Readily dispersible clay and its role in the mobility of transition metals Cd2+, Cu2+ and Zn2+ in an alkaline alluvial soil     

Mohamed Rashad  Essam Elnaggar  Faiz F. Assaad 《Environmental Earth Sciences》2014,71(9):3855-3864

Readily dispersible clay is the part of the clay fraction in soils that potentially disperses in water when a small amount of mechanical energy is applied to soil. Column and batch experiments were conducted to identify the effect of readily dispersible clay on the mobility of some metal ions in a disturbed soil sample. The clay fraction (<0.002 mm) was separated from an alkaline Vertisol from the Nile River Delta. X-ray diffraction technique was used to identify minerals present in the clay fraction. Clay suspensions and deionized H₂O solutions of Cd²⁺, Cu²⁺, and Zn²⁺ were prepared and used as influents in soil columns. Adsorption capability of the studied soil among the three metal ions was investigated. The results showed high adsorption capacity of Cd²⁺, Cu²⁺, but not Zn²⁺ for the studied soil. Cu²⁺ was the highest adsorbed metal by soil and its sorption increased at small equilibrium concentrations compared with Cd²⁺ and Zn²⁺. For the three studied metal ions, Langmuir model represented the best fit to the adsorption data. The concentration of Zn²⁺ and Cd²⁺ in leachates increased as the leaching solution volume increased, while Cu²⁺ showed a homogeneous distribution throughout the soil column. According to DTPA extractable metals, Zn²⁺ was appeared at greater depths than Cd²⁺, while Cu²⁺ had homogeneous distribution through the soil column.  相似文献   

Wien effect of Cd/Zn on soil clay fraction and their interaction     

Tingting Fan  Chengbao Li  Juan Gao  Dongmei Zhou  Marcelo Eduardo Alves  Yujun Wang 《Geochemical transactions》2018,19(1):5

  相似文献   

Biosorption characteristics of heavy metals (Ni2+, Zn2+, Cd2+, Pb2+) from aqueous solution by Hizikia fusiformis     

Woo-Seok Shin  Young-Kee Kim 《Environmental Earth Sciences》2014,71(9):4107-4114

Heavy metal ions (Pb²⁺, Cd²⁺, Ni²⁺, and Zn²⁺) were biosorbed by brown seaweed (Hizikia fusiformis), which was collected from Jeju Island of South Korea. The metal adsorption capacity of H. fusiformis improved significantly by washing with water or by base or acid treatments. The maximum sorption by NaOH-pretreated biomass was observed near a slightly acidic pH (pH 4?6) for Pb²⁺, Cd²⁺, Ni²⁺, and Zn²⁺. This result suggests that the treatment of H. fusiformis biomass with NaOH helped increase the functional forms of carboxylate ester units. Kinetic data showed that the biosorption occurred rapidly during the first 60 min, and most of the heavy metals were bound to the seaweed within 180 min. The maximum metal adsorption capacities assumed by a Langmuir model were on the order of Pb²⁺ > Cd²⁺ > Ni²⁺ > Zn²⁺. Equilibrium adsorption data for the heavy metal ions could fit well in the Langmuir model with regression coefficients R ² > 0.97.  相似文献   

Complexation of cadmium to sulfur and oxygen functional groups in an organic soil   总被引：7，自引：0，他引：7  

Torbjörn Karlsson  Erik Björn 《Geochimica et cosmochimica acta》2007,71(3):604-614

Cadmium (Cd) is a toxic trace element and due to human activities soils and waters are contaminated by Cd both on a local and global scale. It is widely accepted that chemical interactions with functional groups of natural organic matter (NOM) is vital for the bioavailability and mobility of trace elements. In this study the binding strength of cadmium (Cd) to soil organic matter (SOM) was determined in an organic (49% organic C) soil as a function of reaction time, pH and Cd concentration. In experiments conducted at native Cd concentrations in soil (0.23 μg g⁻¹ dry soil), halides (Cl, Br) were used as competing ligands to functional groups in SOM. The concentration of Cd in the aqueous phase was determined by isotope-dilution (ID) inductively-coupled-plasma-mass-spectrometry (ICP-MS), and the activity of Cd²⁺ was calculated from the well-established Cd-halide constants. At higher Cd loading (500-54,000 μg g⁻¹), the Cd²⁺ activity was directly determined by an ion-selective electrode (ISE). On the basis of results from extended X-ray absorption fine structure (EXAFS) spectroscopy, a model with one thiolate group (RS⁻) was used to describe the complexation (Cd²⁺ + RS⁻ ? CdSR⁺; log K_CdSR) at native Cd concentrations. The concentration of thiols (RSH; 0.047 mol kg⁻¹ C) was independently determined by X-ray absorption near-edge structure (XANES) spectroscopy. Log K_CdSR values of 11.2-11.6 (pK_a for RSH = 9.96), determined in the pH range 3.1-4.6, compare favorably with stability constants for the association between Cd and well-defined thiolates like glutathione. In the concentration range 500-54,000 μg Cd g⁻¹, a model consisting of one thiolate and one carboxylate (RCOO⁻) gave the best fit to data, indicating an increasing role for RCOOH groups as RSH groups become saturated. The determined log K_CdOOCR of 3.2 (Cd²⁺ +  RCOO⁻ ? CdOOCR⁺; log K_CdOOCR; pK_a for RCOOH = 4.5) is in accordance with stability constants determined for the association between Cd and well-defined carboxylates. Given a concentration of reduced sulfur groups of 0.2% or higher in NOM, we conclude that the complexation to organic RSH groups may control the speciation of Cd in soils, and most likely also in surface waters, with a total concentration less than 5 mg Cd g⁻¹ organic C.  相似文献   

Soil heavy-metal speciation and wheat phytotoxicity in the vicinity of an abandoned lead–zinc mine in Shangyu City,eastern China     

Yanshan Cui  Xin Du 《Environmental Earth Sciences》2011,62(2):257-264

Sixteen soil samples were collected from the vicinity of an abandoned lead–zinc mine in Shangyu City, eastern China, and the heavy-metal speciation and wheat phytotoxicity in the soils were studied. The results showed that the concentrations of free Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were highly variable and ranged from <0.01 to 0.32, 0.06 to 10.62, <0.01 to 1.40 and 0.02 to 37.10 μmol l⁻¹, respectively. The concentrations of soluble Cu, Zn, Cd and Pb ranged from 0.38 to 3.24, 0.72 to 78.74, <0.01 to 1.95 and 0.15 to 639.34 μmol l⁻¹, respectively. The general trend of mean solid/liquid partition coefficient and percentage of free metal ion to total soluble metal concentration were Cu > Pb > Zn > Cd and Cd > Zn > Cu > Pb, respectively. Stepwise multiple linear regression with pH, log(total metal) and log(organic matter) showed that log(total metal) was an important factor that controlled log(free metal ion) and log(soluble metal). Of the variability in log(free Cu²⁺), log(free Cd²⁺) and log(free Pb²⁺), 55.2, 58.6 and 64.3% could be explained by log(total Cu), log(total Cd) and log(total Pb) alone, respectively. Of the variability in log(soluble Cu) and log(soluble Cd), 77.1 and 72.5% could be explained by log(total Cu) and log(total Cd) alone, respectively. Wheat root length was controlled by the various metals with different free and soluble concentrations, and 99.2% of the variability in root length could be explained by concentrations of free and soluble Pb, soluble Cu and total Zn in the soils.  相似文献   

Effect of multifactors interaction on competitive adsorption of Zn<Superscript>2+</Superscript> and Cd<Superscript>2+</Superscript> by response surface methodology     

Zhenru Niu  Qiang Xue  Shuo Qi  Ying Guo  Honghan Chen 《Environmental Earth Sciences》2018,77(6):244

The problem associated with multi-metals contaminated soils has generated increasingly more attention. Thus, it is necessary within the field to study the mutual influence of environmental factors on competitive adsorption. The majority of studies carried out to date have concentrated on the variation of adsorption capacity or the removal efficiency, with only a single factor changed (including pH, ionic strength, and metal concentration). However, the interaction effect among various environmental factors was ignored in these studies. The purpose of this study was mainly aimed toward the investigation of the interaction of two influential factors, as well as the influential degree of each factor (such as the initial pH, ionic strength, initial metal concentration, and the competitive metal concentration) on competitive adsorption using the response surface method. These results demonstrated that the influential degree of each factor studied on the competitive adsorption of Zn²⁺ and Cd²⁺ followed the trend of having the initial concentration of the target metal?>?initial pH?>?concentration of competitive metal?>?ionic strength. When the metal concentration was held constant, we found that the competitive adsorption of Zn²⁺ initially increased, followed by a decrease with increasing initial pH. However, this was found to change minimally with increasing ionic strength. When the initial pH or ionic strength was held constant, the competitive ability was observed to increase with increasing Zn²⁺ concentration. However, with increasing Zn²⁺ or Cd²⁺ concentrations, the variation degree of the competitive adsorption was found to become smaller. These results provide novel information toward a better understanding of the effect of multifactors on the competitive adsorption of Zn²⁺ and Cd²⁺.  相似文献   

Time-dependent sorption of Cd on CaX zeolite: Experimental observations and model predictions     

Imad A.M. Ahmed  Neil M.J. Crout 《Geochimica et cosmochimica acta》2006,70(19):4850-4861

Sorption, fixation and desorption kinetics of Cd²⁺ on calcium-exchanged zeolite-X were studied using an isotopic dilution technique utilizing ¹⁰⁹Cd. The technique provided reliable measurements of time-dependent fixation of Cd and was validated using chabazite, which demonstrated wholly reversible Cd²⁺ ion exchange. A first-order kinetic model was developed to describe the progressive transfer of Cd²⁺ to a less reactive form in X-zeolite, following initial sorption, and subsequent desorption of Cd subject to different initial contact times. The kinetic model differentiates between two ‘pools’ of sorbed Cd²⁺ on zeolite-X, designated labile and non-labile sorbed Cd in which the labile sorbed Cd is in immediate equilibrium with the free Cd²⁺ ion activity in solution. Additionally, an intra-particle diffusion model was developed and compared with the kinetic model to determine whether time-dependent Cd sorption is controlled by reaction kinetics or diffusion within zeolite particles. The kinetic model provided a much better fit to the experimental data (R² = 0.987) than the diffusion model. The rate constants describing Cd dynamics in CaX zeolite gave a half-time for Cd desorption of ∼77 d, for release to a ‘zero-sink’.  相似文献   

Cadmium (II) distribution in complex aquatic systems containing ferrihydrite, bacteria and an organic ligand: The effect of bioactivity     

Yantao Song  Simon Swift  Peter J. Swedlund  Naresh Singhal   《Applied Geochemistry》2011,26(5):898-906

The distribution of Cd²⁺ in the presence of phthalic acid (H₂L_p), ferrihydrite and bacteria (Comamonas spp.) was investigated in biologically active systems involving H₂L_p biodegradation. Tests showed that Cd²⁺ sorption onto bacteria, ferrihydrite and bacteria-ferrihydrite mixture increased with pH in all systems, irrespective of H₂L_p degradation or not. The use of bacterial growth medium, Bushnell Hass Broth modified for low phosphate, had negligible effect on Cd sorption. In the presence of ferrihydrite, no difference was observed between Cd²⁺ sorption in the ferrihydrite-live bacteria and in the ferrihydrite-dead bacteria systems as ferrihydrite proved to be the dominant sorption phase. Cadmium sorption to ferrihydrite and to bacterial cells was described using the diffuse layer model and a nonelectrostatic 4-site model, respectively, which were developed for systems lacking H₂L_p degradation. For systems experiencing H₂L_p degradation this modeling approach predicted the general trend of Cd²⁺ sorption-edge shift and gave good fits to the observed sorption data. The results obtained demonstrate that Cd²⁺ sorption in the biologically active system was reasonably estimated by a model developed for biologically inactive systems, although uncertainty exists due to processes involving H₂L_p biodegradation products and changes in the bacterial population.  相似文献   

Removal of Lead,Copper, Zinc and Cadmium from Water Using Phosphate Rock   总被引：2，自引：0，他引：2  

Alessia CORAMI  Silvano MIGNARDI  Vincenzo FERRINI 《《地质学报》英文版》2008,82(6):1223-1228

Removal of Pb^2＋, Cu^2＋, Zn^2＋ and Cd^2＋ from aqueous solutions by sorption on a natural phosphate rock （FAP） was investigated. The effects of the contact time and initial metal concentration were examined in the batch method. The percentage sorption of heavy metals from solution ranges generally between 50% and 99%. The amount of sorbed metal ions follows the order Cu〉Pb〉Cd〉Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate. The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb^2＋, Cu^2＋, Zn^2＋ and Cd^2＋ from polluted waters.  相似文献   

Competitive adsorption of metal ions onto goethite–humic acid-modified kaolinite clay     

E. I. Unuabonah  B. I. Olu-Owolabi  K. O. Adebowale 《International Journal of Environmental Science and Technology》2016,13(4):1043-1054

A binary mixture of humic acid and geothite was prepared and used to modify kaolinite to produce geothite–humic acid (GHA)-modified kaolinite adsorbent useful for the adsorption of Pb²⁺, Cd²⁺, Zn²⁺, Ni²⁺ and Cu²⁺ from Single and Quinary (5) metal ion systems. The cation exchange capacity (CEC) and specific surface area of GHA-modified kaolinite clay adsorbent were found to be 40 meq/100 g and 13 m²/g, respectively, with the CEC being five times that of raw kaolinite clay (7.81 meq/100 g). The Langmuir–Freundlich equilibrium isotherm model gave better fit to experimental data as compared with other isotherm models. In Quinary metal ion system, the presence of Zn²⁺ and Cu²⁺ appears to have an antagonistic effect on the adsorption of Pb²⁺, Cd²⁺ and Ni²⁺, while the presence of Pb²⁺, Cd²⁺ and Ni²⁺ shows a synergistic effect on the adsorption of Zn²⁺ and Cu²⁺. The GHA-modified kaolinite showed strong preference for the adsorption of Pb²⁺ in both metal ion systems. Brouers–Weron–Sotolongo (BWS) kinetic model gave better fit to kinetic data compared with other kinetic models used. Data from BWS kinetic model indicate that adsorption of metal ions onto GHA-modified adsorbent in both metal ion systems followed strictly, diffusion-controlled mechanism with adsorption reaction proceeding to 50 % equilibrium in <2 min in the Single metal ion system and <1 min in the Quinary metal ion system. Adsorption of metal ions onto GHA-modified kaolinite is fairly spontaneous and endothermic in nature in both metal ion systems although the rate of metal ion uptake and spontaneity of reaction are reduced in the Quinary metal ion system.  相似文献   

Experimental Study on Surface Reactions of Heavy Metal Ions With Quartz—Aqueous Ion Concentration Dependence     

Wu Honghai  Wu Daqing  Peng Jinlian 《中国地球化学学报》1999,18(3):201-207

Adsorption of divalent metal ions, including Cu²⁺, Pb²⁺, Zn²⁺, Cd²⁺ and Ni²⁺, on quartz surface was measured as a function of metal ion concentration at 30°C under conditions of solution pH= 6. 5 and ion strength I = 0. 1mol/L. Results of the experimental measurements can be described very well by adsorption isotherm equations of Freudlich. The correlation coefficients (r) of adsorption isotherm lines are > 0. 96. Moreover, the experimental data were interpreted on the basis of surface complexation model. The experimental results showed that the monodentate-coordinated metal ion surface complex species (SOM⁺) are predominant over the bidentate-coordinated metal ion surface complex species [(SO)₂M] formed only by the ions Cu²⁺, Zn²⁺ and Ni²⁺. And the relevant apparent surface complexation constants are lgK_M = 2.2–3.3 in order of K_Cd≥K_Pb > K_Zn > K_Ni≥K_Cu, and lgβ_M = 5.9-6.8 in order of β_Ni > β_Zn > β_Cu. Therefore, the reactive ability of the ions onto mineral surface of quartz follows the order of Cd > Pb > Zn > Ni> Cu under the above-mentioned solution conditions. The apparent surface complexation constants, influenced by the surface potential, surface species and hydrolysis of metal ions, depend mainly on the Born solvation coefficient of the metal ions. This project was financially supported by the National Natural Science Foundation of China (No. 49572091).  相似文献   

Sorption and distribution of adsorbed metals in three soils of India     

《Applied Geochemistry》2003,18(11):1723-1731

The mobility and bioavailability of heavy metals depends on the metal retention capacity of soil and also on the geochemical phases with which metals are associated. Laboratory batch experiments were carried out to study the sorption and distribution of Cd, Ni and Pb in 3 soils differing in their physicochemical properties from India: Oxyaquic Haplustalf (SL1), Typic Haplustalf (SL2) and Typic Haplustert (SL3). The heavy metal adsorption was studied by isotherms and the distribution coefficient (K_D) for each metal was obtained from the linear regressions of the concentration of metal remaining in equilibrium solution and the amount adsorbed. In general, the sorption capacity for all the metals decreased in the order: SL3>SL2>SL1. Among metals, the sorption capacity in all the soils decreased in the order: Pb>>Ni>Cd. Distribution of sorbed metals at various equilibrating concentrations was studied by sequential extraction. Results showed significant differences in the distribution of metals in these soils. At higher additions (such as 200 μM l⁻¹) most of the metals were extracted in their more mobile fractions, exchangeable and/or inorganic in contrast to their original partitioning in soils, where they were preferentially associated with the less mobile residual fraction. Largest percentages of metals extracted in the exchangeable fraction corresponded to those soil–metal systems with smaller K_D values, e.g. Cd, Ni and Pb in SL1 and Cd and Ni in SL2. In neutral and alkaline soils (SL2, pH=7.1, and SL3, pH=8.6) Pb was predominantly extracted from the inorganic fractions and this corresponded to higher K_D values for Pb in these soils. The predominance of metals associated with the exchangeable fraction together with low K_D values indicates higher mobility of metals retained in the acidic soil (SL1, pH=5.2) compared with the others.  相似文献   

Influence of operating conditions on the removal of Cu, Zn, Cd and Pb ions from wastewater by adsorption     

N. T. Abdel-Ghani M.Sc.  G. A. Elchaghaby 《International Journal of Environmental Science and Technology》2007,4(4):451-456

Nile Rose Plant was used to study adsorption of several cations (Cu²+, Zn²+, Cd²+ and Pb²+) from wastewater within various experimental conditions. The dried leaves of Nile Rose Plant were used at different adsorbent/ metal ion ratios. The influence of pH, contact time, metal concentration, and adsorbent loading weight on the removal process was investigated. Batch adsorption studies were carried out at room temperature. The adsorption efficiencies were found to be pH dependent, increasing by increasing the pH in the range from 2.5 to 8.5 exept for Pb. The equilibrium time was attained within 60 to 90 min. and the maximum removal percentage was achieved at an adsorbent loading weight of 1.5 g/50 mL mixed ions solution. Isothermal studies showed that the data were best fitted to the Temkin isotherm model. The removal order was found to be Pb²⁺> Zn²⁺> Cu²⁺> Cd²⁺. The surface IR-characterization of Nile rose plant showed the presence of many functional groups capable of binding to the metal cations.  相似文献   

A comparison of organic wastes as bioadsorbents of heavy metal cations in aqueous solution and their capacity for desorption and regeneration   总被引：2，自引：1，他引：1  

Ya-Feng Zhou  Richard J. Haynes 《Environmental Earth Sciences》2012,66(4):1137-1148

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   

Influence of a CO2 long term exposure on the mobilisation and speciation of metals in soils     

《Chemie der Erde / Geochemistry》2015,75(4):475-482

This study investigates the potential risks associated with high levels and long term exposure of carbon dioxide (CO₂) on the mobility and speciation of exchangeable metals in soils. CO₂ incubation batch experiments at high pressure and temperature coupled with geochemical modelling were carried out to elucidate the behaviour and mobilisation of metals and the response of soil chemical parameters as a result of long term CO₂ exposure. A t-Student analysis was performed to ascertain whether differences in the mean concentration of exchangeable metals in soils before and after CO₂-incubations are attributable to increase of metal molibilisation because of the long term CO₂ exposure. The t-Student revealed the CO₂ long term incubation was statistically significant (p < 0.05) for the exchangeable concentration of Ni, Zn, and Pb. The CO₂-soil incubation induces the acidification of the pore water of soils via CO₂ hydrolysis and as a consequence, it increases the exchangeable concentration of Ni, Zn, and Pb in the soils. As, Al, Cr, Cu, and Fe show a different mobilisation pattern depending on the moisture content in soils. Al³⁺, Fe²⁺, Cr³⁺, and Cu²⁺ as free cations, As as HAsO₂, Pb²⁺and PbHCO₃⁻, Zn²⁺ and ZnHCO₃⁻, are predicted to be the predominant aqueous complexes in the pore water of the incubated soils.  相似文献   

Kinetics of Cd sorption, desorption and fixation by calcite: A long-term radiotracer study     

Imad A.M. Ahmed  Neil M.J. Crout  Scott D. Young 《Geochimica et cosmochimica acta》2008,72(6):1498-1512

Time-dependent sorption and desorption of Cd on calcite was studied over 210 days utilizing ¹⁰⁹Cd as a tracer to distinguish between ‘labile’ and ‘non-labile’ forms of sorbed Cd. Stabilizing the calcite suspensions for 12 months under atmospheric P_CO2 and controlled temperature was necessary to reliably follow Cd dynamics following initial sorption. Results revealed time-dependant Cd sorption and marked desorption hysteresis by calcite under environmentally relevant conditions. Data obtained were fitted to a first-order kinetic model and a concentric shell diffusion model. Both models described the progressive transfer of Cd²⁺ to a less reactive form within calcite and subsequent desorption of Cd subject to different initial contact times. The kinetic model provided a better fit to the combined sorption and desorption data (R² = 0.992). It differentiates between two ‘pools’ of sorbed Cd²⁺ on calcite, ‘labile’ and ‘non-labile’, in which labile sorbed Cd is in immediate equilibrium with the free Cd²⁺ ion activity in solution whereas non-labile Cd is kinetically restricted. For the diffusion model (R² = 0.959), the rate constants describing Cd dynamics in calcite produced a half-life for Cd desorption of ∼175 d, for release to a ‘zero-sink’ solution. Results from this study allow comment on the likely mechanisms occurring at the calcite surface following long-term Cd sorption.  相似文献   

矿物-腐植酸-微生物体系对重金属吸附研究     

肖敏  陈永政  赵珊  张玉革  季颖  李士凤 《岩石矿物学杂志》2021,40(5):991-1000

设施农业中土壤重金属污染问题日趋严重。由于土壤中矿物、腐植酸、微生物等多相组分之间存在交互作用,重金属与土壤单组分体系中所获得的结合机制并不能真实有效地评价其在自然条件下的转化与归趋。本研究以蒙脱石(Mont)和高岭石(Kao)为辽宁蔬菜大棚及农田土壤层状硅酸盐代表矿物,选取胡敏酸(HA)为有机质代表,土著微生物革兰氏阳性枯草芽孢杆菌(Bacillus subtilis,B.s)、革兰氏阴性恶臭假单胞菌(Pseudomonas putida,P.p)为细菌微生物代表,以此三元体系为主要供试蔬菜大棚土壤组分,以Cd~(2+)、Cu~(2+)为目标元素,借助宏观吸附实验,结合X射线衍射(XRD)、衰减全反射-傅立叶变换红外光谱(ATR-FTIR)、扫描电镜(SEM)测试分析了Cd~(2+)、Cu~(2+)在矿物-腐植酸-细菌三元混合物上的吸附机理以及Cd~(2+)、Cu~(2+)在复合体上的结合机制。研究结果表明,蒙脱石/高岭石-腐殖酸、蒙脱石/高岭石-B.s及蒙脱石/高岭石-P.p二元复合体对Cd~(2+)及Cu~(2+)的吸附具有加和性,矿物-腐植酸-微生物三元复合体之间表现为拮抗作用。吸附动力学研究表明矿物、有机质、微生物复合体对重金属的吸附动力学符合准二级动力学模型。体系对Cu~(2+)的吸附能力由强到弱为:B. s P. p Mont/Kao-B. s Mont/Kao-P. p Mont/KaoHA-P.p Mont/Kao-HA Mont/Kao。  相似文献   

Aqueous cadmium uptake by calcite: a stirred flow-through reactor study   总被引：1，自引：0，他引：1  

A. Martin-Garin  L. Charlet 《Geochimica et cosmochimica acta》2003,67(15):2763-2774

Uptake of cadmium ions from solution by a natural Mg-containing calcite was investigated in stirred flow-through reactor experiments. Input NaCl solutions were pre-equilibrated with calcite (pH 8.0) or not (pH 6.0), prior to being spiked with CdCl₂. For water residence times in the reactor less than 0.5 h, irreversible uptake of Cd by diffusion into the bulk crystal had a minor effect on the measured cadmium breakthrough curves, hence allowing us to quantify “fast” Cd²⁺ adsorption. At equal aqueous activities of Cd²⁺, adsorption was systematically lower for the pre-equilibrated input solutions. The effect of variable solution composition on Cd²⁺ adsorption was reproduced by a Ca²⁺-Cd²⁺ cation exchange model and by a surface complexation model for the calcite-aqueous solution interface. For the range of experimental conditions tested, the latter model predicted binding of aqueous Ca²⁺ and Cd²⁺ to the same population of carbonate surface sites. Under these circumstances, both adsorption models were equivalent. Desorption released 80 to 100% of sorbed cadmium, confirming that fast uptake of Cd²⁺ was mainly due to binding at surface sites. Slow, irreversible cadmium uptake by the solid phase was measured in flow-through reactor experiments with water residence times exceeding 0.7 h. The process exhibited first-order kinetics with respect to the concentration of adsorbed Cd²⁺, with a linear rate constant at 25°C of 0.03 h⁻¹. Assuming that diffusion into the calcite lattice was the mechanism of slow uptake, a Cd²⁺ solid-state diffusion coefficient of 8.5×10⁻²¹ cm² s⁻¹ was calculated. Adsorbed Cd²⁺ had a pronounced effect on the dissolution kinetics of calcite. At maximum Cd²⁺ surface coverage (∼10⁻⁵ mol m⁻²), the calcite dissolution rate was 75% slower than measured under initially cadmium-free conditions. Upon desorption of cadmium, the dissolution rate increased again but remained below its initial value. Thus, the calcite surface structure and reactivity retained a memory of the adsorbed Cd²⁺ cations after their removal.  相似文献   

In situ formation of AgNPs on <Emphasis Type="Italic">S. cerevisiae</Emphasis> surface as bionanocomposites for bacteria killing and heavy metal removal     

Z. Chen  Z. Li  G. Chen  J. Zhu  Q. Liu  T. Feng 《International Journal of Environmental Science and Technology》2017,14(8):1635-1642

Novel bionanocomposites, S. cerevisiae–AgNPs, were synthesized by in situ formation of AgNPs on S. cerevisiae surface using fulvic acids as reductants under simulated sunlight. S. cerevisiae–AgNPs were characterized using UV–Vis spectroscopy, scanning electron microscope, transmission electron microscope and Fourier transform infrared spectroscopy. These analyses showed that AgNPs were distributed on the surface of S. cerevisiae. The application of S. cerevisiae–AgNPs in bacteria killing and heavy metal removal was studied. S. cerevisiae–AgNPs effectively inhibited the growth of E. coli with increasing concentrations of S. cerevisiae–AgNPs. E. coli was killed completely at high concentration S. cerevisiae–AgNPs (e.g., 100 or 200 µg mL^?1). S. cerevisiae–AgNPs as excellent heavy metal absorbents also have been studied. Using Cd²⁺ as model heavy metal, batch experiments confirmed that the adsorption behavior fitted the Langmuir adsorption isotherms and the Cd²⁺ adsorption capacity of S. cerevisiae–AgNPs was 15.01 mg g^?1. According to adsorption data, the kinetics of Cd²⁺ uptake by S. cerevisiae–AgNPs followed pseudo second-order kinetic model. Moreover, S. cerevisiae–AgNPs possessed ability of different heavy metals’ removal (e.g., Cr⁵⁺, As⁵⁺, Pb²⁺, Cu²⁺, Mn²⁺, Zn²⁺, Hg²⁺, Ni²⁺). The simulated contaminated water containing E. coli, Cd²⁺ and Pb²⁺ was treated using S. cerevisiae–AgNPs. The results indicated that the bionanocomposites can be used to develop antibacterial agents and bioremediation agents for water treatment.  相似文献   

Cadmium and lead interaction with diatom surfaces: A combined thermodynamic and kinetic approach     

A. Gélabert  O.S. Pokrovsky  J. Schott  A. Feurtet-Mazel 《Geochimica et cosmochimica acta》2007,71(15):3698-3716

This work is devoted to the physico-chemical study of cadmium and lead interaction with diatom-water interfaces for two marine planktonic (Thalassiosira weissflogii, TW; Skeletonema costatum, SC) and two freshwater periphytic species (Achnanthidium minutissimum, AMIN; Navicula minima, NMIN) by combining adsorption measurements with surface complexation modeling. Adsorption kinetics was studied as a function of pH and initial metal concentration in sodium nitrate solution and in culture media. Kinetic data were consistent with a two-step mechanism in which the loss of a water molecule from the inner coordination sphere of the metal is rate limiting. Reversible adsorption experiments, with 3 h of exposure to metal, were performed as a function of pH (2-9), metal concentration in solution (10⁻⁹-10⁻³ M), and ionic strength (10⁻³-1.0 M). While the shape of pH-dependent adsorption edge is similar among all four diatom species, the constant-pH adsorption isotherm and maximal binding capacities differ. Measurements of electrophoretic mobilities (μ) revealed negative surface potential for AMIN diatom, however, the absolute value of μ decreases with increase of [Pb²⁺]_aq suggesting the metal adsorption on negative surface sites. These observations allowed us to construct a surface complexation model (SCM) for cadmium and lead binding by diatom surfaces that postulates the Constant Capacitance of the electric double layer and considers Cd and Pb complexation with mainly carboxylic and, partially, silanol groups. In the full range of investigated Cd concentration, the SCM is able to describe the concentration of adsorbed metal as a function of [Cd²⁺]_aq without implying the presence of high affinity, low abundance sites, that are typically used to model the metal interactions with natural multi-component organic substances. At the same time, Cd fast initial reaction requires the presence of “highly reactive sites” those concentration represents only 2.5-3% of the total amount of carboxylic sites. For reversible adsorption experiments, the dominating carboxylic groups, whose concentration is allowed to vary within the uncertainty of experimental acid-base titrations, are sufficient to reproduce the metal adsorption isotherms. Results of this study strongly suggest that laboratory experiments performed in a wide range of metal to biomass ratios, represent robust and relatively simple method for assessing the distribution of metals between aqueous solution and planktonic and periphytic biomass in natural settings.  相似文献