Development of kaolinite supported ferric oxalate heterogeneous catalyst for degradation of 4-nitrophenol in photo-Fenton process

Ferric oxalate catalyst supported on phosphoric acid treated kaolin (ATKaol) was prepared and tested on the degradation of 4-nitrophenol (4-NP). The X-ray fluorescence (XRF) and Brunauer–Emmett–Teller (BET) characterization results showed drastic distortions in the raw kaolin (Kaol) crystalline structure and an increase in specific surface area (SSA) from 18.78 to 166.12 m² g^− 1 after acid treatment. The incorporation of Fe was confirmed with Fourier transformed infra-red spectroscopy (FTIR), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) results. The degradation of 4-NP without UV was slower compared to when UV was used. There was no appreciable degradation in the absence of either catalyst or hydrogen peroxide (HP). The acid treated kaolinite catalyst (ATKaolCat) exhibits high catalytic activity without pH adjustment degrading 99% of 4-NP (100 ppm) in 4 min using 2.0 g ATKaolCat and 20% excess HP at 40 °C. The reusability study shows 9.4% decrease in efficiency after 5 rounds. The kinetic model developed showed good agreement with the experimental data. The model showed that ATKaolCat has higher selectivity for direct oxidation of 4-NP to mineralized products compared to oxidation via intermediates. These qualities make the catalyst promising in 4-NP degradation.     

构建电促铁还原型芬顿氧化法降解水中4-硝基酚

以钛基氧化物涂层材料(Ti/SnO_2-Sb_2O_5-IrO_2)为阳极,碳纳米管修饰的石墨材料(GE-CNT)为阴极构建电化学系统,促进芬顿反应过程中Fe~(3+)还原,从而减少芬顿氧化法中铁盐加量和铁泥产生量。研究表明:GE-CNT具有良好的还原Fe~(3+)性能,其优化的阴极还原电位约为0.30 V(vs.Ag/AgCl),该电位下反应120 min时Fe~(3+)还原率达到85.7%。以Fe~(3+)为催化剂降解4-硝基酚的结果,证实了电化学还原Fe~(3+)促进芬顿反应的有效性。对比考察了电促铁还原型芬顿氧化法与普通芬顿氧化法降解4-硝基酚的效果,优化的条件下两者可获得近似的降解效果,但前者优化的H_2O_2与Fe~(2+)摩尔比为40∶1,而后者为20∶1。因此,相对于普通芬顿氧化法,电促铁还原型芬顿氧化法可显著减少芬顿反应初始Fe~(2+)投加量。     

Effect of phosphoric acid treatment on kaolinite supported ferrioxalate catalyst for the degradation of amoxicillin in batch photo-Fenton process

The effects of phosphoric acid treatment on kaolinite (Kaol) as catalyst support were investigated in this study. The results showed that as the acid concentration was increased from 5 to 10 M, there was increment in the specific surface area from 18.78 in Kaol to 36.0 and 145.5 m² g^− 1 in 5 M acid treated Kaol supported catalyst (5 M-AT-KaolCat) and 10 M acid treated Kaol supported catalyst (10 M-AT-KaolCat), respectively. Characterization results showed that 10 M-AT-KaolCat has higher percentage of Fe than the 5 M-AT-KaolCat due to the effect of acid treatment which provided larger surface area for its anchoring. Consequently, degradation efficiency is comparably faster in 10 M-AT-KaolCat with about 99% of 40 ppm amoxicillin degraded in 8 min without pH adjustments while it takes 12 min using 5 M-AT-KaolCat. The degradation process showed initial enhanced degradation efficiency with increase in the catalyst loadings which later decreased due to the scavenging effect of excess catalyst loading on the reactive hydroxyl radical. The catalysts showed high resistance to leaching due to the presence of the ferrioxalate (FeOx) ligands and the effect of phosphoric acid modification which introduces monolayer of phosphate functional group on the catalyst support through which the FeOx ligands were properly anchored.     

Heterogeneous UV-Fenton catalytic degradation of dyestuff in water with hydroxyl-Fe pillared bentonite

In recent years, much attention has been focused on developing heterogeneous catalyst for Fenton or photo-Fenton process to reuse the catalyst and avoid the possible pollution caused by the metal ions in the solution. Through cation exchange reaction, hydroxyl-Fe pillared bentonite (H-Fe-P-B) was successfully prepared as a solid catalyst for UV-Fenton process. Compared with raw bentonite, the content of iron, interlamellar distance and external surface area of H-Fe-P-B increased remarkably. Heterogeneous UV-Fenton catalytic degradation of azo-dye Acid Light Yellow G (ALYG) was investigated in aqueous using UVA (365 nm) light as irradiation source. The effects of H₂O₂ concentration, catalyst dosage, initial pH and temperature on degradation of ALYG were studied in detail. The results demonstrated that the H-Fe-P-B had high catalytic activity. In optimal operation conditions, more than 98% discoloration and 65% TOC removal of 50 mg/L ALYG could be achieved after 120 min treatment. The iron leaching rates of H-Fe-P-B were all below 0.6% in multiple runs in the degradation of ALYG, which indicated that the heterogeneous catalyst had long-term stability and activity. Another advantage of this catalyst was its strong surface acidity, which made the range of pH for heterogeneous UV-Fenton system extended from 3.0 to 9.0. The results indicated that the H-Fe-P-B was a promising catalyst for heterogeneous UV-Fenton system.     

Enhanced activity of iron oxide dispersed on bentonite for the catalytic degradation of organic dye under visible light

Natural clay-supported iron oxide was prepared by deposition method, and dried at 120 °C. It was found that under visible light in the presence of H₂O₂, this catalyst was highly active for degradation of cationic (malachite and fuchsin basic) and anionic dyes (orange II and X3B) in water at pH 6.5, as compared with bare iron oxide or the clay-supported iron oxide sintered at 350 °C. The excellent performance of the catalyst is correlated with its high sorption capacity toward both types of dyes, thus resulting in enhanced dye degradation via a photosensitization pathway. The catalyst was characterized by XRD, nitrogen adsorption, infrared, and UV–visible spectroscopy.     

金属柱撑黏土催化非均相Fenton技术的研究

金属柱撑黏土(PILC)能够在保证Fenton法对有机污染物的去除功效的同时,较好地克服Fenton法催化剂易流失、适用pH范围小等缺点.介绍了金属柱撑黏土制备的新进展,总结了柱撑黏土单独催化或与紫外等技术联合催化非均相Fenton反应降解水体有机污染物的研究成果,分析了柱撑黏土催化非均相Fenton反应的机理.针对目前研究仍然存在的问题,结合实际应用的需求,提出了今后工作中一些值得关注的方向.     

Efficient degradation of 4-nitrophenol by using functionalized porphyrin-TiO2 photocatalysts under visible irradiation

The effect of a series of carboxylic acids (C₂–C₈), as solvents for the preparation by flame spray pyrolysis of LaCoO₃ catalyst for the flameless combustion of methane, has been investigated. Acetic acid showed to be unsatisfactory from several points of view: low phase purity of the catalyst, higher amount of unburnt carbonaceous residua, lower catalytic activity and low thermal stability. By increasing the carbon chain length of the solvent, the consequent increase of flame temperature led to an increase of crystal phase purity and of particle size and to a decrease of specific surface area of the catalyst. Catalytic activity showed only marginally affected by the last parameter, phase purity seeming more important. Thermal resistance showed directly related to flame temperature, i.e. to the combustion enthalpy of the solvent, but a relatively high amount of residual organic matter can negatively affect this property.     

钒酸铋的制备及可见光降解罗丹明B的研究

以偏钒酸铵和碳酸铋为原料,用NaOH调节体系pH,水热法合成钒酸铋（BiVO₄）光催化剂。利用XRD和UV-Vis漫反射对样品的晶型结构和光吸收特性进行表征分析。以罗丹明B为目标降解物,卤素灯（λ＞400 nm）为光源,探讨水热温度、水热时间对合成BiVO₄催化剂的可见光催化活性影响。结果表明,在水热温度为200 ℃、水热时间为8 h的条件下合成的钒酸铋光解效率最高。实验还研究了罗丹明B水溶液pH、催化剂投加量对光催化罗丹明B降解率的影响。结果表明,在罗丹明B水溶液pH为3、初始质量浓度为10 mg/L、每60 mL溶液催化剂投加量为0.4 g时能达到较好的光催化效果,反应2 h后降解率可达97%。     

Ag seeds mediated growth of Au nanoparticles within PVA matrix: An eco-friendly catalyst for degradation of 4-nitrophenol

The integration of highly monodispersed gold (Au) nanoparticles into polyvinyl alcohol (PVA) film is developed through a new seeded-growth pathway. Silver (Ag) nanoparticles are used during the synthesis as the reactive seeds to induce the reduction of Au under the UV-irradiation. The narrow surface plasmon resonance confirms the success of preparing gold nanoparticles with narrow size and shape distribution. The as-prepared PVA/Au nanocomposite films show sturdy cohesion between the PVA chains and/or between PVA network and gold nanoparticles. This has led to interest in their use as brand-new product in catalytic reduction of 4-nitrophenol with NaBH₄.     

Heterogeneous Fenton degradation of Orange II by immobilization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles onto Al-Fe pillared bentonite

A novel catalyst, Fe₃O₄ nanoparticle decorated Al-Fe pillared bentonite (Fe₃O₄/Al-Fe-P-B), was prepared by in situ precipitation oxidization method. The catalyst was characterized by SEM, XRD and Raman spectroscopy. The Fe₃O₄ nanoparticles mainly exist on the surface or enter into the pore of bentonite, with better dispersing and less coaggregation. The catalytic activity of Fe₃O₄/Al-Fe-P-B was investigated in the degradation of Orange II (OII) by heterogeneous Fenton-like process. The effects of initial concentration of hydrogen peroxide, catalyst loading, temperature and initial pH on the degradation of OII were investigated. The Fe₃O₄/Al-Fe-P-B showed higher degradation efficiency of OII than bare Fe₃O₄ or Al-Fe-P-B in the degradation experiment. The enhanced catalytic activity of Fe₃O₄/Al-Fe-P-B in heterogeneous Fenton system was due to the synergistic effect between Al-Fe-P-B and Fe₃O₄. The novel catalyst can achieve solid-liquid separation easily by sample magnetic separation and has a good reusability and stability.     

Synthesis of AgCl/Bi3O4Cl composite and its photocatalytic activity in RhB degradation under visible light

This work presents a novel composite photocatalyst, AgCl/Bi₃O₄Cl, which was prepared using an ion-exchange method. The synthesized composite was characterized by various techniques and its photocatalytic activity was investigated in RhB degradation under visible light irradiation. Results indicated that the introduction of AgCl into Bi₃O₄Cl promoted the specific surface area, light absorption performance and the separation efficiency of electron–hole pairs, which resulted in a high photocatalytic activity of the composite. The optimal AgCl/Bi₃O₄Cl sample showed a RhB degradation rate of 0.048 min^− 1, which was 2.2 and 2.4 times higher than those of AgCl and Bi₃O₄Cl, respectively.     

Photocatalytic degradation of bisphenol A by Ag3PO4 under visible light

Ag₃PO₄ catalysts exhibited excellent photocatalytic performance in the degradation and the mineralization of bisphenol A, displaying considerably higher photocatalytic activity than N–TiO₂ under visible light (λ > 420 nm). The trapping effects of different scavengers and spectrophotometric results proved that the oxidation of bisphenol A mainly occurred at photogenerated holes on the Ag₃PO₄ surface, along with a two-electron reduction of dissolved oxygen to H₂O₂.     

Synthesis of Ag nanoparticles within the pores of SBA-15: An efficient catalyst for reduction of 4-nitrophenol

Synthesis of uniform, spherical and rod shaped Ag nano particles within the uniform pore channels of mesoporous silica SBA-15 have been reported via a simple chemical method. High resolution transmission electron micrographs showed uniformly distributed spherical and rod shaped nano particles inside the pore channels of SBA-15. Synthesized Ag nano particle incorporated SBA-15 materials were acted as an efficient catalyst for the reduction of 4-nitrophenol to 4-aminophenol.     

石墨烯-Bi2MoO6可见光催化降解4BS染料

采用溶剂热合成法制备性能稳定的可见光石墨烯-Bi₂MoO₆复合催化剂,研究催化剂对4BS染料的光催化降解效果以及4BS溶液浓度pH、催化剂用量和石墨烯-Bi₂MoO₆复合催化剂重复使用次数等对光催化降解效果的影响。结果表明,在催化剂用量0.50 g·L^－1、染料初始浓度20 mg·L^－1和碱性条件下,光照反应150 min后,4BS去除率达98.5%,催化剂重复使用5次,4BS去除率达78%。复合催化剂结构稳定,可见光下能够有效降解4BS染料。     

BiOCl/g-C3N4异质结催化剂可见光催化还原CO2

以KCl、Bi（NO₃）₃和类石墨氮化碳（g-C₃N₄）为前体,采用水热法成功制备了BiOCl/g-C₃N₄异质结光催化剂,并进行可见光催化还原CO₂,考察了催化剂的活性及稳定性,同时研究BiOCl：g-C₃N₄（摩尔比）、催化剂用量和光照强度对光催化还原CO₂的影响。结果表明,在水蒸气的存在下,BiOCl/g-C₃N₄较纯BiOCl和g-C₃N₄具有更高的光催化还原CO₂活性,在催化剂用量为0.1 g,光照强度为2.413×10^-6 einstein·min^-1·cm^-2,BiOCl：g-C₃N₄摩尔比为1：1的异质结催化剂显示了最高的光催化还原CO₂活性,且可见光催化剂在5次套用实验后其活性基本不变。基于X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）、比表面积测试（BET）和紫外-可见（UV-vis）吸收光谱表征,可以推断BiOCl和g-C₃N₄之间形成的p-n结能有效分离光生电子和空穴,是增强光催化剂活性的主要原因。     

Mn-沸石催化剂的制备及其对Fenton工艺处理垃圾渗液催化氧化效果研究

以沸石为载体,硝酸锰为改性剂制备了负载型Mn-沸石催化剂,采用SEM和BET法对制备的催化剂进行了表征。采用Fenton工艺处理垃圾渗滤液原液,通过正交实验和单因素实验考察了Mn-沸石催化剂对Fenton法处理生活垃圾渗滤液的影响。结果表明,一定量的生活垃圾渗滤液,投加1 mL 30%H2O2,H2O2/Fe2+摩尔比为4∶1、pH为4,加入1 g Mn-沸石催化剂,CODCr去除率可高达90.25%。     

Ag3PO4/g-C3N4异质结催化剂可见光降解黄连素

采用原位生长法制备Ag₃PO₄/g-C₃N₄异质结催化剂,在可见光照射下,催化氧化降解废水中的药物大分子黄连素。通过X射线衍射（XRD）、扫描电镜（SEM）、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）分析催化剂的组成和结构,并测试了Ag₃PO₄/g-C₃N₄降解黄连素的光催化活性。结果表明：利用可见光照射,g-C₃N₄掺杂量为0.7 g时,Ag₃PO₄/g-C₃N₄对黄连素的光催化降解活性最好,可见光反应15 min降解率达到100%,重复4次实验后降解率降至73.2%,其具有较好的光稳定性。自由基捕获实验证明h⁺和·O₂^-在降解黄连素废水中起主要作用,结合UV-vis DRS分析可知,Ag₃PO₄/g-C₃N₄遵循Z型异质结机理。     

An efficient CeGeO4 catalyst for degradation of organic dyes without light irradiation at room temperature

In comparison with photocatalytic process, the catalytic degradation of organic dye pollutants in no need of light irradiation is highly interesting from the energy-saving point of view. In this paper, we developed a new CeGeO₄ catalyst that can satisfy the energy-saving requirements in this regard. During the synthesis of CeGeO₄, the influence of synthetic medium pH, the kind of precursor, etc., on the formation of crystalline CeGeO₄ was investigated in detail. Importantly, the CeGeO₄ catalyst exhibited significantly higher performance than that of CeGeO₄/CeO₂ or CeO₂ in degradation of rhodamine B (RhB) or methylene blue (MB) in the dark at room temperature.     

Co-doping g-C3N4 with P and Mo for efficient photocatalytic tetracycline degradation under visible light

Although g-C₃N₄ (CN) materials have been extensively explored for the photocatalytic degradation of organic pollutants, their weak response to visible light and fast recombination of photoexcited electron-hole pairs restrain their practical applications. Herein, we deeply mediated the CN's energy-band structure, morphology, and surface properties by non-metal (P) and metal (Mo) co-doping based on the thermal treatment of a phosphomolybdic acid hydrate and dicyandiamide mixture in a straightforward one-step manner. Meanwhile, cyano groups and nitrogen vacancies were generated as a result of the co-doping, and the resulting P, Mo co-doped CN (PM-CN) exhibited thinner layers, smaller sizes, and superior visible-light harvesting capacity and charge separation efficiency. Consequently, highly active PM-CN was obtained for photocatalytic tetracyclines (TC) degradation, and the rate was calculated to be 0.01 min^?1, 3.3 times greater than that of the pure CN, outstripping the single P- and Mo-doped counterparts. A free radical scavenging test demonstrated that the reactive species ?O^2? and h⁺ were critical in TC degradation. The present work is expected to shed light on co-doping CN with non-metal and metal elements to obtain high-performance, visible-light-responsive photocatalysts for practical environmental remediation.     

Graphite-supported TiO2 for 4-nitrophenol degradation in a photoelectrocatalytic reactor

Amorphous TiO₂, prepared at room temperature through a sol–gel method implementing hydrolysis of TiCl₄, has been supported on graphite rods and then annealed at 673 K. In this way graphite was completely covered by a porous anatase TiO₂ layer, with an external thickness of about 1 μm, with graphite pores completely filled by the semiconductor particles. The obtained electrode was structurally characterized by SEM microscopy coupled to EDAX mapping and by Raman spectroscopy. A Pyrex annular reactor was designed in order to test the prepared electrodes for the photoelectrocatalytic degradation of 4-nitrophenol, a target pollutant dissolved in aqueous conductive solution. The continuous reactor worked in total recirculation mode and the degradation runs were carried out by applying near UV-light, bias or both energy sources. The influence of flow rate, initial 4-nitrophenol concentration and applied potential on the degradation rate was studied.