Adsorption of copper and cobalt from fresh and marine systems

The adsorption of copper and cobalt from aqueous solution on to illite and other substrates has been studied as a function of pH, solution composition and solid phase concentration. The results are interpreted in terms of a model whereby the trace metals are adsorbed in exchange for surface bound H⁺ ions. Adsorption varies with solution ionic strength and the concentrations of complex forming ligands; both of these parameters tend to reduce the trace metal adsorption. The Cu²⁺ is two orders of magnitude more reactive toward solid surfaces than Co²⁺ , which is consistent with the general reactivities of these two metal ions. It is also found that Mg₂₊ interferes with adsorption, presumably by competing with the trace metals for the surface sites. A quantitative model was developed which describes adsorption of these metals from natural waters ranging from river water to sea water as a function of pH, complexing ligands and magnesium activity.     

Effects of photoirradiation on the adsorption of dissolved organic matter to goethite

The effects of photoirradiation of dissolved organic matter (DOM) on its subsequent adsorption to the Fe(III)oxyhydroxide mineral goethite were investigated at 22°C in 0.10 mol L⁻¹ NaClO₄ solutions at pH 3.5 and 5.5, Photoirradiation of DOM decreased the abundance of high molecular-weight components and formed new lower molecular-weight components, including low molecular weight carboxylic acids (i.e., formic, malonic, and acetic acids). Adsorption of non-irradiated DOM decreased from pH 3.5 to 5.5 and was dominated by the intermediate molecular weight (1251-3750 Da) fraction, although the 451-1250 and 3751-11350 Da fractions also contributed to adsorption at pH 3.5. Irradiation resulted in a substantial decrease in DOM adsorption affinity at pH 3.5, primarily due to loss of components in the 1251-3750 and 3751-11350 Da fractions. Irradiation resulted in only a small decrease in DOM adsorption affinity at pH 5.5; the loss of components in the 3751-11350 Da fraction upon irradiation had little effect on adsorption because they played little or no role in the non-irradiated sample at this pH. Irradiation of DOM also affected its interactions with Fe in solution and the solution iron(II)/iron(III) speciation. The combined effects of irradiation followed by adsorption produced DOM that was lower in molecular weight and had a decreased UV-Vis absorptivity than either process, alone. Together, these two processes are likely to have important environmental consequences in terms of UV penetration of surface waters, contaminant mobility, and DOM bioavailability.     

土壤溶解性有机质对植物吸收-输送-贮存重金属的影响研究现状与进展

土壤溶解性有机质对重金属生物地球化学循环中的生物可利用性起着重要作用。近年来,在土壤溶解性有机质对植物吸收、输送和贮存重金属过程的影响研究领域,国际上主要聚焦于以下三个探索方向:①土壤溶解性有机质与重金属形成配位体,改变重金属在土壤中的迁移性和植物根际环境的作用机理研究;②土壤溶解性有机质可突破植物细胞内重金属吸附点位的限制,通过控制植物细胞壁-重金属复合体的形态及重金属在细胞壁内外的吸收平衡,来干预重金属穿过细胞壁进入植物体的动力学过程研究;③土壤溶解性有机质-重金属的络合形态影响重金属在植物体内的输送和贮存作用过程与机理研究。本文基于研究溶解性有机质和重金属的植物过程中,水体溶解性有机质研究多而土壤溶解性有机质研究少的现状,针对溶解性有机质异质性的研究难点和溶解性有机质与植物亚细胞结构的配位特征的复杂性与局限性,从极性、官能团、配位结构等角度,分析并评述了土壤溶解性有机质和重金属生物地球化学中,植物吸收、输送和贮存重金属过程的研究现状和未来发展趋势。     

Adsorption of 2,4-dinitrophenol and 2,4-dichlorophenol on Cationic Surfactant modified red soil

Adsorption isotherms of 2,4-dinitrophenol and 2,4-diehlorophenol on hexadeeyhrimethylammonium (HDTMA) bromide modified red soil under different ionic strength, divalent cation Cu2 or different pH conditions were studied. All the adsorption isotherms were well fitted to the Freundlich equation. The adsorption capacities of 2,4-dinitrophenol or 2,4-dichlorophenol were dramatically enhanced by HDTMA treatment of red soil. The increase of ionic strength and the addition of divalent heavy metal cation Cu^2 significantly enhanced the adsorption of 2,4-dinitrophenol or 2,4-dichlorophenol on the HDTMA-modified red soil. Adsorption capacities of HDTMA-modified red soil for 2,4-dinitrophenol and 2,4-dichlorophenol gradually increased with decreasing pH in the aqueous phase.     

Adsorption of 2,4-dinitrophenol and 2,4-dichlorohpenol on Cationic Surfactant Modified Red Soil

Adsorption isotherms of 2,4-dinitrophenol and 2,4-dichlorophenol on hexadecyltrimethylammonium (HDTMA) bromide modified red soil under different ionic strength, divalent cation Cu 2 or different pH conditions were studied. All the adsorption isotherms were well fitted to the Freundlich equation. The adsorption capacities of 2,4-dinitrophenol or 2,4-dichlorophenol were dramatically enhanced by HDTMA treatment of red soil. The increase of ionic strength and the addition of divalent heavy metal cation Cu 2 significantly enhanced the adsorption of 2,4-dinitrophenol or 2,4-dichlorophenol on the HDTMA-modified red soil. Adsorption capacities of HDTMA-modified red soil for 2,4-dinitrophenol and 2,4-dichlorophenol gradually increased with decreasing pH in the aqueous phase.     

Retention of heavy metal ions in bentonites from Grau Region (Northern Peru)

Experimental studies on the retention of metals (Cu, Co, Ni, and Zn) in bentonite samples from the Grau Region (Northern Peru) have been accomplished using monometallic, bimetallic, trimetallic, and tetrametallic solutions. Parameters such as pH and concentration of dissolved metals and organic compounds have been evaluated by means of batch adsorption experiments. Adsorption rates indicate the suitability of these bentonites in the environmental industry for heavy metals retention purposes. In addition to its quality as physical barrier to avoid the dispersion through the environment of polluted leachates, bentonite, due to its high cation exchange capacity, can act also as a chemical barrier, protecting the quality of surface and groundwater systems, while limiting the migration of heavy metals in solid residues or sludge stocked in security landfills. Adsorption rates of tested bentonites were proved to decrease when concentrations of both metal and organic compounds, as well as the number of ionic species, increase in solution; additionally, lower metal removal rates from solution were obtained when extremely acidic conditions were achieved.     

Metal binding to dissolved organic matter and adsorption to ferrihydrite in shallow peat groundwaters: Application to diamond exploration in the James Bay Lowlands,Canada

The speciation and solubility of kimberlite pathfinder metals (Ni, Nd, Ba and K) in shallow peat groundwaters is investigated over the Yankee, Zulu and Golf kimberlites in the Attawapiskat region, James Bay Lowlands, Canada. The purpose of this study is to examine the relationship between dissolved organic matter (DOM) complexation with kimberlite pathfinder metals and determine the spatial distribution of those metals in shallow peat groundwaters along sampling transects over subcropping kimberlites. Nickel, Nd, Ba and K complexation with DOM and the adsorption of these metals onto ferrihydrite were calculated using Visual MINTEQ 3.0 and the NICA-Donnan database. Calculations predict almost 100% of soluble Nd, Ni and Ba form complexes with DOM at sampling sites with little to no contribution from upwelling groundwater (i.e., dissolved organic C (DOC) concentrations = 40–132 mg/L, pH = 3.9–5.5, and log ionic strength ??3). In only the most ombrotrophic peat groundwater conditions does a majority fraction of K bind to DOM. By contrast, under conditions with large contributions from upwelling groundwaters (i.e., DOC concentrations ?40 mg/L, pH = 5.5–6.5, and log ionic strength = ?3 to ?2), as little as 10% of Nd and Ni, and 0% K and Ba are predicted to complex with DOM. The modeling calculations suggest the dominant control on metal–DOM complexation, particularly with respect to Ni and Nd, is competitive effects for DOM binding sites due to elevated ionic strength where there is evidence of strong groundwater upwelling. Visual MINTEQ modeling of metal adsorption on ferrihydrite surfaces predicts that under strong upwelling conditions, Ni and Nd are scavenged from solution due to increased ferrihydrite precipitation and decreased fractions of metals complexed with DOM. Analytical geochemical data are consistent with model predictions of metal adsorption on ferrihydrite. Total dissolved Ni and Nd concentrations at sites of strong upwelling are up to five times lower than waters with little to no upwelling and log ferrihydrite saturation indices (logSI_ferr) indicate precipitation (values up to 5) at sites of strong groundwater upwelling. Where the majority of Ni and Nd complex with DOM and ferrihydrite is highly under saturated (logSI_ferr = ?18 to ?5), the concentrations of total Ni and Nd are elevated compared to other sites along sampling transects. Metal complexation with DOM effectively inhibits metal scavenging from solution via adsorption and/or from forming secondary mineral precipitates. Also, because alkaline earth metals do not compete strongly with Ni and Nd for adsorption sites on ferrihydrite surfaces, but do compete strongly for insoluble organic sites, Ni and Nd are more likely to adsorb onto ferrihydrite.     

Application of dried plant biomass as novel low-cost adsorbent for removal of cadmium from aqueous solution

Heavy metals are a threat to human health and ecosystem. These days, great deal of attention is being given to green technologies for purification of water contaminated with heavy metal ions. Biosorption is one among such emerging technologies, which utilizes naturally occurring waste materials to sequester heavy metals from wastewater. Cadmium has hazardous impact on living beings; therefore, its removal through green and economical process is an important task. The aim of the present study was to utilize the locally available Portulaca oleracea plant biomass as an adsorbent for cadmium removal from aqueous solution. The biomass was obtained after drying and grinding the portulaca leaves and stem. No chemical treatment was done on the adsorbent so that it remained green in a true sense. Batch experiments were performed at room temperature. The critical parameters studied were effects of pH, contact time, initial metal ion concentration and adsorbent dose on the adsorption of cadmium. The maximum adsorption was found to be 72 %. The kinetic data were found to best fit the pseudo-second-order equation. High adsorption rates were obtained in the initial 45 min, and adsorption equilibrium was then gradually achieved in about 100 min. Adsorption increased with increase in pH for a range 2 and 6. The equilibrium adsorption results closely followed both the Langmuir and Freundlich isotherms. The values of constants were calculated from isotherms. Results indicated that portulaca plant biomass could be developed as a potential material to be used in green water treatment devices for removal of metal ions.     

A study on the adsorption characteristics of cadmium and zinc onto acidic and alkaline soils

The adsorption of cadmium (Cd) and zinc (Zn) with similar chemical properties is examined onto three soil samples: one is alkaline and the others are acidic. The distribution coefficient (K _d) and the Freundlich constant (K _F) for Zn are slightly higher than those for Cd, implying that the adsorption affinity of Zn is a little greater and less mobile. However, Cd and Zn usually show comparable results in the kinetic, isotherm, and envelope experiments. The adsorption of the heavy metals is relatively rapid and the reaction is almost completed within 15 min. The kinetics for both Cd and Zn are very well explained by the parabolic diffusion model. The maximum adsorption of the heavy metals is obtained at high pH, high temperature, and low ionic strength. The adsorption capacity on the alkaline soil is more significantly affected by the temperature as compared to the acidic soil. It is found that the adsorption affinity of the two heavy metals is mainly affected by the soil properties, such as pH, pH_PZC, organic matter, and total carbon. It is also confirmed that the chemical properties of the heavy metals are important factors in their adsorption onto soil. The adsorption isotherms of Cd and Zn are well described in both Freundlich and Langmuir models at the usual pH (soil pH). Under acidic and alkaline pHs, however, only the Freundlich model describes the adsorption of both heavy metals satisfactorily.     

Pb and Co removal from paint industries effluent using wood ash

The release of heavy metals into the environment is a worldwide major concern. Different studies have demonstrated that natural agents have a high removal capacity for divalent heavy metal ions. Wood ash is a natural adsorbent and, in comparison with others, has a very low price. In this study, the removal of heavy metals (Pb and Co) from Binalood paint industry (Kerman, Iran) effluent was investigated in batch condition. Pb and Co measurement in samples were done with atomic absorption equipment and test methods were adapted from standard methods for the examination of water and wastewater. The effect of pH and the amount of adsorbent was determined and different adsorption isotherms were also obtained. This study shows that the adsorption process follows the adsorption Langmuir isotherm. The amount of wood ash has a great role in the adsorption rate and adsorption rate increased as wood ash increased. In the study, the reactions reached equilibrium in 3 h contact time. The maximum Pb removal efficiency was 96.1 % at pH 2 with a contact time of 3 h and 100 g/L wood ash and the maximum Co removal efficiency was 99 % at pH 2 with a contact time of 3 h and 100 g/L wood ash. According to the results, wood ash is recommended as a low cost and available adsorbent to remove Pb and Co from municipal and industrial wastewaters.     

Adsorption of brilliant green from aqueous solution by unmodified and chemically modified Tarap (<Emphasis Type="Italic">Artocarpus odoratissimus</Emphasis>) peel

Tarap peel (TP) and oxalic-acid-modified Tarap peel (TP-OX) were used to remove brilliant green (BG) dye from aqueous solution. Surface modification of TP suggested that functional groups such as carboxyl, hydroxyl and amino were involved in the adsorption of BG onto TP. Parameters such as effects of pH, contact time, ionic strength, initial dye concentration and temperature were included to study the adsorption of BG onto TP and TP-OX. Adsorption isotherm models were used to investigate the adsorption process, while kinetics models were used to provide insight into the adsorption mechanisms. Optimised contact time of 2 h with no pH adjustment was used. Adsorption of BG onto TP was best fitted to the Freundlich model, while experimental data for TP-OX are best described by the Tempkin model. The maximum adsorption capacities were determined as 174 and 275 mg g^?1 for TP and TP-OX, respectively. Thermodynamics study indicated the endothermic nature of adsorptions of BG onto both adsorbents. According to kinetics study, the adsorption mechanisms on both adsorbents followed pseudo-second-order model, and film diffusion might have major role in the adsorption process.     

An experimental study of heavy metal attenuation and mobility in sandy loam soils

Column flow-through experiments reacting wastewater solutions with sandy loam soil samples were performed to study heavy metal attenuation by two soils with different physical and chemical properties. Reacted soil columns were leached with synthetic acid rain to study the mobility of attenuated heavy metals under leaching conditions. This study demonstrates that cation exchange, surface adsorption, chelation with solid organic material, and precipitation were the important attenuation mechanisms for the heavy metals (Cd, Cr, Cu, Mo, Ph, and Zn). Adsorption on soil hydrous oxide surfaces was the primary attenuation mechanism for Cd and Zn in both soils, and for Cu in a soil with low organic matter content. Wastewater solution pH is also an important factor that influences the retention of heavy metals. Cadmium, Cu, Cr, and Zn became mobile after prolonged application of spiked wastewater solution, either through saturation of soil adsorption sites or due to decreasing pH. Only Cr, Pb, and Mo, which are attenuated primarily through precipitation, show significant net retention by soil. Acid rain water removed heavy metals left in the column residual pore solution and weakly sorbed heavy metals in the soils, and has the ability to mobilize some strongly attenuated heavy metals, especially when the soil organic matter content is high. The results have important applications in predicting heavy metal mobility in contaminated soil, the disposal of acid mine drainage, and assessing the risks of landfall leachate leakage.     

矿物材料与环境污染治理—以粘土矿物和沸石为例

矿物的性能，矿区地质测试和吸附能力实验表明，粘土矿物和沸石等矿物材料对于Cr,Cd,Pb,Hg,As等有害元素具有很强的吸附能力，是理想的低成本吸附剂，在废水处理中可用来取代活性炭或离子交换树脂来去除重金属等有害元素。     

Removal of lead(II) from aqueous stream by hydrophilic modified kapok fiber using the Fenton reaction

A hydrophilic kapok fiber was prepared by a chemical process of the Fenton reaction and used as an adsorbent to remove Pb(II) from aqueous solution. The effects of experimental parameters including pH, contact time, Pb(II) concentration, and coexisting heavy metals were estimated as well as evaluated. The optimum concentrations of FeSO₄ and H₂O₂ for the Fenton reaction-modified kapok fiber (FRKF) were 0.5 mol L^?1 and 1 mol L^?1, respectively. The adsorption kinetic models and isotherm equations of Langmuir and Freundlich were conducted to identify the most optimum adsorption rate and adsorption capacity of Pb(II) on FRKF. The FRKF displayed an excellent adsorption rate for Pb(II) in single metal solution with the maximum adsorption capacity of 94.41?±?7.56 mg g^?1 at pH 6.0. Moreover, the FRKE still maintained its adsorption advantage of Pb(II) in the mixed metal solution. The FRKF exhibited a considerable potential in removal of metal content in wastewater streams.     

Utilization of ochre as an adsorbent to remove Pb(II) and Cu(II) from contaminated aqueous media

The ability of ochre to remove Pb(II) and Cu(II) from aqueous media has been studied by batch sorption studies varying the contact time, initial metal concentration, initial solution pH and temperature to understand the adsorption behaviour of these metals through adsorption kinetics and isotherms. The pH of the solution and the temperature controlled the adsorption of metal ions by ochre and rapid uptake occurred in the first 30 min of reaction. The kinetics of adsorption followed a pseudo-second-order rate equation (R ² > 0.99) and the isotherms are well described by the Freundlich model. Adsorption of metals onto ochre is endothermic in nature. Between the two metals, Pb(II) showed more preference towards the exchangeable sites on ochre than Cu(II). This study indicates that ochre is a very effective adsorbent in removing Pb(II) and Cu(II) from the aqueous environment with an adsorptive capacity of 0.996 and 0.628 mg g^?1 and removal efficiency of 99.68 and 62.80 %, respectively.     

河北保定典型污灌区土壤Cu吸附特性研究

我国部分地区土壤污染形势严峻,主要表现为Cu等重金属元素严重超标。污水灌溉以及含Cu饲料过量使用等不合理的农业生产方式是导致Cu在耕地中富集的主要因素,严重威胁粮食安全和人类健康。以河北保定典型污灌区为研究区,通过静态吸附批量实验探究土壤吸附Cu的动力学和热力学特性。吸附动力学模型和等温吸附经验模型中得到的参数一致表明,表层土壤S1对Cu的吸附能力强于底部土壤S2。S1的有机质含量高于S2,提供了更多的表面吸附点位,这可能是导致土壤S1对Cu的吸附能力更强的原因之一。离子强度对土壤Cu吸附率的影响较小。溶液pH和溶解性有机物(DOM)含量对土壤Cu吸附率的影响明显,pH值与吸附量呈正相关,DOM浓度与吸附量呈负相关。由于土壤对pH有很强的缓冲能力,短时间的酸雨可能不会导致Cu的迁移。施用有机肥时,有机肥浸出液中高浓度的DOM可能会与Cu形成水溶性Cu-DOM络合物,促进Cu在土壤中的迁移,导致浅层地下水污染。     

溶液pH对自然水体中多种固相介质吸附铅、镉、铜影响的比较

采用实验室内模拟吸附方法,研究不同溶液pH下沉积物、悬浮颗粒物和生物膜吸附重金属的热力学特征。结果表明：在不同pH下,Langmuir方程均可以很好地描述自然水体三种固相介质吸附重金属的热力学过程。在相同pH条件下,三种固相介质对重金属的吸附能力从大到小依次为悬浮颗粒物、生物膜、沉积物,它们对重金属的吸附能力为铅>铜>镉;这三种固相介质对重金属的吸附能力都随着pH值的升高而增大,其中悬浮颗粒物对重金属的吸附能力受溶液pH影响最大;另外,相对于铜和镉,三种固相介质对铅的吸附受溶液pH影响较大。     

Adsorption of copper and zinc onto natural clay in single and binary systems

Calcareous and smectitic clay samples from the Coniacian–Lower Campanian system, Tunisia, were used as adsorbents for the removal of copper and zinc from aqueous solutions in single and binary systems. Calcareous clay sample was treated with acetic acid to obtain carbonate-free sample that was also used for metals removal. The adsorption of metal ions onto natural clay was tested in a batch method by mixing 1 g/L of each sample with a metal ion solution of zinc (300 μmol/L) and/or copper 600 μmol/L under the operating pH of 6, and agitation speed of 200 rpm within the equilibrium time of 60 min at 25 °C for single and binary systems. Our results showed that natural clay samples were mainly composed of silica, alumina, iron, and magnesium oxides. Adsorption data showed that the studied clay samples removed substantial amounts of heavy metals in single and mixed systems. Initial solution pH and carbonates contents enhanced the removal capacities of the studied clay samples, confirming their strong influencing effects. Thermodynamic parameters indicated an endothermic adsorption for metals removal by calcareous clay, but exothermic process for the smectitic sample. These results suggest that the Late Cretaceous clays, Tunisia, can be effectively used as natural adsorbents for the removal of toxic heavy metals in aqueous systems.     

Adsorption characteristics of heavy metals in soil zones developed on spilite

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.     

Impact of NaSO4 dominated ionic strength on trace metal removal products in vertical flow bioreactors

Vertical flow bioreactors (VFBR) are often used as a component of passive treatment systems (PTS) to treat mine drainage. One of the primary purposes of VFBR is to remove trace metals from mine drainage and retain them in the organic substrate. Elevated ionic strength may impact the performance of VFBR and affect their ability to remove trace metals. A paired-comparison study was performed to determine how products of trace metal removal may change when ionic strength is elevated due to increased concentrations of common contributors to TDS, specifically sodium and sulfate. A sequential extraction procedure (SEP) and acid-volatile sulfide/simultaneously extracted metals analyses (AVS/SEM) were used to determine dominant Cd, Mn, Ni, Pb, and Zn removal products in bench-scale VFBR. Elevated ionic strength resulted in more Pb being retained in the substrates as an insoluble sulfide and less Mn being removed via adsorption to the substrates. An increase in ionic strength had a greater impact on adsorption when sulfate reduction was inhibited, with percentages of Mn and Zn removed via this mechanism decreasing by at least half. This finding could be particularly significant at the start of VFBR operation when adsorption is expected to be the primary removal mechanism.