生物吸附剂改性栗蓬的制备及其对Cr(Ⅵ)吸附性能的研究

以农林废弃物栗蓬为原料,过氧化氢为改性剂,制备了对Cr(Ⅵ)具有良好吸附性能的生物吸附材料。以吸附率为优化目标,在单因素实验的基础上进行正交试验得到最佳改性条件为温度80℃、过氧化氢浓度10.0%、盐酸浓度0.01 mol·L^(-1)、时间0.5 h。采用傅立叶红外光谱(FT-IR)及扫描电镜(SEM)对改性栗蓬结构进行了表征。通过正交试验优化改性栗蓬对Cr(Ⅵ)的吸附条件,在改性栗蓬投加量0.8 g、Cr(Ⅵ)初始浓度20 mg·L^(-1)、吸附时间60 min条件下,对Cr(Ⅵ)的吸附率为61.8%。通过动力学方程拟合得到改性栗蓬对Cr(Ⅵ)的吸附过程符合准二级动力学方程。热力学实验表明,改性栗蓬对Cr(Ⅵ)的吸附为放热、熵减小的过程。

Thickness Dependence of Structural and Optical Properties of Chromium Thin Films as an Infrared Reflector for Solar-thermal Conversion Applications

The thermal emittance of Cr film, as an IR reflector, was investigated for the use in SSAC. The Cr thin films with different thicknesses were deposited on silicon wafers, optical quartz and stainless steel substrates by cathodic arc ion plating technology as a metallic IR reflector layer in SSAC. The thickness of Cr thin films was optimized to achieve the minimum thermal emittance. The effects of structural, microstructural, optical, surface and cross-sectional morphological properties of Cr thin films were investigated on the emittance. An optimal thickness about 450 nm of the Cr thin film for the lowest total thermal emittance of 0.05 was obtained. The experimental results suggested that the Cr metallic thin film with optimal thickness could be used as an effective infrared reflector for the development of SSAC structure.

Interpenetrating polymers supported on microporous polypropylene membranes for the transport of chromium ions

Modifying polypropylene membranes with interpenetrating polymer networks(IPNs) through the incorporation of poly(glycidyl methacrylate-N-methyl-D-glucamine)(P(GMA-NMG)) was performed by in situ synthesis via radical polymerization. The surface of the polypropylene membrane was activated by hydrophilic grafted polyelectrolyte, and then, pressure injection was used for the impregnation of the reactive solution in the membrane.Two types of pore-filled membranes were synthesized, chelating interpenetrating homopolymer networks of P(GMA-NMG), and chelating-ion exchange interpenetrating polymer networks(e.g., P(GMA-NMG)/P(AA),P(GMA-NMG)/P(AMPSA), and P(GMA-NMG)/P(Cl VBTA)). After their synthesis, the modified polypropylene membranes were characterized using techniques such as the electrokinetic potential, SEM, FT-IR, and Donnan dialysis to corroborate the chromium ion transport. The P(GMA-NMG) and complex network membranes exhibited a hydrophilic character with a water-uptake capacity between 20% and 35% and a percentage of modification between 4.0% and 7.0% in comparison with the behavior of the unmodified polypropylene membrane.Hexavalent chromium ions were efficiently transported from the food chamber at p H 9.0 when the 65.2%MTA1 P(Cl VBTA) homopolymer IPN membrane and 48.5% MTAG P(GMA-NMG)/P(Cl VBTA) IPN membrane were used. Similarly, hexavalent chromium ions were removed from the food chamber at pH 3.0 when MTAG(63.30%) and MTA1(35.68%) were used in 1 mol·L^(-1)Na Cl solution as the extraction reagent.

The Electrode for Potentiometric Determinаtion of Chromium (III, VI) in Wаter Solutions

The possibility of determining of chromium (III, VI) ions was investigated in this paper. It is shown that the electrode on а basis of heаzlewoodite has high selectivity to chromium (III) ions. Also the stability constants of complexes, forming in system “Cr3+-Mohr’s salt-Ca(OH)2-PVA ÷ PAA” were determined by potentiometric titration with ion-selective electrode.

Speciation of chromium in soil inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4

Cr(Ⅵ)-amended soil was inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4 and incubated at 28 ℃in an incubator. Cr(Ⅵ)reduction,available Cr and Cr fractionin soils were studied.The results show that addition of Bacillus sp.XW-4 can promote Cr(Ⅵ)reduction,but inoculation of this strain has a negative effect on the decrease of available Cr content in soil.In controls (without this strain)amended with 100 and 200 mg/kg of Cr(Ⅵ),Cr(Ⅵ)contents decrease to about 41 and 92 mg/kg respectively after incubation of 4 d,while in soil inoculated with XW-4,Cr(Ⅵ)contents decrease to about 18 and 60 mg/kg,respectively.The content of available Cr in soils with inoculation of XW-4 is higher than that in controls.Chromium is partitioned into water soluble Cr,exchangeable Cr,precipitated Cr,Cr bound to organics and residual Cr.The highest content of Cr is observed in residual form and water soluble Cr is not detected for all treatments after 42 d,but the soils inoculated with Bacillus sp.XW-4 contain higher content of exchangeable Cr and lower content of precipitated Cr than the soil without the inoculum.Inoculation of Bacillus sp.XW-4 can increase chromium activity in soils.

Kinetic Studies for the Extraction of Chromium (Ⅵ) from Hydrochloric Acid Solution with Tri-n-octylamine

Kinetic studies of the extraction of chromium（Ⅵ）[Cr（Ⅵ）] from the hydrochloric acid solution with tri-n-octylamine（N235） have been made by a Lewis cell. The influences of various kinetic parameters, such as stirring rate, interfacial area, temperature, N235 and initial Cr（Ⅵ） concentrations were evaluated. The rate equations for the extraction of Cr（Ⅵ） by N235 were obtained on the basis of the slope analysis data. The results indicated that the reaction rate of Cr（Ⅵ） increased with increasing of the stirring rate and interfacial area until that a "plateau" was observed with increasing stirring rate. The activation energies of Cr（Ⅵ） extraction by N235 dissolved in diluents were calculated. Kinetics analysis proved that the mass transfer was controlled mainly by diffusion and the chemical reaction between Cr（Ⅵ） anions and N235 could be achieved at the liquid-liquid interface. On the basis of the relation between ln[Cr（Ⅵ）] and ln R0 or ln[N235] and ln R0, the rate equations can be obtained. This research provides a proof-in-concept analysis for kinetic mechanism.

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.

Preparation of Al2O3-Supported Nanoscale FeS Based on High-Gravity Technology and Its Application for Removing Chromium (Ⅵ) in Wastewater

AbstFeS has an excellent performance in removing heavy metal chromium(Ⅵ)in wastewater due to its good adsorption and reduction.The properties of easy aggregation and oxidization of nano-FeS,however,limit the applications of FeS in engineering.In this study,one FeS adsorbent supported by Al_(2)O_(3) was prepared using high-gravity technology in IS-RPB(Impinging Stream Rotating Packed Bed)to overcome polymerization and oxidation of nano-FeS.Experimental results showed that FeS was uniformly loaded on the surface and pores of Al_(2)O_(3).The specific surface area of FeS/Al_(2)O_(3) is 125 m2·g^(-1) which is nearly 1.6 times that of pure FeS.The adsorption capacity of FeS/Al_(2)O_(3) for chromium(Ⅵ)is 200 mg·g^(-1),1.4 times that of pure FeS.pH value and ionic strength are strongly correlated with the chromium removal performance of FeS/Al_(2)O_(3).Over 98%of chromium can be removed when pH values of FeS/Al_(2)O_(3) ranged from 4 to 6.Higher adsorption capacity is achieved with higher ionic strength in FeS/Al_(2)O_(3).The FeS/Al_(2)O_(3) maintained more than 95%of the adsorption capacity after being preserved for one month,but only 70%for pure FeS.The removal processes of chromium(Ⅵ)conformes to a pseudo-second-order kinetic model(R2≥0.9986),indicating that the rate-limiting step is a chemical sorption process instead of a mass transfer.

基于纸基微流控芯片快速检测饮用水中铬(Ⅵ)含量

目的建立一种可以在纸基微流控芯片上快速检测饮用水中铬(Ⅵ)的方法。方法将普通中性笔进行改装,在笔芯中灌注烷基烯酮二聚体溶液,然后利用在滤纸上直接绘制的方法制作纸芯片,干燥后在此纸芯片上检测铬(Ⅵ)。实验优化了硫酸溶液浓度、二苯碳酰二肼浓度、反应温度、反应时间等参数。结果本研究检测铬的线性范围为0~0.20 mg/L,检出限为0.0036 mg/L,加标回收率为97.7%~109.0%。其线性范围宽,灵敏度高,重复性好。结论该方法操作简单、结果准确,不需要昂贵复杂的大型仪器,对于多样品的同时检测及现场即时检测具有适应性。

水泥中水溶性铬(Ⅵ)的测定实验影响因素研究

研究了水泥中水溶性铬(Ⅵ)含量检测的实验原理,采用分光光度计测量显色剂与水溶性铬(Ⅵ)在酸性溶液中的络合反应物的吸光度,可以间接测量计算出水泥样品中水溶性铬(Ⅵ)的含量。采用不同水溶性铬(Ⅵ)含量的水泥标准样品和对照样品进行实验,研究了显色剂质量、实验溶液pH值、调酸时间、显色后静置时间和实验温度等对测定结果准确性的影响。结果显示,显色剂质量不同,测定结果准确性不同;实验溶液pH值偏大,会导致测量结果产生负误差,pH值偏小对测定结果影响不大;实验溶液调酸时间应控制在30s内,显色完成后实验溶液静置时间宜在15min以上、20min以内;一定区间内的实验温度对水溶性铬(Ⅵ)测定结果影响不大。

一株耐铬细菌的分离鉴定及其对Cr(Ⅵ)的抗性

从山东省某含铬农田土壤取样进行宏基因测序、16SrDNA以及构建系统树等方法分离、鉴定耐铬细菌,并通过扫描电子显微镜等研究其对Cr(Ⅵ)的抗性。某含铬农田土壤中的优势菌为Enterobacter cloacae(阴沟肠杆菌),将其命名为Enterobacter cloacae SD。SD的Cr(Ⅵ)耐受质量浓度可达3 200 mg/L;在150 mg/L Cr(Ⅵ)中培养时,菌落较不加Cr(Ⅵ)时少且分散,但单菌落较大;SD细胞表面粗糙,似有沉淀物产生。以酵母浸粉为碳源,pH值为7,培养温度为30℃时菌株SD可较好生长。在150 mg/L Cr(Ⅵ)下,SD对Cr(Ⅵ)的去除率为39.67%。研究表明Enterobacter cloacae SD可耐受高质量浓度Cr(Ⅵ)的同时,对Cr(Ⅵ)有一定的去除能力,这为Cr(Ⅵ)污染的微生物修复提供了可能的菌种资源。

Catalysis of Manganese(II) on Chromium(VI) Reduction by Citrate

The catalysis of manganese（Ⅱ） （Mn^2＋） on chromium（Ⅵ） （Cr^6＋） reduction by citrate was studied through batch experiments with the concentration of citrate greatly in excess of Cr^6＋ at 25 ℃ and in pH ranges of 4.0 go 5.0. Results showed that at pH 4.5 within 22 h direct reduction of Cr^6＋ by citrate was not observed, bug for the same time when Mn^2＋ （50 to 200 μmol L^-1） was added, nearly all Cr^6＋ was reduced, with the higher initial Mn^2＋ concentration having faster Cr^6＋ reduction. In the initial stage of the reaction, the Cr^6＋ reduction could be described with a pseudo-first-order kinetics equation. In the lager stage of the reaction, plots of lnc（Cr^6＋） versus t, where c（Cr^6＋） is the Cr^6＋ concentration in the reaction and t is the reaction time, deviated from the initial linear trend. The deviations suggested that the pseudo-first-order kinetics did not apply go the whole experimental period and that some reaction intermediates could have greatly accelerated Cr^6＋ reduction by citrate. The catalysis of the intermediates increased with the reaction time and gradually reached stability. Then, the plot of lnc（Cr^6＋） versus t in the presence of Mn^2＋ was linear again, with the rate constant increasing by 102 times compared with the absence of Mn^2＋. Complexation between Mn^2＋ and citrate was likely a prerequisite for the catalysis of Mn^2＋ on the reaction. Additional experiments showed that introducing eghylenediaminegegraacegic acid （EDTA） into the reaction system strongly suppressed the catalysis of Mn^2＋.

Chromium accumulation, microorganism population and enzyme activities in soils around chromium-containing slag heap of steel alloy factory

The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by chromium. 45 soil samples obtained from different places of the slag heap in a steel alloy factory were analyzed for chromium contamination level and its effect on soil microorganisms and enzyme activities. The results show that the average concentrations of total Cr in the soil under the slag heap, adjacent to the slag heap and outside the factory exceed the threshold of Secondary Environmental Quality Standard for Soil in China by 354%, 540% and 184%, respectively, and are 15, 21 and 9 times higher than the local background value, respectively. Elevated chromium loadings result in changes in the activity of the soil microbe, as indicated by the negative correlations between soil microbial population and chromium contents. Dehydrogenase activity is greatly depressed by chromium in the soil. The results imply that dehydrogenase activity can be used as an indicator for the chromium pollution level in the area of the steel alloy factory.

Adsorption of XSD-296 resin for Cr(Ⅵ)

The adsorption properties of XSD-296 for Cr(Ⅵ) were studied by using chemical analysis and infrared spectrometry. Experimental results show that XSD-296 resin has a good adsorption ability for Cr(Ⅵ) at pH=2.6 in the HAc-NaAc medium. The statically saturated adsorption capacity is 235 mg/g resin. The apparent activation energy of adsorption reaction, Ea, is 16.73 kJ/mol, and the thermodynamic parameters are △H=11.62 kJ/mol, △G298 K=-4.13 kJ/mol. The adsorption behavior of resin for Cr(Ⅵ) is in accordance with Freundlich adsorption isotherm. Cr( Ⅵ ) adsorbed on resin can be eluted by 5%NaCl-5%NaOH or 5%NH4Cl-5%NH3·H2O quantitatively. Infrared spectra and adsorption mechanism show that the functional group of resin coordinates with Cr(Ⅵ) to form co-ordination compound. The coordination molar ratio of the functional group of resin to Cr(Ⅵ) is 1:1.

螯合剂与低分子有机酸复配淋洗修复Cr(Ⅵ)污染土壤

为探究可生物降解螯合剂氨三乙酸(NTA)替代乙二胺四乙酸二钠(EDTA)在复配淋洗剂中的作用,本文研究了NTA和EDTA与草酸和酒石酸所配制的复配淋洗剂在不同浓度、固液比、pH值和淋洗时间下对Cr(Ⅵ)污染土壤淋洗效果的影响及淋洗动力学,此外还使用顺序提取方案(BCR)分析了淋洗前后土壤中重金属的形态、迁移率和稳定性变化。结果表明:混合等体积的0.25 mol·L^(-1)NTA和0.3 mol·L^(-1)草酸在固液比为1∶9、pH为3、淋洗时长为240 min条件下达到最大Cr(Ⅵ)去除效率82.94%,这与使用EDTA淋洗时的效率相近;该复配淋洗剂淋洗Cr(Ⅵ)污染土壤时的动力学符合拟二级动力学方程;BCR实验结果表明,NTA和草酸复配淋洗后土壤中Cr的弱酸可提取态、可氧化态和残渣态组分含量分别从6346.67、4280.00、2387.67 mg·kg^(-1)下降至1161.67、433.35、741.00 mg·kg^(-1),可还原态组分从2746.67 mg·kg^(-1)上升至6016.67 mg·kg^(-1),污染土壤重金属迁移率下降。淋洗后土壤有机质含量从13.47%上升至30.56%,脲酶和脱氢酶活性分别从46.32、329.09μg·d^(-1)·g^(-1)降低至29.36、131.98μg·d^(-1)·g^(-1),土壤结构基本与原土一致。因此,NTA与草酸复配淋洗剂是一种高效且对土壤影响较小的淋洗剂。

Spatial distribution of chromium in soils contaminated by chromium-containing slag

To evaluate the metal chromium (Cr) contamination of soil at a chromium-containing slag site by ferrochromium production, the contaminated sites, under slag heap, in the vicinity of slag heap and arable soils near the outlet of sewer channel, and unpolluted site 5 km away from one ferroalloy plant in Hunan Province, China, were selected. The concentrations of total Cr and water soluble Cr in bulk soil samples and profile depth samples were determined. The results show that the soils in the vicinity of slag heap have the highest total Cr content followed by the soils under the slag heap and near the outlet of sewer channel of the factory. The mean concentrations of total Cr in the top soils at above three contaminated locations exceed the critical level of Secondary Environmental Quality Standard for Soil in China by 3.5, 5.4 and 1.8 times. In most Cr polluted soils, total Cr has a relative accumulation in soil depth of 40-60 cm, but this trend is not found in unpolluted soils. The average concentrations of water soluble Cr (Ⅵ) in top soils under slag heap and in the vicinity of slag heap are 176.9 times and 52.7 times higher than that in the uncontaminated soils, respectively. However, water soluble Cr (Ⅵ) contents in soils near sewer channel are all low and the values are close to that in the uncontaminated soils. Although water soluble Cr (Ⅵ) content in soil profiles decreases with soil depths, it in soils under slag heap maintains a high level even at a depth of 100-150 cm. The results imply that the transportation of Cr (Ⅵ) can result in a potential risk of groundwater system in this area.

Trace-Level Analysis of Hexavalent Chromium in Lake Sediment Samples Using Ion Chromatography Tandem Mass Spectrometry

The analysis of hexavalent chromium, Cr(VI), in soil and sediment samples has been predominantly carried out in materials containing elevated levels. Reliable analysis of trace-level of Cr(VI) in sediment samples remains challenging. Cr(VI) analyses with multipoint calibration and speciated isotope dilution (SID) adapted from U.S. EPA method 6800 were used to measure lower-level Cr(VI) on an ion chromatograph coupled with a tandem mass spectrometer (IC-MS/MS). Lake sediment samples were collected from various locations in Northern Ontario and Cr(VI) was extracted using both alkaline digestion and ethylene diaminetetraacetic acid (EDTA) extraction. Certified reference materials were extracted and analyzed by IC-MS/MS and UV-VIS detection. The SID-MS approach allowed for the quantification of Cr(VI) in samples with concentration levels below 0.5 μg.g-1 wet weight.

Detoxification of chromium-containing slag by Achromobacter sp.CH-1 and selective recovery of chromium

Based on the principle of bacterial leaching and bacterial metallurgy,a novel technology for the detoxification of chromium-containing slag by Achromobacter sp.CH-1 and chromium recovery was proposed.Strain CH-1 cell morphology before and after Cr(Ⅵ) reduction was observed with a scanning electron microscope(SEM),and the reduction product is found to adhere to terminals of CH-1 cells.Energy-dispersive X-ray(EDX) and electron paramagnetic resonance(EPR) analyses reveal that the main component of the reduction product is Cr(Ⅲ).Furthermore,small and large-scale demonstration projects reveal that Achromobacter sp.can be used to detoxify chromium-containing slag and to selectively recover chromium by using this novel technique.Chromium recovery rate increases with decreasing particle sizes of chromium-containing slag and slagheap height.Chromium recovery rates in 10 t/batch and 20 t/batch of on-site demonstration projects for chromium-containing slag detoxification are more than 90%.

Fluorescence sensor based on glutathione capped CdTe QDs for detection of Cr^3+ ions in vitamins

In this work,glutathione capped CdTe QDs(GSH-QDs)were prepared through a one-pot process and found to be quenched by Cr^3+,Ag^+and Cu^2+ions.Cr^3+and chromium(III)picolinate could be quantitatively measured after masking Cu^2+and Ag+ions by sulfide.Under optimal conditions,linear quenching was observed for Cr^3+in the ranges of 0–2.0M and the limit of detection was 3.0 nM.The recoveries for Cr^3+in vitamin supplements obtained were from 92.5%to 106%.The determination results of chromium(III)picolinate in vitamin supplement samples were compared to that obtained using flame atomic absorption spectrometry(FAAS)method,and the result showed good reliability.

Using Ferrous Ion for the Reductive Degradation of Hexavalent Chromium

This paper discusses the toxicity and mobility of chromium species. And it presents the extent and kinetics of reductive remediation of hexavalent chromium, Cr+ using ferrous ion, Fe2+. Molar ratios of 1:3 and 1:6 of Cr (VI) to Fe (II) were used. Integral method of data analysis showed reaction followed second-order kinetics with R square values near unity. Reaction was initially fast but with a rapid precipitation attributed to Cr (III)-Fe (III) in previous studies. This colloidal precipitate ultimately stops the reaction, which explains while conversion efficiency increases with increased molar ratio of Cr (VI) to Fe (II). The impact of pH was investigated by adjusting the Cr (VI)-Fe (II) medium to pH 2.78, 5.24, 7.00, 9.00 and 11.96 using predetermined drops of acid or base. Reaction was more rapid under alkaline conditions with higher extent of degradation consistent with previous research. In soil system, mass transfer limitation was hardly noticed as high extent of reduction was recorded relative to aqueous phase. The high solubility of Cr (VI) aided the release into the aqueous media for reduction by ferrous sulfate.