Electro-oxidation of the dye azure B: kinetics,mechanism, and by-products

In this work, the electrochemical degradation of the dye azure B in aqueous solutions was studied by electrochemical advanced oxidation processes (EAOPs), electro-Fenton, and anodic oxidation processes, using Pt/carbon-felt and boron-doped diamond (BDD)/carbon-felt cells with H₂O₂ electrogeneration. The higher oxidation power of the electro-Fenton (EF) process using BDD anode was demonstrated. The oxidative degradation of azure B by the electrochemically generated hydroxyl radicals (^?OH) follows a pseudo-first-order kinetics. The apparent rate constants of the oxidation of azure B by ^?OH were measured according to pseudo-first-order kinetic model. The absolute rate constant of azure B hydroxylation reaction was determined by competition kinetics method and found to be 1.19?×?10⁹ M^?1 s^?1. It was found that the electrochemical degradation of the dye leads to the formation of aromatic by-products which are then oxidized to aliphatic carboxylic acids before their almost mineralization to CO₂ and inorganic ions (sulfate, nitrate, and ammonium). The evolution of the TOC removal and time course of short-chain carboxylic acids during treatment were also investigated.     

The effects of henna (hair dye) on the embryonic development of zebrafish (Danio rerio)

The powder of henna is extensively used as decorative skin paint for nail coloring and as a popular hair dye in Asian countries. Its human health risk is extensive, and it is frequently released as waste into the aquatic environment raising the concerns. Zebrafish (Danio rerio) embryos were employed to study the developmental effects of henna. Normal fertilized zebrafish embryos under standard water were selected for the control and test chambers. Three predetermined sublethal concentrations (100, 200, and 275 μM) of henna in 24-well cell culture plates were tested on 1-h postfertilized embryo (pfe) for 96 h. Observation for rates of survival and mortality was recorded; digital camera was used to image morphological anomalies of embryos with a stereomicroscope; and functional abnormalities at 24, 48, 72, and 96 h were performed. The hatching rates of embryos were reduced significantly when treated with 200 and 275 μM or higher concentrations of henna. Slow blood circulation in the whole body was observed with a median effect on hatching exposed to 200 and 275 μM of henna at 48-h pfe. At 72- and 96-h pfe, blood circulation was ceased in the whole body but still had a heartbeat. At 96-h pfe, pericardial sac edema, yolk sac edema, head deformation, spine crooked malformation, and tail malformation (bent tails or hook-like tails) were observed in the surviving larvae at 100 μM. In summary, exposure to henna at 100, 200, and 275 μM causes some altered morphological and physiological abnormalities including increased mortality, hatching delay, slow blood circulation, pericardial sac edema, yolk sac edema, abnormal body axes, twisted notochord, tail deformation, weak heartbeat, and growth retardation and was also detected in some treated embryos and groups having adverse effects on embryonic development of zebrafish provoking potential human developmental risk studies.     

Interaction of tebuconazole with bovine serum albumin: determination of the binding mechanism and binding site by spectroscopic methods

Abstract

This study investigates the interaction between tebuconazole and bovine serum albumin (BSA) in a physiological buffer (pH = 7.4) using the fluorescence quenching method to obtain the apparent binding constants (K) and number of binding sites (n) in the interaction between tebuconazole and BSA. The results revealed that tebuconazole can quench the intrinsic fluorescence of BSA through a static quenching procedure. It also shows that the thermodynamic parameters of enthalpy change (ΔH) and entropy change (ΔS) are negative, indicating that the interaction of tebuconazole with BSA is mainly driven by van der Waals forces and hydrogen bonds. The process of binding was a spontaneous process in which Gibbs free energy change was negative. The distance of r between the donor (BSA) and acceptor (tebuconazole) was calculated to be 0.68?nm based on Forster’s non-radiative energy transfer theory. Analysis of synchronous fluorescence, three-dimensional fluorescence and circular dichroism (CD) spectra demonstrates that tebuconazole can induce conformational changes of BSA.     

活性炭多维电极法处理活性染料模拟废水的机理研究

以活性嫩黄K-4G染料模拟废水为处理对象,探讨了多维电极系统处理活性染料废水时色度、COD降解的效果和机理。结果表明,活性炭多维电极法对染料废水的处理效果优于单纯电解法和单纯活性炭吸附法;氧化和还原作用对染料的色度和COD去除效果相差不大;增大处理系统中溶液的循环流量可显著改善活性炭多维电极系统对COD和色度的去除效果。     

Studies on the mechanism of PCDD/PCDF formation during the bleaching of pulp

Laboratory bleaching experiments were performed to investigate PCDD/PCDF formation mechanisms. The results indicated that there were two (or more) mechanisms; direct chlorination of DBD/DBF and formation from precursors which are not extractable. In general, PCDDs/PCDFs are formed in the C stage but some minor isomers were found to be formed in the E stage.     

Ozonation of azo dye Acid Red 14 in a microporous tube-in-tube microchannel reactor: decolorization and mechanism

Despite the great success of time-weighted average passive sampling of hydrophobic contaminants, such as PCBs and PAHs, the sampling of polar organic compounds still presents a challenge because the equilibrium between water and most sampling phases is attained in a relatively short time. In this study, we proposed a new time-integrative sampler using in situ solvent extraction (TISIS) for polar organic chemicals. The sampler was composed of a 15 cm poly(dimethylsiloxane) (PDMS) tubing, with an internal diameter of 0.5 mm and wall thickness of 0.5 mm, through which an extraction solvent (acetonitrile) was passed. Four polar organic contaminants, caffeine, atrazine, diuron and 17α-ethynylestradiol, were chosen for the evaluation of the performance of the sampler. Without the use of in situ solvent extraction, the PDMS tubing when exposed to a constant aqueous concentration of the four model compounds was able to linearly accumulate those compounds for less than 12 h and equilibrium between the PDMS tubing and water was attained in 2 d under our laboratory conditions. However, TISIS when exposed to a constant aqueous concentration was able to linearly accumulate all the model compounds without any exposure time limitation. The measured sampling rates at three different extraction flow rates (0.2, 0.5, 1.5 mL min⁻¹) were similar, regardless of the chemicals, indicating that the overall mass transfer from aqueous solution to the extraction solvent was most likely dominated by partitioning to the PDMS tubing and the internal diffusion within PDMS. In addition, a pulsed exposure experiment confirmed that TISIS operated in a time-integrative mode when the environmental concentration was highly fluctuated.     

Investigations on the binding mechanism of the herbicide simazine to dissolved organic matter in leachates of compost

14C-labelled simazine was composted together with biowaste on a pilot (m3) scale. The herbicide was quickly bound to the compost matrix. By aqueous extraction of 29 and 200 days old compost (equivalent to thermophilic and mesophilic phase of composting) only 4.2% and 3.1% respectively of the radioactivity in the compost samples could be extracted with water. Analysis of the extracts using high-performance size exclusion chromatography (HPSEC) revealed that the dissolved organic matter (DOM) had molecular weights ranging between 2 and 28 kDa. The amount of DOM-associated radioactivity increased from 53% (day 29) to 65% (day 200) of total extractable radioactivity. The type of binding of the 14C-labelled residues and the DOM was elucidated by silylation of humic matter and subsequent HPSEC. The data demonstrated that besides polar metabolites also intact simazine was bound to the DOM. A distinct shift from rather weak interactions to strong covalent linkages of simazine and its metabolites with increasing age of the compost was observed. The results showed that only low amounts of free simazine and its degradates can be extracted with water. We concluded that the shift towards stable covalent linkages is equivalent to a detoxification of the contaminant in aged compost. Consequently, the use of the analysed compost in its mature stage should not pose an environmental risk to the groundwater or the subsoil.     

A comparative study on the biosorption characteristics of some yeasts for Remazol Blue reactive dye

Biosorption capacities and rates of different kinds of dried yeasts (Saccharomyces cerevisiae, Schizosaccharomyces pombe, Kluyveromyces marxianus, Candida sp., C. tropicalis, C. lipolytica, C. utilis, C. quilliermendii and C. membranaefaciens) for Remazol Blue reactive dye from aqueous solutions were compared under laboratory conditions as a function of initial pH and initial dye concentration. Optimum initial biosorption pH was determined as 2 for all the yeasts. All the yeast species showed comparable and very high dye sorption at 100 mg/l initial dye concentration. The equilibrium sorption capacity of the biomass increased with increasing initial dye concentration up to 400 mg/l for Candida sp. C. lipolytica and C. tropicalis; up to 300 mg/l for C. quilliermendii and C. utilis and up to 200 mg/l for S. cerevisiae, S. pombe, K. marxianus and C. membranaefaciens while the adsorption yield of dye showed the opposite trend for all the yeasts. Among the nine yeast species, C. lipolytica exhibited the highest dye uptake capacity (Q(0) = 250 mg/g). Both the Freundlich and Langmuir adsorption models were found suitable for describing the biosorption of the dye by all the Candida yeasts (except C. membranaefaciens). The results indicated that the dye uptake process followed the pseudo-second-order kinetics for each dye-yeast system.     

苯酚分子印迹聚合物的合成、表征及吸附性能研究

以苯酚为模板,2-Vpy为功能单体,EGDMA为交联剂,采用本体聚合方式在氯仿溶剂中合成了一系列分子印迹聚合物,并通过静态吸附实验对聚合物的选择吸附性进行评价.结果显示,以氯仿作为致孔剂,模板分子与功能单体的摩尔比为1∶2时,聚合物对模板分子的印迹因子为3.96,最大表现结合量(Qmax)为120.7 mmol/g,具...     

染料类型对膜生物反应器性能的影响

为了考察染料类型对膜生物反应器(MBR)处理性能的影响,在相同的染料浓度条件下,探究了阳离子染料MB和阴离子染料CR对MBR去除效果、活性污泥特性及膜污染的影响。结果表明,MBR对亚甲基蓝印染废水中的COD、${{\rm{NH}}_4^ + } $-N和亚甲基蓝的去除率分别为83.07%、25.11%和52.26%,均低于处理刚果红印染废水中的相应污染物去除率(88.93%、87.44%和92.39%)。前者系统中污泥代谢产物为71.43 mg·g⁻¹,高于后者的35.22 mg·g⁻¹,且D₅₀为110.9 μm,导致系统分别在第10和17天的TMP达到清洗压力。扫描电子显微镜、阻力分析和红外光谱表征结果表明,处理亚甲基蓝印染废水的MBR滤饼层较厚(137 μm),膜孔阻力较大(9.01%),污染物主要成分为多糖和蛋白质。     

Studies on the indicator for heavy metal contamination in environments (1) Heavy metal contents of hair,nail and moustache

Heavy metal (Hg, Pb, Cd, Cu, Ni, Fe, Zn, and Mn) contents of the samples from 10 males were followed throughout a year. The values were characteristic of the individuals, and some correlationships between the contents of different metals were shown.     

染料结晶紫降解菌分离及其特性研究

从印染废水中筛选分离得到结晶紫（CV）降解菌株H，并对其脱色条件和机理进行了研究。结果表明，在外加生长基质条件下，菌株H不仅对CV降解脱色而且能降解中间产物。在pH7．0、35℃、摇床转速180r／min条件下，菌株H有最佳的脱色效果。对于20mg／L CV溶液，生长细胞降解0．5h，脱色率可达95％。休眠细胞对CV的降解规律也进行了对比探讨。菌株H对CV脱色过程遵循一级动力学方程，脱色速率常数k随CV浓度升高而降低，生长细胞的k值约为休眠细胞的6～7倍。     

染料结晶紫降解菌分离及其特性研究

从印染废水中筛选分离得到结晶紫(CV)降解菌株H,并对其脱色条件和机理进行了研究.结果表明,在外加生长基质条件下,菌株H不仅对CV降解脱色而且能降解中间产物.在pH 7.0、35℃、摇床转速180 r/min条件下,菌株H有最佳的脱色效果.对于20 mg/L CV溶液,生长细胞降解0.5 h,脱色率可达95%.休眠细胞对CV的降解规律也进行了对比探讨.菌株H对CV脱色过程遵循一级动力学方程,脱色速率常数k随CV浓度升高而降低,生长细胞的k值约为休眠细胞的6～7倍.     

蒸发壁式超临界水氧化反应器处理分散红和活性红染料废水的比较

采用蒸发壁式超临界水氧化反应器对染料分散红C.I.60和活性艳红M-2B配制的模拟废水进行降解实验.实验结果表明,2种染料的COD和TN去除率随着反应温度、氧化剂过量比(r)的升高而上升.COD去除率活性红要高于分散红,而TN去除率则相反.根据GC-MS分析和陶瓷膜SEM图像,分析测得2种染料主要反应中间产物均含有苯酚和苯甲酸,2种染料的反应对陶瓷膜均有轻微的腐蚀.     

催化臭氧氧化染料溶液的研究

采用催化臭氧化技术降解染料废水,以甲基紫溶液为目标污染物,研究了过渡型金属离子的类型,Fe2+的浓度,溶液初始pH值,染料浓度和正丁醇等因素对其降解率的影响。实验结果表明:臭氧氧化甲基紫溶液的过程中,加入一定浓度的过渡型金属离子对甲基紫的去除具有促进作用;当臭氧浓度为16 mg/L,一定浓度范围内,Fe2+催化臭氧化的效果随着浓度的增加而增加,但Fe2+浓度为13 mg/L时,甲基紫的降解率下降;在酸性范围时,pH值增大其降解率会减小;染料浓度增加,甲基紫的降解率减小,但是其绝对降解值会增加;正丁醇的加入抑制氧化反应的进行,甲基紫的降解率下降,说明催化臭氧化过程中有羟基自由基产生。染料降解过程符合一级反应动力学规律。     

Transthyretin (prealbumin) binding of PCBS, a model for the mechanism of interference with vitamin A and thyroid hormone metabolism

In this study a direct interaction of a metabolite of 3,4,3′,4′-tetrachlorobiphenyl with transthyretin (prealbumin) was observed, leading to reduced plasma levels of retinol, RBP and thyroxin in rats and mice.     

Two stage biological treatment of a diazo reactive textile dye and the fate of the dye metabolites

A two stage anaerobic/aerobic bacterial process was used to decolorize and partially mineralize a reactive vinyl sulfone diazo dye C.I. Reactive Black 5 (RB5) in a synthetic wastewater. Since the anchor group of reactive dyes reacts during the dyeing process, the effect the degree of hydrolysis of the vinyl sulfone dye had on decolorization, mineralization and toxicity in each stage was investigated. An overall color removal of approximately 65% was found for both the fully and partially hydrolyzed dye. Partial mineralization of the fully hydrolyzed RB5 was achieved in the two stage rotating disc reactors. While the anchor group metabolite p-aminobenzene-2-hydroxyethylsulfonic acid (p-ABHES) was mineralized, an oxidized form of the center metabolite (1,2-ketimino-7-amino-8-hydroxynaphthalene-3,6-disulfonic acid) remained in the aerobic stage effluent, causing the effluent to be colored although no RB5 was present. Partially hydrolyzed dye in the influent with vinyl forms of the anchor group caused cessation of biogas production and a reduction in decolorization efficiency in the anaerobic stage. No evidence for mineralization of the partially hydrolyzed dye or its metabolites was found. A method for evaluating dye mineralization using lumped parameters is presented.     

A passively immobilized novel biomagsorbent for the effective biosorptive treatment of dye contamination

A new magnetic bio-based composite was designed by the magnetic modification of passively immobilized fungal cells. It was utilized for biosorptive decolorization of reactive dye-contaminated aquatic media. As a greener option, waste tea leaf tissues were used for the first time as an immobilization matrix for microbial cells. Immobilized magnetic cells (biomagsorbent) could be effectively used in both batch and dynamic flow mode treatment processes and real environmental application. Rapid equilibrium and high decolorization yields were observed for the target dye (reactive violet 1). The temperature did not significantly affect the process. Langmuir and the pseudo-second-order models could be better used to fit the process equilibrium and kinetics, respectively. Maximum monolayer sorption capacity was 152.88 mg g^?1. High biosorption and desorption yields for 50 consecutive dynamic flow decolorization cycles were recorded as striking results. The breakthrough time was 3420 min. Simulated and industrial water treatment performance of biomagsorbent was found to be more than 90%. The mechanism was evaluated by IR and zeta potential analysis. The magnetic character of the sorbent provided good mechanical durability, easy separation, and excellent regeneration ability. Consequently, this work provides new insight into scalar enhancement of water treatment.