heterogeneous catalysts consisting of potassium supported on zeolites are active for transesterification, but the effect of zeolite properties is not clearly understood. This work compares catalysts containing 12 wt.% potassium on zeolite sodium A and X (12K/NaA and 12K/NaX) in terms of performance and physicochemical properties. Both catalysts were prepared by ultrasound-assisted impregnation with potassium acetate buffer. 12K/NaA is a better catalyst in transesterification of palm oil, giving a higher biodiesel yield than 12K/NaX in the first run (99.1 ± 0.3 % and 77.9 ± 2.2 %, respectively). From characterization by CO2-TPD, XRD, FTIR, XPS, and SEM-EDS, both catalysts have similar basicity but different dispersion of carbonates and interaction on the zeolites. The 12K/NaA has those species on external surfaces and more monodentate carbonate than 12K/NaX. Ion exchange occurs between potassium ions from the precursor and sodium ions from the zeolite. Moreover, 12K/NaA is more stable, providing higher biodiesel yields in the second and third catalytic cycles.

Cu2(OH)3NO3/γ-Al2O3 catalyzes Fenton-like oxidation for the advanced treatment of effluent organic matter (EfOM) in fermentation pharmaceutical wastewater: The synergy of Cu2(OH)3NO3 and γ-Al2O3

The secondary effluent of fermentation pharmaceutical wastewater exhibits high chromaticity, elevated salinity, and abundant refractory effluent organic matter (EfOM), presenting significant treatment challenges and environmental threats. Herein, Cu2(OH)3NO3/γ-Al2O3 was fabricated through ultrasound-assisted impregnation and calcination to catalyze the Fenton-like oxidation for degrading organic pollutants in this secondary effluent. Under neutral conditions, with 400.00 mg/L H2O2, 8 g/L catalyst, and at 30 ℃, the EfOM and CODCr removal efficiencies can reach 96.90 % and 51.56 %, respectively. The Cu2(OH)3NO3/γ-Al2O3 catalyst possesses ideal reusability, maintaining CODCr, chromaticity, and EfOM removal efficiencies at 44.44 %-64.59 %, 85.45 %-93.45 %, and 61.00 %-95.00 % over 220 h in a continuous-flow catalytic oxidation system operated at room temperatures (15–25 ℃). Electron paramagnetic resonance results and density functional theory calculations indicate that •OOH may be the predominant reactive oxygen species, facilitated by the easier elongation of the OH bond in H2O2 compared to the OO bond. The adjusted electronic structure endows Cu2(OH)3NO3/γ-Al2O3 composite sites with superior catalytic selectivity for H2O2 activation compared to Cu2(OH)3NO3 single crystal sites, with γ-Al2O3 additionally facilitating H2O2 activation through electron donation. This research highlights the efficacy of Cu2(OH)3NO3/γ-Al2O3 in the advanced treatment of complex industrial wastewater, elucidating its catalytic mechanisms and potential applications.

Enhanced solar-driven photocatalytic degradation of organic dyes using sono-dispersed mesoporous MgAl2O4 over carbon based materials

BackgroundThe presence of organic dyes in water poses serious environmental and health concerns, necessitating effective remediation strategies. MethodThis research investigates the synthesis of mesoporous MgAl2O4-carbon active nanocomposites, MAS-CA(10) and MAS-C3N4(10), via a two-step method: (1) MAS prepared by solution combustion technique, and (2) MAS-CA(10) and MAS-C3N4(10) nanocomposites obtained by ultrasound-assisted impregnation of MAS with carbon active and graphitic carbon nitride, respectively. FindingThe incorporation of carbon active significantly enhanced the textural properties of MAS-CA, including a high specific surface area (194.9 m2/g), large pore volume (0.81 cm3/g), and increased pore diameter (16.6 nm), facilitating improved dye adsorption and photocatalytic efficiency. The optimized MAS-CA(10) nanocomposite demonstrated remarkable photocatalytic performance, achieving 87.1 % methylene blue (MB) removal, 73 % eosin Y (EY) degradation, and 64.1 % acid orange 7 (AO7) degradation within 140 min under simulated solar irradiation. The influence of initial solution pH, photocatalyst reusability (only 7 % activity drop after 4 cycles), and the proposed mechanism for MB degradation over MAS-CA(10) were investigated. The calculated apparent rate constant for MB degradation over MAS-CA(10) was 0.0174 min−1. This study presents a facile and cost-effective approach for developing highly efficient mesoporous nanophotocatalysts for organic dye remediation under solar light.

Experimental and theoretical studies on effective synergistic low-temperature removal of NO and typical volatile organic compounds (VOCs) from flue gas based on Cu@VWTi catalyst

The transition metal-modified VWTi structural catalysts hold great promise for simultaneously removing nitrogen oxides (NOx) and volatile organic compounds (VOCs) from industrial flue gases. A series of Cu@VWTi catalysts were prepared to investigate their synergistic low-temperature removal performance towards NO and typical VOCs, including toluene, benzene, chlorobenzene (CB), p-chlorotoluene (p-CT), and dichloromethane (DCM). The copper-enhanced samples prepared via ultrasound-assisted impregnation exhibited irregular globular and varying crystallinity. The catalysts displayed a typical anatase crystal structure with high TiO2 content or high dispersion of V and W species along with a certain adjustment effect on the morphology. Various controlling factors affecting the synergistic removal of NO and VOCs were evaluated. It was observed that the presence of VOCs in flue gas has weak impact on NO removal, except for the waste incineration using the Cu@VWTi catalyst. However, a high initial NO concentration had an adverse effect on VOCs removal. Impressively, the optimized copper-doped catalyst (5 wt% Cu loaded of smelting plant and coal-fired power plant used catalyst) exhibited excellent performance for p-CT, toluene and DCM removal of 95.0%, 99.6% and 100% at 300 °C, respectively. The toluene and p-CT conversion efficiencies were highest over the catalyst used in the smelting plant after Cu loading, surpassing the benzene conversion efficiency. Cu@VWTi demonstrated excellent performance for p-CT, toluene, and DCM removal at 250 °C. Although 5 wt% Cu loading on the catalysts significantly enhanced the stability and anti-jamming of VOCs removal, as well as their tolerance to both SO2 and water vapor. The enhanced mechanism of Cu decoration attributed to the enhanced intensity of acid sites and the stable relative proportion of Oads/Olatt species in the used 5% Cu loaded catalyst due to the redox cycles of Cu and V species. Compared with Brønsted acid, which primarily adsorbs NH4+, Lewis acid mainly adsorbs gas phase acid and forms coordinated NH3 in gas phase. The bonding between toluene and the Cu site was enhanced with an adsorption energy of −130.9 kJ mol−1, as well as the cracking adsorption of the CH2Cl2 on the Ti site with a bonding energy of −436.7 kJ mol−1, both indicating strong chemical adsorption. The first step of dechlorination and demethylation was thermodynamically and kinetically favorable for DCM and toluene decomposition.

Remove elemental mercury from simulated flue gas by CeO2-modified MnOx/HZSM-5 adsorbent.

In this study, we synthesized a Ce-modified Mn/HZSM-5 adsorbent via the ultrasound-assisted impregnation for Hg0 capture. Given the addition of 15% CeO2, ~ 100% Hg0 efficiency was reached at 200°C, suggesting its promotional effect on Hg0 removal. The doped Ce introduced additional chemisorbed oxygen species onto the adsorbent surfaces, which facilitated the oxidation of Hg0 to HgO. Even though adding CeO2 led to a weakened adsorbent acidity, yet it appeared that this negative affect could be completely overcome by the enhanced oxidative ability, which finally endowed Ce-modified Mn/HZSM-5 with a satisfactory Hg0 removal performance within the whole investigated temperature range. During the Hg0 capture process, chemisorption was predominant with Mn4+operating as the main active site for oxidizing Hg0 to Hg2+. Finally, the 15Ce-Mn/HZSM-5 adsorbent exhibited good recyclability and stability. However, its tolerance to H2O and SO2 appeared relatively weak, suggesting that some modification should be conducted to improve its practicality.

The effect of the preparation method of asphalt waste foam ceramic loaded Pd/Ce-P-Al2O3 coatings on their properties

Asphalt waste-based foam ceramics were prepared by organic foam impregnation, followed by ultrasound-assisted impregnation and calcination to deposit 3-5 wt.% Pd/Ce-P-Al2O3 active coatings. The results show that γ-Al2O3 as an aluminum source provides a higher specific surface area and facilitates the dispersion of the catalytic components, so that low-temperature conversion of CO can be achieved, but the coating uniformity, stability, and the ability to modify the defects on ceramic surfaces are lower than those of the aluminum nitrate calcination products. Aluminum dihydrogen phosphate as a P source could rapidly convert 60% of CO, but the performance decreased at a later stage, while phosphoric acid as a P source could achieve the complete conversion of CO at a lower temperature. The mechanical properties of the samples with the addition of aluminum dihydrogen phosphate and aluminum nitrate baked products were better, which was 0.6 MPa higher than the uncoated foam ceramics.

A sustainable solution for diclofenac adsorption: Chitosan-modified fibrous silica KCC-1 adsorbent

This work aims to assess the potential of chitosan/fibrous silica KCC-1 composite in diclofenac adsorption. Fibrous silica KCC-1 was synthesized by microemulsion technique and chitosan/fibrous silica KCC-1 composite was prepared by ultrasound assisted impregnation. The physical and chemical properties were characterized by using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), point zero charge (PZC) and N2 physisorption. The removal of diclofenac was analysed through ultraviolet-visible spectroscopy (UV-Vis) under different parameters such as contact time, pH value and initial concentration of diclofenac. The characterization results showed that chitosan/fibrous silica KCC-1 composite has an amorphous structure with dendritic morphology, good thermal stability, various functional groups such as amine and hydroxyl that act as the active site for diclofenac adsorption, large surface area of 510 m2/g and total pore size of 0.4922 cm3/g, as well as pHPZC at pH 4.6 for efficient removal of diclofenac. The results showed that chitosan/fibrous silica KCC-1 composite can interact and adsorb more diclofenac as compared to pure fibrous silica KCC-1. Chitosan/fibrous silica KCC-1 composite gives an adsorption capacity of 142.01 mg/g whereas fibrous silica KCC-1 gives an adsorption capacity of 65.33 mg/g under the optimum contact time at 40 min, pH value of 4.0 and initial concentration of diclofenac at 160 mg/L. Langmuir adsorption isotherm and Elovich kinetic model resulted to be the best fit for diclofenac adsorption by chitosan/fibrous silica KCC-1 composite with the R2 value of 0.9721 and 0.9597, respectively.

Heteropoly acid supported on hierarchical Y zeolite decorated SiC foam as the structured catalytic packing for reactive distillation synthesis of ethyl lactate

Rational design of catalytic packing is crucial in developing reactive distillation (RD) processes as efficient in-situ coupling of reaction and separation is required. Structured catalytic packings are advantageous than the conventional packings (e.g., inert packing + catalyst ‘tea bags’), due to the integration of the catalysis and separation function in one unit, mitigating mass/heat transfer limits. Herein, we present one of the latest developments in the field of structured catalytic packings, which was applied to a pilot-scale RD process of ethyl lactate (EL) synthesis via acid-catalyzed esterification and showed the advantages. The tungstophosphoric acid and hierarchical Y zeolite were uniformly decorated on corrugated silicon carbide (SiC) foam sheets via new preparation method (of ultrasound-assisted impregnation and microwave-assisted drying). The activity of the resulting materials was first assessed in a batch reactor, then the best candidate was employed by the pilot process. Findings from the pilot-scale RD experiments show that the developed structured SiC foam catalytic packing (SSFCP) exhibited an excellent performance (with the normalized conversion of 0.155 mol/gcatalyst), outperforming the conventional seepage catalytic packing internal (0.002 mol/gcatalyst). The influence of various variables (including molar feed ratio, feed position and reflux ratio) on the process performance of the pilot RD rig was also investigated and optimized, achieving a lactic acid conversion of 46.9 % and EL purity of 44.9 % (bottom). The good performance was attributed to the improved mass transfer thanks to SiC foam corrugated sheet (which encourage the vortex formation), thereby enabling more efficient coupling with the reaction. The SSFCP demonstrated reasonable stability, making it a promising candidate for relevant practical RD applications.

Elemental mercury removal over MnOx-CoOx-modified HZSM-5 adsorbents: Performance and characterizations

In this study, MnOx-CoOx-modified HZSM-5 sorbents were prepared via the ultrasound-assisted impregnation method for Hg0 removal from the coal-fired flue gas. With the introduction of MnOx-CoOx, the Hg0 removal performance exhibited an increasing trend. Given that the mass content of MnOx-CoOx and the molar ratio of Mn/Co were fixed to 12 wt% and 1:3, the sorbent exhibited a relatively high Hg0 removal efficiency of 81% at 150 °C. Compared to virgin MnOx- or CoOx-modified HZSM-5 sorbent, the synergistic effect between MnOx and CoOx generated abundant surface acid sites and active oxygen species, which facilitated the adsorption of Hg0 and accelerated the oxidation of the adsorbed Hg0. Throughout the Hg0 capture cycles, Mn4+ and Co3+ acted as the active sites with HgO being the end product. Among the various gas constitutes, both O2 and NO demonstrated promotional effect on Hg0 removal, while SO2 interfered with the reaction to some degree. With the co-introduction of NO and SO2, an Hg0 removal efficiency of ∼94% was attained. Given its excellent recyclability, this sorbent system shows promising application potential.

Constructing AgBr/BiOBr@silkworm cocoons photocatalytic degradation and antibacterial material: Based on the excellent adsorption properties of silkworm cocoons

The silkworm cocoon (SC) possesses excellent adsorption performance due to the specific composite structure. Silk fibroin, the main component of SC, possesses lots of functional groups which are suitable for attachment of ligands, it plays an important role in the adsorption and chelation of metal ions, thus making SC a meaningful carrier. As a result, SC exhibits the best adsorption effect on Malachite green (MG), reaching 86.8% within 3 h in the present work. Additionally, AgBr/[email protected] visible light-driven (VLD) photocatalyst was successfully fabricated by ultrasound-assisted impregnation method with AgBr/BiOBr as a model and SC as a support. AgBr/[email protected] showed a remarkable photocatalytic degradation rate for Rhodamine B (Rh B, 98.52%), MG (80.08%) and Tetracycline (TC, 70.92%) under 120 min irradiation. Besides, it displayed superior activity in Staphylococcus aureus (S. aureus) disinfection, and the antibacterial efficiency above 99% upon 20 min of visible-light irradiation. The outstanding photocatalytic and antibacterial properties were mainly attributed to intimate contact and matched energy band positions between AgBr and BiOBr, which efficiently produce more active e--h+ pairs, and availably restrict the recombination of photogenerated carriers. This work could arouse an increasing interest in designing more SC-based photocatalysts for wastewater treatment.

Solar-driven photocatalytic transformation of toluene to benzoic acid over perovskite-type NiTiO3 decorated with reduced GO and g-C3N4 nanosheets

In this work, a perovskite-type nickel (II) titanate (NiTiO3; labeled as NTO) was synthesized and supported with reduced graphene oxide (rGO) and graphitic carbon nitride (CN: g-C3N4) nanosheets by ultrasound-assisted impregnation method. The solar-induced photocatalytic activity and selectivity of the prepared NTO-based perovskite catalysts were evaluated for toluene (TOL) oxidation to benzoic acid (B_COOH) under varying operating conditions. Results revealed that the NTO perovskite exhibited a higher selectivity (95–98%) for the photooxidation of TOL to B_COOH by 125–95 times higher than benzaldehyde (B_CHO) and benzyl alcohol (B_CH2OH) at 1 vol% H2O2 and O2 flow. At zero H2O2 level, the selective oxidation of TOL to B_CHO and B_CH2OH enhanced by 5.4 and 2.7 times as compared with the B_COOH production rate. Besides, NTO@CN (NTN) outperformed NTO@rGO (NTG) for the selective photocatalytic oxidation of TOL to B_COOH in solvent-free and water media under UV, visible, and sunlight irradiation. The production yield of B_COOH was 388.4, 491.2, and 455.6 µmol/L over NTO, NTN, and NTG, respectively at 1 vol% H2O2 and O2 flow for 3 h of solar irradiation. In both composites, carbon sheets supported the photocatalytic stability of NTO and potential energy for H2O2 decomposition to ∙OH radicals. This is validated by the radical scavenger test and electron paramagnetic resonance (EPR) analysis, which verified the crucial role of hydroxyl (•OH) radicals in the photocatalytic oxidation of TOL to B_COOH. These findings proved the effectiveness of NTN and NTG perovskite composites for solar-induced organic synthesis of benzoic acid from water contaminated with toluene using sunlight (as a renewable energy source).

Superior stability and activity of a PbMoO4/BiOBr nanocomposite for enhanced catalytic oxidative desulfurization of actual fuel

Novel PbMoO4/BiOBr nanocomposites were fabricated via a facile ultrasound-assisted impregnation method.

Characteristics and Mechanisms of Phosphorous Adsorption by Peanut Shell-Derived Biochar Modified with Magnesium Chloride by Ultrasonic-Assisted Impregnation.

Recovery of phosphate (P) from sludge, domestic wastewater, and industrial wastewater is beneficial for overcoming the problem of shortage of P rock resources. In this study, Mg-functionalized peanut shell-derived biochar was prepared by ultrasound-assisted impregnation. The obtained Mg-laden biochar had a higher content of Mg, a larger specific surface area, and more porosity. The prepared Mg-modified biochar exhibited excellent adsorption properties of phosphorus. Modified biochar has a higher amount of adsorbed P than raw biochar. The capacity of P adsorption by modified biochar was 30.48-114.24% higher than that by raw biochar. Moreover, the Mg-laden biochar can be applied in a wide working environment (pH: 2-10; temperature range: 15-40 °C). This study not only develops a new strategy for the preparation of high-capacity P adsorbents but also provides a new green use for agricultural peanut shells.

Comparative Properties of K/NaX and K/NaY from Ultrasound-Assisted Impregnation and Performance in Transesterification of Palm Oil.

This work aims to compare physicochemical properties and catalytic performance of potassium supported on zeolite NaX and NaY (K/NaX and K/NaY, respectively) prepared by ultrasound-assisted impregnation from potassium acetate buffer precursor. Calcination converts the potassium precursor to carbonate, which occupies the zeolite cavities and disperses on the external surface. Both calcined samples show a decrease in zeolite phases, BET surface areas, and pore volumes. With the smaller changes, K/NaX is more stable than K/NaY. Moreover, K/NaX has higher basicity than K/NaY and is more active in the decomposition of 2-methylbut-3-yn-2-ol (MBOH), producing dominant products from basic sites. Both K/NaX and K/NaY are active in the transesterification of palm oil, producing more than 94% of the biodiesel yields in the first run. However, the yields drop in the second run because of the leaching of potassium species into glycerol and biodiesel products. The spent K/NaX has a similar phase to the fresh one, whereas the spent K/NaY shows more structure collapse. With better structural stability, less potassium leaching, and less decline in biodiesel yields in the second run, K/NaX is a better catalyst than K/NaY.

Cavitation in thermoplastic melts: New insights into ultrasound-assisted fibre-impregnation

The impregnation of continuous carbon fibre roving with thermoplastic melt is a challenging task due to the high viscosity and surface tension of the melt. A new technique is under development utilizing ultrasonic oscillations within the thermoplastic melt which encloses a fibre roving, to achieve fibre impregnation. Despite ultrasonic processing being very efficient, the specific conditions created in the thermoplastic melt have never been studied before. This study investigated whether cavitation effects could be present during ultrasound-assisted fibre impregnation. The observed acoustic effects allowed us to suggest the possible underlying mechanisms. For the purpose of the study a melt-bath impregnation setup with polylactide was built. To detect the cavitation effects and acoustic parameters a calibrated high-temperature cavitometer was used. The results showed the formation of small cavitation zones in the direct vicinity to the sonotrode tip where the fibre roving would be positioned. Therefore, the occurrence of cavitation was established, and induced effects like shock waves, microjets and microstreaming should be further considered for detailed investigation of the ultrasound-assisted impregnation mechanism.

Hydrogen Storage in Untreated/Ammonia-Treated and Transition Metal-Decorated (Pt, Pd, Ni, Rh, Ir and Ru) Activated Carbons

Hydrogen storage may be the bottle neck in hydrogen economy, where hydrogen spillover is in dispute as an effective mechanism. In this context, activated carbon (AC) was doped with nitrogen by using ammonia gas, and was further decorated with platinum, palladium, nickel, rhodium, iridium and ruthenium, via an ultrasound-assisted impregnation method, with average particle sizes of around 74, 60, 78, 61, 67 and 38 nm, respectively. The hydrogen storage was compared, before and after modification at both ambient and cryogenic temperatures, for exploring the spillover effect, induced by the decorating transition metals. Ammonia treatment improved hydrogen storage at both 298 K and 77 K, for the samples, where this enhancement was more remarkable at 298 K. Nevertheless, metal decoration reduced the hydrogen uptake of AC for all of the decorated samples other than palladium at cryogenic temperature, but improved it remarkably, especially for iridium and palladium, at room temperature. This observation suggested that metal decoration’s counter effect overcomes hydrogen spillover at cryogenic temperatures, while the opposite takes place at ambient temperature.

Catalytic reduction of nitrophenol and MB waste water using homogeneous Pt NPs confined in hierarchically porous silica

Pt-containing catalysts are considered promising for diverse catalytic reactions, and their activity strongly depends on the dispersion degree of Pt nanoparticles (Pt NPs). In this study, we report an ultrasound assisted impregnation (UAI) strategy to promote Pt NPs dispersion in the nanoconfined spaces of as-prepared ZSM-5 derived micro-/mesoporous silica (MMZ) occluded with template. The precursor of Pt is successfully inserted into the nanoconfined spaces inherent in as-prepared MMZ (between the silica walls and cetyltrimethylammonium bromide (CTAB) template). The Pt NPs formed in the confined spaces were of smaller size than those generated through traditional ZSM-5 without confined spaces. Further calculations based on transmission electron microscopy (TEM) images indicates that the size of 1 wt% Pt per gram of MMZ (denoted as 1 wt%Pt/MMZ) is 3.8 nm, which is lower than that in 1 wt%Pt/ZSM-5. Experimental results demonstrated that well dispersive Pt NPs in 1 wt%Pt/MMZ catalyst led to the complete reduction of para nitrophenol (P-NP) and methylene blue (MB) with reaction rate constant (K) of 0.321 and 0.512 min−1, respectively, which are obviously higher than those of 1 wt%Pt/ZSM-5 and other reported Pt-based catalysts. 1 wt%Pt/MMZ catalyst exhibited good stability and recyclability than 1 wt%Pt/ZSM-5, and hence can be deemed of potential value for practical applications of wastewater treatment on industrial level.

Evaluation of post synthesis treatments over commercial ZSM-5 zeolite in the reaction route of oleic acid esterification with methyl acetate

The objective of this work was to evaluate the influence of post-synthesis treatments applied on high ratio Si/Al commercial ZSM-5 zeolite on its properties and catalytic activity in oleic acid esterification with methyl acetate. Treatments as acidification, desilication, ion exchange and mechanical and ultrasound-assisted impregnation tungsten oxide were applied. The catalysts were properly characterized and the esterification reactions were performed at 240 °C, 1:10 oleic acid:methyl acetate molar ratio and 10% (m/m) catalyst concentration. Properties of the catalysts were significantly changed by the applied treatments, resulting in different yields and isomers distribution of cis and trans esters. The highest ester yield, equal to 66.71%, was obtained with zeolite subjected to ion exchange. This catalyst also provided an equal distribution between the two isomers. It was proposed, based on kinetic experiments, a mechanism for the reaction consisting of isomerization of oleic acid to elaidic acid followed by esterification of both fatty acids.

Storage and separation of methane and carbon dioxide using platinum- decorated activated carbons treated with ammonia

Activated carbon (AC) was treated with ammonia for nitrogen doping and then was further anchored with platinum nanoparticles through ultrasound-assisted impregnation method. Methane (CH4) and carbon dioxide (CO2) storage of the pristine and modified activated carbon were determined at ambient temperature. All the samples showed high storage capacities with preference towards carbon dioxide storage, which would be favorable for both energy and environmental applications. Ammonia treatment slightly improved the storage of both CH4 and CO2 for all the samples, which could be attributed to the little improvement in the micropore properties upon nitrogen doping. Platinum decoration had an opposite influence on both CH4 and CO2 storage, which might be due to the absence of metal encouraging storage mechanism such as gas dissociation or reconstruction on platinum’s surface in addition to the harmful effect of metal pore-blocking and higher density of metal particles.

TiO2 Doped with Noble Metals as an Efficient Solution for the Photodegradation of Hazardous Organic Water Pollutants at Ambient Conditions

This work highlights new insights into the performance of TiO2 doped with noble metal catalysts for the photocatalytic degradation of organic water pollutants. Different samples of titanium dioxide doped with noble metals (Au and Pd) were successfully synthesized via incipient wet impregnation (IWI) and ultrasound-assisted impregnation (US) methods. X-ray diffraction, scanning electron microscopy and UV-Vis reflectance spectroscopy were used for the characterization of the obtained materials. Their photocatalytic efficiency was investigated in aqueous suspension thorough a series of laboratory tests performed under ultraviolet (UV-A) irradiation conditions using 2,4 dinitrophenol (2,4 DNP) as a target molecule. The results clearly show that the method used for the catalyst synthesis affects its photocatalytic activity. It was found that the samples prepared by the IWI method exhibited high photocatalytic activity, and the removal rate obtained with TiO2-Pd/IWI was higher than that found for TiO2-Au/IWI. Furthermore, for the best catalyst, some extra photocatalytic experiments were conducted with rhodamine 6G (R6G), a highly stable molecule with a very different chemical structure to 2,4 DNP, in order to check the reactivity of this material. Moreover, the recycling experiments carried out with TiO2-Pd/IWI clearly demonstrated the high photocatalytic stability of this material for the degradation of 2,4 DNP. All of the collected data confirmed the interesting photocatalytic potential of the selected catalyst in the elimination of organic pollutants with no obvious change in its reactivity after four reaction cycles, which is very promising for promoting future applications in water depollution.