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1.
This work describes a laboratory study concerning the adsorption of isopropylxanthate ions onto modified zeolites particles. The separation of the loaded carrier and their removal, from aqueous solutions, was conducted by flocculation followed by dissolved air flotation, DAF. The zeolite employed was a natural sample (approximately 48% clinoptilolite and 30% mordenite) which was previously treated with sodium ions (activation) and modified with copper ions (Cu–Z) before the xanthate ions uptake. Adsorption capacities (qm) for Cu–Z were 0.34 meq g− 1 for the powdered form, and 1.12 meq g− 1 for the floc form. The adsorption capacity for the floc form appears to involve an enhanced electrostatic adsorption due to the positive sites on the floc surface. In all cases, the isopropylxanthate concentration in the treated water was found to be negligible (< 0.04 mg L− 1). The flotation technique showed to be a fast process, requires a low recycle ratio (20%) in air saturated water, and the treated water ended up with a very low residual turbidity (6.8 NTU). It is believed that this adsorption–flotation technique, here named adsorptive particulate flotation, using activated and modified natural zeolite has a high potential as an alternative for pollutants removal (copper and isopropylxanthate ions) from waste mining effluents.  相似文献   

2.
采用NaOH对围场地区天然沸石进行处理,采用X射线衍射仪、红外光谱仪、N_2吸附-脱附技术、扫描电子显微镜等对材料进行表征分析,采用水蒸气吸附法评价材料的亲水性,采用Cr~(3+)和Mn~(2+)评价材料的离子交换性能,探讨了碱处理对天然沸石的结构、亲水性和离子交换性能的影响及其机理。实验结果表明,围场地区天然沸石中主要含有斜发沸石、石英和伊利石;碱处理可降低天然沸石的硅铝比,且沸石的硅铝比随着碱处理浓度的提高而不断降低;碱处理对斜发沸石结构的影响较石英和伊利石更大;高浓度碱处理导致天然沸石的结构发生破坏,比表面积降低,孔体积提高;伴随着天然沸石硅铝比的降低,其亲水性和离子交换性能不断提高。  相似文献   

3.
The potential use of the immobilized microalgae (in Ca-alginate) of Chlamydomonas reinhardtii to remove Hg(II), Cd(II) and Pb(II) ions from aqueous solutions was evaluated using bare Ca-alginate bead as a control system. Ca-alginate beads containing immobilized microalgae were incubated for the uniform growth at 22 °C for 5 days. Effects of pH, temperature, initial concentration of metal ions and biosorbent dosages on the adsorption of Hg(II), Cd(II) and Pb(II) ions were studied. Adsorption of Hg(II), Cd(II) and Pb(II) ions on the immobilized microalgae showed highest values at around pH 5.0 to 6.0. The adsorption equilibrium was represented with Langmuir and Freundlich adsorption isotherms. The adsorption of these ions on the immobilized microalgae followed second-order kinetics and equilibrium was established in about 60 min. The temperature change in the range of 5–40 °C did not affect the adsorption capacities of the immobilized microalgae. The immobilized-algal systems can be regenerated using 2 M NaCl for Hg(II), Cd(II) and Pb(II) ions.  相似文献   

4.
Zeolites are known to possess valuable physiochemical properties such as adsorption, cation exchange, molecular sieving, and catalysis. In addition, zeolites are highly selective scavengers of a variety of heavy metals from liquid effluents through the process of ion exchange. The present study was performed to hydrothermally synthesize Na8[AlSiO4]6(OH)2·2H2O (also known as hydroxy sodalite hydrate). Due to its small aperture size, this material can be an ideal candidate for the separation of small molecules and ions from aquatic and gas mixtures. Synthetic zeolites offer many advantages over natural zeolites, such as higher ion affinity and adsorption capacity. Batch adsorption isotherm studies were conducted to evaluate the obtained adsorbent for the lead ion removal from aqueous media. Modeling lead ion adsorption using Langmuir and Freundlich isotherm expressions determined the capacity of the adsorbent. A removal efficiency of 98.1 % in a 3.0 g/l adsorbent/solution mixture with a maximum adsorption capacity of 153.8 mg/g was obtained. One potential application of the synthesized zeolite is for the lead removal in point-of-use treatment devices.  相似文献   

5.
Sorption of heavy metal cations (Pb(II), Cr(III), Cd(II), Ni(II)) from aqueous solutions on natural Na-clinoptilolite was studied using atomic absorption spectrometry (AAS) and FT-IR spectroscopy. It was found that the sorption capacity of clinoptilolite decreases in the following order: Pb(II) (22,600 mg/kg), Cr(III) (21,200 mg/kg), Cd(II) (10,400 mg/kg) and Ni(II) (6,200 mg/kg). In the FT-IR spectra of the samples, in the region of pseudolattice vibrations (500–800 cm–1), systematic changes connected with the type of cation and its concentration in the initial solution were observed. The proportions of ion exchange and chemisorption in the whole process of sorption were also estimated. It was found that the amount of cations sorbed on clinoptilolite depended on the concentrations and pH of the solutions used as well as on the contact time of zeolite-solution system. After 120 min of the reaction, despite the metal type, 90–100% of the total amount of cations were immobilized.  相似文献   

6.
This study deals with the use of the natural, low-cost sorbents bentonite and zeolite for the removal of lead from aqueous solutions. The mineral material is from large deposits of bentonite and zeolite that have been discovered recently in Iran. Experimental and modeling data from our kinetic and equilibrium investigations reveal that (1) the pseudo-second-order kinetic model gave the best fit, and (2) the Koble–Corrigan sorption model describes the interaction between Pb(II) and the two mineral materials better than the Freundlich and Langmuir models. However, the sorption of Pb(II) ions by zeolite and bentonite is complex and probably involves several mechanisms. The experimental data show that natural zeolite and bentonite used in this study exhibited a reasonable sorption capacity for Pb(II), and thus may be useful for the immobilization of Pb(II) from polluted sites.  相似文献   

7.
Adsorption of H2O, NH3 and C6H6 on H- and alkali metal-exchanged structures of mordenite and on corresponding cations on the smectite layer is investigated by ab initio density-functional calculations. Proton or an alkali metal cation compensates one Al/Si framework substitution and resides in the extra-framework position of zeolite or above flat smectite layer close to the Al/Si substitution. Pronounced similarities between zeolite and smectite are observed in changes of the adsorption energies and location of the external cation with changing character of the external cation. Calculated adsorption energies exhibit the following trend: E(NH3) > E(H2O) > E(C6H6). Because of looser contact with the framework, zeolitic cations are stronger adsorption centers and calculated adsorption energies of zeolites are by ~20–30% larger than cations of smectites. The highest adsorption energy is calculated for H-exchanged structures and down the group of alkali metal cations a decrease of the adsorption energy is observed. Deviations from the smooth variation of the adsorption energy are caused by: (1) formation of strong hydrogen bonds in H-exchanged structures, (2) adsorption induced migration of the external Li+ cation, and (3) steric hindrances of the flat C6H6 molecule adsorbed on the cation in the cage of zeolite.  相似文献   

8.
The adsorption capacity of seven organic wastes/by-products (slash pine, red gum and western cypress bark, composted green waste, prawn exoskeletons, spent brewery yeast and mill mud from a sugar mill) for transition metals were determined at two metal concentrations (10 and 100 mg L−1) and three equilibrium pH values (4.0, 6.0 and 8.0) in batch adsorption experiments. All tested materials indicate a positive affinity to adsorb metal cations from aqueous solution and spent yeast was the least effective. Adsorption generally increased with increasing pH and the order of selectivity of metals was: Cr3+ > Cu2+ > Pb2+ > Zn2+ ≥ Cd2+. For pine bark, compost, spent yeast and prawn shell, quantities of previously adsorbed Pb and Cd desorbed in 0.01 M NaNO3 electrolyte were negligible. However, 0.01 M HNO3, and more particularly 0.10 and 0.50 M HNO3 were effective at removing both adsorbed Pb and Cd. Using 0.10 M HNO3 as the regenerating agent, pine bark and compost maintained their Pb and Cd adsorption capacity over eight successive adsorption/regeneration cycles. For mill mud and prawn shell, there was a pronounced decrease in adsorption capacity after only one regeneration cycle. A subsidiary experiment confirmed that acid pre-treatment of the latter two materials appreciably reduced their Pb and Cd adsorption capacity. This was ascribed to the metal adsorption capacity of prawn shell and mill mud being partially attributable to their significant CaCO3 content and acid treatment induces dissolution of the CaCO3. It was shown that in relation to both adsorption capacity and desorption/regeneration capability, composted green waste showed the greatest potential.  相似文献   

9.
利用13X沸石分子筛净化含Pb~(2+)废水的实验研究   总被引：11，自引：0，他引：11  
马鸿文  肖万  陶红 《现代地质》2003,17(2):157-162
采用静态间歇法 ,实验研究了含Pb2 +废水的 pH值及吸附时间对 13X沸石分子筛吸附Pb2 +性能的影响 ,得出了最佳去除效果的优化条件为 :废水的 pH值接近中性 ,吸附时间 10min。通过吸附实验 ,确定了在Pb2 +初始浓度为 2 0mg/L的条件下 ,13X沸石对Pb2 +的吸附量为 2 1 4 2mg/g ,即每克沸石净化含Pb2 +废水的最大体积量约为 75 0mL。解析实验表明 ,加入沉淀剂 ,浓缩洗脱液中的Pb2 +即以PbS的形式生成沉淀 ,为回收金属铅提供了可能 ;13X沸石在循环使用 5次的条件下 ,对废水中Pb2 +的吸附率仍高达 98% ,重复使用性能良好。经处理后的净化水中Pb2 +的浓度小于 0 4mg/L ,显著低于国家废水排放标准GB8978 88的指标 ( 1 0mg/L)。 13X沸石对Pb2 +的主要吸附形式是离子交换和表面络合反应。  相似文献   

10.
用离子交换、酸和碱处理斜发沸石来提高它的吸水能力没有取得明显效果。测得的斜发沸石、丝光沸石吸附水的等温线具有非线性特征,但25℃的等温线在水蒸气分压高于2400Pa 时,斜发沸石、丝光沸石和有粘合剂的合成分子筛的吸水量随着分压的升高而增加。这是由于样品中含有粘土矿物产生水蒸气的毛细凝聚作用而引起的。根据沸石的吸附热和水的蒸发热,用沸石作为吸附剂和水作为工质能建立一个高效的沸石太阳能利用体系。  相似文献   

11.
An investigation was conducted into the Tertiary ignimbrite formations in the Romana area in NW Sardinia. Scanning electron microscopy–energy-dispersive spectrometry indicated the presence of clinoptilolite and subordinate smectite, quartz, mordenite and calcite. Laboratory analyses of representative samples collected from the deposit indicated a cation exchange capacity ranging from 85 to 135 mEq per 100 g. Ion exchange experiments conducted in flasks containing different initial cation concentrations and in columns supplied with solution having constant cation concentration, showed different selectivity towards the cations examined, in the order: NH4+> Pb2+> Cd2+> Cu2+> Zn2+> Mn2+> Ni2+. Compared to the untreated material, under the experimental conditions used and considering the eluate, and the Italian regulatory limits for discharge into surface waters, the zeolite treated with a 1-N NaCl solution yielded a 1.3–5-fold increase in the volume of treated water, depending on the cation examined. The experimental results obtained show that the cationic exchange properties of the zeolite rock from the Romana deposit are comparable with the average quality of zeolites currently imported into Italy from non-European countries.  相似文献   

12.
Inorganic elements analyses of Carapicuíba lake reveal that As, Cr, Pb and Mn are above the recommended drinking water standards. The mean total concentrations of toxic elements in surface water decrease in the order Mn > Cr > Pb > As. At elevated concentrations, toxic elements like Cr can accumulate in soils and enter the food chain, leading to serious health hazards and threatening the long-term sustainability of the local ecosystem. Absorbing materials has often been used to improve water quality. In this investigation three types of material were studied: the natural zeolite (mordenite); synthetic goethite and the powdered block carbon modified. The adsorption of Pb2+ and Mn2+ onto natural zeolite as a function of their concentrations was studied at 24°C by varying the metal concentration from 100 to 400 mg L−1 while keeping all other parameters constant. The low-cost zeolites removed Pb from water without any pretreatment at pH values <6. The maximum adsorption attained was as follows: Pb2+ 78.7% and Mn2+ 19.6%. The modified powdered block carbon effectively removed As(V) and Cr(VI) while goethite removed more chromate than arsenate in the pH range 5–6. Results of this study will be used to evaluate the application these materials for the treatment of the Carapicuíba lake’s water.  相似文献   

13.
Simultaneous competitive adsorption behavior of Cd, Cu, Pb and Zn onto nine soils with a wide physical–chemical characteristics from Eastern China was measured in batch experiments to assess the mobility and retention of these metals in soils. In the competitive adsorption system, adsorption isotherms for these metals on the soils exhibited significant differences in shape and in the amount adsorbed. As the applied concentration increased, Cu and Pb adsorption increased, while Cd and Zn adsorption decreased. Competition among heavy metals is very strong in acid soils with lower capacity to adsorb metal cations. Distribution coefficients (K dmedium) for each metal and soil were calculated. The highest K dmedium value was found for Pb and followed by Cu. However, low K dmedium values were shown for Zn and Cd. On the basis of the K dmedium values, the selectivity sequence of the metal adsorption is Pb > Cu > Zn > Cd and Pb > Cu > Cd > Zn. The adsorption sequence of nine soils was deduced from the joint distribution coefficients (K dΣmedium). This indicated that acid soils with low pH value had lower adsorption capacity for heavy metals, resulting in much higher risk of heavy metal pollution. The sum of adsorbed heavy metals on the soils could well described using the Langmuir equation. The maximum adsorption capacity (Q m) of soils ranged from 32.57 to 90.09 mmol kg−1. Highly significant positive correlations were found between the K dΣmedium and Q m of the metals and pH value and cation exchange capacity (CEC) of soil, suggesting that soil pH and CEC were key factors controlling the solubility and mobility of the metals in soils.  相似文献   

14.
高岭石对重金属离子的吸附机理及其溶液的pH条件   总被引：14，自引：0，他引：14  
高岭石对Cu^2+,Pb^2+离子的吸附实验及高岭石的溶解实验表明,高岭石对重金属离子的吸附有别于石英单一表面配位模式,离子交换和表面配位模式并存,并随溶液pH由酸性往碱性的变化发生规律性的演替：pH<6.5时主要表现为外圈层配位的离子交换吸附,且在pH<4时由于受到高岭石表层中铝的高溶出及溶液中较高离子强度的影响,高岭石对Cu^2+,Pb^2+离子的吸附率较低,pH为5～6时由于高岭石端面的荷电性为近中性,吸附率则有明显的提升并且表现为一个吸附平台;pH>6.5时离子交换和表面配位均为重要吸附机制,pH再升高时沉淀机制则起着重要作用。研究表明,pH调控高岭石-水界面溶解与质子化-去质子化反应过程,并影响着Cu^2+,Pb^2+离子的吸附行为。最后采用Sverjensky(1993)表面配位的物理模型对吸附结果作了描述。  相似文献   

15.
The clinoptilolite rich zeolite from Bigadiç which was formed from alteration of volcanic glass were treated with acidic (HCl, H3BO3, H3PO4), alkaline (KOH, NaOH) solutions. Hydrothermally treated and untreated samples were heat treated at 400, 550 and 700°C. XRD, ICP-MS and N2 gas adsorption were used for physicochemical characterization of zeolites. Considering the Si/Al > 4 and Na+K/Ca+Mg < 1 ratios, zeolite sample is included to earth alkali clinoptilolite class (Heu II) which is also revealed by thermal treatments. Since zeolite structure contains low alkalies it was at collapsed 550°C. The removal of oxide elements efficiency of acids and alkalies were in the order of HCl > H3PO4 > HBO3 > KOH > NaOH. XRD analysis indicated that the structure of zeolite was not altered with acids and alkali treatments. The structure of zeolite treated with HCl and other acids started to deform at 400 and 550°C respectively. In treatment with HCl, Si/Al ratio increases with significant a decrease in K content which resulted in a decrease in the heat stability of zeolite. No change was observed in the structure and thermal stability of clinoptilolite after alkali treatments. The fact that although significant amount of Na is removed with H3BO3 acid and Na is increased with NaOH but the thermal stability remains the same indicates that Na cation is not an important parameter as much as K. HCl and H3PO4 acid treatments increased the surface area depending on the dissolution of amorphous material and H3PO4 was found to be more effective. However, the total pore size decreased due to formation of new micropores.  相似文献   

16.
天然沸石吸附性能与阳离子组分之间的关系   总被引：7，自引：0，他引：7  
吸附性能是沸石矿物的重要特性之一，也是相关领域应用的重要依据。以嫩江、海林和穆棱三大沸石矿床为例，通过对天然沸石矿的化学成分、沸石类型、矿石品位（CEC值）、比表面积及吸附性能的系统研究与对比分析，总结天然沸石矿附吸性能差异变化规律与原因。研究表明，天然沸石对气体CO2、H2S、SO2、NO2和气态H2O的吸附容量均与其（CaO MgO)/(Na2O K2O)比值之间呈正相关性关系，富二价阳离子组分者吸附容量大，富一价阳离子组分者吸附容量较小。据此，可作为天然沸石矿吸附性能预测评价的重要依据。  相似文献   

17.
Recent studies suggest that siderophores form stable complexes with divalent metals and affect their mobility. In this work, effects of trihydroxamate microbial siderophores and desferrioxamine-B (DFOB) on Pb(II), Zn(II), and Cd(II) sorption by two kinds of synthesized zeolites (13X and Na?CY) as a function of pH were investigated. Results showed that 13X zeolite has a higher sorption affinity for studied metals than Na?CY. DFOB strongly affected metal sorption on both zeolites. Under slightly acidic to neutral condition, DFOB increased the metal sorption on zeolites due to the sorption of positively charged heavy metal?CDFOB complexes. Whereas by increasing pH (>7), the mobilizing effect of DFOB was observed for Pb, Zn, and Cd. DFOB drastically decreased (80?%) Zn sorption in alkaline condition. As a result, siderophores can weaken the treatment efficiency of zeolites and increase the bioavailability of metals in soils. Surface complexation modeling revealed that the effects of DFOB on metal sorption by 13X and Na?CY zeolites can be explained by the differences in their surface charge. In general, the result shows the influence of DFOB on metal sorption by zeolites over the pH range 4?C9 and decreasing in the sequence Zn?>?Pb?>?Cd.  相似文献   

18.
Activated carbons have been proven to be effective adsorbents for the removal of Pb (II) and Zn (II) dissolved in aqueous media. The study of adsorption of Pb (II) and Zn (II) on two different size fractions from a composite coal sample of Maghara coal mine, C63 (63–125 μm) and C250 (125–250 μm) is presented in this paper. C63 and C250 were treated in water solutions of 50 mM lead and zinc acetates. X-ray photoelectron spectroscopy (XPS) was used to characterize the starting and treated coal surfaces. The high surface area and surface functional groups (carboxy and phenolic) enable activated bituminous coal of Maghara to act as efficient adsorbents for removing dissolved Pb (II) and Zn (II) in alkaline medium.  相似文献   

19.
Amorphous tin(VI) hydrogen phosphate (ATHP) was synthesized using the liquid phase precipitation method and served as an adsorbent to remove Pb(II), Cu(II), and Zn(II) from aqueous solutions. The ATHP was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption techniques. Adsorption properties were evaluated as a function of pH, reaction time, concentration of reactants, and salinity. Their equilibrium adsorption data were modeled using Freundlich, Langmuir, and Dubinin–Kaganer–Radushkevich isotherms, respectively. The results revealed that adsorption equilibrium reached within 180 min. ATHP indicated good adsorption even below the pHZPC, and best adsorption at pH 5 for Pb(II) and Cu(II) and at pH 5.5 for Zn(II) was observed. Equilibrium data fitted better to the Langmuir model for Pb(II) and Cu(II) and fitted better to the Freundlich model for Zn(II). The saturated adsorption capacities deduced from the Langmuir model were 2.425, 1.801, and 0.600 mmol/g for Cu(II), Pb(II), and Zn(II), respectively, indicating an adsorption affinity order of Cu > Pb > Zn. There is a negative correlation between the concentration of NaCl and adsorption capacity of ATHP, yet ATHP still exhibited excellent adsorption having an adsorption capacity of 19.35, 15.16, 6.425 mg/g when the concentration of NaCl was 0.6 mol/L. The free energy (E) was 12.33, 10.70, and 14.74 kJ/mol for Pb(II), Cu(II), and Zn(II), respectively. An adsorption mechanism based on ion exchange between heavy metal ions and H+ in the ATHP is proposed. Furthermore, the used ATHP was regenerated by HCl solution and the adsorbent was used repeatedly.  相似文献   

20.
Part I: Chemical and structural effects of cation-exchange Attempts were made to prepare, by appropriate exchange methods, homoionic samples of phillipsite, gismondite, harmotome, chabazite and gmelinite containing Ba, Ca, K, Na or Li-ions. Powdered natural samples were used as starting material. All samples were analysed chemically before and after the cation exchange. The results of the analyses demonstrated clearly that the „exchange capacity“ depends on the method used, the structure of the zeolite and the nature of the cation involved in the exchange. The analyses also disclosed the important fact that the ratio in Mole % of the sum of exchangeable cations: Al2O3 of the natural and of the exchanged samples is generally <1, and can be as low as 0.74. Examples are presented where cation exchange results in a substantial change in the framework structure. Part II: Dehydration behavior and structural changes at elevated temperatures Samples of the natural zeolites mentioned above, and of some of their cation exchange products were dehydrated in air of controlled humidity up to 600° C. The slopes of the weight loss curves of chabazite and gmelinite are continuous, whereas those of phillipsite, gismondite, and harmotome show a discontinuity between 90–190° C, indicating the existence of two discrete hydrated phases for each of these zeolites. High temperature x-ray studies of powdered samples confirmed this result. The high temperature hydrates of phillipsite, gismondite, and harmotome persist reversibly up to approximately 230° C. At higher temperatures, new probably anhydrous phases form. Gmelinite, at 240° C, transforms irreversibly to anhydrous gmelinite which is stable up to >700° C. The transition was studied by single crystal techniques. The chabazite structure remains intact up to >700° C. The absolute water content and the dehydration behavoir of the zeolites investigated are primarily dependent on the nature of the exchange cation. The structural changes at elevated temperatures are determined by the silica alumina framework. Part III: Hydrothermal stability* and interconversions The stability of phillipsite, gismondite, harmotome, chabazite, gmelinite, their exchange products, and of the synthetic Linde zeolites Faujasite and Type A was studied in the temperature range between 150° and 350° C at a constant pressure of 1000 atm of H2O. Between 180° and 260° C all examined Sodium and Calcium zeolites were metastable with respect to analcite (wairakite**). Phillipsite and sodium-rich zeolites generally converted to analcite (wairakite) directly. Caex-chabazite and Caex-gmelinite formed phillipsite, whereas Ca-gismondite and Ca-Type A formed natrolite as intermediate phases. Li-gmelinite converted to bikitaite***. (This represents the first successful preparation of natrolite and bikitaite. Attempts starting from gels or glasses have been unsuccessful so far.) Ba-gmelinite converted to harmotome at 250° C. This transformation was studied microscopically and by single crystal x-ray techniques. The transformations that take place on hydrothermal treatment as well as on low temperature cation exchange of zeolites (see Part I) indicate that, unlike the conditions prevailing in clays, the type of cation and the ratio of cations in the exchange positions have an important influence on the structure of the silicaalumina-oxygen framework. This explains two phenomena: The lack of solid solution between two potential end members of a solid solution series (for instance phillipsite-gismondite), and the large number of different zeolites in nature, where a great variety in the ratios of available alkali and alkaline earths ions must be expected. Any classification of zeolites becomes still more difficult in view of the fact that conversions among different groups (chabazite → phillipsite) and different structures (three-dimensional framework → fibre) take place relatively easily. Contribution No. 59–92, College of Mineral Industries, The Pennsylvania State University, University Park, Pennsylvania.  相似文献   

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