Hydrodynamic cavitation-enhanced photocatalytic activity of P-doped TiO2 for degradation of ciprofloxacin: Synergetic effect and mechanism

Hybrid methods with an enhanced oxidation capacity have been proposed for the removal of organic contaminants based on combining hydrodynamic cavitation (HC) with advanced oxidation processes (AOPs). In this study, we utilize the synergetic effect between photocatalytic processes and HC to strengthen ciprofloxacin (CIP) degradation by P-doped TiO₂ catalysts. In comparison to a degradation ratio of 20.37 % in HC and 55.7 % in P-TiO₂-based photocatalytic processes alone, the CIP degradation ratio reached as high as 90.63 % in HC-assisted photocatalytic processes with the optimal experimental parameters. The mechanic microjets treatment originated from HC make P-TiO₂ nano photocatalysts with significantly increased surface area, smaller particle sizes, cleaner surface and improved dispersion, which were found using SEM, TEM, and BET analysis. Possible degradation mechanisms and reaction pathways of CIP during hybrid HC + photocatalytic processes were explored by coupling free radical capture experiments and liquid chromatography-mass spectrometry . This hybrid HC + photocatalytic technique has a potential application in the treatment of antibiotic sewage at the industrial level.     

Intensification of Red-G dye degradation used in the dyeing of alpaca wool by advanced oxidation processes assisted by hydrodynamic cavitation

Red-G dye is one of the main dyes used in the textile industry to dye alpaca wool. Therefore, considering the large volume of processed wool in Perú, the development of efficient technologies for its removal is a present scientific issue. In this study, an integrated system based on hydrodynamic cavitation (HC) and photo-Fenton process was evaluated to remove the Red-G dye. Using a hybrid cavitation device (venturi + orifice plate), the effect of pH was evaluated, achieving 21 % of removal at pH 2 which was more than 80 % higher compared to pH 4 and 6. The effect of temperature was also evaluated in HC-system at pH 2, where percentage of dye degradation increased at lower temperatures (around 20 °C). Then, 50.7 % of dye was removed under optimized condition of HC-assisted Fenton process (FeSO₄:H₂O₂ of 1:30), that value was improved strongly by UV-light incorporation in the HC-system, increasing to 99 % removal efficiency with respect to HC-assisted Fenton process and reducing the time to 15 min. Finally, the developed cavitation device in combination with photo-Fenton process removed efficiently the dye and thus could be considered an interesting option for application to real wastewater.     

Hydrodynamic cavitation-assisted continuous pre-treatment of sugarcane bagasse for ethanol production: Effects of geometric parameters of the cavitation device

For biotechnological conversion of lignocellulosic biomass, a pre-treatment step is required before enzymatic hydrolysis of carbohydrate fractions of the material, which is required to produce fermentable sugars for generation of ethanol or other products in a biorefinery. The most of the reported pre-treatment technologies are in batch operation mode, presenting some disadvantages as dead times in the process. In this context, hydrodynamic cavitation (HC)-assisted alkaline hydrogen peroxide (AHP) pre-treatment in continuous process was proposed for pre-treatment of sugarcane bagasse (SCB). The system was designed with a main reactor containing two devices to generate cavitation by passing liquid medium through orifice plates. For SCB pretreated in continuous process, 52.79, 34.31, 22.13 and 15.81 g of total reducing sugars (TRS) per 100 g of SCB were released in samples pretreated using orifice plates with a number of holes of 24 (d = 0.45 mm), 16 (d = 0.65 mm), 12 (d = 0.8 mm) and 8 (d = 1 mm), respectively. Computational Fluid Dynamics (CFD) tools showed that 0.94 of vapor phase volume fraction and 0.19 of cavitation number were achieved at 31 m/s of throat velocity and upstream pressure of 350,000 Pa. By using pretreated SCB, 28.44 g of ethanol/L (84.31% of yield respect to theoretical value) was produced by immobilized Scheffersomyces stipitis NRRL-Y7124 in a simultaneous hydrolysis and fermentation process at high solid loading (16% S/L). Thus, HC-assisted process was proved as a promising technology for valorization of lignocellulosic biomass.     

A new water treatment technology for degradation of B[a]A by hydrodynamic cavitation and chlorine dioxide oxidation

Managing environmental contamination with Benz[a]anthracene (B[a]A) is essential due to its carcinogenic, teratogenic and mutagenic effects on humans and the environment. At present, the mainly B[a]A degradation methods used are photodegradation, bioremediation and traditional advanced oxidation, although they all have disadvantages. In this study, B[a]A was degraded by hydrodynamic cavitation (HC), chlorine dioxide (ClO₂), or an innovative combination of the two methods. According to high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC–MS) analysed the degradation products and degradation pathway of B[a]A, with the kinetics of different degradation methods discussed. Under optimal conditions, HC combined with ClO₂ oxidation can further degrade products to achieve ring cleavage. Compared with the two separate degradation process methods, the combined method exerts a synergistic effect on the degradation of B[a]A, with an enhancement factor of 1.48. Experimental results showed that the combination method can realize enhanced complete degradation of B[a]A, reduce ClO₂ requirements, improve efficiency, reduce energy consumption and produce less harmful products with ring cleavage achieved.     

Simultaneous hydrodynamic cavitation and glow plasma discharge for the degradation of metronidazole in drinking water

In this study, a novel hydrodynamic cavitation unit combined with a glow plasma discharge system (HC-GPD) was proposed for the degradation of pharmaceutical compounds in drinking water. Metronidazole (MNZ), a commonly used broad-spectrum antibiotic, was selected to demonstrate the potential of the proposed system. Cavitation bubbles generated by hydrodynamic cavitation (HC) can provide a pathway for charge conduction during glow plasma discharge (GPD). The synergistic effect between HC and GPD promotes the production of hydroxyl radicals, emission of UV light, and shock waves for MNZ degradation. Sonochemical dosimetry provided information on the enhanced formation of hydroxyl radicals during glow plasma discharge compared to hydrodynamic cavitation alone. Experimental results showed a MNZ degradation of 14% in 15 min for the HC alone (solution initially containing 300 × 10⁻⁶ mol L⁻¹ MNZ). In experiments with the HC-GPD system, MNZ degradation of 90% in 15 min was detected. No significant differences were observed in MNZ degradation in acidic and alkaline solutions. MNZ degradation was also studied in the presence of inorganic anions. Experimental results showed that the system is suitable for the treatment of solutions with conductivity up to 1500 × 10⁻⁶ S cm⁻¹. The results of sonochemical dosimetry showed the formation of oxidant species of 0.15 × 10⁻³ mol H₂O₂ L⁻¹ in the HC system after 15 min. For the HC-GPD system, the concentration of oxidant species after 15 min reached 13 × 10⁻³ mol H₂O₂ L⁻¹. Based on these results, the potential of combining HC and GPD systems for water treatment was demonstrated. The present work provided useful information on the synergistic effect between hydrodynamic cavitation and glow plasma discharge and their application for the degradation of antibiotics in drinking water.     

Combined effect of acoustic cavitation and pulsed discharge plasma on wastewater treatment efficiency in a circulating reactor: A case study of Rhodamine B

The present study investigates the wastewater treatment performance of an acoustic cavitation assisted plasma (ACAP) process in a circulating reactor using Rhodamine B (RhB) as a model water pollution. The concept of this process was proposed by the authors recently for a batch type rector. The measurements revealed that combining the ultrasound irradiation with pulsed discharge plasma allows the RhB degradation efficiency to be drastically increased as compared with the plasma-alone case. This effect is especially significant at higher values of solution electrical conductivity examined in a range of 20 ~ 400 μS/cm. Acidic conditions and larger flow rates of solution were found to be favorable for the degradation efficiency. The effect of flow rate was also analyzed through numerical simulation. The results indicated that the mass transfer of RhB to the plasma-cavitation zone is one of the controlling parameters influencing the degradation performance. Behavior of bubbles and pulse discharge frequency were examined using a high-speed video camera. Relatively large bubbles were found to favor the plasma pulse generation and propagation when move near the high-voltage electrode. On the whole, the results of this study suggest that the ACAP process has the potential to synergistically extend the application area of underwater plasma in both research and industry.     

Improvement of sonocatalytic activity of TiO2 by using Yb,N and F-doped Er3+:Y3Al5O12 for degradation of organic dyes

In this study, several up-conversion luminescence agents (Er³⁺:Y₃Al₅O₁₂, Er³⁺:Yb_0.2Y_2.79Al₅O₁₂, Er³⁺:Yb_0.2Y_2.79Al₅N_0.01O_11.99, Er³⁺:Yb_0.2Y_2.79Al₅F_0.01O_11.99 and Er³⁺:Yb_0.2Y_2.79Al₅N_0.01F_0.01O_11.98) were synthesized using sol–gel method. And then, the corresponding sonocatalyst (Er³⁺:Y₃Al₅O₁₂/TiO₂, Er³⁺:Yb_0.2Y_2.79Al₅O₁₂/TiO₂, Er³⁺:Yb_0.2Y_2.79Al₅N_0.01O_11.99/TiO₂, Er³⁺:Yb_0.2Y_2.79Al₅F_0.01O_11.99/TiO₂ and Er³⁺:Yb_0.2Y_2.79Al₅N_0.01F_0.01O_11.98/TiO₂ coated composites) were prepared by sol–gel coating process. The synthesized up-conversion luminescence agents and their coated composites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). And that, the sonocatalytic activities were detected through the degradation of Azo Fuchsine (AF) dye in aqueous solution by UV–vis spectroscopy. Some key influences such as heat-treated temperature and heat-treated time on the sonocatalytic activity of Er³⁺:Yb_aY_2.99−aN_xF_yAl₅O_12−x−y/TiO₂ coated composite, as well as ultrasonic irradiation time and initial dye concentration on the sonocatalytic degradation were studied. The results showed that the doping of Yb, N and F into Er³⁺:Y₃Al₅O₁₂/TiO₂ significantly enhanced the sonocatalytic activity of Er³⁺:Y₃Al₅O₁₂/TiO₂ coated composite in the degradation of organic dyes. Particularly, Er³⁺:Yb_0.2Y_2.79Al₅N_0.01F_0.01O_11.98/TiO₂ coated composites with 3:7 M ratio heat-treated at 550 °C for 60 min showed the highest sonocatalytic activity. At last, the experiments also indicated that the Er³⁺:Yb_0.2Y_2.79Al₅N_0.01F_0.01O_11.98/TiO₂ coated composites has a good sonocatalytic activity to degrade other organic dyes under ultrasonic irradiation.     

Thermal behavior,microstructure, phase transformation,and crystal growth kinetics of nano-scale Fe3+-doped TiO2 xerogel powders

Titania based ceramics are promising materials for environmental sensors, high efficiency photocatalyst. Ion doping is an effective method to improve the properties by modifying their microstructure and phase composition. In this study, TiO₂ particles doped with Fe³⁺ were prepared by sol-gel method using Ferric nitrate and tetrabutyl titanate as precursors. Fe³⁺ was incorporated in the TiO₂ matrix during thermal treatment in different temperatures. Thermal analysis, TEM and X-ray diffraction were used to characterize the TiO₂ powder. Microstructure, phase content, and cell parameters were calculated according to Rietveld refinement software GSAS. The interaction mechanism of Fe³⁺ in crystal lattice of titanium dioxide and the crystal growth kinetics of Fe³⁺-doped TiO₂ are discussed.     

染料敏化太阳能电池Eu~(3+),Sm~(3+)掺杂TiO_2下转换光阳极的制备及性能

用溶胶-凝胶法制备了Eu,Sm共掺TiO_2粉体,将其与P25复合,制备了下转换光阳极,用于染料敏化太阳能电池,利用其下转换特性提高电池的光电性能.用荧光光谱对粉体的发光性能进行表征,荧光光谱显示:Eu,Sm共掺TiO_2粉体受463nm光激发可以发射550~700nm的可见光,具有下转换功能.当Eu~(3+)的摩尔掺杂含量为1%,Sm~(3+)的摩尔含量为0.5%时,制备的Eu~(3+),Sm~(3+)共掺下转换光阳极,短路电流达到14.08mA/cm2,与使用Eu~(3+)掺杂TiO_2的下转换光阳极电池相比,提高了32.08%,转换效率也达到5.29%.     

掺Fe3+A-TiO2粉末的制备及其可见光催化降解碱性品红

以硫酸钛为原料用水热法制备了掺Fe3+TiO2粉末,用SEM测定了样品的形貌和晶型,研究了以自制的掺Fe3+ A-TiO2对碱性品红溶液的光催化降解作用.结果表明:所制备的TiO2为锐铁矿型TiO2(A-TiO2).可见光照射下,用自制的掺Fe3+A-TiO2降解碱性品红溶液的最佳条件是:2mg·L-1的碱性品红溶液中...     

Enhanced luminescence and degradation of SiO2:Ce,Tb powder phosphors prepared by a sol-gel process

Enhanced green photoluminescence and cathodoluminescence (CL) from Tb³⁺ ions due to co-doping with Ce³⁺ ions were observed from SiO₂:Ce,Tb powder phosphors prepared by a sol-gel technique. Blue emission from the Ce³⁺ ions was completely suppressed by Tb co-doping, presumably due to energy transfer from Ce³⁺ to Tb³⁺. In addition, the green CL intensity from SiO₂:Ce,Tb degraded by ∼50% when the powders were irradiated for 10 h with a 2 keV, 54 mA/cm² beam of electrons in an ultra-high vacuum chamber containing either 1×10⁻⁸ or 1×10⁻⁷ Torr O₂. Desorption of oxygen from the surface was observed during the decrease of CL intensity. The mechanisms for energy transfer from Ce³⁺ ions to Tb³⁺ ions to enhance the green luminescence, and mechanisms for desorption of oxygen from the phosphor surface that would result in decreased CL intensity are discussed.     

A comprehensive spectroscopic study of synthetic Fe2+, Fe3+, Mg2+ and Al3+ copiapite by Raman,XRD, LIBS,MIR and vis–NIR

The identification of iron sulfates on Mars by the Mars Exploration Rovers (MERs) and the Mars Reconnaissance Orbiter emphasized the importance of studying iron sulfates in laboratory simulation experiments. The copiapite group of minerals was suggested as one of the potential iron sulfates occurring on the surface and subsurface on Mars, so it is meaningful to study their spectroscopic features, especially the spectral changes caused by cation substitutions. Four copiapite samples with cation substitutions (Fe³⁺, Al³⁺, Fe²⁺, Mg²⁺) were synthesized in our laboratory. Their identities were confirmed by powder X‐ray diffraction (XRD). Spectroscopic characterizations by Raman, mid‐IR, vis‐NIR and laser‐induced‐breakdown spectroscopy (LIBS) were conducted on those synthetic copiapite samples, as these technologies are being (and will be) used in current (and future) missions to Mars. We have found a systematic ν₁peak shift in the Raman spectra of the copiapite samples with cation substitutions, a consistent atomic ratio detection by LIBS, a set of systematic XRD line shifts representing structural change caused by the cation substitutions and a weakening of selection rules in mid‐IR spectra caused by the low site symmetry of (SO₄)²⁻ in the copiapite structures. The near‐infrared (NIR) spectra of the trivalent copiapite species show two strong diagnostic water features near 1.4 and 1.9 µm, with two additional bands near 2.0 µm. In the vis‐NIR spectra, the position of an electronic band shifts from 0.85 µm for ferricopiapite to 0.866 µm for copiapite, and this shift suggests the appearance of a Fe²⁺ electronic transition band near 0.9 µm. Copyright © 2010 John Wiley & Sons, Ltd.     

Detection of hypersound by means of a phonon-photon double-resonance technique in the paramagnetic systems MgO: Fe3+ and MgO: Fe2+

We report a novel technique for the detection of hypersound by means of phonon-photon double resonance. This technique seems especially suitable for very-high-frequency phonons. Experiments were performed in the X-band with a modified apparatus for Electron Paramagnetic Resonance (EPR) combined with a hypersound pulse-echo equipment. Phonon pulses of about 1 μs duration could be detected in the paramagnetic systems MgO: Fe³⁺ and MgO: Fe²⁺. This kind of incoherent phonon detector is sensitive only in a narrow frequency band, can be tuned, and can easily be applied in several frequency ranges without changing the experimental set-up.     

Preparation and characterization of hollow TiO2 nanospheres: The effect of Fe3+ doping on their microstructure and electronic structure

Hollow Fe-doped TiO₂ spheres with various Fe dopant concentrations, 0.25, 0.50 and 1.0 wt%, were synthesized via a hydrothermal method using carbon spheres as templates. The prepared samples were calcined in air at temperatures of 500 and 550 °C for 3 h and characterized using XRD, SEM, TEM, SAED, EDX, XPS and UV–vis spectroscopy. The analytical results showed that the presence of a very low concentration of Fe³⁺ incorporated into hollow nanoporous TiO₂ spheres inhibited the growth of nanocrystals as well as the anatase to rutile phase transformation inside the anatase TiO₂ lattice. Doping with 1.0 wt% Fe³⁺ resulted in a reduction of the TiO₂ sphere diameter from 205.71 ± 25.29 nm to 68.70 ± 7.07 nm. The optical energy gap of the samples was determined from UV–Vis absorption spectra. The results showed that the absorption edge of TiO₂@Fe was shifted toward the visible light region with increased Fe content.     

丙醇水溶液中Fe2+与Ga3+、Ru3+、Pd2+、W（Ⅵ）和V（Ⅴ）的析相萃取分离

研究了在抗坏血酸存在下邻二氮菲-正丙醇-水体系析相萃取分离和富集铁的行为及与一些金属离子分离的条件。结果表明,在一定条件下,该体系能使Fe2+与Ga3+、Ru3+、Pd2+、W(Ⅵ)和V(Ⅴ)分离。     

EPR,optical absorption and superposition model studies of Fe3+-doped cesium chloride single crystals: a case of substitutional as well as interstitial sites

An electron paramagnetic resonance study of Fe³⁺-doped cesium chloride single crystals was carried out at room temperature. Three sites are observed. The spin Hamiltonian parameters were determined from the angular variation of the observed resonance lines. The hyperfine structure is observed due to the presence of Fe⁵⁷ centers. At site I, Fe³⁺ enters the lattice substitutionally, replacing Cs⁺ in the cubic symmetry of the crystal, whereas at sites II and III, Fe³⁺ enters the lattice interstitially. The local site symmetry of Fe³⁺ in the host lattice is considered to be orthorhombic. An optical absorption study of the crystal was also performed at room temperature. The observed bands were assigned and the Racah inter-electronic repulsion parameters (B and C) and the cubic crystal field splitting parameter (Dq) were determined. On the basis of EPR and optical data, the nature of the metal–ligand bonding in the crystal was determined. The crystal field parameters were evaluated using the superposition model and then used in the microscopic spin Hamiltonian and perturbation equations to determine the zero-field splitting parameters (ZFSPs) theoretically for all sites observed. The theoretical ZFSPs are in good agreement with the experimental values.     

实验优化设计Sr_2MgSi_2O_7:Eu~(2+),Dy~(3+)的合成及长余辉特性

为了得到最长有效余辉时间的Sr_2MgSi_2O_7:Eu~(2+),Dy~(3+)荧光粉,应用二次通用旋转组合设计对实验进行全程优化,建立了稀土离子掺杂浓度Eu~(2+),Dy~(3+)和有效余辉时间的二元二次回归方程模型,应用遗传算法计算得到有效余辉时间的理论最大值.采用高温固相法合成了最优掺杂浓度Sr_2MgSi_2O_7:0.5mol%Eu~(2+),1.0mol%Dy~(3+)的荧光粉,在370nm激发下观察到了465nm的特征发射,这归因于Eu~(2+)的4f65d1—4f7跃迁.测量了最优荧光粉的热释发光特性,计算得到了陷阱深度为0.688eV,讨论了长余辉发光的特性.     

Spin glass behavior probed by various methods with different time- and space-scale of observation: Ising spin glass Fe0.50Mn0.50TiO3

Under the expectation that the behavior of a spin glass (SG) system shows various aspects depending on the time- and space-scale of observations, we have studied the typical Ising spin glass Fe_0.50Mn_0.50TiO₃ by measuring dc-magnetization, ac-susceptibility, Mössbauer spectrum, neutron scattering intensity and μ⁺SR time spectrum. We have demonstrated that the application of various methods with different time- and space-scale of observations to the same system is useful to clarify the property of the spin glass freezing, the Ising character and the de Almeida and Thouless-line.     

NH_4NO_3掺杂Na~+、K~+、Ag~+、Pb_(2+)晶体相变拉曼峰强行为研究:掺杂效应的标度性

从掺杂晶体（Ｎａ＋、Ｋ＋、Ａｇ＋、Ｐｂ２＋）ｘ（ＮＨ４）１－ｘＮＯ３相变时，拉曼峰强与温度的变化关系着手，深入讨论了掺杂离子的效应，揭示了其中的标度性质。本文分下列章节：（１）前言、（２）实验、（３）ｌｎＩＲ与ｌｎ｜Ｔ－Ｔｃ｜之线性关系、（４）不同振动模对不同掺杂程度的反应、（５）ν１振动模对不同离子掺杂的刻画、（６）‘反转’行为、（７）ｄｃ与Ｍ１／２的线性关系、（８）掺杂效应的标度性、（９）结语     

Structural and electronic properties of Fe 3+ -O 2− Pairs in KMF 3 lattices (M=Mg,Zn): Is the superposition model valid?

The geometrical and electronic properties of the tetragonal FeF 5 O 4 m complex which is likely formed in KMgF 3 and KZnF 3 fluoroperovskites have been investigated by means of Density Functional calculations. The properties of this centre are dependent on the Fe-O distance ( R ox ) and also on the distances R eq and R ax between Fe 3+ and the four equatorial F m ions and the apical F m ion respectively. The calculated equilibrium distance for the isolated Fe 3+ -O 2 m pair is equal to R ox =1.63 v + while when it is introduced in KMF 3 lattices ( M =Mg, Zn) R ox ～1.82 v + . Compared to FeF 6 3 m in KMgF 3 ( R eq = R ax =1.94 v + ) the obtained equilibrium distances R ax =2.05 v + and R eq =2.02 v + mean an outwards relaxation of 6% and 4% respectively induced by the F m M O 2 m substitution. The ratio of the associated superhyperfine ( shf ) constants of equatorial ( A eq ) and axial ( A ax ) F m ligands is A eq / A ax , 2 and thus account for an experimental fingerprint of this centre. The huge difference between A s (eq) and A s (ax) cannot be explained assuming that the law relating A s to the metal-ligand distance, R , for the octahedral FeF 6 3 m unit can be transferred to the present case involving a lower symmetry . The present analysis casts doubts on the conclusions previously reached using the empirical superposition model.