Isotherms and thermodynamics for the sorption of heavy metal ions onto functionalized sporopollenin

In this study, sporopollenin of Lycopodium clavatum spores was used for the sorption experiment. Glutaraldehyde (GA) immobilized sporopollenin (Sp), is employed as a sorbent in sorption of selected heavy metal ions. The sorbent prepared by sequential treatment of sporopollenin by silanazing compound and glutaraldehyde is suggested for sorption of Cu(II), Zn(II) and Co(II) from aqueous solutions. Experimental conditions for effective sorption of heavy metal ions were optimized with respect to different experimental parameters using batch method in detail. Optimum pH range of Cu(II) has occurred at pH ≥ 5.5 and Zn(II), Co(II) at pH ≥ 5.0, for the batch method. All of the metal ions can be desorbed with 10 cm³ of 0.5 mol dm⁻³ of ethylenediaminetetraacetic acid (EDTA) solution. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm equations were applied to the experimental data. Thermodynamic parameters such as free energy (ΔG^o), entropy (ΔS^o) and enthalpy (ΔH^o) were also calculated from the sorption results used to explain the mechanism of the sorption. The results indicated that this sorbent is successfully employed in the separation of trace Cu(II), Zn(II) and Co(II) from the aqueous solutions.     

Isotherms and thermodynamics by linear and non-linear regression analysis for the sorption of methylene blue onto activated carbon: comparison of various error functions

A comparison of linear and non-linear regression method in selecting the optimum isotherm was made to the experimental equilibrium data of methylene blue sorption by activated carbon. The r2 was used to select the best fit linear theoretical isotherm. In the case of non-linear regression method, six error functions, namely coefficient of determination (r2), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), average relative error (ARE), sum of the errors squared (ERRSQ) and sum of the absolute errors (EABS) were used to predict the parameters involved in the two and three parameter isotherms and also to predict the optimum isotherm. For two parameter isotherm, MPSD was found to be the best error function in minimizing the error distribution between the experimental equilibrium data and predicted isotherms. In the case of three parameter isotherm, r2 was found to be the best error function to minimize the error distribution structure between experimental equilibrium data and theoretical isotherms. The present study showed that the size of the error function alone is not a deciding factor to choose the optimum isotherm. In addition to the size of error function, the theory behind the predicted isotherm should be verified with the help of experimental data while selecting the optimum isotherm. A coefficient of non-determination, K2 was explained and was found to be very useful in identifying the best error function while selecting the optimum isotherm.     

Adsorption characteristics of heavy metal ions onto a low cost biopolymeric sorbent from aqueous solutions

In this study, the adsorption conditions of Cu(II), Pb(II) and Cd(II) metal ions onto sporopollenin have been studied. The different variables effecting the sorption capacity such as pH of the solution, adsorption time, initial metal ion concentration and temperature have been investigated. Adsorption isotherms correlated well with the Freundlich type adsorption isotherm and adsorption capacities were found to be 0.0195, 0.0411 and 0.0146 mmol g(-1) for Cu(II), Pb(II) and Cd(II) metal ions, respectively. Experimental data were also evaluated to find out kinetic characteristics of the adsorption process. Adsorption processes for three target heavy metal ions were found to follow pseudo-second order type adsorption kinetics. Intraparticle diffusion was found to take part in adsorption processes but it could not be accepted as the primary rate-determining step. The mean free energies of adsorption (E) were found to be between 8 and 16 kJ mol(-1) for the metal ions studied and therefore adsorption mechanism for the adsorbent was explained as an ion-exchange process. But it was observed that chelating effect is also playing an important role in the adsorption of metal ions onto sporopollenin. Thermodynamic parameters, DeltaH degrees , DeltaS degrees and DeltaG degrees were also calculated from graphical interpretation of the experimental data. Standard heats of adsorption (DeltaH degrees ) were found to be endothermic and DeltaS degrees values were calculated to be positive for the adsorption of Cu(II), Pb(II) and Cd(II) ions onto the adsorbent. Negative DeltaG degrees values indicated that adsorption process for these three metal ions onto sporopollenin is spontaneous.     

Preparation of iminodiacetic acid functionalized multi-walled carbon nanotubes and its application as sorbent for separation and preconcentration of heavy metal ions

In this paper, a novel material was prepared with functionalizing multi-walled carbon nanotubes (MWCNTs) using iminodiacetic acid (IDA) and characterized by FT-IR. Isotherm and kinetics of adsorption were studied and the experimental data fitted the Langmuir model and pseudo-second-order equation very well. An on-line method for simultaneous determination of trace V (V), Cr (VI), Pb (II), Cd (II), Co (II), Cu (II) and As (III) in biological samples was developed using this material as sorbent coupled with inductively coupled plasma mass spectrometry (ICP-MS). A series of experimental parameters, including sample pH, sample flow rate and loading time, eluting solution and the effect of interfering ions have been investigated systematically. Under the optimum experimental conditions, the enrichment factors for above metal ions were ranged from 66 to 101. Detection limit (3 s) was achieved at 1.3, 1.2, 0.70, 0.40, 2.5, 3.4, 0.79 ng L(-1), respectively. At the 1.0 μg L(-1) level, the precision (RSD, %) for 11 replicate measurements was from 1.0 to 4.0. In spiked biological samples, good recoveries (n=3) were obtained in the range of 90-110%. These results had proved that the proposed method was with good accuracy and could be applied to the analysis of trace metal ions in biological samples.     

碳纳米管的表征和重金属阴离子吸附性能

通过化学修饰使碳纳米管表面富含各种氧功能团,利用XPS和TPD方法表征了碳纳米管表面氧功能团的化学物理特性.研究发现:对比于未修饰的碳纳米管,化学修饰后的碳纳米管对高毒性的铬酸根阴离子有很强的吸附能力;其优异的吸附能力归结于金属阴离子与纳米管表面氧功能团的相互作用.研究指出碳纳米管可以作为替代吸附材料用于处理废水中重金...     

Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions

Surface properties of montmorillonite (MMT) and its adsorption characteristics for heavy metals have been investigated with nickel and copper as sorbate from aqueous solutions. Employing the potentiometric and mass titration techniques in batch experimental methods, the point of zero charge (PZC) and point of zero net proton charge (PZNPC) of MMT edges at different ionic strengths present pH_PZC and pH_PZNPC to be 3.4 ± 0.2. A crossing point was observed for the proton adsorption vs. pH curves at different ionic strengths of KCl electrolyte and in investigating MMT remediation potentialities as sorbent for heavy metals polluted waters, the effects of heavy metal concentration, pH, MMT dosage, reaction time and temperature for Cu²⁺ and Ni²⁺ uptake were studied. The sorption of metal ions by MMT was pH dependent and the adsorption kinetics revealed sorption rate could be well fitted by the pseudo-second-order rate model. The data according to mass transfer and intraparticle diffusion models confirmed diffusion of solutes inside the clay particles as the rate-controlling step and more important for the adsorption rate than the external mass transfer. Adsorption isotherms showed that the uptake of Cu²⁺ and Ni²⁺ could be described by the Langmuir model and from calculations on thermodynamic parameters, the positive ΔG° values at different temperatures suggest that the sorption of both metal ions were non-spontaneous. Change in enthalpy (ΔH°) for Ni²⁺ and Cu²⁺ were 28.9 and 13.27 kJ/mol K respectively, hence an endothermic diffusion process, as ion uptake increased with increase in temperature. Values of ΔS° indicate low randomness at the solid/solution interface during the uptake of both Cu²⁺ and Ni²⁺ by MMT. Montmorillonite has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater.     

RG090/03+04型组合式空压机轴承温度高的解决方法

简介RG090/03+04型组合式空压机的结构、运行原理及润滑系统流程。根据该齿轮型压缩机在生产运行中出现轴承温度高的故障现象,对压缩机轴承以及润滑系统进行相应的处理和改进,在处理过程中不断摸索并积累了大量经验。通过借鉴处理相关油膜轴承的经验,加工各轴承瓦片的旋出侧,最终解决了困扰多年的轴承温度高问题。     

改性木质素磺酸盐制备及吸附重金属离子研究

工业废水中的铅离子和镉离子对人类健康构成重大威胁。为开发一种高效绿色的吸附剂,本文运用自由基聚合法合成了改性木质素磺酸盐复合材料(LC),同时将改性木质素磺酸盐复合材料应用于处理Pb^{2+和Cd2+。采用傅里叶红外光谱仪、扫描电镜以及热分析仪对改性木质素磺酸盐复合材料进行表征,研究了pH、吸附剂用量、时间、质量浓度4种因素对改性木质素磺酸盐复合材料吸附性能的影响,并在此基础上探究了改性木质素磺酸盐复合材料的吸附动力学和等温线模型。研究表明,改性木质素磺酸盐复合材料具有多孔的结构,且热稳定性高。当pH=5时,改性木质素磺酸盐复合材料对Pb2+}的吸附容量为345 mg/g,对Cd²⁺的吸附容量为278 mg/g。针对动力学和等温线模型的研究表明,改性木质素磺酸盐复合材料对Pb^{2+和Cd2+的吸附主要由静电吸引和化学螯合主导。此外,经过5次吸附-解吸实验后,改性木质素磺酸盐复合材料对Pb2+和Cd2+的吸附效率仍可达84%以上。改性木质素磺酸盐复合材料具有高效、绿色的吸附性能,能够有效地处理Pb2+和Cd2+}。     

石墨烯及其复合材料对水中重金属离子的吸附性能研究

石墨烯作为一种新型的碳纳米材料,具有独特的物理化学性质如高的机械强度、良好的稳定性、超大的比表面积及极强的表面化学活性等,使得石墨烯成为一种得天独厚的吸附材料。综述了石墨烯及其复合材料的制备方法,并对其在去除水中重金属离子的研究进展与吸附机理方面进行了综述,最后对石墨烯及其复合材料的后续研究方向进行了展望。     

胶束强化超滤技术在重金属废水处理中的研究进展

胶束强化超滤技术(MEUF)作为一种新兴的水处理技术,在重金属废水净化方面有着较好的应用前景。本文通过总结前人的研究结果,综合讨论了影响金属离子截留效果的各个因素,为优化MEUF提出了一些建议。并就当前采用胶束强化超滤法处理金属离子技术的最新发展与表面活性剂的循环再利用作了简要的介绍。     

一种新型纳米清净剂产品的胶体结构与性能关系研究

介绍一种碱值达到350mgKOH/g以上的纳米级高碱度混合基质型金属清净剂的胶体结构与其性能之间的关系。研究中采用红外光谱、热重分析法等表征了产品的基本结构及产品中碱性组分碳酸盐的晶型结构,通过冷冻蚀刻电镜法观察了含碳酸盐的胶体粒子结构及粒度分布情况,应用四球试验法等考察了产品的极压抗磨性能,结果表明,产品的高温清净性及氧化安定性均有显著改善,抗摩擦磨损性能也有很大提高。添加剂中碳酸盐含量及胶体粒子的组成结构是影响产品性能的重要因素。产品中胶体粒子分布越均匀,其胶体稳定性越好。     

Effect of the heat treatment on the morphology and sorption ability to metal ions of metallurgical slag

The effect of the phase composition of metallurgical slag on its ability to adsorb copper ions from aqueous solutions has been investigated. Granulated slag samples, mainly amorphous, have been pre-heated at 400, 600, 800 and 1000°C, then cooled slowly in the absence of moisture. Above 600°C crystallisation of a mineral gehlenite of the melilite group and of calcium silicates of the Ca₂SiO₄ structure type begins. The appearance of crystalline phases facilitates exchange and adsorption and the amount of copper adsorbed per a gram slag increasing about 2–4 times. The important role of the crystalline phases in the slag permits the synthesis of new materials adsorbing heavy metal ions on the basis of controlled liquid slag crystallization.     

PAAS高吸水树脂对重金属离子盐溶液的吸液及吸附性能

用聚丙烯酸高吸水树脂(PAAS)研究了单一和混合重金属离子硝酸盐溶液中的吸液和吸附性能.在Pb2 、Ni2 、Cd2 、Zn2 、Mn2 和Cu2 的一、二元溶液中,PAAS的吸液倍率随时间延长而增加,约50min达吸液平衡,一元金属离子溶液中平衡吸液倍率为160～190g/g,而对Cr3 溶液,最大为120g/g;二元金属离子混合溶液中平衡吸液倍率都在150～180g/g之间,有Cr3 存在时平衡吸液倍率最小.对上述单一金属离子的吸附量随时间延长而增加,约180min达吸附平衡,平衡吸附量顺序为:Pb2 ＞Cd2 ＞Ni2 ＞Cu2 ＞Zn2 ＞Mn2 ＞Cr3 .对二元混合金属离子溶液,吸附量随时间增加而增加,30min后逐渐变慢,约70min后达吸附平衡.     

Multi-element coprecipitation for separation and enrichment of heavy metal ions for their flame atomic absorption spectrometric determinations

A preconcentration-separation technique for lead(II), cadmium(II), chromium(III), nickel(II) and manganese(II) ions has been established. The procedure is based on coprecipitation of these ions by the aid of Cu(II)-dibenzyldithiocarbamate precipitate. The precipitate was dissolved in 0.5 mL of concentrated HNO(3), and made up to 5 mL with distilled water. The heavy metals were determined by flame atomic absorption spectrometer. The effects of analytical parameters like pH, amounts of reagents, sample volume, etc. on the recoveries of heavy metals were investigated. The influences of matrix ions were also examined. The detection limits for the heavy metals based on 3 sigma (N=21) were found in the range of 0.34-0.87 microg L(-1). In order to validate the proposed method, two certified reference materials of NIST SRM 2711 Montana soil and NIST SRM 1515 Apple leaves were analyzed with satisfactory results. The proposed method was applied for the determination of lead, cadmium, chromium, nickel and manganese in environmental samples.     

高产量制备石墨烯及其优异的重金属离子检测性能

以氧化石墨的高温膨胀为基础,研发了一种简便经济的高产量制备石墨烯的工艺,考察了制备得到的石墨烯对痕量重金属离子的检测性能,检测离子包括Cu2+、Pb2+和Cd2+.所制薄层石墨烯存在部分结构缺陷和残余羟基官能团,电化学检测结果表明,这种结构的石墨烯在检测液相中重金属离子的过程中表现出了很好的性质,尤其是对铅离子的检测限...     

Investigation of the stability of hardened slag paste for the stabilization/solidification of wastes containing heavy metal ions

We have studied the effect of chromium ions and lead ions on the chemical stability of hardened slag paste with toxic wastes during the stabilization/solidification process. The influences of Cr and Pb ions on the hydration of slag were also investigated. Sodium silicate (Na(2)SiO(3)), 5 wt.% of slag, was used as an alkali activator for slag hydration. The physical stability of hardened paste containing partial replacement of slag with fly ash and gypsum was also examined.When gypsum was added to slag, the compressive strength of hardened slag paste developed, accompanying the activation of alumino-ferrite-tricalciumsulfate (Al(2)O(3)-Fe(2)O(3)-3CaSO(4), AFt) and alumino-ferrite-monocalciumsulfate (Al(2)O(3)-Fe(2)O(3)-CaSO(4), AFm) phase generation. Those phases caused densification of the microstructure. Concurrently, the leaching amount of heavy metal ions was decreased. When fly ash was added to slag, the compressive strength increased and the leaching amount decreased with both active formation of aluminate hydrates and ion substitution. Lead ions were mostly stabilized through physical encapsulation by the hardened slag paste's hydrate matrix. In the case of chromium ions, we observed that it was mainly solidified through the formation of a substitutional solid solution with aluminum atoms in the structure of aluminate hydrates.     

PAM/SiO2磺甲基化改性及吸附重金属离子研究

以正硅酸乙酯为前驱体,采用原位溶胶-凝胶方法,合成聚丙烯酰胺/二氧化硅(PAM/SiO2)复合树脂;以甲醛和亚硫酸氢钠为磺甲基化试剂对PAM/SiO2进行磺甲基化改性,制得改性PAM/SiO2复合吸附树脂(SPAM)。考察正硅酸乙酯用量、离子浓度、树脂用量、吸附时间等因素对SPAM吸附重金属性能的影响,通过红外光谱(IR)和扫描电子显微镜(SEM)表征SPAM的结构。结果表明,SPAM对铅离子的吸附容量为2.5mmol/g,吸附率为96.3%,对铜离子的吸附容量1.5mmol/g,吸附率为68.3%。