The elimination of toluene is an obligatory target with increasing VOC emission in recent years. This study successfully prepared a single-atom Ir catalyst (Ir1/CeO2) by a simple incipient wetness impregnation method, confirmed by in situ CO DRIFTS and AC-HAADF-STEM. Compared to the cluster Ir catalyst (Ir/CeO2-C), Ir1/CeO2 exhibited excellent catalytic performance, stability, and water resistance for the oxidation of toluene. By Raman, H2-TPR, O2-TPD, and XPS experiments, abundant oxygen defects and a unique Ir3+-Ov-Ce3+ structure were formed for the Ir1/CeO2 sample because it had a lower oxygen vacancy formation energy. Furthermore, the DFT results revealed that the Ir1/CeO2 sample had a lower ring-opening energy barrier and adsorption energy of the ring-opening products, which was the rate-determining step for the oxidation of toluene. This work provides instructive insights into the construction of Ir/CeO2 catalysts for the highly efficient removal of VOCs.
Alloy catalysts have been reported to be robust in catalyzing various heterogeneous reactions due to the synergistic effect between different metal atoms. In this work, aimed at understanding the effect of the coordination environment of surface atoms on the catalytic performance of alloy catalysts, a series of PtxCu1-x alloy model catalysts supported on anatase-phase TiO2 (PtxCu1-x/Ti, x = 0.4, 0.5, 0.6, 0.8) were developed and applied in the classic photocatalytic CO2 reduction reaction. According to the results of catalytic performance evaluation, it was found that the photocatalytic CO2 reduction activity on PtxCu1-x/Ti showed a volcanic change as a function of the Pt/Cu ratio, the highest CO2 conversion was achieved on Pt0.5Cu0.5/Ti, with CH4 as the main product. Further systematic characterizations and theoretical calculations revealed that the equimolar amounts of Pt and Cu in Pt0.5Cu0.5/Ti facilitated the generation of more Cu-Pt-paired sites (i.e., the higher coordination number of Pt-Cu), which would favor a bridge adsorption configuration of CO2 and facilitate the electron transfer, thus resulting in the highest photocatalytic CO2 reduction efficiency on Pt0.5Cu0.5/Ti. This work provided new insights into the design of excellent CO2 reduction photocatalysts with high CH4 selectivity from the perspective of surface coordination environment engineering on alloy catalysts.
We report a noble-metal-free photocatalyst, ultrathin TiO2 with atomic layer thickness, which is a potential catalyst for CO2 photoreduction. An excellent liquid-product yield of 463.9 µmol gcat-1 in 8 h with 98% selectivity to alcohols was achieved, owing to sufficient surface defects favoring CO2 adsorption/activation.
The effect of size of Pt nanoparticles has an important influence on the performance of supported Pt-based catalysts for the elimination of toluene. Herein, uniform Pt nanoparticles with average sizes of 1.5, 2.0, 2.5, 2.9, and 3.6 nm were obtained and supported on manganese oxide octahedral molecular sieves (OMS-2), and their catalytic performances for toluene oxidation were evaluated. Benefiting from the moderate interfacial interaction between nanoparticles and manganese oxide support, Pt/OMS-2-3 with the Pt particle size of 3.0 nm showed the best catalytic performance owing to the highest content of Pt2+ species. It also facilitates the formation of more abundant Mnδ+ (Mn2+ and Mn3+) and oxygen vacancies than that of the other sizes of the OMS-2-supported Pt nanoparticles, which can be filled by a large amount of adsorbed oxygen and converted into reactive oxygen species. We further showed that the resulting surface synergetic oxygen vacancies (Pt2+-Ov-Mnδ+) play a decisive part in catalyzing the complete oxidation of toluene. The result will provide new insights for designing efficient Pt-based catalysts for deep purification of toluene.
Experiment evaluation and mechanism analysis of separation performance are crucial for oily wastewater treatment. In this work, a fluorinated superhydrophobic/superoleophilic (F-SHPB/SOPL) surface was fabricated on a steel mesh substrate by double depositions of SiO2-TiO2 nanoparticles for high-roughness improvement and composite modification of fluorine-alkyl groups for low-energy achievement. Measurements of SEM, XPS, FTIR, laser scanning confocal microscope (LSCM), and excitation-emission matrix (EEM) were carried out for surface property characterization. The oil-water separation performances at the prepared F-SHPB/SOPL surface were investigated from experimental and simulation aspects. Separation tests, flux tests, and anti-contamination tests were performed by experimental methods. The results indicated that the surface showed excellent separation efficiencies (>99.2%) for oil-water mixture and oil-in-water emulsion, high permeate flux (>3000 L·m-2·h-1) for organic oils, and perfect anti-pollution/self-cleaning capacity for liquid and solid contaminations. The interaction energies and interaction distances were measured by ab initio molecular dynamics simulation (AIMD) simulations. With lower interaction energy (Eoil = -456.52â¼-1044.22 eV) than that of water molecules (Ewater = -172.73 eV) and shorter distance (Doil = 4.42â¼5.13 Å) than that of water molecules (Dwater = 11.49 Å), oil molecules showed higher interaction stability than water molecules on the F-SHPB/SOPL surface. The calculation revealed the essence of the oil-water separation phenomenon. This work not only proposes the fabrication methodology of the SHPB/SOPL material but also elucidates the intermolecular interaction for oil-water separation. The results can provide a fundamental basis for separation operation and removal treatment in industrial and domestic applications.
Strong metal-support interactions (SMSIs) have a significant effect on the performance of supported noble-metal catalysts for volatile organic compound (VOC) elimination. Herein, the strength of the SMSI of Pt/OMS-2 between Pt and the OMS-2 support is regulated by simply changing calcination temperatures, and the catalyst calcined at 300 °C (Pt/OMS-2-300) performs the best in the catalytic combustion of toluene. Through systematic structural characterizations, it is revealed that much more Pt2+-Ov-Mnδ+ species are formed in Pt/OMS-2-300, which can help facilitate the generation of more reactive oxygen species and promote lattice oxygen mobility. Moreover, the results of in situ DRIFTS experiments further confirm that abundant Pt2+-Ov-Mnδ+ species at the Pt-MnO2 interface on Pt/OMS-2-300 can better enhance the adsorption and activation of toluene, thus boosting the catalytic performance in toluene combustion. This newly developed strategy of thermal-driven regulation of the SMSI provides a novel perspective for constructing highly efficient catalysts for VOC emission control.
Herein the adsorption characteristics of zwitterionic dye pollutant Rhodamine B (Rh+B-) on a g-C3N4 surface were investigated by both an attenuated total reflection spectroscopy (ATRS) experiment and a molecular dynamics simulation (MDS). For experimental investigation, g-C3N4 was coated on a silica optical fiber (SOF) surface to fabricate an adsorption film. According to the ATRS response, adsorption thermodynamics and thermodynamics results were in situ obtained and evaluated. The isothermal Langmuir model was used to calculate the adsorption equilibrium constants (Kads) and adsorption energies (ΔGads) for Rh+B- as 27.25 × 104 M-1 and -31.01 kJ mol-1, respectively, which indicated the spontaneous adsorption behavior of Rh+B- at the g-C3N4 surface. Using dynamic Elovich modeling, the rate constants of Rh+B- were found to be k1 = 0.0063 min-1 and k2 = 0.0004 min-1, which indicated two-stage adsorption at the g-C3N4 surface. For theoretical simulation, adsorption configurations and adsorption energies were systematically calculated by a molecular dynamics simulation (MDS) . Rh+B- molecules were inclined to orient in a parallel position at the g-C3N4 surface during low concentration but a perpendicular position at the g-C3N4 surface during high concentration. Combined with experimental and calculation results, this work revealed the microscopic adsorption performance and elucidated the intermolecular interaction between localized interfaces of g-C3N4 and hazardous dye pollutant. We propose an adsorption model to explain the process of surface interaction, which is based on molecular orientation and a force-driven mechanism. Electrostatic attraction and π-π interaction dominated the adsorption interaction with an adsorption energy of ΔGlow(ads) = -38.96 kJ mol-1 for low Rh+B- concentration, and electrostatic attraction dominated the adsorption interaction with an adsorption energy of ΔGhigh(ads) = -25.76 kJ mol-1 for high Rh+B- concentration. This work can provide a fundamental basis for a dye-pollutants removal application by g-C3N4 in both adsorption and photocatalyzation.
The adsorption performances on graphitic carbon nitride (g-C3N4) surface were investigated for organic dye pollutants by both experimental and calculation methods. For experimental investigation, adsorption thermodynamics and kinetics results were in-situ obtained and evaluated. With [Formula: see text] by Langmuir modeling, g-C3N4 showed superior adsorption spontaneity of MB+ >MO-. With linear and exponential modeling, g-C3N4 showed only adsorption process for MB+ but both diffusion and adsorption processes for MO-. For simulation insight, all MB+ molecules but only parts of MO- molecules were inclined to orient in parallel position at g-C3N4 surface after optimization during low concentration. And both MB+ and MO- molecules were inclined to orient in perpendicular position at g-C3N4 surface after optimization during high concentration. Combined with experimental and calculation results, a molecular-orientation and force-dominance mechanism adsorption model are proposed to explain the surface interaction processes between dyes and g-C3N4. Electrostatic interaction and π-π stacking interaction were revealed to dominate for MB+ adsorption, and π-π stacking interaction and van der Waals force were revealed to dominate for MO- adsorption. This work obtained 'localized' interfacial information and elucidated in-situ intermolecular interactions at g-C3N4 interface, which can provide fundamental basis for operation removal of organic dye pollutants by g-C3N4.
Environmental Pollutants , Adsorption , Coloring Agents , Graphite , Nitrogen Compounds , Spectrum Analysis
Ir-based heterogeneous catalysts for photocatalytic CO2 reduction have rarely been reported and are worthy of investigation. In this work, TiO2 nanosheets with a higher specific surface area and more oxygen vacancies were employed to support Ir metal by impregnation (Imp) and ethylene glycol (EG) reduction methods. In comparison with Ir/TiO2 (Imp) and TiO2, Ir/TiO2 (EG) exhibited excellent photocatalytic performance toward CO2 reduction, especially for CH4 production on account of the oxygen defect of TiO2 and rich surface hydroxyl groups produced from the interaction between TiO2 nanosheets and metallic Ir. In situ ESR suggested that the oxygen defect was significant for CO2 adsorption/activation. Furthermore, metallic Ir was beneficial for photogenerated electron transfer, surface hydroxyl generation, and adsorption of the CO intermediate, generating more available electrons and reducing agents for CH4 production. In situ CO2 DRIFTS confirmed the key synergistic interaction between the oxygen defect and metallic Ir in the photoreduction from CO2 to CH4.
For further the understanding of the adsorption mechanism of heavy metal ions on the surface of protein-inorganic hybrid nanoflowers, a novel protein-derived hybrid nanoflower was prepared to investigate the adsorption behavior and reveal the function of organic and inorganic parts on the surface of nanoflowers in the adsorption process in this study. Silk fibroin (SF)-derived and copper-based protein-inorganic hybrid nanoflowers of SF@Cu-NFs were prepared through self-assembly. The product was characterized and applied to adsorption of heavy metal ion of Pb(II). With Chinese peony flower-like morphology, the prepared SF@Cu-NFs showed ordered three-dimensional structure and exhibited excellent efficiency for Pb(II) removal. On one hand, the adsorption performance of SF@Cu-HNFs for Pb(II) removal was evaluated through systematical thermodynamic and adsorption kinetics investigation. The good fittings of Langmuir and pseudo-second-order models indicated the monolayer adsorption and high capacity of about 2000 mg g-1 of Pb(II) on SF@Cu-NFs. Meanwhile, the negative values of Δ r G m ( T ) θ and Δ r H m θ proved the spontaneous and exothermic process of Pb(II) adsorption. On the other hand, the adsorption mechanism of SF@Cu-HNFs for Pb(II) removal was revealed with respect to its individual organic and inorganic component. Organic SF protein was designated as responsible 'stamen' adsorption site for fast adsorption of Pb(II), which was originated from multiple coordinative interaction by numerous amide groups; inorganic Cu3(PO4)2 crystal was designated as responsible 'petal' adsorption site for slow adsorption of Pb(II), which was restricted from weak coordinative interaction by strong ion bond of Cu(II). With only about 10% weight content, SF protein was proven to play a key factor for SF@Cu-HNFs formation and have a significant effect on Pb(II) treatment. By fabricating SF@Cu-HNFs hybrid nanoflowers derived from SF protein, this work not only successfully provides insights on its adsorption performance and interaction mechanism for Pb(II) removal, but also provides a new idea for the preparation of adsorption materials for heavy metal ions in environmental sewage in the future.
NO reduction by CO was investigated over CO-pretreated CuO/MnOx/γ-Al2O3 catalysts with different metal precursors (nitrate and acetate). It was found that the catalyst prepared from acetate salts (Cu/Mn/Al-A) exhibited significantly higher activity than counterpart catalyst from nitrate precursors (Cu/Mn/Al-N). XRD, XPS and in situ DRIFT were carried out to approach the nature for the different catalytic performance. For both catalysts, copper mainly existed as CuO, but the status of manganese oxide was markedly different. Mn(IV) was predominant in Cu/Mn/Al-N and Mn(III) was enriched in Cu/Mn/Al-A. As a result, different dispersion behaviors of manganese oxide on γ-Al2O3 were displayed, which induced inconsistent Cu-Mn contact. The catalyst obtained from acetate precursor exhibited enriched Cu-Mn contact and thus more Cu+-â¡-Mn3+/2+ entities would be produced after CO pretreatment, leading to promoted NO dissociation and favorable performance in NO reduction by CO. The present study sheds light on the effective tuning of Cu-O-Mn interfacial sites in CuO/MnOx/γ-Al2O3 via modulating the dispersion behaviors of surface components.
Bimetallic AgPd nanoparticles have been synthesized before, but the interfacial electronic effects of AgPd on the photocatalytic performance have been investigated less. In this work, the results of hydrogen evolution suggest that the bimetallic AgPd/g-C3 N4 sample has superior activity to Ag/g-C3 N4 and Pd/g-C3 N4 photocatalysts. The UV/Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, CO adsorption diffuse reflectance FTIR spectroscopy, and FTIR results demonstrate that in the AgPd/g-C3 N4 , the surface electronic structures of Pd and Ag are changed, which is beneficial for faster photogenerated electron transfer and greater H2 O molecule adsorption. Inâ situ ESR spectra suggest that, under visible light irradiation, there is more H2 O dissociation to radical species on the AgPd/g-C3 N4 photocatalyst. Furthermore, DFT calculations confirm the interfacial electronic effects of AgPd/g-C3 N4 , that is, Pdδ- â â â Agδ+ , and the activation energy of H2 O molecule dissociation on AgPd/g-C3 N4 is the lowest, which is the main contributor to the enhanced photocatalytic H2 evolution.
The reuse, deactivation and regeneration of carbon nanotubes (CNT) and N-doped carbon nanotubes (NCNT) were studied in catalytic peroxymonosulfate (PMS) activation for phenol degradation. The results showed that for catalytic PMS activation, marked deactivation was observed on both CNT and NCNT, resulting in marked variation of the surface functionalities of the catalysts. Catalytic PMS activation led to markedly increased oxygen-containing functionalities and decreased points of zero charge (PZCs) of CNT and NCNT. The catalytic activity of CNT was strongly dependent on the initial PMS concentration but was independent of the initial phenol concentration. Furthermore, the dependency of the CNT activity on the initial PMS concentration closely followed the Langmuir-Hinshelwood model, indicating that the catalytic activation of adsorbed PMS was the rate controlling step. For the used CNT and NCNT, chemical reduction by NaBH4 or thermal treatment regeneration under inert atmosphere could effectively remove surface O-containing functionalities and enhance PZCs, restoring their catalytic activities; meanwhile, the N-containing functionalities of NCNT decreased with regeneration treatment, resulting in a negative impact on catalyst regeneration. The present findings indicate that surface functionalities are closely correlated with catalyst deactivation and regeneration, playing crucial roles in the catalytic activation of PMS.
As a broad-spectrum preservative, toxic o-phenylphenol (OPP) was frequently detected in aquatic environments. In this study, N-doped mesoporous carbon was prepared by a hard template method using different nitrogen precursors and carbonization temperatures (i.e., 700, 850 and 1000⯰C), and was used to activate peroxymonosulfate (PMS) for OPP degradation. For comparison, mesoporous carbon (CMK-3) was also prepared. Characterization results showed that the N-doped mesoporous carbon samples prepared under different conditions were perfect replica of their template. In comparison with ethylenediamine (EDA) and dicyandiamide (DCDA) as the precursors, N-doped mesoporous carbon prepared using EDA and carbon tetrachloride as the precursors displayed a higher catalytic activity for OPP degradation. Increasing carbonization temperature of N-doped mesoporous carbon led to decreased N content and increased graphitic N content at the expense of pyridinic and pyrrolic N. Electron paramagnetic resonance (EPR) analysis showed that PMS activation on N-doped mesoporous carbon resulted in highly active species and singlet oxygen, and catalytic PMS activation for OPP degradation followed a combined radical and nonradical reaction mechanism. Increasing PMS concentration enhanced OPP degradation, while OPP degradation rate was independent on initial OPP concentration. Furthermore, the dependency of OPP degradation on PMS concentration followed the Langmuir-Hinshelwood model, reflecting that the activation of adsorbed PMS was the rate controlling step. Based on the analysis by time-of-flight mass spectrometry, the degradation pathway of OPP was proposed.
Biphenyl Compounds/chemistry , Models, Chemical , Peroxides/chemistry , Water Pollutants, Chemical/chemistry , Adsorption , Biphenyl Compounds/analysis , Carbon/chemistry , Catalysis , Nitrogen/chemistry
Supported Ni catalysts on three mesoporous SiO2 supports (i.e., SBA-15, MCM-41, and HMS) were prepared using a solid-state reaction between Ni(NO3)2 and organic template-occluded mesoporous SiO2. For comparison, supported Ni catalysts on mesoporous SiO2 synthesized by the conventional impregnation method were also included. The catalysts were characterized by scanning electron microscopy, X-ray diffraction, UV-vis diffuse reflectance spectroscopy, N2 adsorption, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, transmission electron microscopy, and transmission electron microscopy-energy-dispersive X-ray. The catalytic properties of the catalysts were evaluated using gas-phase catalytic hydrodechlorination of 1,2-dichloroethane. The results showed that upon grinding Ni(NO3)2 with template-occluded mesoporous SiO2, strong coordination between Ni2+ and dodecylamine was identified in the Ni(NO3)2-HMS system. Additionally, the results of H2 temperature-programmed reduction revealed that NiO in calcined NiO/HMS was reduced at higher temperature than those in calcined NiO/SBA-15 and NiO/MCM-41, reflecting the presence of a strong interaction between NiO and mesoporous SiO2 in NiO/HMS. Consistently, the average particle sizes of metallic Ni were found to be 2.7, 3.4, and 9.6 nm in H2-reduced Ni/HMS, Ni/SBA-15, and Ni/MCM-41, respectively, indicative of a much higher Ni dispersion in Ni/HMS. For the catalytic hydrodechlorination of 1,2-dichloroethane, Ni/MCM-41 synthesized by the solid-state reaction method exhibited a catalytic activity similar to that prepared by the impregnation method, while higher catalytic activities were observed on Ni/HMS and Ni/SBA-15 than on their counterparts prepared by the impregnation method. Furthermore, a higher conversion was identified on Ni/HMS than on Ni/SBA-15 and Ni/MCM-41, highlighting the importance of template type for the preparation of highly dispersed metal catalysts on mesoporous SiO2.
A novel TiO2 supported core-shell (Pd@Ag) bimetallic catalyst was fabricated via the sequential photodeposition method. The Ag shell effectively blocks the high coordination sites on the Pd core, and therefore pronouncedly enhances the ethylene selectivity for the catalytic hydrogenation of acetylene in excess ethylene.
Phosphate pollution may cause eutrophication of the aquatic environment. In the present study, magnetic mesoporous SiO2 (denoted as MMS) and ZrO2-functionalized magnetic mesoporous SiO2 (denoted as ZrO2-MMS) were prepared and phosphate adsorption over the materials was investigated. The adsorbents were characterized by X-ray diffraction, transition electron microscopy, vibration sample magnetometer, N2 adsorption/desorption, zeta-potential measurement, and X-ray photoelectron spectroscopy. The results showed that MMS consisted of magnetite with particle sizes of 10-20 nm and ordered mesoporous SiO2 with the most probable pore diameter of 2.0 nm. The adsorbents could be readily separated and recovered under external magnetic field. The surface grafting of ZrO2 onto MMS led to an increase in surface zeta potential due to the formation of covalently linked ZrO2 functionality on the surface of MMS. Moreover, ZrO2 functionalization resulted in enhanced phosphate adsorption. Phosphate adsorption isotherms over the adsorbents could be well described by the Freundlich model. Phosphate adsorption kinetics followed the pseudo-second-order kinetics and the adsorption rate decreased with initial phosphate concentration. Additionally, increasing pH led to suppressed phosphate adsorption, and phosphate adsorption slightly increased with ionic strength.
Magnetics , Phosphates/chemistry , Silicon Dioxide/chemistry , Zirconium/chemistry , Adsorption , Hydrogen-Ion Concentration , Kinetics , Microscopy, Electron, Transmission , Osmolar Concentration , Photoelectron Spectroscopy , Thermodynamics , X-Ray Diffraction
The synthesis of mesoporous carbons CMK-3 was implemented using SBA-15 samples as the hard templates and sucrose as the carbon source. Ordered mesoporous carbon CMK-3 supported palladium catalyst with a loading amount of 20% (Pd/CMK-3) was prepared by a complexing reduction method. XRD and TEM results showed that the p6mm hexagonal symmetric pore structures of CMK-3 were highly ordered and the Pd nanoparticles with the average size of 4. 2 nm and 4. 5 nm were well dispersed on CMK-3 and activated carbon (AC) surfaces respectively. Raman results revealed that CMK-3 presented higher graphitization and a higher electric conductivity than AC. The most probable pore size of CMK-3 was 4.5 nm, which is larger than that of AC (0.54 nm). The BET surface area of CMK-3 was 1 114 m2 x g(-1), which was also larger than that of AC(871 m2 x g(-1)). The mesoporous structure of CMK-3 was also observed. The Pd/CMK-3 catalyst exhibited more excellent initial electrocatalytic activity for formic acid oxidation than Pd/AC by cyclic voltammetry (CV). But the chronoamperometry (CA) demonstrated that the stability of the two catalysts were almost equal after 100 s polarization at 0.2 V (vs. SCE).
Carbon/chemistry , Metal Nanoparticles/chemistry , Nanocomposites/chemistry , Nanopores , Palladium/chemistry , Catalysis , Electric Power Supplies , Electrochemistry/methods , Formates/chemistry , Oxidation-Reduction , Silicon Dioxide
Pd/TiO2 catalysts were prepared by the deposition-precipitation and impregnation methods, and were further characterized by TEM, XRD and ICP-AES. The liquid catalytic hydrodechlorination of 2,4-dichlorophenol over the catalysts was investigated. It is demonstrated that despite catalyst prepared by deposition-precipitation method exhibits higher activity than that synthesized from impregnation method, both catalysts show good performance in hydrodechlorination process. When initial concentration of the reactant was 3.11 mmol x L(-1), pH was 12 and amount of catalyst used was 50 mg, hydrodechlorination of 2,4-dichlorophenol was completed within 45 min. Acidic condition facilitates hydrodechlorination process. The initial activity was not significantly influenced when the amount of catalyst used varied between 15-80 mg, which proves that mass transport limitation exerts little impact on hydrodechlorination reaction. Finally, the initial activity sharply enhanced with the increase of initial concentration of 2,4-dichlorophenol when the concentration was in the range of 0.62-3.11 mmo x L(-1) while it almost remained constant with further increasing the initial concentration. Therefore, the catalytic hydrodechlorination of 2,4-dichlorophenol over Pd/TiO2-DP follows the Langumuir-Hinshelwood model, indicating that the catalytic hydrodechlorination is controlled by 2,4-dichlorophenol adsorption.
Chlorophenols/chemistry , Palladium/chemistry , Titanium/chemistry , Water Pollutants, Chemical/chemistry , Water Purification/methods , Adsorption , Catalysis , Chlorine/chemistry , Chlorophenols/isolation & purification , Water Pollutants, Chemical/isolation & purification
In the present study, photocatalytic Pb(II) reduction over TiO(2) and Ag/TiO(2) catalysts in the presence of formic acid was explored to eliminate Pb(II) pollution in water. Ag/TiO(2) catalysts were prepared by the photo-deposition method and characterized using UV-Vis diffuse reflectance spectra, X-ray reflection diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Ag deposition on TiO(2) led to enhanced photocatalytic Pb(II) reduction and the Ag/TiO(2) catalyst with a Ag loading amount of 0.99 wt.% exhibited the optimum photocatalytic activity. For Pb(II) reduction over Ag/TiO(2) with a Ag loading amount of 0.99 wt.%, initial Pb(II) reduction rate was found to be dependent on the initial concentrations of formic acid and Pb(II). Increasing initial Pb(II) concentration led to linearly increased initial Pb(II) reduction rate. At low formic acid concentration, in parallel, initial Pb(II) reduction rates increased with formic concentration, but remained nearly identical at high formic acid concentration. Solution pH impacted the photocatalytic Pb(II) reduction and after irradiation for 100 min Pb(II) was removed by 11.8%, 91.2% and 98.6% at pH of 0.8, 2.0 and 3.5, respectively, indicative of enhanced Pb(II) reduction with pH in the tested pH range. The results showed that Ag/TiO(2) displayed superior catalytic activity to TiO(2), highlighting the potential of using Ag/TiO(2) as a more effective catalyst for photocatalytic Pb(II) reduction.
Lead/chemistry , Lead/radiation effects , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/radiation effects , Water Purification/methods , Catalysis , Formates/chemistry , Hydrogen-Ion Concentration , Microscopy, Electron, Transmission , Oxidation-Reduction , Photochemistry , Photoelectron Spectroscopy , Rivers , Silver/chemistry , Spectrophotometry, Ultraviolet , Titanium/chemistry , Ultraviolet Rays , Water Supply , X-Ray Diffraction
