Optimal decolorization and kinetic modeling of synthetic dyes by Pseudomonas strains

Pseudomonas spp were isolated from an anaerobic-aerobic dyeing house wastewater treatment facility as the most active azo-dye degraders. Decolorization of azo dyes and non-azo dyes including anthraquinone, metal complex and indigo was compared with individual strains and a bacterial consortium consisting of the individual strain and municipal sludge (50 50wt). The consortium showed a significant improvement on decolorization of two recalcitrant non-azo dyes, but little effect on the dyes that the individual strains could degrade to a great or moderate extent. Decolorization of Acid violet 7 (monoazo) by a Pseudomonas strain GM3 was studied in detail under various conditions. The optimum decolorization activity was observed in a narrow pH range (7-8), a narrow temperature range (35-40 degrees C), and at the presence of organic and ammonium nitrogen. Nitrate had a severe inhibitory effect on azo dye decolorization: 10 mg/L led to 50% drop in decolorization activity and 1000 mg/L to complete activity depression. A kinetic model is established giving the dependence of decolorization rate on cell mass concentration (first-order) and dye concentration (half order). The rate increased with temperature from 10 to 35 C, which can be predicted by Arrhenius equation with the activation energy of 16.87 kcal/mol and the frequency factor of 1.49 x 10(11) (mg L)1/2/g DCM min.     

External mass transport processes during the adsorption of dyes onto bagasse pith

The kinetics of the adsorption of four dyestuffs onto bagasse pith has been studied. Two basic dyes, Basic Blue 69 and Basic Red 22, and two acid dyes, Acid Blue 25 and Acid Red 114, were used in an agitated batch adsorber. The effect of agitation, initial dye concentration, pith mass, pith particle size and dye solution temperature were investigated. A model is proposed to determine the external mass transfer coefficients, k_f, for the systems and these are correlated with the system variable by the following equation: k_f = A(variable)^B.     

Effect of temperature on the residual compressive strength of laterized concrete

Tests are reported on 100 mm laterized concrete cubes, containing ordinary portland cement, crushed granite, sharp sand and fine laterite in varying proportions. The percentage of sand by weight of total fine aggregate was varied in steps of 25% up to a maximum of 100% corresponding to normal concrete. The mix proportion was . The test specimens were exposed to varying temperatures ranging from 30°C (i.e. room temperature) to 800°C and allowed to cool for 24 hours before crushing. The results showed that unlike normal concrete the residual compressive strength of laterized concrete increaed, by up to 50% of the nominal strength, with increasing temperature up to 200°C before falling to about 20% of the nominal strength at 800°C. The gain in strength depended on the sand content. The results further showed that within the limits of water/cement ratios normally used in concrete works (i.e. 0.55 to 0.65), the residual strength of laterized concrete was independent of the water/cement ratio. Also, the density of laterized concrete was not significantly affected by changes in temperature but that the tangent modulus of elasticity was reduced from 18 kN/mm² at 30°C to 0.12 kN/mm² at 600°C.     

Mineralisation of coloured aqueous solutions by ozonation in the presence of activated carbon

The degradation of organic matter in coloured solutions of different classes of dyes by ozonation in the presence of activated carbon is investigated. The kinetics of the decolourisation and mineralisation of three different dyes solutions (CI Acid Blue 113, CI Reactive Red 241 and CI Basic Red 14) were studied in a laboratory scale reactor by three different processes: adsorption on activated carbon, oxidation with ozone and ozonation in the presence of activated carbon. The mineralisation of the solutions was followed by measuring the total organic carbon (TOC). Under the experimental conditions used in this work, activated carbon was not capable of completely removing the colour of the solutions in reasonable time. On the other hand, ozonation quickly decolourised all the solutions, but satisfactory removal of TOC was never achieved by this process. The combination of activated carbon with ozone enhanced the decolourisation of the solutions and especially the mineralisation of the organic matter. Activated carbon acts both as an adsorbent and as a catalyst in the reaction of ozonation. The surface chemistry of the activated carbon is an important parameter; it was observed that basic samples improve TOC removal. The main conclusions of this work were validated by treating a real textile effluent collected after the conventional biological treatment.     

The potentials of lateritic soil—Clay and clay-sand mixes in the manufacturing of bricks for masonry units

Bricks were manufactured from lateritic soil-clay and clay-sand mixes with various mix proportions; 30, 40, 50, and 60% sand (by weight) were mixed with clay soil, 20 and 40% clay (by weight) were mixed with lateritic soil. The bricks were burnt at 1000°C for periods of 2, 4 and 6 h. Various properties of the bricks such as linear shrinkage, density, compressive strength and water absorption were measured. Test results showed that the addition of 40% clay in lateritic soil was the optimum for the production of bricks from lateritic soil. The addition of 30% sand in clay was optimum for the production of bricks from clay. The compressive strength of the investigated bricks was also compared with British starutory requirements for the minimum compressive strengths in bricks for various walls. The comparison showed that both lateritic soil-clay and clay-sand mixed bricks could be used in load bearing walls.     

基于有限元极限分析的双孔隧道稳定性分析

为进一步探讨在考虑土体内摩擦角情况下,双孔隧道在支护反力及地面超载共同作用下的相互作用规律及稳定性分析,首先,基于有限元极限分析法,采用MATLAB平台编制了相关计算程序;此外,为减少各参数之间的交叉影响,引入无量纲分析方法;然后,将本文模型的计算结果与已有成果进行对比,验证了本文分析方法的合理性;最后,在此基础上求得各影响因素下的隧道稳定性参数(N_s),并绘制了无量纲分析图表。结果表明:(1)N_s随φ的增大逐渐增大,且当φ较大时,在N_s未达到稳定值之前,对其产生显著影响;(2)N_s随S/B的增大而增大并趋于稳定;(3)φ的存在与否对N_s随着γB/c的变化产生相反的规律,且随φ的增大,γB/c的变化对临界间距比(S/B)的值影响减弱;(4)临界间距比随H/B的增大不断增大;(5)S/B和φ是影响隧道破坏模式的关键因素。     

Fast and highly efficient removal of dyes under alkaline conditions using magnetic chitosan-Fe(III) hydrogel

The dyeing effluent of high alkalinity, which could not be treated efficiently by traditional wastewater technologies, highlighted the need to explore a technically feasible, highly efficient and cost effective method. Thus, a fast and highly efficient method for the removal of dyes under alkaline conditions using magnetic chitosan-Fe(III) hydrogel was proposed. Firstly, chitosan-Fe(III) hydrogel was prepared by a chelation procedure with cheap and environmentally friendly chitosan and iron salts. We characterized the sorption and desorption of C. I. Acid Red 73, a common type of anionic dye, on magnetic chitosan-Fe(III) hydrogel, to understand its availability for alkaline dyeing wastewater. Sorption of dye to chitosan-Fe(III) hydrogel was fast (adsorption could reach equilibrium in less than 10 min) in a wide pH range, and agreed well to the Langmuir-Freundlich adsorption model with a high maximum adsorption capacity of 294.5 mg/g under pH = 12. Meanwhile, 1 mol/L NaOH was used to desorb the dye efficiently (desorption efficiency 94.4%) and 0.1 mol/L HCl was applied to regenerate the chitosan-Fe(III) hydrogel. The results showed that the chitosan-Fe(III) hydrogel could retain its high efficiency after the desorption and regeneration. The common coexisting ions almost had no negative effect on the dye adsorption of chitosan-Fe(III) and the removals of a variety of anionic dyes suggest that the magnetic chitosan-Fe(III) hydrogel could efficiently adsorb both the acid and reactive dyes under alkaline condition. Overall, the results reported herein indicated that magnetic chtisoan-Fe(III) with high adsorption efficiency and strong magnetic property is very attractive and implies a potential of practical application for alkaline dyeing effluent treatment.     

Decolorization of textile dyes by laccases from a newly isolated strain of Trametes modesta

Four ligninolytic fungi, Trametes modesta, Trametes hirsuta, Trametes versicolor and Sclerotium rolfsii, were compared for their ability to produce laccases. The fungal laccases were screened for their ability to decolorize eight synthetic dyes (anthraquinone, azo, indigo and triarylmethane). The decolorization rate depended both on the source of the enzyme preparation and on the structure of the dye. Based on laccase production and dye decolorizing ability, T. modesta was selected for further studies. All the tested dyes were decolorized by the T. modesta laccase most efficiently under acid conditions (pH 3-6) but the optimum pH for decolorization of the individual dye varied. The decolorization rate of this laccase increased with the rise in temperature to 50-60 degrees C. The decolorization efficiency of T. modesta laccase was improved remarkably in the presence of mediators like 1-hydroxybenzotriazole and 2-methoxyphenothiazine.     

Biodegradation potential of pure and mixed bacterial cultures for removal of 4-nitroaniline from textile dye wastewater

Environmentally toxic aromatic amines including nitroanilines are commonly generated in dye contaminated wastewater in which azo dyes undergo degradation under anaerobic conditions. The aim of this study was to develop a process for biological treatment of 4-nitroaniline. Three bacteria identified as Acinetobacter sp., Citrobacter freundii and Klebsiella oxytoca were isolated from enrichment cultures of activated sludge on 4-nitroaniline, after which the isolates and the mixed culture were studied to determine optimal conditions for biodegradation. HPLC analyses showed the mixed culture was capable of complete removal of 100 μmol/L of 4-nitroaniline within 72 h under aerobic conditions. There was an inverse linear relationship (R² = 0.96) between the rate of degradation (V) and 4-nitraoaniline concentrations [S] over 100-1000 μmol/L. The bacterial culture was also capable of decolorizing structurally different azo dyes (Acid Red-88, Reactive Black-5, Direct Red-81, and Disperse Orange-3) and also degraded nitrobenzene. Our findings show that enrichment cultures from activated sludge can be effective for the removal of dyes and their toxic intermediates, and that treatment may best be accomplished using an anaerobic-aerobic process.     

Equilibrium studies during the removal of dyestuffs from aqueous solutions using Bagasse pith

The adsorption of four dyestuffs, namely, Basic Blue 69 (BB69), Basic Red 22 (BR22), Acid Red 114 (AR114) and Acid Blue 25 (AB25), onto bagasse pith has been studied. Bagasse pith is a cheap, abundant waste product from the sugar industry in Egypt and was found to have the following monolayer equilibrium saturation capacities: 158, 77, 23 and 22 mg dye g⁻¹ pith.

The effects of pith particle size range and dye solution temperature were studied. The equilibrium data were analysed using Langmuir, Freundlich and Jossens isotherms.     

考虑应力路径的软黏土小应变特性试验研究

以苏南地区原状软黏土经K₀固结形成的试样为对象,利用配备了弯曲元系统和局部位移测量系统的GDS应力路径三轴测试系统,研究了小应变范围内应力路径转角θ对剪切模量衰减曲线以及阈值剪应变(γ_0.7)的影响。试验结果表明,土体的初始剪切模量G₀值与初始固结应力大小呈正相关关系,并可表示为与孔隙比e、平均有效应力p′相关的函数关系式。土体的剪切模量在10^-6~10^-3的应变范围内随着剪应变的增加而逐渐衰减,并表现出和试验应力路径与近期应力历史间夹角θ的相关性:应力路径对衰减曲线的影响随着应力路径转角θ的增大逐渐增大,当两者完全相反时,其影响最大。在K₀固结条件下,应力路径转角θ对γ_0.7的影响大于初始固结平均有效应力p′,同时γ_0.7值随着应力路径转角θ的增大而逐渐增大。     

管棚注浆支护隧道开挖引起地表变形特征分析

隧道开挖引起的地表变形是工程安全的重要指标,基于管棚注浆隧道开挖引起的地层受力分析,将地表变形影响因素分为注浆压力、附加荷载和地层损失,并引入Mindlin解和Peck公式,获得了隧道引起的地表变形计算公式。通过对地表变形特征进行分析,结果表明:岩土力学参数对地表变形最大值有显著影响,但对沉降影响宽度影响甚微;沉降槽宽度、地层损失率和沉降宽度与沉降槽宽度比值(I/i)均随内摩擦角和黏聚力增大而减小,弹性模量对沉降槽宽度几乎没有影响,随弹性模量增大,沉降槽宽度稳定在7.6~7.9,地层损失率迅速减小并在1.2‰左右趋于稳定,I/i则迅速增大并稳定在3.0左右。隧道参数对沉降最大值和沉降影响宽度均有显著影响,且影响幅度没有减缓的趋势;在单一地层中,随着埋深增加,沉降槽宽度、地层损失率均呈直线增大,I/i值先增大后减小;随洞径增大,沉降槽宽度呈线性增大,地层损失率呈线性减小,I/i值先增大后减小,最大值为3.1左右。     

PBL加劲型矩形钢管混凝土支管受拉节点有效分布宽度

为研究PBL加劲型矩形钢管混凝土支管受拉节点应力分布规律及其有效分布宽度,采用ABAQUS软件建立42个矩形空钢管、钢管混凝土及PBL加劲型矩形钢管混凝土节点有限元模型并进行位移加载;根据有限元计算结果拟合得到矩形空钢管、钢管混凝土及PBL加劲型矩形钢管混凝土节点的有效分布宽度表达式,将拟合公式计算值与CIDECT规范计算值和有限元计算值进行对比。结果表明:在节点受力全过程中,PBL加劲型矩形钢管混凝土节点相对于矩形空钢管节点和钢管混凝土节点的应力分布不均匀性减小;当加载位移达到3%b₀（b₀为主管宽度）时,PBL加劲型节点的有效分布宽度更大,具有更好的受力性能,支板应力分布效率ξ随主管宽厚比2γ与支主管厚度比τ的增大而减小,其中τ对ξ的影响更大;支板应力分布效率ξ随支主管宽度比β变化较小,且呈抛物线变化;拟合公式计算值与CIDECT规范计算值及有限元计算值吻合良好,验证了公式的正确性     

Photocatalytic degradation of Acid Red 88 using Au-TiO(2) nanoparticles in aqueous solutions

Metal loaded semiconductors in general possess greater photocatalytic activity than pure semiconductors. Hence, with an attempt to achieve higher photocatalytic activity, Au-TiO₂ photocatalysts were prepared by deposition-precipitation method and used for the photocatalytic degradation of an azo dye (Acid Red 88; AR88). The materials were characterized by different analytical techniques. A possible mechanism for the photocatalytic degradation of AR88 by Au-TiO₂ in the absence and presence of other oxidizing agents (peroxomonosulfate (PMS), peroxodisulfate (PDS) & hydrogen peroxide (H₂O₂)) has been proposed. The extent of mineralization of the target pollutant was also evaluated using Total Organic Carbon (TOC) analysis.     

Removal of azo and anthraquinone dyes from aqueous solutions by Eichhornia Crassipes

The rate of adsorption of two azo and four anthraquinone anionic dyes on Eichhornia Crassipes (E.C.) has been studied. Raw E.C. and three aminated derivatives of E.C. with different nitrogen percent were used as dye adsorbents. The parameters studied include the amount of substrate, shaking time, chemical structure, concentration of dyestuff and pH of dyeing bath. Simple kinetic adsorption models of dynamics and adsorption parameters for the Langmuir and Freundlich isotherms were determined. A higher nitrogen percent of aminated E.C. showed a higher adsorption capacity than other derivatives. The kinetic adsorption models indicate that the decolourization was complete in a relatively short time (10 min) and the reaction taking place is of the first order. The equilibrium data fit well with the Freundlich model of adsorption for the six dyes. Only dye IV (C.I.A Acid Blue 25) conform both Freundlich and Langmuir adsorption isotherms.     

原状与重塑黄土抗拉强度差异性研究

轴向压裂法是一种间接测定土体抗拉强度的试验方法,本文通过该法分析了原状黄土抗拉变形破坏的一般规律以及试样破坏类型。探讨了原状与重塑黄土的劈裂角以及在强度参数比方面(无侧限抗压强度与抗拉强度比以及粘聚力与抗拉强度比)的差异性。结果表明:原状黄土根据抗拉应力-贯入深度曲线走势将变形破坏模式分为3类:弹性变形破坏无残余应力、弹性破坏有残余应力、塑性破坏;原状与重塑黄土在强度参数比方面也存在较大差异。另外,原状黄土劈裂角(α)略小于重塑黄土且均与内摩擦角(φ)呈互补关系;抗拉强度计算公式中的系数K=tan(2α+φ)对于原状黄土建议取值为1.5,对重塑黄土建议取值为2.0。     

洱海泥炭质土动剪切模量和阻尼比试验研究

为探究洱海地域泥炭质土动力学特性,利用GDS动三轴仪对重塑土样进行循环加载试验,得到了一系列围压、固结比、频率控制条件下的泥炭质土动应力-应变关系曲线,分析了不同围压、固结比、频率对土体动剪切模量G_d、动剪切模量比G_d/G_dmax和阻尼比λ的影响规律。结果表明:动剪切模量G_d随剪应变γ_d增大而减小,γ_d较小时,衰减速率较小,随着γ_d继续增大,衰减速率先增大后减小;在同一剪应变下,G_d随围压、固结比增大而增大,G_d对频率变化表现不敏感;采用Hardin-Drnevich双曲线模型(H-D模型)对重塑泥炭质土动应力-应变曲线拟合效果较好,动剪切模量比G_d/G_dmax随剪应变γ_d增大而减小,围压、固结比和频率对G_d/G_dmax的衰减规律无明显的倾向性;阻尼比λ随剪应变γ_d增大而增大,围压对λ变化规律影响较复杂,γ_d较小时,λ随围压增大而减小,γ_d较大时,λ随围压增大而增大;固结比越大,λ越大,频率越大,λ越小,λ对频率变化表现更敏感,体现了循环加载下泥炭质土的速率效应。     

The physical and chemical action of fire suppressants

This work measures the suppression action of inert gas phase agents in extinguishing an air/liquid organic fuel pool fire. It then gives a predictive model for determining the physical contribution involved in non-inert agent fire suppression. Chemical suppression effectiveness can then be calculated. Further, studying the CF₃Y and SF₅Y (Y = F, Cl, Br, I) series allows quantitation of chemical suppression action of the individual radical moieties. CF₃ is shown to be a strong chemical suppressant while SF₅ is a flame promoter. CF₃Br (Halon 1301) suppression action is 20% physical, 25% chemical due to CF₃, and 55% chemical due to Br. Such quantitation provides guidance in selecting alternative fire suppressants to replace ozone layer depleting halons.     

循环剪切作用下泥质软岩本构模型研究

库区微震频发现象使泥质软岩受循环剪切动力作用。基于分数阶西原模型,将Able黏壶进行改进,获得相应条件下的本构模型,并通过泥质软岩试样循环剪切试验对该本构模型进行了验证。研究表明:①原有分数阶西原本构模型可归纳为本模型正弦函数(循环作用)为零时的特殊解;②模型表现出较好的适用性(R²∈(0.96,0.98)),且方程曲线具备试验曲线的“单双拐点”特征;③模型主要影响因素为分数阶阶数n,其中稳定型方程n∈(0,0.6)、破坏型方程n∈(0.6,1.0);④随n的增加,抗剪模量G与黏滞系数η大致呈现降低趋势,可较好反映宏观现象;⑤从参数扰动的角度解释了以往文献出现的η随n增加可能表现出的无规律波动现象。研究成果可为微震条件下含泥质软岩边坡长期稳定性控制提供理论参考。     

Relationship between the concentration of denitrifiers and Pseudomonas spp. in soils: Implications for BTX bioremediation

Aquifer microcosms were used to investigate the effect of stimulating denitrification on microbial population shifts and BTX degradation potential. Selective pressure for facultative denitrifiers was applied to a treatment set by feeding acetate and nitrate, and cycling electron acceptor conditions twice between aerobic and denitrifying stages. A second (control) set degraded the same amount of acetate under aerobic conditions. The resulting concentrations of total heterotrophs were not significantly different between the two sets. Nevertheless, the concentrations of denitrifiers, Pseudomonas spp., and BTX degraders were significantly higher in the cycled microcosms than in the aerobic controls. The predominant isolates from the cycled microcosms were fluorescent Pseudomonas species that are known to degrade BTX. Following the complete removal of acetate, cycled microcosms also showed higher aerobic BTX degradation activity. These results suggest that nitrate addition to oxygen-limited aquifers might enhance BTX bioremediation not only by supplementing the electron acceptor pool as is widely accepted, but also by fostering favorable changes in the composition of the microbial consortium. Specifically, denitrifying conditions could have the ancillary benefit of fortuitously selecting for Pseudomonas spp. that can degrade BTX. This syllogism is supported by a survey of international soils (from France, Denmark, Brazil and Iowa, USA), which showed a correlation between the concentration of denitrifers and Pseudomonas spp.