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1.
The sign and the magnitude of the zeta potential must be known for many engineering applications. For clay soils, it is usually negative, but it is strongly dependent on the pore fluid chemistry. However, measurement of zeta potential time is time-consuming and requires special and expensive equipment. In this study, the prediction of zeta potential of kaolinite has been investigated by artificial neural networks (ANNs) and multiple regression analyses (MRAs). To achieve this, ANN and MRA models based on zeta potential measurements of kaolinite in the presence of salt and heavy metal cations at different pH values have been developed. The results of the models were compared with the experimental results. The performance indices, including coefficient of determination, root mean square error, mean absolute error, and variance, were used to assess the performance of the prediction capacity of the models developed in this study. The obtained indices make it clear that the constructed ANN models were able to predict zeta potential of kaolinite quite efficiently and outperformed the MRA models. Results showed that ANN models can be used satisfactorily to predict zeta potential of kaolinite as a rapid inexpensive substitute for laboratory techniques.  相似文献   

2.
The purpose of this study was to determine the effects of pH, ion type (salt and metal cations), ionic strength, cation valence, hydrated ionic radius, and solid concentration on the zeta potential of kaolinite and quartz powder in the presence of NaCl, KCl, CaCl2, CuCl2, BaCl2, and AlCl3 solutions. The kaolinite and quartz powder have no isoelectric point (iep) within the entire pH range (3 < pH < 11). In the presence of hydrolysable metal ions, kaolinite and quartz powder have two ieps. As the cationic valence increases, the zeta potential of kaolinite and quartz powder becomes less negative. Monovalent cation, K+, yields more negative zeta potential values than the divalent cation Ba2+. As concentration of solid increases, the zeta potential of the minerals becomes more positive under acidic conditions; however, under alkaline conditions as solid concentration increases the zeta potential becomes more negative. Hydrated ionic radius also affects the zeta potential; the larger the ion, the thicker the layer and the more negative zeta potential for both kaolinite and quartz powder.  相似文献   

3.
Results of the experimental study of ion exchange properties of deep-sea pelagic sediments and related ferromanganese nodules (FMN) are considered. The exchange complex of sediments and nodules includes Na+, K+, Ca2+, and Mg2+ cations. The FMNs also include Mn2+ cations. Series of reactivity of metal cations during exchange reactions in different types of pelagic clayey sediments and diagenetic-sedimentary FMN are compiled. Series of exchange capacity of the sediments and FMN for alkali and heavy metal cations are also presented. The exchange capacity of FMN is always higher than that of enclosing sediments. Sediments are characterized by reversible equivalent sorption of cations of both alkali and heavy metals. Irrespective of the mineral composition, the FMNs are characterized by the reversible equivalent sorption of alkali metal cations, whereas sorption of heavy metal cations is only partly reversible. More over, alkali metal cations do not replace heavy metal cations. The results obtained refine the role of ion exchange processes in the redistribution of heavy metal cations at the water-bottom sediment interface during the diagenetic-sedimentary formation of ferromanganese nodules.  相似文献   

4.
The results of experimental studies of ion exchange properties of Co-bearing ferromanganese crusts in the Magellan Seamounts (Pacific Ocean) are discussed. Maximum reactivity in reactions with the participation of manganese minerals (Fe-vernadite, vernadite) is typical of Na+, K+, and Ca2+ cations, whereas minimum activity is recorded for cations Pb2+ and Co2+. The exchange complex of ore minerals in crusts is composed of Na+, K+, Ca2+, Mg2+, and Mn2+ cations. The exchange capacity of manganese minerals increases from the alkali metal cations to rare and heavy metal cations. Peculiarities of the affiliation of Co2+, Mn2+, and Mg2+ cations in manganese minerals of crusts are discussed. In manganese minerals, Co occurs as Co2+ and Co3+ cations. Metal cations in manganese minerals occur in different chemical forms: sorbed (Na+, K+, Ca2+, Mn2+, Co2+, Cu2+, Zn2+, Cd2+, and Pb2+); sorbed and chemically bound (Mg2+, Ni2+, Y3+, La3+, and Mo6+); and only chemically bound (Co3+). It is shown that the age of crust, its preservation time in the air-dry state, and type of host substrate do not affect the ion exchange indicators of manganese minerals. It has been established that alkali metal cations are characterized by completely reversible equivalent sorption, whereas heavy metal cations are sorbed by a complex mechanism: equivalent ion exchange for all metal cations; superequivalent, partly reversible sorption for Ba2+, Pb2+, Co2+, and Cu2+ cations, relative to exchange cations of manganese minerals. The obtained results refine the role of ion exchange processes during the hydrogenic formation of Co-bearing ferromanganese crusts.  相似文献   

5.
In environmental studies, it is necessary to be able to predict the behaviour of contaminants in more or less complex physico-chemical contexts. The improvement of this prediction partly depends on establishing thermodynamic models that can describe the behaviour of these contaminants and, in particular, the sorption reactions on mineral surfaces. In this way, based on the mass action law, it is possible to use surface complexation models and ion exchange models. Therefore, the aim of this study is (i) to develop an ion-exchange model able to describe the sorption of transition metal onto pure clay minerals and (ii) to test the ability of this approach to predict the sorption of these elements onto natural materials containing clay minerals (i.e. soils/sediments) under various chemical conditions. This study is focused on the behaviour of Zn(II) in the presence of clayey sediments. Considering that clay minerals are cation exchangers containing multiple sorption sites, it is possible to interpret the sorption of Zn(II), as well as competitor cations, by ion-exchange equilibria with the clay minerals. This approach is applied with success to interpret the experimental data obtained previously in the Zn(II)–H+–Na+–montmorillonite system. The authors’ research team has already studied the behaviour of Na+, K+, Ca2+ and Mg2+ versus pH in terms of ion exchange onto pure montmorillonite, leading to the development of a thermodynamic database including the exchange site concentrations associated with montmorillonite and the selectivity coefficients of Na+, K+, Ca2+, Mg2+, and Zn2+ versus H+.  相似文献   

6.
Coal, as an initial source of energy, requires a detailed investigation in terms of ultimate analysis, proximate analysis, and its biological constituents (macerals). The rank and calorific value of each type of coal are managed by the mentioned properties. In contrast to ultimate and proximate analyses, determining the macerals in coal requires sophisticated microscopic instrumentation and expertise. This study emphasizes the estimation of the concentration of macerals of Indian coals based on a hybrid imperialism competitive algorithm (ICA)–artificial neural network (ANN). Here, ICA is utilized to adjust the weight and bias of ANNs for enhancing their performance capacity. For comparison purposes, a pre-developed ANN model is also proposed. Checking the performance prediction of the developed models is performed through several performance indices, i.e., coefficient of determination (R 2), root mean square error and variance account for. The obtained results revealed higher accuracy of the proposed hybrid ICA-ANN model in estimating macerals contents of Indian coals compared to the pre-developed ANN technique. Results of the developed ANN model based on R 2 values of training datasets were obtained as 0.961, 0.955, and 0.961 for predicting vitrinite, liptinite, and inertinite, respectively, whereas these values were achieved as 0.948, 0.947, and 0.957, respectively, for testing datasets. Similarly, R 2 values of 0.988, 0.983, and 0.991 for training datasets and 0.989, 0.982, and 0.985 for testing datasets were obtained from developed ICA-ANN model.  相似文献   

7.
Biosorption is a promising technology for the removal of heavy metals from industrial wastes and effluents. In the present study, biosorption of Pb2+, Cu2+, Fe2+ and Zn2+ onto the dried biomass of Eucheuma denticulatum (Rhodophyte) was investigated as a function of solution pH, contact time, temperature and initial metal ion concentration. The experimental data were evaluated by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The sorption isotherm data followed Langmuir and Freundlich models, and the maximum Langmuir monolayer biosorption capacity was found as 81.97, 66.23, 51.02 and 43.48 mg g?1 for Pb2+, Cu2+, Fe2+ and Zn2+, respectively. The sorption kinetic data followed pseudo-second-order and intraparticle diffusion models. Thermodynamic study revealed feasible, spontaneous and endothermic nature of the sorption process. Fourier transform infrared analysis showed the presence of amine, aliphatic, carboxylate, carboxyl, sulfonate and ether groups in the cell wall matrix involved in metal biosorption process. A total of nine error functions were applied in order to evaluate the best-fitting models. We strongly suggest the analysis of error functions for evaluating the fitness of the isotherm and kinetic models. The present work shows that E. denticulatum can be a promising low-cost biosorbent for removal of the experimental heavy metals from aqueous solutions. Further study is warranted to evaluate its potential for the removal of heavy metals from the real environment.  相似文献   

8.
The present study attempts to model the spatial variability of three groundwater qualitative parameters in Guilan Province, northern Iran, using artificial neural networks (ANNs) and support vector machines (SVMs). Data collected from 140 observation wells for the years 2002–2014 were used. Five variables, X and Y coordinates of the observation well, distance of the observation well from the shoreline, areal average 6-month rainfall depth, and groundwater level at the day of water quality sampling, were considered as primary input variables. In addition, nine qualitative variables were also considered as auxiliary input variables. Electrical conductivity (EC), sodium concentration (Na+), and sulfate concentration (SO4 2?) of the groundwater in the region were estimated using ANNs and SVMs with different input combinations. The results showed that both ANNs and SVMs work well when the only primary input variable is the well location. The ANN yielded an RMSE of 1.03 mEq/l for SO4 2?, 1.05 mEq/l for Na+, and 203.17 μS/cm for EC, using the X and Y coordinates of the observation wells in the study area. In the case of SVM, these values were, respectively, 0.87, 0.87, and 176.68. Considering the auxiliary input variables (pH, EC, and the concentrations of Na+, K+, Ca2+, Mg2+, Cl?, SO4 2?, and HCO3 ?) resulted in a significant decrease in the RMSE of both ANNs (0.22, 0.30, and 33.04) and SVMs (0.26, 0.34, and 36.23). Comparing these RMSE values with those of cokriging interpolation technique (0.59, 0.98, and 177.59) indicated that ANNs and SVMs produced more accurate estimates of the three qualitative parameters. The relative importance of auxiliary input variables was also determined using Gamma test. The output uncertainty of ANNs and SVMs were determined using p-factor and d-factor. The results showed that SVMs have less uncertainty than ANNs.  相似文献   

9.
The results of experimental studies of ion exchange properties of manganese and iron minerals in micronodules (MN) from diverse bioproductive zones of the World Ocean are considered. It was found that the sorption behavior of these minerals is similar to that of ore minerals from ferromanganese nodules (FMN) and low-temperature hydrothermal crusts. The exchange complex of minerals in the MN includes the major (Na+, K+, Ca2+, Mg2+, and Mn2+) and the subordinate (Ni2+, Cu2+, Co2+, Pb2+, and others) cations. Reactivity of theses cations increases from Pb2+ and Co2+ to Na+ and Ca2+. Exchange capacity of MN minerals increases from the alkali to heavy metal cations. Capacity of iron and manganese minerals in the oceanic MN increases in the following series: goethite < goethite + birnessite < todorokite + asbolane-buserite + birnessite < asbolane-buserite + birnessite < birnessite + asbolane-buserite < birnessite + vernadite Fe-vernadite + Mn-feroxyhyte. The data obtained supplement the available information on the ion exchange properties of oceanic ferromanganese sediments and refine the role of sorption processes in the redistribution of metal cations at the bottom (ooze) water-sediment interface during the MN formation and growth.  相似文献   

10.
Various soil zones such as Bw, C1, and C3 are developed on spilite. Montmorillonite, vermiculite and chlorite is moderately occurred in the C1 and C3 soil zones, in contrast montmorillonite and vermiculite are absent in Bw soils whereas illite and sesquioxide are relatively increased. The high cation exchange capacity (CEC) of montmorillonite and vermiculte and moderate CEC of chlorite and illite resulted in the high adsorption of heavy metals. The adsorption of the heavy metals on spilite soil zones was studied at different concentrations and pH levels. Heavy metals like lead, cadmium, and copper were selected for adsorption studies considering their contribution as toxic metals in the environment. The initial solute concentrations ranged from 7.0 × 10−3 to 1.0 × 102 mg/L. The sorption behavior of Cd2+, Pb2+, and Cu2+ on soil zones of spilite was investigated using the batch equilibrium technique at 25°C. The characteristics of the adsorption process were investigated using Scatchard plot analysis (q/C vs. q) by the batch equilibrium technique at 25°C. In the adsorption of heavy metals, deviation from linearity in the plot of q/C versus q was observed, indicating the presence of multi-model interaction and non-Langmuirean behavior. When the Scatchard plot showed a deviation from linearity, greater emphasis was placed on the analysis of the adsorption data in terms of the Freundlich model, in order to construct the adsorption isotherms of the metal(s) at particular concentration(s) in solutions. The adsorption behavior of these metal ions on spilite soil zones is expressed by the Freundlich isotherms. Adsorption constants and correlation coefficients for the Cd, Pb, and Cu on spilite soil zones were calculated from Freundlich plots.  相似文献   

11.
An application of artificial intelligence for rainfall-runoff modeling   总被引：5，自引：0，他引：5  
This study proposes an application of two techniques of artificial intelligence (AI) for rainfall-runoff modeling: the artificial neural networks (ANN) and the evolutionary computation (EC). Two different ANN techniques, the feed forward back propagation (FFBP) and generalized regression neural network (GRNN) methods are compared with one EC method, Gene Expression Programming (GEP) which is a new evolutionary algorithm that evolves computer programs. The daily hydrometeorological data of three rainfall stations and one streamflow station for Juniata River Basin in Pennsylvania state of USA are taken into consideration in the model development. Statistical parameters such as average, standard deviation, coefficient of variation, skewness, minimum and maximum values, as well as criteria such as mean square error (MSE) and determination coefficient (R 2) are used to measure the performance of the models. The results indicate that the proposed genetic programming (GP) formulation performs quite well compared to results obtained by ANNs and is quite practical for use. It is concluded from the results that GEP can be proposed as an alternative to ANN models.  相似文献   

12.
The impacts of common ions on the adsorption of heavy metal   总被引：1，自引：0，他引：1  
Researches on the impact of common ions onto sediments are of great importance for the study of the heavy metal adsorption mechanisms. Considering the surface sediments from the relatively clean reach in the Baotou section of the Yellow River as the adsorbent, this work presents the impacts of common ions (Na+, Mg2+, K+, Ca2+, Cl−, SO4 2−, and NH4 +) on heavy metals (Cu2+, Zn2+, Cd2+, and Pb2+) adsorption. The experimental results reveal that the adsorptive capacities of the heavy metals are controlled by different adsorption mechanisms in different ion concentration ranges. With the increase of the ionic strength, the adsorption of the heavy metals increases for the compression of the electric double layer, whereas decreases for the decreasing of the ionic activities of the heavy metals. The competitive adsorption and complexations between the heavy metals and common ions are also important factors controlling the heavy metal adsorption. According to the experimental results and the real concentration of common ions in the Baotou section of the Yellow River, the increase of the concentrations of Na+, Mg2+, K+, and Ca2+ would cause the increase of Zn2+ adsorption and reduce the Zn pollution. The NH4 + from the industrial discharge of the tributaries has a strong impact on the heavy metal adsorption.  相似文献   

13.
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   

14.
作为高放废物处置罐候选金属材料,低碳钢在处置库服役期间,其腐蚀产物侵入缓冲屏障,导致缓冲材料矿物相变与性能变异,威胁多重屏障体系的长期安全稳定。本文详细综述了国内外处置库深部还原环境所处的弱碱性化学场与中低温度场的变化趋势,认为处置库深部化学-温度还原条件可导致处置罐Fe腐蚀释放Fe~(2+)。在处置库长期运行过程中,蒙脱石与Fe~(2+)接触发生矿物相变,一方面Fe~(2+)置换蒙脱石八面体晶格中的Al~(3+)和Mg~(2+),还原Fe~(3+)或直接占据空位,生成次生矿物;另一方面Fe~(2+)交换蒙脱石层间的Na~+、K~+和Ca~(2+),转化为铁基蒙脱石。矿物相变可诱发缓冲屏障性能变异甚至退化。基于"抗矿物转化"理念,提出了下一阶段缓冲材料矿物相变研究方向,为地下实验室碳素钢选型、缓冲屏障验证试验设计以及屏障体系安全评价提供科学依据。  相似文献   

15.
This work aims to estimate the levels of lead (Pb), nickel (Ni), manganese (Mn), vanadium (V) and chromium (Cr) corresponding to a 3-month PM10 sampling campaign conducted in 2008 in the city of Dunkerque (northern France) by means of statistical models based on partial least squares regression (PLSR), artificial neural networks (ANNs) and principal component analysis (PCA) coupled with ANN. According to the European Air Quality Directives, because the levels of these pollutants are sufficiently below the European Union (EU) limit/target values and other air quality guidelines, they may be used for air quality assessment purposes as an alternative to experimental measurements. An external validation of the models has been conducted, and the results indicate that PLSR and ANNs, with comparable performance, provide adequate mean concentration estimations for Pb, Ni, Mn and V, fulfilling the EU uncertainty requirements for objective estimation techniques, although ANNs seem to present better generalization ability. However, in accordance with the European regulation, both techniques can be considered acceptable air quality assessment tools for heavy metals in the studied area. Furthermore, the application of factor analysis prior to ANNs did not yield any improvements in the performance of the ANNs.  相似文献   

16.
The purpose of the study was to evaluate the influence of polyvalent cations known to form complexes with natural organic substances on the operational fractionation of dissolved organic matter (DOM) using XAD-8 adsorber resin. Dissolved organic matter solutions from a forest floor were treated with increasing concentrations of polyvalent metal cations (Ca2+, Al3+, Fe3+) at different pH levels. Then the concentrations of total dissolved organic carbon (DOC) and the distribution between hydrophilic and hydrophobic DOC were determined. The concentrations of total DOC decreased slightly when the C/metal ratio was less than 10, especially for Al and Fe. Hydrophilic DOC increased and hydrophobic DOC decreased with increasing concentrations of metal cations. Effects increased in the order Ca<Al<Fe and were more pronounced at low DOC concentrations and high pH values. The reason for the reduction of the DOC concentrations seemed to be the formation of insoluble metal–DOM complexes, while soluble metal–DOM complexes may induce an alteration of the distribution between hydrophilic and hydrophobic DOC. Thus, the polyvalent cations and their concentration need to be considered when DOM fraction distributions, determined with XAD-8 resin, of different waters are compared, especially at low DOC contents and high pH.  相似文献   

17.
The objective of the present study is to evaluate the absorption efficacy of H. fusiformis biochar (HFB) for the removal of phenol and heavy metals from single and mixed solute systems of these species under different experimental conditions. The effects of contact time, pH change, initial phenol concentration, and heavy metal concentration on the adsorption capacity of HFB were investigated. The kinetics and equilibrium models of sorption of the components of the single and mixed solute systems on HFB were also studied. The experimental data were fitted to kinetic and equilibrium models. The batch experiments revealed that 360 min of contact time was sufficient to achieve equilibrium for the adsorption of both phenol and heavy metals. The adsorption of phenol and nickel by HFB followed the pseudo-second-order kinetic model, which was quite adequate for describing the adsorption mechanism. The equilibrium data for the adsorption of phenol and heavy metals fit well to the Langmuir model with regression coefficients of R 2 > 0.819. The maximum Langmuir adsorption capacities were 10.39, 12.13, 22.25, 2.24, 2.89, and 22.03 mg/g for phenol, Ni2+, Zn2+, Cu2+, Pb2+, and Cd2+, respectively. Moreover, HFB exhibited optimal sorption under slightly acidic conditions at pH 6. The HFB used in the present study exhibited higher adsorption capacity for the removal of phenol and heavy metals from aqueous solutions compared to documented sorbents. These results demonstrate that HFB is potentially useful for alleviating the harmful effects of phenol and heavy metal in wastewater treatment systems.  相似文献   

18.
The total mineralization of solutions squeezed out of montmorillonite clay saturated in sea water was determined at different overburden pressures. The subsequent fractions of expelled solutions were also analysed for various anions (Cl?, SO2-4, HCO?3, F?) and cations (Na+, K+, Mg2+, Ca2+, B3+). The results indicate that the concentrations of squeezed-out solutions during the initial stages of compaction (at pressures up to 35 kg/cm2) are slightly higher than that of interstitial solution present initially. The concentration of squeezed-out solution goes through a maximum, or at least remains constant, before starting to decrease with increasing overburden pressure.  相似文献   

19.
Removal of Lead,Copper, Zinc and Cadmium from Water Using Phosphate Rock   总被引：2，自引：0，他引：2  
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   

20.
Effects of Zn2+, Cu2+ and Cd2+ in the synthetic acid mine drainage on the performance of the anaerobic sulfidogenic reactor using rape straw as carbon source were explored. Two different cases were respectively observed for the different metal dosages: stimulatory at lower concentrations and toxic/inhibitory at higher concentrations. Cellulose and hemicellulose were the major components hydrolyzed in the rape straw. Analysis of the heavy metals distribution in the anaerobic digested solid residue showed that adsorption and precipitation were the major mechanisms for the removal of heavy metals. This was also confirmed by the results of scanning electron microscopy and energy-dispersive spectrometry analysis.  相似文献   

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