光助Fenton反应催化氧化降解罗丹明B表观动力学研究

Fenton反应作为处理难降解有机污染物有效的高级氧化技术之一,其氧化能力来自于在酸性条件下催化分解H₂O₂产生强氧化性(2.8 eV)的羟基自由基。而太阳光照下可促进羟基自由基的产生,从而提高Fenton反应氧化降解能力。文章在初始pH 3.5,太阳光直射的情况下研究了罗丹明B,Fe2+和H₂O₂等因素的初始浓度对光助Fenton反应降解罗丹明B速率的影响,采用求解拟合幂函数动力学方程获得了该反应体系的表观动力学方程。主要研究内容包括：罗丹明B溶液的紫外-可见光谱图;罗丹B溶液的浓度-吸光度工作曲线;不同初始罗丹明B浓度体系反应的分析;不同初始Fe2+浓度体系反应的分析;不同初始H₂O₂浓度体系反应的分析;表观动力学方程参数的计算。实验结果表明,该反应体系的动力学方程为：V=5×10-9P1.28F0.366E0.920,反应总级数为2.57。     

A new sono-electrochemical method for enhanced detoxification of hydrophilic chloroorganic pollutants in water

A new method for detoxification of hydrophilic chloroorganic pollutants in effluent water was developed, using a combination of ultrasound waves, electrochemistry and Fenton's reagent. The advantages of the method are exemplified using two target compounds: the common herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and its derivative 2,4-dichlorophenol (2,4-DCP). The high degradation power of this process is due to the large production of oxidizing hydroxyl radicals and high mass transfer due to sonication. Application of this sono-electrochemical Fenton process (SEF) treatment (at 20 kHz) with quite a small current density, accomplished almost 50% oxidation of 2,4-D solution (300 ppm, 1.2 mM) in just 60 s. Similar treatments ran for 600 s resulted in practically full degradation of the herbicide; sizable oxidation of 2,4-DCP also occurs. The main intermediate compounds produced in the SEF process were identified. Their kinetic profile was measured and a chemical reaction scheme was suggested. The efficiency of the SEF process is tentatively much higher than the reference degradation methods and the time required for full degradation is considerably shorter. The SEF process maintains high performance up to concentrations which are higher than reference methods. The optimum concentration of Fe²⁺ ions required for this process was found to be of about 2 mM, which is lower than that in reference techniques. These findings indicate that SEF process may be an effective method for detoxification of environmental water.     

Hybrid reactor based on combined cavitation and ozonation: From concept to practical reality

The present work gives an in depth discussion related to the development of a hybrid advanced oxidation reactor, which can be effectively used for the treatment of various types of water. The reactor is based on the principle of intensifying degradation/disinfection using a combination of hydrodynamic cavitation, acoustic cavitation, ozone injection and electrochemical oxidation/precipitation. Theoretical studies have been presented to highlight the uniform distribution of the cavitational activity and enhanced generation of hydroxyl radicals in the cavitation zone, as well as higher turbulence in the main reactor zone. The combination of these different oxidation technologies have been shown to result in enhanced water treatment ability, which can be attributed to the enhanced generation of hydroxyl radicals, enhanced contact of ozone and contaminants, and the elimination of mass transfer resistances during electrochemical oxidation/precipitation. Compared to the use of individual approaches, the hybrid reactor is expected to intensify the treatment process by 5–20 times, depending on the application in question, which can be confirmed based on the literature illustrations. Also, the use of Ozonix® has been successfully proven while processing recycled fluids at commercial sites on over 750 oil and natural gas wells during hydraulic operations around the United States. The superiority of the hybrid process over conventional chemical treatments in terms of bacteria and scale reduction as well as increased water flowability and better chemical compatibility, which is a key requirement for oil and gas applications, has been established.     

Improvement in sonochemical degradation of 4-chlorophenol by combined use of Fenton-like reagents

Studies on the sonolysis of a wide range of organic compounds have demonstrated that ultrasonic irradiation has potential for decomposition of organic pollutants in hazardous wastewater. However, the ultrasonic irradiation alone cannot provide high enough rate of decomposition to be used practically. One of the solutions to increase the degradation efficiency is to combine the ultrasound application with other advanced chemical oxidation processes (AOPs). In this study, in order to increase the efficiency of ultrasonically assisted degradation of organic pollutants in water, we examined effects of three kinds of solid Fe-containing catalysts, namely iron powder, basic oxygen furnace (BOF) slag and mill scale on the degradation rate of 4-CP (4-chlorophenol) in aqueous solutions containing hydrogen peroxide. In the experiments, 4-CP was considered as a model organic compound. All three Fe-containing matters when react with hydrogen peroxide are involved in the Fenton-like reaction system, which is one of the promising AOPs. The results showed that both the iron powder and mill scale additions can accelerate the degradation of 4-CP, although the effect is dependent on the solution pH. All 4-CP could be decomposed for 2 min at pH=3 and for 1h at pH=5.6. On the other hand, the BOF slag had no catalysis effect on the 4-CP degradation because of higher concentration of calcium and lower concentration of iron.     

Niobian iron oxides as heterogeneous Fenton catalysts for environmental remediation

Heterogeneous Fenton or Fenton-like reagents consist of a mixture of an iron-containing solid matrix and a liquid medium with H₂O₂. The Fenton system is based on the reaction between Fe^2?+? and H₂O₂ to produce highly reactive intermediate hydroxyl radicals (^???OH), which are able to oxidize organic contaminants, whereas the Fenton-like reaction is based on the reaction between Fe^3?+? and H₂O₂. These heterogeneous systems offer several advantages over their homogeneous counterparts, such as no sludge formation, operation at near-neutral pH and the possibility of recycling the iron promoter. Some doping transition cations in the iron oxide structure are believed to enhance the catalytic efficiency for the oxidation of organic substrates in water. In this work, goethites synthesized in presence of niobium served as precursors for the preparation of magnetites (niobian magnetites) via chemical reduction with hydrogen at 400°C. These materials were used as Fenton-like catalysts. Both groups of (Nb, Fe)-oxide samples were characterized by ⁵⁷Fe Mössbauer spectroscopy at 298 K. The results show that increasing niobium contents raise the catalytic potential for decomposition of methylene blue, which was, in this work, used as a model molecule for organic substrates in water.     

氮气对电晕放电等离子体降解甲基蓝的影响

电晕放电等离子体技术是近年发展起来的一种新型高级氧化工艺,因其处理效果好、操作简单、占地面积小的特点在印染废水处理领域得到了广泛应用。目前因大部分有机污染物的降解机理不详,该技术尚处于探索阶段。因此,为了尽早将电晕放电等离子体技术应用于工业印染废水的处理,不同污染物降解机理的研究对该技术的工业化和产业化应用具有重要意义。至今,电晕放电等离子体技术对研究较多的染料的降解效果均较好,然而,是否适合所有染料的降解有待进一步研究。采用电晕放电等离子体技术处理三苯甲烷类染料甲基蓝,研究了溶液的初始浓度对甲基蓝紫外-可见光谱中芳香环的降解率、发色基团吸光度变化的影响,测定了溶液的浓度、总有机碳（TOC）、总氮（TN）、pH值等指标随着放电时间的变化,并对其相关性进行了分析。结合紫外-可见光谱（UV-Vis）、三维荧光光谱（3D-fluorescence）和傅里叶变换红外光谱（FTIR）三种光谱学手段分析了电晕放电降解甲基蓝过程溶液的颜色、荧光物质和官能团变化,分析了电晕放电降解甲基蓝30 min后生成的中间产物。结果表明：电晕放电等离子体降解甲基蓝过程,溶液的浓度随着放电时间的延长逐渐减小,表明该技术对甲基蓝溶液有一定的降解能力;降解过程高压电极放电击穿含有大量氮气的空气产生N,NO·,N+₂等含氮高活性粒子,这些粒子通过扩散作用迁移至液相,使得溶液中TN含量在整个降解过程逐渐升高;另有部分含氮高活性粒子与钨钢针电极溶出的C元素键合生成发色的CN双键,使得溶液中的总有机碳在放电5 min时有所升高。延长反应时间产生的高活性粒子与溶液中的有机物（甲基蓝及中间产物）继续作用,部分有机物矿化生成CO₂,引起溶液中TOC含量的下降。电晕放电相同时间内产生的活性粒子数量相当,增大甲基蓝浓度,未被降解的甲基蓝分子越多,导致甲基蓝降解率的减小。电晕放电过程甲基蓝分子之间的聚合与发色CN双键的生成共同促使甲基蓝发色基团吸光度在放电5 min时达到最大;且甲基蓝溶液的初始浓度越高,吸光度（A₅-A₀）升高的越多。概括来说,甲基蓝结构中发色CN双键的存在是电晕放电等离子体降解甲基蓝过程溶液颜色加深再变浅的主要原因。反应过程羟基自由基的消耗导致放电5 min时溶液的pH值升高;随着反应的进行溶液中生成的硝酸及小分子酸增强了溶液的酸性,导致pH值降低。三维荧光光谱结果表明,甲基蓝降解过程出现了三类明显的荧光峰,位于E_X/E_M=310~320/430~450,E_X/E_M=240~250/320~340和E_X/E_M=280/340,分别代表腐殖酸类物质、芳香族蛋白质和溶解性微生物代谢副产物。甲基蓝溶液降解前的荧光物质主要为腐殖酸类,随着降解时间的延长,腐殖酸类物质首先降解生成了芳香族蛋白质,进一步降解产生可溶性微生物代谢副产物。比较电晕放电前后甲基蓝溶液的红外光谱图和红外分峰图发现,甲基蓝结构中N-H键3 432.8 cm-1处不对称伸缩振动峰红移了0.3 cm-1,烯烃和苯环上C-H键2 975.9 cm-1处的伸缩振动峰向高波数偏移了0.5 cm-1,1 638.7 cm-1处RCHCHR的双键伸缩振动位置蓝移了3.2 cm-1,芳仲胺的C-N伸缩振动峰1 341.6 cm-1向高波数偏移了1.3 cm-1,磺酸基SO的伸缩振动峰1 121.1和1 034.3 cm-1分别红移了3.8和13 cm-1,甲基蓝结构中的环外CC双键与CN双键吸收峰消失,在1 692.4和1 400.4 cm-1处分别出现了CO和NO的伸缩振动吸收峰,产生了2,5-环己二烯-1,4-二酮、对硝基苯磺酸钠和芳香酮类等中间产物。该结果对于利用电晕放电等离子体技术处理甲基蓝废水具有重要的理论意义和实用价值。     

Fabrication of antimicrobial bacterial cellulose–Ag/AgCl nanocomposite using bacteria as versatile biofactory

In recent years, the search for environmentally friendly alternative energy sources with reduced carbon footprints has increased. The coupling of photovoltaic power sources with advanced electrolysis systems for hydrogen production via water splitting using organic contaminants as sacrificial electron donors has been considered to a be viable alternative. In this report, we demonstrated the feasibility of a scaled-up rooftop prototype of the proposed hybrid photovoltaic-electrolysis system, which utilizes semiconductor nanoparticles coated on to metal substrates as electrodes for the generation of hydrogen coupled with the oxidation of wastewater. Application of an anodic bias of >2.0?V to bismuth-doped TiO₂ (BiO _x ?CTiO₂) on Ti metal anodes with a sequential under-coatings of nanoparticulate SnO₂, IrO₂, Ta₂O₅, and Bi₂O₃ results in the electrochemical degradation of a variety of organic chemical contaminants in water (i.e., rhodamine B (Rh.B), methylene blue (MB), salicylic acid, triclosan, and phenol) and actual wastewater from a chemical manufacturing plant, while at the same time, molecular hydrogen is produced at stainless steel (SS) cathodes. The kinetics of the anodic substrates oxidation is investigated as a function of the cell current (I _cell), substrate concentration, and background electrolyte composition (e.g., NaCl, Na₂SO₄, or seawater). Average current efficiencies were found to be in the range of 4?C22?%, while the cathodic current and energy efficiencies for hydrogen production were found to be in the range of 50?C70?% and 20?C40?%, respectively.     

季铵型纤维素的红外光谱及对持久性有机污染物的吸附特征

文章研究了季铵型阳离子纤维素(QACC)的红外光谱和对持久性有机污染物的吸附及循环利用问题。研究了吸附工艺参数对QACC吸附容量的影响。研究了QACC对染料的吸附等温式,测定了QACC吸附染料过程的热力学参数(ΔH, ΔS, ΔG)、吸附速率常数和吸附活化能,探讨了QACC吸附机理。在近中性水溶液中,QACC对含磺酸基、羧基、羟基的水溶性芳香族有机污染物具有较大的饱和吸附容量,常见共存离子对吸附不产生影响。QACC对上述污染物的吸附既有化学吸附,也有物理吸附,而以化学吸附为主。吸附符合Langmuir等温式和一级动力学方程,吸附速率随温度升高而增大。水溶性有机污染物用0.5 mol·L-1氢氧化钠水溶液洗脱,再生后QACC可以循环利用。QACC是一种性能优良的新型功能材料,可应用于环境中持久性有机污染物的治理。     

Sonochemical advanced oxidation process for the degradation of furosemide in water: Effects of sonication’s conditions and scavengers

The intensive consumption of pharmaceuticals and drugs in the last decades has led to their increased concentrations in wastewaters from industrial sources. The present paper deals, for the first time, with the sonochemical degradation and mineralization of furosemide (FSM) in water. FSM is a potent loop diuretic used to treat fluid build-up due to heart failure, liver scarring, or kidney disease. The influence of several operating parameters such as acoustic intensity, ultrasonic frequency, initial FSM concentration, solution’s pH, nature of the dissolved gas (Ar, air and N₂) and radical scavengers (2-propanol and tert-butanol) on the oxidation of FSM was assessed. The obtained results showed that the degradation rate of the drug increased significantly with the increase of the acoustic intensity in the range of 0.83 to 4.3 W cm⁻² and decreased with the augmentation of the frequency in the range of 585–1140 kHz. It was also found that the initial rate of the sonolytic degradation of FSM increased with the increase of its initial concentration (2, 5, 10, 15 and 20 mg/L). The most significant degradation was achieved in acidic conditions at pH 2, while in terms of saturating gas, the rate of FSM degradation decreased in the order of Ar > air > N₂. The FSM degradation experiments with radical scavengers showed that the diuretic molecule degraded mainly at the interfacial region of the bubble by hydroxyl radical attack. Additionally, in terms of acoustic conditions, the sono-degradation of 30.24 µmol L^-1 of FSM solution demonstrate an optimal performance at 585 kHz and 4.3 W/cm², the results indicated that even if the ultrasonic action eliminated the total concentration of FSM within 60 min, a low degree of mineralization was obtained due to the by-products formed during the sono-oxidation process. The ultrasonic process transforms FSM into biodegradable and environmentally friendly organic by-products that could be treated in a subsequent biological treatment. Besides, the efficiency of the sonolytic degradation of FSM in real environmental matrices such as natural mineral water and seawater was demonstrated. Consequently, the sonochemical advanced oxidation process represent a very interesting technique for the treatment of water contaminated with FSM.     

Sonochemical degradation of phenol in water: a comparison of classical equipment with a new cylindrical reactor

Cavitation due to ultrasonic waves produces highly reactive oxidising species in water. As a result, it can be used to oxidise organic pollutants such as aromatic compounds in dilute aqueous solutions. Recent studies have demonstrated that reactors operating in the high frequency range (e.g. 500 kHz) are more efficient than reactors working at lower frequency (20 kHz) for the destruction of these kinds of contaminants. Our study describes the degradation of phenol with the help of a cylindrical ultrasonic apparatus that operates at 35 kHz (Sonitube-SODEVA). To date, the use of this type of reactor has not been reported. The reaction rates thus obtained were compared to those obtained at the same ultrasonic power (50 W) with more classical devices operating at 20 and 500 kHz. The general result is that in aqueous solution, the rate of phenol destruction is higher at 500 kHz than at 35 or 20 kHz. Addition of hydrogen peroxide and copper sulphate to the medium provides a different oxidative system that proceeds more efficiently at 35 kHz; the time of destruction was about one-third of the time needed at 500 kHz. It was also observed that the intermediate organic compounds are eliminated much faster at 35 kHz in comparison with the two frequencies. The observation of such different behaviour is not necessarily a pure frequency effect, but can be due to a response to other parameters such as the acoustic field and intensity.