Electro-Fenton decoloration of dyes in a continuous reactor: A promising technology in colored wastewater treatment

This study focuses on the application of Electro-Fenton technique for the remediation of wastewater contaminated with synthetic dyes. A bubble reactor was designed to develop this treatment operating in continuous mode. In order to increase the efficiency of Electro-Fenton treatment, the effect of key parameters (iron dosage and pH) that play an important role in this process was investigated for Lissamine Green B decoloration in batch mode. Operating at the optimal conditions, determined for Lissamine Green B, several dyes (Methyl Orange, Reactive Black 5 and Fuchsin Acid) were decolorized by using Electro-Fenton process. A first-order kinetic model was used to simulate the experimental results operating at different pH, and iron concentration of 150 mg L⁻¹. This kinetic model for Lissamine Green, Methyl Orange and Reactive Black 5 was successfully used in the progression of the process from batch to continuous mode. About 80% color removal was achieved for Lissamine Green and Methyl Orange with a residence time of 21 h. The decoloration for Reactive Black 5 was lower, reached a value around 60% at the same residence time. Nevertheless in all assays a good agreement between experimental results and proposed model in a continuous bubble reactor was detected. In addition a continuous treatment with a mixture of dyes was carried out. Operating with a residence time of 21 h the obtained decoloration was close to 43% which is squared with a TOC reduction around 46%. Therefore, the results provide fundamental knowledge for the treatment of a real wastewater stream.     

Analysis of cosmetic dyes V identification of organic synthetic dyes in toilet soaps

The soap is fused in formic acid. Fatty acids are removed with heptane from which later the oil-soluble and some pigment dyes are removed by means of formic acid. The defatted solution of soap in formic acid is diluted and partly neutralized and therefrom the basic, pigment and some acid dyes are isolated with chloroform. Other acid dyes are isolated with help of benzalkonium chloride/chloroform or polyamide. Insoluble dyes are isolated by filtration followed by dissolving in one of the series of solvents. Separation and identification are achieved by means of thin-layer chromatography, absorption spectra and reactions.     

UV/H2O2 treatment of Rhodamine B in aqueous solution: Influence of operational parameters and kinetic modeling

The decolorization and degradation of Rhodamine B (RB) were investigated using UV radiation in the presence of H₂O₂ in a batch photoreactor at different light intensities. H₂O₂ and UV light have a negligible effect when they were used on their own. Removal efficiency of RB was sensitive to the operational parameters such as initial concentrations of H₂O₂ and RB, initial pH and light intensity. The results indicated that efficiency of process decreased with addition of inorganic ions and alcohols to the dye solution as hydroxyl radical scavengers. The semilogarithmic graphs of the concentrations of RB versus time were linear, suggesting pseudo-first order reaction for decolorization and degradation processes. A simple kinetic model is proposed which confirms pseudo-first-order reaction. The electrical energy per order (EE/O) values for decolorization and degradation of RB solution were calculated. Results shows that applying an optimum hydrogen peroxide concentration can reduce the EE/O.     

Electrochemical denitrification of metal-finishing wastewater: Influence of operational parameters

Experimental results are presented for the electrolytic ChemDen (Chemical-Denitrification) process which was designed to investigate the effect of operational parameters on the nitrate (NO₃⁻) removal from metal-finishing wastewater. The parameters included electrode materials, electrode gap, reducing agent, hydraulic retention time (HRT) and recycle ratio in the single electrolytic ChemDen reactor for lab-scale tests. The removal efficiency of nitrate is based upon a non-biological process which consists of chemical and electrolytic treatment. Results showed that removal efficiency of nitrate was highest when the zinc (Zn) electrodes were used for both anode and cathode. In the case of insoluble electrode, combining Pt anode with Ti cathode provided great improvement of nitrate removal. For the Pt-Ti electrode combination, increasing electrode gap tended to increase removal efficiency of nitrate significantly. However, no further increase in the nitrate removal was observed when the electrode gap was longer than 10mm. Using sulfamic acid and Zn metal powder as reducing agents for the electrolytic ChemDen reaction, highest nitrate removal was achieved when the mole ratio of Zn: sulfamic acid: nitrate was 1.2: 1: 1. Remarkable improvement in the nitrate removal was also observed with increasing HRT from 10 to 30 min, while the effectiveness was limited when HRT was increased to 60 min. Recycling in electrolytic ChemDen reactor affected nitrate removal positively because it could improve both dispersion and reuse of Zn metal powder as reducing agent in the reactor. Recycling effects were thought to be associated with increasing surface reactivity of the Zn metal powder in the electrolytic ChemDen reactor.     

Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods: A general review

Effluents of a large variety of industries usually contain important quantities of synthetic organic dyes. The discharge of these colored compounds in the environment causes considerable non-aesthetic pollution and serious health-risk factors. Since conventional wastewater treatment plants cannot degrade the majority of these pollutants, powerful methods for the decontamination of dyes wastewaters have received increasing attention over the past decade. This paper presents a general review of efficient electrochemical technologies developed to decolorize and/or degrade dyeing effluents for environmental protection. Fundamentals and main applications of typical methods such as electrocoagulation, electrochemical reduction, electrochemical oxidation and indirect electro-oxidation with active chlorine species are reported. The influence of iron or aluminium anode on decolorization efficiency of synthetic dyes in electrocoagulation is explained. The advantages of electrocatalysis with metal oxides anodes and the great ability of boron-doped diamond electrodes to generate heterogeneous hydroxyl radical as mediated oxidant of these compounds in electrochemical oxidation are extensively discussed. The effect of electrode material, chloride concentration, pH and temperature on the destruction of dyestuffs mediated with electrogenerated active chlorine is analyzed. The degradation power of these pollutants with an emerging electrochemical advanced oxidation process such as electro-Fenton, based on the mediated oxidation by homogeneous hydroxyl radical formed from Fenton's reaction between cathodically produced hydrogen peroxide and catalytic Fe²⁺, is examined. Recent progress of emerging photoassisted electrochemical treatments with UV irradiation such as photoelectro-Fenton and photoelectrocatalysis is also described.     

液化天然气接收站再冷凝工艺优化研究

目前液化天然气(LNC)接收站终端普遍采用再冷凝工艺来处理蒸发气体(BOG).对BOG再冷凝工艺进行了热力学模拟,并通过单变量法对影响BOG再冷凝工艺的运行参数进行了分析.结果表明:LNG输出量随下游用气负荷波动的变化及LNG组成及储存压力的不同,都将引起BOG再冷凝工艺的运行参数(压缩机压比和功耗)的改变.建议在实际工艺运行中,确保管网输气系统安全平稳运行,适当调整压缩机压比、物料比等再冷凝工艺参数,从而实现BOG再冷凝工艺的优化运行.     

Adsorption and photocatalytic degradation of organic dyes onto crystalline and amorphous hydroxyapatite: Optimization,kinetic and isotherm studies

We evaluated the adsorptive/photodegradation properties of hydroxyapatite. Hydroxyapatite was synthesized by two different precipitation methods and examined for the removal of two kinds of textile dye. The physicochemical properties of the products were characterized using Fourier transform infrared, X-ray diffraction, inductively coupled plasma atomic emission spectroscopy and scanning electron microscopy. The effects of different parameters, including hydroxyapatite synthesis method and removal process type, pH, reaction time, temperature and amount of hydroxyapatite, were investigated and optimized by Taguchi design. The kinetics of adsorption and isotherm studies showed that the pseudo-second-order model and the Freundlich isotherm were the best choices to describe the adsorptive behavior of hydroxyapatite. Photocatalytic degradation of dye followed Langmuir-Hinshelwood mechanism, illustrated a pseudo-first-order kinetic model with the adsorption equilibrium constant and kinetic rate constant of surface reaction equal to 0.011 (l mg^-1) and 1.3 (mg l ^-1 min^-1), respectively.     

结构参数和操作参数对生物质气化制氢技术的影响

生物质气化制氢技术不仅是一种清洁能源技术,而且有助于缓解我国能源压力,优化能源结构。介绍并对比了生物质制氢的主要方法,包括生物法和热化学法制氢技术。热化学法制氢技术的工业化发展较受关注,主要包括气化法、热解法和超临界转化法,其中气化法因产氢量高、废弃物少和工艺要求较易实现等优点,成为目前热化学法制氢的主要方法。阐述了生物质气化过程的基本原理,分别从结构参数(物料特性、气化剂、气化炉种类、催化剂)和操作参数(反应温度、当量比、水蒸气配气比)系统地分析了影响生物质气化过程的主要影响因素及其变化规律,指出应从优化结构参数和操作参数上促进生物质气化制氢技术的发展。     

操作工况对酸性天然气水合物生成动力学的影响分析

水合物的快速生成受诸多因素的影响,操作工况是其主要的影响因素之一。以67.7%CH4+32.3%CO2（摩尔分数）混合气为例模拟酸性天然气,采用自行设计的水合物动力学实验装置,分别对初始压力为3.0 MPa、3.5 MPa、4.2 MPa、5.0 MPa和实验温度分别为1.42 ℃、3.27 ℃、5.48 ℃、7.45 ℃时的水合物生成动力学进行实验研究。定义诱导期、平衡总耗时、生长速率为水合物动力学评价指标,指标通过分析水合物生成过程中的压力及气相组成变化得到,进而综合分析了操作工况对酸性天然气水合物生成动力学的影响。实验结果表明：初始压力越高,实验温度越低,水合物平衡时气相CO2的浓度越低,水合物的生成量和生长速率越大;此外,初始压力对体系诱导期影响不够显著,而操作温度的降低可以明显缩短体系诱导期。     

Water-soluble BODIPY and aza-BODIPY dyes: synthetic progress and applications

In recent years, boron-dipyrromethene (BODIPY) and boron-azadipyrromethene (aza-BODIPY) dyes have attracted considerable multidisciplinary attention due to their diverse applications. By introducing various hydrophilic groups, such as quaternary ammonium, sulfonate or oligo-ethyleneglycol moieties into the BODIPY core, the solubilities of these dyes in aqueous solution can be greatly improved while maintaining their high fluorescence quantum yields. Accordingly, applying these fluorescent dyes in aqueous systems to areas such as chemosensors, biomacromolecule labeling, bio-imaging and photodynamic therapy has been achieved. In this article, the recent progress on the synthesis, optical properties and application of water-soluble BODIPY dyes and aza-BODIPY dyes is reviewed.     

Emerging bioremediation technologies for the treatment of textile wastewater containing synthetic dyes: a comprehensive review

The tremendous increase in human population and industrialization has exacerbated the existing problem of water pollution to a great extent. The textile industry is the major cause of this problem due to its significant use of organic synthetic dyes as coloring materials during the dyeing process. The presence of color in wastewater is a major environmental concern, as these dyes are resistant to degradation by physio-chemical treatments. Bioremediation is an attractive method that can completely degrade these dyes while also being cost-effective. This comprehensive review aims to provide a brief insight into bioremediation based on some of the latest emerging wastewater treatment technologies for the removal of synthetic dyes. Starting with the importance of decolorization of synthetic dyes and their environmental impacts, different physio-chemical treatment technologies are analyzed with a special emphasis on their limitations. The bioremediation of textile wastewater with detailed biodegradation mechanisms using different bacterial species (bacteria, fungal, algae, enzyme, and mixed culture) under aerobic and anaerobic conditions is thoroughly discussed. In this article, the major factors affecting the implementation of biological treatment are explained. In addition, the latest emerging treatment technologies, such as nano-bio materials, genetic engineering, phytoremediation, electro-bioremediation (microbial electrochemistry technology, MET), and integrated/hybrid technologies (such as biological processes with physio-chemical processes, electro-coagulation, adsorption, ultra-filtration, membrane, and advanced oxidation) are critically reviewed; their challenges and the future perspectives in textile wastewater treatment are also highlighted. © 2021 Society of Chemical Industry (SCI).     

Effect of polypropylene morphology on thermal cis-trans isomerization and photofading of some azo dyes: A kinetic study

Five polypropylene films were prepared having different crystallinity and morphology, the latter having been modified by stretching. They were colored with azo dyes XC₆H₄N?NC₆H₄N(C₂H₅)₂ (where X?H, OCH₃, CN, and NO₂). The kinetics of the thermal cis-trans isomerization of these dyes has been studied in the range 21–41°C, much above the glass transition temperature of the polymer. The isomerization process was found to be strictly first-order; the kinetic parameter values have been correlated with the free volume extent in the amorphous regions of the matrix. Lightfastness of the dyes in the polymer matrices has been also investigated: It appeared to be more important for the unoriented samples with respect to the stretched ones and substantially independent on the crystalinity degree.     

Thermogravimetric analysis of polystyrene: Influence of sample weight and heating rate on thermal and kinetic parameters

This article studies the influence of the heating rate and sample weight on the thermal decomposition of polystyrene (first-order kinetics). For this purpose, the kinetic parameters (i.e., frequency factor and activation energy), variables at the maximum decomposition rate (such as conversion, reaction rate, and temperature), as well as some characteristic temperatures have been determined for a series of experiments where the heating rate varies (0.5–11.5 K/min) and also, the sample weight (6.0–25.1 mg). Some mathematical equations have been developed that allow: (1) evaluation of the activation energy of thermal decomposition by different ways and comparing the results obtained; (2) relating different parameters between themselves, such as the heating rate with the temperature at the maximum decomposition rate or the frequency factor with the heating rate and sample weight. Finally, some theoretical explanations of the variation of thermal and kinetic parameters have been proposed. © 1996 John Wiley & Sons, Inc.     

光电功能性有机染料及其应用研究进展

该文论述了不同性能染料的合成方法,尤其是用溶胶-凝胶法合成高分子染料;综述了有机染料在光电功能材料方面的应用及其研究进展,并对光电功能性有机染料的今后的发展方向做了展望.     

集装箱喷漆废水处理工艺试验研究

在实验室对集装箱喷漆废水处理工艺及主要参数进行了研究。结果表明，采用SBR生化降解-物化混凝处理喷漆废水在技术上完全可行。采用SBR法处理喷漆废水时，喷漆废水与生活污水按6：4左右的比例混合．使进水COD控制在1400—1600mg／L。在此条件下，经过24h的生物好氧处理，能将出水的COD降至150mg／L以下。之后．再投加混凝剂[V（聚铝）：V（聚丙烯酰胺）=2：1]进行混凝处理，可进一步将出水COD降到80mg／L以下，达到国家二级排放标准。     

数据处理方法对无烟煤燃烧动力学参数求解结果的影响

针对利用热分析仪研究无烟煤燃烧动力学参数时数据处理方法和机理函数的选择影响其结果的问题进行了分析和研究.采用Achar微分法、Coats-Redfern积分法以及多重速率扫描Popescu法相结合的方法分析了三种无烟煤燃烧过程最可能的反应机理,考察了不同数学处理方法对求解动力学参数的影响,分析了数学处理过程的误差.研究结果表明:所测试的无烟煤燃烧反应的可能燃烧机理应为相边界反应的收缩体模型:不同数学处理方法所得动力学参数不同;数学处理过程不可避免的引入了较大的误差;所得动力学参数为表观参数.