乙烯菌核利在水溶液中的光解动力学

以高压汞灯和太阳光为光源,研究乙烯菌核利在重蒸水、自来水、湖水及pH缓冲液中的光解动力学。高压汞灯下,乙烯菌核利在重蒸水中的光解半衰期约为28 m in,而在太阳光下为3.86 h。自来水和湖水中溶解性物质对乙烯菌核利在高压汞灯下的光解动力学仅有微弱的淬灭效应,但在太阳光下表现出显著的敏化效应,照光3 h的敏化效率分别为138%和126%。2种光源下,pH 5.0和pH 7.0缓冲液对乙烯菌核利的光解均表现为光淬灭效应,高压汞灯照光60 m in的淬灭效率分别为69%和57%,太阳光照光7 h的淬灭效率分别为77%和33%;pH 9.0缓冲液则表现出显著的敏化效应,高压汞灯照光20 m in的敏化效率为58%,而太阳光照光1 h的敏化效率则达到了415%。     

乙烯菌核利在水溶液中的光解动力学

以高压汞灯和太阳光为光源，研究乙烯菌核利在重蒸水、自来水、湖水及pH缓冲液中的光解动力学。高压汞灯下，乙烯菌核利在重蒸水中的光解半衰期约为28min，而在太阳光下为3．86h。自来水和湖水中溶解性物质对乙烯菌核利在高压汞灯下的光解动力学仅有微弱的淬灭效应，但在太阳光下表现出显著的敏化效应，照光3h的敏化效率分别为138％和126％。2种光源下，pH5．0和pH7．0缓冲液对乙烯菌核利的光解均表现为光淬灭效应，高压汞灯照光60min的淬灭效率分别为69％和57％，太阳光照光7h的淬灭效率分别为77％和33％；pH9．0缓冲液则表现出显著的敏化效应，高压汞灯照光20min的敏化效率为58％，而太阳光照光1h的敏化效率则达到了415％。     

Removal of Mo(VI) from aqueous solutions using sulfuric acid-modified cinder: kinetic and thermodynamic studies

Removal of Mo(VI) from aqueous solutions was investigated using cinder modified by sulfuric acid. Various parameters such as pH, agitation time, Mo(VI) concentration, and temperature have been studied. The maximum adsorption of Mo(VI) occurred at pH between 4.0 and 6.0. Kinetic studies showed that the adsorption generally obeyed a pseudo second-order model. The activation energy was 31.4?kJ?mol^?1, indicating that the adsorption process was governed mainly by interactions of physical nature. Furthermore, application of Langmuir and Freundlich isotherm models to the adsorption equilibrium data showed that the adsorption behavior obeyed the Langmuir model. The adsorption capacity was found to be 10.8?g Mo(VI)?kg^?1 adsorbent. Finally, thermodynamic parameters such as ΔH ⁰, ΔS ⁰, and ΔG ⁰ were also evaluated, which showed that the adsorption of Mo(VI) on the treated cinder was endothermic, entropy increasing, and spontaneous. In conclusion, the sulfuric acid-modified cinder was shown to be an inexpensive, effective, and simple adsorbent for the removal of Mo(VI) from water.     

Simultaneous leaching and carbon sequestration in constrained aqueous solutions

The behavior of metal ions’ leaching and precipitated mineral phases of metal-rich fly ash (FA) was examined in order to evaluate microbial impacts on carbon sequestration and metal immobilization. The leaching solutions consisted of aerobic deionized water (DW) and artificial eutrophic water (AEW) that was anaerobic, organic- and mineral-rich, and higher salinity as is typical of bottom water in eutrophic algae ponds. The Fe- and Ca-rich FAs were predominantly composed of quartz, mullite, portlandite, calcite, hannebachite, maghemite, and hematite. After 86 days, only Fe and Ca contents exhibited a decrease in leaching solutions while other major and trace elements showed increasing or steady trends in preference to the type of FA and leaching solution. Ca-rich FA showed strong carbon sequestration efficiency ranging up to 32.3 g CO₂/kg FA after 86 days, corresponding to almost 65% of biotic carbon sequestration potential under some conditions. Variations in the properties of FAs such as chemical compositions, mineral constituents as well as the type of leaching solution impacted CO₂ capture. Even though the relative amount of calcite increased sixfold in the AEW and the relative amount of mineral phase reached 37.3 wt% using Ca-rich FA for 86 days, chemical sequestration did not accomplish simultaneous precipitation and sequestration of several heavy metals.     

Selective photoreduction of acetonitrile to acetaldehyde in dilute aqueous solutions

Acetonitrile is a commonly used solvent in both industry and research. The treatment of acetonitrile wastes in dilute aqueous solutions with visible light offers advantages to chemical treatment and ultraviolet (UV) irradiation. This study presents the degradation of acetonitrile via a photoinduced electron transfer reaction in the presence of a photosensitizer (dye) and a sacrificial reductant under visible light. Acetonitrile photodegradation (photoreduction) was investigated utilizing a variety of sacrificial reductants and photosensitizers. Optimal results were observed in the presence of methylene green and tri-isopropanolamine with a decrease of acetonitrile in solution to 86% in 24 hours. The only photoreaction product observed was acetaldehyde and a plausible mechanism for the photochemical degradation of acetonitrile is proposed.     

The sorption of selenite from aqueous solutions by pyrite

Selenium (Se) is an essential trace nutrient for mammals; however, the range between deficit and toxic levels is narrow. In this study, the potential sorption of selenite onto pyrite particles from an aqueous solution was investigated. An intraparticle diffusion model was used to describe kinetic data of sorption, yielding diffusivity values of 5 × 10^?7 cm²/s. The Langmuir isotherm equation could be used to describe the experimental data. The fitting results indicated that b and {Se(IV)}_max have values of 0.37 L/mg and 3.49 mg/g, respectively. The sorption of selenite onto the surface of pyrite particles was dependent on a pH range of 2–12, and the quantity of sorption onto pyrite was negatively correlated with pH; that is, the amount of sorption onto pyrite increased with a decrease in pH. In addition, organic matter did not exert a significant effect on removal of selenite. With a reaction time greater than 1 week, sorption of selenite onto pyrite particles was found to partially reduce the amount of elemental Se.     

Dibutyl phthalate adsorption characteristics using three common substrates in aqueous solutions

• DBP adsorption was tested using three kinds of substrates in constructed wetlands. • The DBP adsorption capacity followed the order: steel slag>gravel>shell sand. • High temperatures increased the DBP adsorption capacity in the substrates. • DOM consistently inhibited the DBP adsorption onto steel slag and gravel. In recent years, the presence and adverse impacts of phthalic acid esters in aquatic environments have gained increasing attention. This work investigated the adsorption behavior of a typical phthalic acid ester, dibutyl phthalate (DBP), onto steel slag, gravel, and shell sand (substrates commonly used in constructed wetlands). The influence of dissolved organic matter (DOM) on DBP adsorption was investigated using humic acid as a proxy for DOM. The results demonstrated that the adsorption of DBP to three substrates reached equilibrium within 96 h, and the adsorption kinetics were well fitted by a pseudo-second-order model. The DBP adsorption isotherms were best fitted by the Langmuir adsorption model. The DBP adsorption capacity decreased in the order of steel slag>gravel>shell sand, with values of 656 mg/kg, 598 mg/kg, and 6.62 mg/kg at 25°C, respectively. DBP adsorbed to the surface of all substrates in a monolayer via an endothermic process. The DBP adsorption capacities of steel slag and gravel decreased as the DOM content increased. The DBP adsorption mechanisms to steel slag and gravel mainly involved the surface coordination of DBP with –OH or –COOH groups and electrostatic interactions. The results of this work suggest that steel slag and gravel may be ideal substrates for use in constructed wetlands to treat wastewater polluted with DBP.     

活性炭纤维对水中罗丹明B的吸附性能

研究了活性炭纤维对水中罗丹明B的吸附.结果表明,pH=2时,罗丹明B的吸附量最大,并随着pH的增高吸附量随之降低;离子强度对吸附的影响不大;Langmuir等温线更适合于描述罗丹明B的吸附行为;活性炭纤维对罗丹明B的吸附量随着温度的升高逐渐增加;热力学数据表明,较高温度下,活性炭纤维对罗丹明B的吸附是自发行为,且为吸热反应;吸附动力学符合假二级动力学模型;吸附过程可以很好地用内扩散模型来说明.     

固定化多酚氧化酶对水中苯酚和氯酚的去除

以壳聚糖/蒙脱土插层复合物为载体,吸附法制备固定化多酚氧化酶,并以此催化氧化去除水中的苯酚、4-氯苯酚和2,4-二氯苯酚.考察了固定化多酚氧化酶的制备条件,对酚类化合物的催化氧化条件、动力学特性以及固定化酶的重复使用性能.结果表明,固定化多酚氧化酶的最佳制备条件为p H 5.0,酶与载体质量比20 mg·g-1,固定化6 h,所得固定化酶的载酶量为12.12 mg·g-1,每克单位载体酶活为12.76×103U·g-1.固定化多酚氧化酶对酚类化合物的最佳去除条件为:苯酚溶液p H 7.0,温度30℃;4-氯苯酚溶液p H 5.0,温度20℃;2,4-二氯苯酚溶液p H 5.0,温度30℃.在最佳反应条件下,酶与底物质量比为20 mg·mg-1时,固定化多酚氧化酶对苯酚、4-氯苯酚和2,4-二氯苯酚溶液去除率分别为63.6%、85.8%和87.8%.苯酚、4-氯苯酚和2,4-二氯苯酚的米氏常数Km值依次减小,最大反应速率Vmax依次增大,表明固定化酶对2,4-二氯苯酚的亲和力最强,催化速度最快.固定化酶循环使用6次(24 h)后对苯酚、4-氯苯酚和2,4-二氯苯酚的去除率分别为15.7%、24.2%和27.8%.     

Analytical solutions for flow induced by a vertically distributed turbulent plume

Environmental Fluid Mechanics - Analytical solutions are developed for the flow induced by a vertically distributed turbulent plume in an otherwise quiescent uniform environment. The plume...     

水溶液重金属离子在蛭石上的动态吸附行为与化学势变

测试了蛭石-水溶液体系中Pb2+、Cd2+、Zn2+离子的等温动态吸附曲线.实验结果表明蛭石具有较强的去除水溶液中Pb2+、Cd2+、Zn2+离子的能力.基于等温条件下物理化学反应组分的标准化学势为常数的原理,建立了反应体系的动态化学势变方程,为分析离子吸附机理和发展离子吸附技术提供了理论依据与实用方法.测试离子化学势的动态变化证明离子吸附反应遵循电化学势作用定律.     

Biosynthesis of iron nanoparticles and their application in removing phosphorus from aqueous solutions

This paper reports the biosynthesis of nanoscale zero-valent iron (nZVI) using the extracts of Shirazi thyme leaf (Th-nZVI) and pistachio green hulls (P-nZVI). Scanning electron microscopy verified the successful synthesis of the poorly crystalline nZVI with a spherical shape and diameter in the range of 40–70 nm. According to X-ray diffraction and Fourier transform infrared spectroscope analyses, the synthesised nZVI were composed of iron oxides nanoparticles and ployphenol obtained from Shirazi thyme leaf and pistachio green hulls extracts acting as both reducing and capping agents. The phosphorus removal efficiency of Th-nZVI and P-nZVI increased with time and reached equilibrium at about 4 and 2h, respectively. Sorption of phosphorus on both sorbents was observed to be pH-dependent with maximum phosphorus removal occurring in the pH range of 2–5. Langmuir, Freundlich, Redlich–Peterson, and Temkin models were used to describe phosphorus sorption at pH 5 and maximum sorption capacity for Th-nZVI and P-nZVI was about 40.52 and 29.33?mg?g^?1, respectively. Correlation coefficient (R²) and standard errors of estimate showed that the Elovich model was better than other models at describing the kinetic data. These results suggested that the synthesised nZVI with Shirazi thyme leaf and pistachio green hulls extracts could be employed as an efficient sorbent for the remediation of phosphorus from contaminated water sources.     

Sulfonated cross-linked polyethylenimine for selective removal of mercury from aqueous solutions

Polymeric materials are among the most promising, effective, and increasingly important adsorbents for the removal of toxic metals from wastewater. This study was dedicated to the development of an insoluble, modified chelating polymer for use as an adsorbent for abstraction of Hg from aqueous solutions. Cross-linked polyethylenimine (CPEI) was sulfonated by 3-chloropropanesulfonyl chloride for selective removal of Hg. The binding affinity of the sulfonated CPEI (SCPEI) to Hg was assessed as well as its ability to be regenerated for reuse. It exhibited high removal percentage for Hg up to 87% in synthetic solutions, with high selectivity even in the presence of competing ions: “Mn, Ni, Fe, Pb, Zn, and Cr.” The removal mechanism followed was observed to be adsorption and precipitation at pH 3 and 8, respectively. High adsorption capacities were also observed for wastewater to which the polymer was applied. The Freundlich isotherm was found to be the best fit describing the adsorption process of Hg onto the SCPEI. The pseudo second-order equation was found to better explain the adsorption kinetics, implying chemisorption. The thermodynamic study of the adsorption revealed high activation energies which confirmed the chemisorption as the mechanism of adsorption. The polymer exhibited up to 72% removal efficiency after regeneration, thus showing potential for re-use.     

Analytical solutions of nonlinear and variable-parameter transport equations for verification of numerical solvers

All numerical codes developed to solve the advection–diffusion-reaction (ADR) equation need to be verified before they are moved to the operational phase. In this paper, we initially provide four new one-dimensional analytical solutions designed to help code verification; these solutions are able to handle the challenges of the scalar transport equation including nonlinearity and spatiotemporal variability of the velocity and dispersion coefficient, and of the source term. Then, we present a solution of Burgers’ equation in a novel setup. Proposed solutions satisfy the continuity of mass for the ambient flow, which is a crucial factor for coupled hydrodynamics-transport solvers. By the end of the paper, we solve hypothetical test problems for each of the solutions numerically, and we use the derived analytical solutions for code verification. Finally, we provide assessments of results accuracy based on well-known model skill metrics.     

Analytical solutions of three-dimensional contaminant transport in uniform flow field in porous media: A library

The purpose of this study is to present a library of analytical solutions for the three-dimensional contaminant transport in uniform flow field in porous media with the first-order decay, linear sorption, and zero-order production. The library is constructed using Green’s function method (GFM) in combination with available solutions. The library covers a wide range of solutions for various conditions. The aquifer can be vertically finite, semi-infinitive or infinitive, and laterally semi-infinitive or infinitive. The geometry of the sources can be of point, line, plane or volumetric body; and the source release can be continuous, instantaneous, or by following a given function over time. Dimensionless forms of the solutions are also proposed. A computer code FlowCAS is developed to calculate the solutions. Calculated results demonstrate the correctness of the presented solutions. The library is widely applicable to solve contaminant transport problems of one- or multiple- dimensions in uniform flow fields.     

Biosorption of copper from aqueous solutions by date stones and palm-trees waste

The removal of toxic metals from wastewaters by biosorption, based on the metal-binding capacities of various biological materials, has received much interest. However, the success of this approach depends on economic feasibility, which can be obtained by optimization of the environmental conditions. This paper evaluates, for the first time, the use of low-cost biosorbent (date stones (DS) and palm-tree waste (PTW)) to eliminate Cu(II) from aqueous solutions. The effect of some parameters on copper biosorption has been studied using date stones and palm-tree waste as solid sorbents. Results show that the highest percentage of copper adsorption was obtained for the smallest size of the sorbent particles. The biosorption process was found to occur rapidly, i.e. the maximum sorption capacity was reached within 20 min. The process involved pseudo-second-order kinetics with an activation energy value within the normal range considered for processes, where a physical interaction between the sorbate and the sorbent solid predominated. The thermodynamic parameters of the copper ions uptake onto the solid sorbents indicated that, the process was endothermic and proceeds spontaneously from the date stones. However, the thermodynamic studies of the adsorption of copper on palm-tree waste indicated that the process was exothermic and proceeds spontaneously.     

Removing phosphorus from aqueous solutions by using iron-modified corn straw biochar

Iron-modified corn straw biochar was used as an adsorbent to remove phosphorus from agricultural runoff. When agricultural runoffs with a total phosphorus (TP) concentration of 1.86 mg·L⁻¹ to 2.47 mg·L⁻¹ were filtered at a hydraulic retention time of 2 h through a filtration column packed with the modified biochar, a TP removal efficiency of over 99% and an effluent TP concentration of less than 0.02 mg·L⁻¹ were achieved. The isotherms of the phosphorus adsorption by the modified biochar fitted the Freundlich equation better than the Langmuir equation. The mechanism of the phosphorus adsorbed by the modified biochar was analyzed by using various technologies, i.e. scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results indicated that the surface of the modified biochar was covered by small iron granules, which were identified as Fe₃O₄. The results also showed that new iron oxides were formed on the surface of the modified biochar after the adsorption of phosphorus. Moreover, new bonds of Fe-O-P and P-C were found, which suggested that the new iron oxides tend to be Fe₅(PO₄)₄(OH)₃. Aside from removing phosphorus, adding the modified biochar into soil also improved soil productivity. When the modified biochar-to-soil rate was 5%, the stem, root, and bean of broad bean plants demonstrated increased growth rates of 91%, 64%, and 165%, respectively.     

Biosorption of Cu2+ from aqueous solutions by pretreated Cladosporium sp

In this paper, adsorption properties of a pretreated of Cladosporium sp. for Cu2 were studied. The fungi pretreated with some chemical reagents exhibited higher Cu2+ removal capacities than native biomass. The optimum chemical reagent was 0.2M NaOH. After 0.2M NaOH pretreatment, optimum conditions of biosorption were found to be pH 5.0, temperature 35 degrees C, and stirring speed of 100rpm. Equilibrium isotherms were obtained from adsorption experiments and the biosorption maximun capacity obtained was at 28.31mg/g. The biosorbed metal ions were effectively eluted by 0.05M HNO3 solution. After eluting, the biosorbed metal ions biomass was regenerated by washing with deionized water and then contacted with a solution containing 0. 1M of Ca2+, Mg2+ ions before further adsorption tests. The pretreated fungi biomass could be used for three cycles: biosorption, elution of biosorbed ion, regeneration of biomass.     

溴、碘离子吸附研究进展

吸附法是从盐湖卤水等溴、碘含量较低的溶液中直接分离溴、碘离子的适用方法,也是去除饮用水中过高含量的溴和碘,以及去除水中放射性碘离子的有效方法.本文简要介绍了溴、碘的用途、制备方法及吸附分离溴、碘离子的实际意义,系统评述了单质银、银复合、氧化银复合、氯化银复合、有机胺复合、层状双氢氧化物等吸附剂对溶液中溴或碘离子的吸附.研究省去氧化步骤,直接从溶液中吸附回收溴、碘离子的工艺路线,对环保及溴、碘的开发利用具有重要意义.