Preparation of diphenylcarbazide-directed CdSe quantum dots and selective determination for Cr(VI)

CdSe quantum dots (QDs) were synthesized using diphenylcarbazide (DL) to sequester QDs precursors (Cd²⁺) in situ. Fluorescence (FL) analysis showed the successive synthesis of QDs could be realized by capping with DL and the binding between DL and Cd²⁺. The average QDs particle size was about 5-20 nm by high-resolution transmission electron microscopy (HRTEM). Fourier transform infrared (FT-IR) spectra showed that CdSe QDs could be chemically bonded with DL. The formation of QDs-DL-Cr(VI) could lower the fluorescence intensity of QDs. In a certain concentration range, the fluorescence intensity and Cr(VI) concentration presented a linear relationship. As a result, this phenomenon could be used to determine the Cr(VI) concentration in the range of 0-24 ×10^?6 mol· L^?1.     

Removal of anionic ions from single material solution by bauxite tailings modified with FeCl3·6H2O

The adsorbabilities of the unmodified and modified bauxite tailings for Cr（Ⅵ）, As（Ⅴ） and F（Ⅰ） ions were investigated. Batch experiments were carried out to determine the removal rate as a function of adsorbent dosage, solution pH value and shaking time. The results show that the maximum removal rates of Cr（Ⅵ）, As（Ⅴ） and F（Ⅰ ） are respectively 99%, 99% and 90% by using the modified bauxite tailings. The isoelectric point of the unmodified bauxite tailings is 3.6, and that of the modified bauxite tailings is 5.0, which shifts to lower pH values in Cr（Ⅵ） solution. This indicates a specific adsorption of the anionic species on the modified bauxite railings. A new band of Cr2O72 appears in the FTIR, showing that Cr（Ⅵ） is adsorbed on the modified bauxite railings in the form of chemistry adsorption. The adsorption data of Cr（Ⅵ） on the modified bauxite tailings are well described by Freundlich model. The investigations of kinetic models show that pseudo-second-order kinetic model provides the best correlation for the experimental data.     

改性煤基活性炭对Cr(VI)吸附性能的试验

研究以改性煤基活性炭为吸附剂对Cr(VI)进行静态吸附试验,探讨了吸附时间、溶液pH、吸附剂质量、Cr(VI)起始质量浓度对吸附剂吸附性能的影响.试验表明,煤基活性炭经改性后,对Cr(VI)具有良好的吸附性能;在室温时酸性条件下能快速达到吸附平衡,Cr(VI)去除率可达99%以上.改性煤基活性炭对Cr(VI)吸附效率明显提高.     

柚子皮对水中六价铬的吸附性能研究

采用柚子皮制备生物吸附剂用于去除水中的Cr（VI）,考察了pH值、柚子皮投加量、柚子皮粒径、溶液离子强度、反应温度等因素对吸附效果的影响。结果表明,当溶液中Cr（VI）离子初始浓度15mg／L、pH 1．5、反应温度25℃、柚子皮投加量1．Og／100mL、吸附时间7h时,Cr（VI）离子去除率可达90％以上。柚于皮对Or（VI）离子的吸附过程可以用Langmuir和Freundlich吸附等温模型来描述,吸附等温线线性相关性均较显著,吸附过程符合准二级动力学方程。柚子皮对水中Cr（VI）离子吸附性能较好,且运行成本低,可推广应用于水中重金属离子的治理。     

Removal of Cr (VI) from aqueous solution using ultrafine coal fly ash

Coal fly ashes WSRA and BQRA were ball milled for 5 h to produce their ultrafine coal fly ashes WSUA and BQUA, respectively. Batch kinetic, isotherm and pH effect on adsorption were studied to evaluate removal of Cr (VI) from aqueous solutions by ultrafine coal fly ashes comparing with raw coal fly ashes. The kinetics of adsorption indicates the process to be intraparticle diffusion controlled and follows the Lagergren first-order kinetics for all coal fly ashes. The first-order rate constants (k ₁) of Cr (VI) adsorption onto WSRA, WSUA, BQRA and BQUA are 1.981, 1.497, 2.119 and 1.500 (×10⁻²) min⁻¹, respectively. The adsorption capacities of WSUA and BQUA are much better than those of WSRA and BQRA. Equilibrium adsorption data of all coal fly ashes well satisfy the Langmuir isotherm. The adsorbed amounts of Cr (VI) onto WSUA and BQUA decrease from pH 2 to pH 6 and then increase up to pH 12.     

Removal of Cr（Ⅲ） and Cr（Ⅵ） from aqueous solution by adsorption on sugarcane pulp residue

Sugarcane pulp residue (SPR), a waste from sugar-refinery, which possesses a large surface area, can be used for removing chromium (Cr(III) and Cr(VI)) from wastewater. In this work, the kinetics, isotherms of Cr(III) and Cr(VI) adsorption and their removal by SPR were investigated. The results show that the removal percentages of Cr(VI) and Cr(III) increase with increasing SPR dosage and temperature and decrease with increasing SPR particle size and the initial concentration of chromium ions. However, the influence of pH value on the Cr(VI) removal differs from that of the Cr(III) removal. The Cr(VI) removal percentage decreases with increasing pH values, while the Cr(III) removal percentage increases with increasing pH value. The adsorption kinetics of Cr(VI) and Cr(III) well fits with pseudo-second-order model. Langmuir adsorption isotherm can well describe the adsorption phenomena of chromium ions with the maximum adsorption capacity of 0.567 mg/g for Cr(VI) and 3.446 mg/g for Cr(III). Moreover, SPR reveals higher adsorption capacity for Cr(III) than that for Cr(VI), which implies that SPR has more potential application for Cr(III)-containing wastewater treatment than that for Cr(VI)-containing wastewater treatment. Foundation item: Projects(2006AA06Z374, 2007AA021304) supported by the National High-Tech Research and Development Program of China; Project(2008SK2007) supported by the Key Program of Science and Technology of Hunan Province, China     

Adsorption of copper（ Ⅱ ） and chromium（Ⅵ） on diaspore

The adsorption of Cu（ Ⅱ ） and Cr（Ⅵ） on diaspore was studied with the help of X-ray diffraction analysis, BET measurement, zeta potential measurement and atomic adsorption spectrometry. The adsorption equilibrium almost reaches within 60 min. The adsorption isotherms of Cu（ Ⅱ ） and Cr（Ⅵ） could be well described by the Langmuir equation. The adsorption capacities of Cu（Ⅱ） and Cr（Ⅵ） are 1.944 and 1.292 mg/g, respectively. The adsorption percentage of Cr（Ⅱ ） increases with the increment of solution pH, but the adsorption percentage of Cr（Ⅵ） decreases. This could be explained by zeta potential theoretical and electrostatic attraction between metal ions and diaspore surface.     

改性花生壳对重金属含铬废水的吸附研究

对改性花生壳处理含Cr6＋废水进行研究,考察吸附时间、改性花生壳投加量、pH值、Cr6＋溶液初始浓度对吸附效果的影响。实验结果表明,在吸附时间100min、改性花生壳投加量为5.0g/L、pH值2.0、Cr6＋溶液初始浓度25mg/L、常温的优化实验条件下,硝酸改性花生壳比盐酸改性花生壳吸附效果好,硝酸改性花生壳吸附率达到87%,盐酸改性花生壳为71%。改性花生壳是一种较高效的重金属离子吸附剂。     

Biosorption mechanism of Cr （Ⅳ） onto cells of Synechococcus sp.

The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr （Ⅳ） consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-LR spectra of K2Cr2O7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp show that the speciation of chromium that binds to the cells ofSynechococcus sp. is Cr （Ⅲ）, instead of Cr （Ⅳ）, and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr （Ⅲ）. Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr （Ⅵ）, and the results of FT-IR show that the biosorption of Cr （Ⅵ） follows two subsequent steps, biosorption of Cr2O7 ^2- by electrostatical force at the protonated active sites and reduction of Cr2O7^2- to Cr^3＋ by the reductive groups on the surface of the biosorbents.     

响应面法优化空气氛围下制备S-nZVI对水中Cr(VI)的去除

在空气氛围下制备硫化纳米零价铁（SnZVI）,通过SEM、XRD等进行表征,并对其去除水中Cr（VI）进行研究。以Cr（VI）去除率为响应值建立了4因素5水平的响应面模型。SEM和XRD结果显示S-nZVI具有片状结构,主要成分为Fe⁰并含有少量的FeS和铁氧化物。响应面法分析结果表明模型可信度高,适用于模拟4种因素对S-nZVI去除Cr（VI）的影响。以伪一级、伪二级动力学模型拟合S-nZVI去除Cr（VI）,结果显示伪二级动力学模型R²为0.999拟合度更好,说明S-nZVI对Cr（VI）的去除主要以化学吸附为主,平衡吸附量达到156.3mg/g.     

Selective leaching of chromium-containing slag by HCl

A batch of column experiments was carried out to investigate the change of Cr（Ⅵ） concentration leached out from chromium-containing slag with HCI as leaching agent, and to study influences of pH, ratio of solid mass to solution volume, flow velocity and temperature on Cr（Ⅵ） leaching. The optimal parameters were obtained for Cr（Ⅵ） leaching and a fitting model was established to describe the procedure of Cr（Ⅵ） leaching. The results show that Cr（Ⅵ） concentration in leachate increases with decreasing pH and increasing flow velocity and temperature. Moreover, Cr（Ⅵ） leaching percentage increases with increasing ratio of solid mass to solution volume. The optimal parameters for Cr（Ⅵ） selective leaching are as follows： pH=3.0, 1：5 of ratio of solid mass to solution volume, 180 mL/min of flow velocity and 40 ℃ of temperature. The procedure of Cr（Ⅵ） leaching fits well with the model： v= 1.87t^-0.54, indicating that the leaching rate of Cr（Ⅵ） declines in an exponential order of-0.54.     

活性炭和活性氧化铝对六价铬的吸附行为比较

Cr(Ⅵ)是一种公认的致癌物质,用途广泛且造成水体突发性污染的可能性大.本文比较分析了活性炭和活性氧化铝对六价铬的吸附性能,并对两种吸附剂用于水体六价铬污染处理的可行性进行了讨论.结果表明,初始pH值、投加量、吸附时间对六价铬的吸附效果影响较大,分别在pH为2和3的酸性条件下效果最好,活性炭与活性氧化铝对铬的吸附去除率...     

腐殖酸-柱撑膨润土的制备及其对铀（VI）的吸附性能

采用腐殖酸（ HA）修饰铝-柱撑膨润土（ Al-PILC）,制备得到腐殖酸-柱撑膨润土（ HA-Al-PILC）,用于去除含铀废水中的铀.通过静态吸附实验考察了投加量、pH值,接触时间、U（ VI）初始浓度对吸附的影响,同时进行了吸附解吸实验.试验结果表明,HA修饰后的Al-PILC对U（ VI）的去除能力有了一定程度的提高;HA-Al-PILC对U（VI）有很好的去除效果,150 min左右吸附达到平衡,最佳投加量为1.0 g/L,最佳pH值在6左右;HA-Al-PILC能重复使用.     

Adsorption and desorption properties of D318 resin for Cr（Ⅵ）

The adsorption capability of D318 resin for Cr(VI) was investigated by chemistry analysis. Experimental results show that D318 resin has the best adsorption ability for Cr(VI) at pH=3.16 in HAc-NaAc medium. The statically saturated adsorption capacity of the resin is 265.4 mg/g. The thermodynamic adsorption parameters, enthalpy change ΔH and free energy change ΔG ₂₉₈ of the adsorption reaction are 4.81 and −5.16 kJ/mol, respectively. The apparent activation energy E _a is 22.4 kJ/mol. The adsorption behavior obeys the Freundlich isotherm. The molar coordination ratio of the functional group of resin to Cr(VI) is 3:2. Cr(VI) adsorbed on D318 resin can be eluted by 5%NaOH-5%NaCl quantitatively. Foundation item: Project (Y304121) supported by the Natural Science Foundation of Zhejiang Province, China     

Adsorption of sodium oleate at the microfine hematite/aqueous solution interface and its consequences for flotation

The adsorption of sodium oleate(NaOL) at the microfine hematite/aqueous solution interface was investigated in this paper. Experimental research indicated that negative effects stemmed from the dissolution of the microfine hematite(D50=19.21 μm) could be effectively eliminated via the appropriate dosage of NaOL at alkali pH conditions. Solution chemistry calculation and adsorption test results indicated that RCOO^- and(RCOO)₂^2- ions were responsible for microfine ...     

Adsorption of D113 resin for dysprosium(III)

The adsorption behavior and mechanism of D113 resin for Dy(III) was investigated by using the method of resin adsorption. Experimental results show that the optimum medium pH of adsorption of D113 resin for Dy³⁺ is pH=6.00 in the HAc-NaAc medium. The static adsorption capacity of D113 resin for Dy³⁺ is 292.7 mg·g⁻¹. The optimum eluant is 0.5 mol·L⁻¹ HCl. The adsorption rate constant is k ₂₉₈=6.8×10⁻⁶s⁻¹. The apparent activation energy of D113 resin for Dy(III) is 14.79 kJ·mol⁻¹. The adsorption behavior of D113 resin for Dy(III) obeys the Freundlich isotherm. The adsorption parameters of thermodynamic are ΔH=14.48 kJ·mol⁻¹, ΔS=54.69 J·mol⁻¹·K⁻¹, ΔG=−1.82 kJ·mol⁻¹.The adsorption mechanism of D113 resin for Dy³⁺ was confirmed by chemical analysis and IR spectra. Funded by the Natural Science Foundation of Zhejiang Province (No.201027), Foundation of Zhejiang Provincial Education Bureau (No.20040551) and Zhoushan Science Technology Bureau (No.04114)     

改性磁性壳聚糖去除水中双氯芬酸

为改善壳聚糖的吸附能力,探究壳聚糖吸附水中双氯芬酸的作用机理,采用原位共沉淀法制备磁性壳聚糖小球,并利用乙二胺对其进行改性.分别研究戊二醛、环氧氯丙烷和乙二胺等交联剂的投加量不同时,改性磁性壳聚糖对水中双氯芬酸吸附能力的差异.当戊二醛、环氧氯丙烷和乙二胺的投加量分别为4,12和6 mL时,制备的吸附剂(EMMCS-G)...     

Preparation of elemental tellurium nanoparticles — sucrose sol and its antioxidant activity in vitro

The elemental tellurium nanoparticles (TeNPs) — sucrose sol was prepared by the reaction of sodium tellurite with ascorbic acid in sucrose aqueous solution. The results indicated that TeNPs were dispersion excellent in the TeNPs — sucrose sol and the morphology of TeNPs was needle-like with about 70 nm in width and 500 nm in length. The antioxidant activity of the TeNPs — sucrose sol in vitro was estimated by pyrogallol autoxidation method, Fenton method and oxygen radical absorbance capacity (ORAC) assay. The results showed that a certain amount of TeNPs — sucrose sol could effectively scavenge superoxide anion free radical and hydroxyl free radical with scavenging rates of 73 % and 57 %, respectively. ORAC assay was used to measure the total antioxidant capacity of TeNPs — sucrose sol. The order of ORAC values was 2.25 μmol·L^?1 TeNPs — 0.025 % sucrose sol > 0.025 % sucrose > 2.25 μmol·L^?1 Na₂TeO₃ > 1.63 μmol·L^?1 ascorbic acid. The results suggested that the TeNPs — sucrose sol had the excellent antioxidant activity and TeNPs were the dominating contributors to antioxidant capacity of the TeNPs — sucrose sol.     

水中刚果红的磁性活性炭纤维素微球法脱除

为了开发高效的可生物降解的高效染料吸附剂,采用氢氧化钠/尿素水溶液在低温下直接溶解纤维素,加入活性炭和磁性纳米粉末,通过直接滴落法制备磁性的纤维素微球,研究了吸附剂用量、刚果红溶液pH 值、初始浓度、吸附时间、温度等因素对吸附剂吸附刚果红的影响.结果表明:湿态吸附剂在实验用刚果红量时合适的用量是25 g; 微球对刚果红的脱除率在20 min内时基本达到吸附平衡;溶液pH=7.50 时,微球对刚果红的脱除率达到96.4%;温度对吸附效果有较大的影响,在40 ℃时效果最好;微球对刚果红的吸附形为可以用Langmuir和Freundlich等温吸附方程描述,吸附为物理吸附和化学吸附的综合过程.     

生物炭负载零价纳米铁对溶液中的 Cr6+ 去除的研究

生物炭(biochar, BC)作为载体,负载纳米零价铁(nano zero valent iron, nZVI)形成复合吸附材料,利用电子扫描显微镜(SEM)和X射线衍射仪(XRD)表征材料的结构特征。研究了不同材料、初始溶液初始p H、不同初始浓度、去除剂的投加量对BC负载nZVI (nZVI-BC)去除含Cr~(6+)废水的影响。结果表明:BC的加入提高了nZVI的分散性和抗氧化性,同时提升稳定性,对于水中Cr~(6+)的去除具有较好的效果;当Cr~(6+)的初始浓度为15 mg/L,去除剂的投加量为2.5 g/L, pH=4的条件下,其去除率达到了98%; nZVI-BC去除含Cr~(6+)废水的过程符合Langmuir吸附等温式和准一级动力学方程,其中最大吸附量为209.93 mg/g。