浮游球衣菌对Pb2+、Cu2+、Zn2+、Cd2+的吸附性能研究

研究了浮游球衣菌（Sphaerotilus natans）在不同吸附条件下对溶液中Pb^2＋、Cu^2＋、Zn^2＋、Cd^2＋的吸附规律。结果表明,Sphaerotilus natans对这4种重金属离子均有一定的吸附作用,并在20min内达到吸附平衡,pH对吸附过程影响较大,pH为5.5时Sphaerotilus natans对这4种金属离子的吸附效果最好,Sphaerotilus natans对它们的吸附选择性为Pb^2＋〉Cu^2＋〉Zn^2＋〉Cd^2＋,Pb^2＋、Cu^2＋能部分置换出已被菌体吸附的Zn^2＋、Cd^2＋。HCI和EDTA溶液可有效地将金属离子从菌体上解吸下来,解吸后的菌体可重复使用。     

Sorption kinetics and leachability of heavy metal from the contaminated soil amended with immobilizing agent (humus soil and hydroxyapatite)

Release of heavy metals onto the soil as a result of agricultural and industrial activities may pose a serious threat to the environment. This study investigated the kinetics of sorption of heavy metals on the non-humus soil amended with (1:3) humus soil and 1% hydroxyapatite used for in situ immobilization and leachability of heavy metals from these soils. For this, a batch equilibrium experiment was performed to evaluate metal sorption in the presence of 0.05 M KNO(3) background electrolyte solutions. The Langmuir isotherms applied for sorption studies showed that the amount of metal sorbed on the amended soil decreased in the order of Pb(2+)>Zn(2+)>Cd(2+). The data suggested the possibility of immobilization of Pb due to sorption process and immobilization of Zn and Cd by other processes like co-precipitation and ion exchange. The sorption kinetics data showed the pseudo-second-order reaction kinetics rather than pseudo-first-order kinetics. Leachability study was performed at various pHs (ranging from 3 to 10). Leachability rate was slowest for the Pb(2+) followed by Zn(2+) and Cd(2+). Out of the metal adsorbed on the soil only 6.1-21.6% of Pb, 7.3-39% of Zn and 9.3-44.3% of Cd leached out from the amended soil.     

Simultaneous heavy metal removal mechanism by dead macrophytes

The use of dead, dried aquatic plants, for water removal of metals derived from industrial activities as a simple biosorbent material has been increasing in the last years. The mechanism of simultaneous metal removal (Cd2+, Ni2+, Cu2+, Zn2+ and Pb2+) by 3 macrophytes biomass (Spirodela intermedia, Lemna minor and Pistia stratiotes) was investigated. L. minor biomass presented the highest mean removal percentage and P. stratiotes the lowest for all metals tested. Pb2+ and Cd2+ were more efficiently removed by the three of them. The simultaneous metal sorption data were analysed according to Langmuir and Freundlich isotherms. Data fitted the Langmuir model only for Ni and Cd, but Freundlich isotherm for all metals tested, as it was expected. The K(F) values showed that Pb was the metal more efficiently removed from water solution. The adsorption process for the three species studied followed first order kinetics. The mechanism involved in biosorption resulted ion exchange between monovalent metals as counter ions present in the macrophytes biomass and heavy metal ions and protons taken up from water. No significant differences were observed in the metal exchange amounts while using multi-metal or individual metal solutions.     

Removal of Pb(II), Cd(II), Cu(II), and Zn(II) by hematite nanoparticles: effect of sorbent concentration, pH, temperature, and exhaustion

Nanoparticles offer the potential to improve environmental treatment technologies due to their unique properties. Adsorption of metal ions (Pb(II), Cd(II), Cu(II), Zn(II)) to nanohematite was examined as a function of sorbent concentration, pH, temperature, and exhaustion. Adsorption experiments were conducted with 0.05, 0.1, and 0.5 g/L nanoparticles in a pH 8 solution and in spiked San Antonio tap water. The adsorption data showed the ability of nanohematite to remove Pb, Cd, Cu, and Zn species from solution with adsorption increasing as the nanoparticle concentration increased. At 0.5 g/L nanohematite, 100 % Pb species adsorbed, 94 % Cd species adsorbed, 89 % Cu species adsorbed and 100 % Zn species adsorbed. Adsorption kinetics for all metals tested was described by a pseudo second-order rate equation with lead having the fastest rate of adsorption. The effect of temperature on adsorption showed that Pb(II), Cu(II), and Cd(II) underwent an endothermic reaction, while Zn(II) underwent an exothermic reaction. The nanoparticles were able to simultaneously remove multiple metals species (Zn, Cd, Pb, and Cu) from both a pH 8 solution and spiked San Antonio tap water. Exhaustion experiments showed that at pH 8, exhaustion did not occur for the nanoparticles but adsorption does decrease for Cd, Cu, and Zn species but not Pb species. The strong adsorption coupled with the ability to simultaneously remove multiple metal ions offers a potential remediation method for the removal of metals from water.     

Impacts of pH and ammonia on the leaching of Cu(II) and Cd(II) from coal fly ash

Many coal-fired power plants are implementing ammonia-based technologies to reduce NO(x) emissions. Excess ammonia in the flue gas often deposits on the coal fly ash. Ammonia can form complexes with many heavy metals and change the leaching characteristics of these metals. This research tends to develop a fundamental understanding of the ammonia impact on the leaching of some heavy metals, exemplified by Cu(II) and Cd(II), under different pH conditions. Batch results indicated that the adsorption is the main mechanism controlling Cu(II) and Cd(II) leaching, and high concentrations of ammonia (>5,000 mg/l) can increase the release of Cu(II) and Cd(II) in the alkaline pH range. Based on the chemical reactions among fly ash, ammonia, and heavy metal ion, a mathematical model was developed to quantify effects of pH and ammonia on metal adsorption. The adsorption constants (logK) of Cu(2+), Cu(OH)(+), Cu(OH)(2), and Cu(NH(3))(m)(2+) for the fly ash under investigation were respectively 6.0, 7.7, 9.6, and 2.9. For Cd(II), these constants were respectively 4.3, 6.9, 8.8, and 2.6. Metal speciation calculations indicated that the formation of less adsorbable metal-ammonia complexes decreased metal adsorption, therefore enhanced metal leaching.     

Potentially toxic metals in ombrotrophic peat along a 400 km English-Scottish transect

Four samples of ombrotrophic peat were collected from each of 10 upland locations in a transect from the southern Pennines to the Highland Boundary Fault, a total distance of ca. 400 km. Bulk compositions and other properties were determined. Total contents of Al and heavy metals (Ni, Cu, Zn, Cd, Pb) were determined following digestion with hydrofluoric acid, and concentrations of metals extractable with dilute nitric acid were also measured. Supernatants obtained from aqueous extractions of the peat samples were analysed for pH, major cations and anions, dissolved organic carbon and dissolved metals, and concentrations of free metal ions (Al(3+), Ni(2+), etc.) were estimated by applying a chemical speciation model. Both total and HNO(3)-extractable metal concentrations varied along the transect, the highest values being found at locations close to industrial and former mining areas. The HNO(3)-extractable soil metal contents of Ni, Cu and Cd were appreciably lower than lowest-observed-effect-concentrations (LOEC) for toxicity towards microorganisms in acid, organic rich soils. However, the contents of Zn at two locations, and of Pb at five locations exceeded LOECs, suggesting that they may be exerting toxic effects in the peats. Soil solution concentrations of free heavy metal ions (Cu(2+), Zn(2+), Cd(2+), Pb(2+)) were substantially lower than LOECs for toxicity towards vascular plants, whereas concentrations of Al(3+) were near to toxic levels at two locations.     

Equilibrium, kinetic, and thermodynamic biosorption of Pb(II), Cr(III), and Cd(II) ions by dead anaerobic biomass from synthetic wastewater

Purpose

Heavy metals are toxic pollutants released into the environment as a result of different industrial activities. Biosorption of heavy metals from aqueous solutions is a new technology for the treatment of industrial wastewater. The aim of the present research is to highlight the basic biosorption theory to heavy metal removal.

Materials and methods

Heterogeneous cultures mostly dried anaerobic bacteria, yeast (fungi), and protozoa were used as low-cost material to remove metallic cations Pb(II), Cr(III), and Cd(II) from synthetic wastewater. Competitive biosorption of these metals was studied.

Results

The main biosorption mechanisms were complexation and physical adsorption onto natural active functional groups. It is observed that biosorption of these metals was a surface process. The main functional groups involved in these processes were hydroxyl (–OH) and carboxylic groups (C=O) with 37, 52, and 31 and 21, 14, and 34 % removal of Pb(II), Cr(III), and Cd(II), respectively. Langmuir was the best model for a single system. While extended Langmuir was the best model for binary and ternary metal systems. The maximum uptake capacities were 54.92, 34.78, and 29.99 mg/g and pore diffusion coefficients were 7.23, 3.15, and 2.76?×?10^?11 m²/s for Pb(II), Cr(III), and Cd(II), respectively. Optimum pH was found to be 4. Pseudo-second-order was the best model to predict the kinetic process. Biosorption process was exothermic and physical in nature.

Conclusions

Pb(II) offers the strongest component that is able to displace Cr(III) and Cd(II) from their sites, while Cd(II) ions are the weakest adsorbed component.     

可渗透反应复合电极法对土壤重金属的电动去除

将零价铁(Fe0)、沸石等活性材料附着在电极上形成可渗透反应层并构成可渗透反应复合电极,采用不同的复合电极对Cd2+、Ni 2+、Pb2+和Cu2+等4种阳离子型重金属污染土壤进行了电动力学修复。研究了不同可渗透反应复合电极对土壤pH的控制效果以及对重金属的去除作用,分析了迁移到复合电极中的重金属形态变化。结果表明,复合电极中添加酸、碱性沸石并适时更换,可有效中和、截留阴阳极电解产生的OH-和H+,避免或减缓土壤酸碱迁移带的形成,防止重金属离子的过早沉淀及土壤过度酸化,极大提高了重金属的去除率。复合电极中Fe0可将迁移进来的重金属离子进行还原稳定,实现重金属污染物的捕获与固定,与迁移到沸石复合电极中的4种重金属不稳定态相比,"Fe0+沸石"复合电极中重金属不稳定态分别下降了61.4、60.5、61.4、57.1百分点。结果还显示,阴极采用"Fe0+沸石"复合电极并适时进行更换,施加1.5V/cm的直流电压修复10d后,土壤中Cd、Ni、Pb、Cu的总去除率分别为44.5%、41.5%、33.5%和36.7%,且进一步延长修复时间和持续更换电极可获得更为理想的修复效果。     

Evaluation of remediation process with plant-derived biosurfactant for recovery of heavy metals from contaminated soils

A washing process was studied to evaluate the efficiency of saponin on remediating heavy metal contaminated soils. Three different types of soils (Andosol: soil A, Cambisol: soil B, Regosol: soil C) were washed with saponin in batch experiments. Utilization of saponin was effective for removal of heavy metals from soils, attaining 90-100% of Cd and 85-98% of Zn extractions. The fractionations of heavy metals removed by saponin were identified using the sequential extraction. Saponin was effective in removing the exchangeable and carbonated fractions of heavy metals from soils. In recovery procedures, the pH of soil leachates was increased to about 10.7, leading to separate heavy metals as hydroxide precipitates and saponin solute. In addition recycle of used saponin is considered to be effective for the subsequent utilization. The limits of Japanese leaching test were met for all of the soil residues after saponin treatment. As a whole, this study shows that saponin can be used as a cleaning agent for remediation of heavy metal contaminated soils.     

The solid-solution partitioning of heavy metals (Cu,Zn, Cd,Pb) in upland soils of England and Wales

Ninety-eight surface soils were sampled from the uplands of England and Wales, and analysed for loss-on-ignition (LOI), and total and dissolved base cations, Al, Fe, and trace heavy metals (Cu, Zn, Cd, Pb). The samples covered wide ranges of pH (3.4-8.3) and LOI (9-98%). Soil metal contents measured by extraction with 0.43 mol l-1 HNO3 and 0.1 mol l-1 EDTA were very similar, and generally lower than values obtained by extraction with a mixture of concentrated nitric and perchloric acids. Total heavy metal concentrations in soil solution depend positively upon soil metal content and [DOC], and negatively upon pH and LOI, values of r2 ranging from 0.39 (Cu) to 0.81 (Pb). Stronger correlations (r2=0.76-0.95) were obtained by multiple regression analysis involving free metal ion (Cu2+, Zn2+, Cd2+, Pb2+) concentrations calculated with the equilibrium speciation model WHAM/Model VI. The free metal ion concentrations depend positively upon MHNO3 and negatively upon pH and LOI. The data were also analysed by using WHAM/Model VI to describe solid-solution interactions as well as solution speciation; this involved calibrating each soil sample by adjusting the content of "active" humic matter to match the observed soil pH. The calibrated model provided fair predictions of total heavy metal concentrations in soil solution, and predicted free metal ion concentrations were in reasonable agreement with the values obtained from solution-only speciation calculations.     

Selective removal of the heavy metal ions from waters and industrial wastewaters by ion-exchange method

By ion exchange undesirable ions are replaced by others which don't contribute to contamination of the environment. The method is technologically simple and enables efficient removal of even traces of impurities from solutions. Examples of selective removal of heavy metal ions by ion-exchange are presented. They include removal of Pb(II), Hg(II), Cd(II), Ni(II), V(IV,V), Cr(III,VI), Cu(II) and Zn(II) from water and industrial wastewaters by means various modern types of ion exchangers.     

Influence of metal ion on sorption of p-nitrophenol onto sediment in the presence of cetylpyridinium chloride

Heavy metals and surfactants have a significant effect on the sorption of organic contaminants. In this study, batch equilibrium experiments were carried out to investigate the influence of Pb(NO(3))(2) on the sorption of p-nitrophenol (PNP) onto sediments in the presence of cationic surfactant cetylpyridinium chloride (CPC). Results indicated that in the complex system containing PNP, Pb(NO(3))(2) and CPC, the sorption of PNP decreased with increasing concentration of Pb(NO(3))(2) due primarily to competing for adsorption sites. Likewise, partitioning of PNP in adsorbed surfactant layers and micelles decreased with increasing level of Pb(NO(3))(2). Moreover, the influence of different metal ions (Pb(2+), Cd(2+), Zn(2+)) was examined and results indicated that the presence of heavy metals inhibited the sorption of PNP in the order: Pb(2+)>Cd(2+)>Zn(2+). The competitive effect of the heavy metals was in agreement with the hydration energy and hydrated radius. The results are believed to provide a useful insight into describing the transport and fate of PNP in natural environments.     

Biosorption of heavy metals using rice milling by-products. Characterisation and application for removal of metals from aqueous effluents

The morphological characteristics as well as chemical composition of rice husks were evaluated by different techniques such as spectroscopy and thermogravimetry. The material, which is considered a by-product obtained from rice milling, was then investigated as a potential decontaminant of toxic heavy metals present in laboratory effluents. Studies using glass columns were carried out at room temperature employing 100 ml of synthetic solutions containing Cd(II) and Pb(II) at 100 mg l(-1) in order to study the effects of pH, flow rate and particle size on Cd(II) and Pb(II) adsorption. After establishing the optimised conditions, the potentiality of rice husks for removing Cd(II) and Pb(II) ions from 100 ml of laboratory effluent, presenting concentrations before treatment of 22 and 12 mg l(-1), respectively, was evaluated. The ability to take up other metals species, such as Al(III), Cu(II) and Zn(II), present in this effluent was also studied. According to the data obtained, under the optimised conditions (pH=4.0, flow rate of 8.0 ml min(-1) and < or =355 microm rice husk particle size), 30 g of husks were necessary to attain the permissible limits for effluent release, as recommend by the EPA, for those species evolved in this work (Al, Cd, Cu, Pb and Zn).     

Copper and cadmium removal from synthetic industrial wastewater using chitosan and nylon 6

Purpose

Chitosan with nylon 6 membranes was evaluated as adsorbents to remove copper and cadmium ions from synthetic industrial wastewater.

Methods

Chitosan and nylon 6 with glutaraldehyde blend ratio with (1:1+Glu, 1:2+Glu, and 2:1+Glu) have been prepared and these were used as membranes to remove copper and cadmium ions from synthetic industrial wastewater. Characterization of the synthesized membrane has been done with FTIR, XRD, TGA/DTA, DSC, and SEM. Chemical parameters for quantities of adsorption of heavy metal contamination have been done and the kinetics of adsorption has also been carried out.

Results

The optimal pH for the removal of Cd(II) and Cu(II) using chitosan with nylon 6. Maximum removal of the metals was observed at pH 5 for both the metals. The effect of adsorbent dose also has a pronounced effect on the percentage of removal of the metals. Maximum removal of both the metals was observed at 5 g/100 ml of the adsorbent.

Conclusion

Copper and cadmium recovery is parallel at all time. The percentage of removal of copper increased with increase in the pH from 3 to 5. In the case of cadmium containing wastewater, the maximum removal of metal occurred at pH 5. The uptake amount of Cu²⁺ ions on chitosan increased rapidly with increasing contact time from 0 to 360 min and then reaches equilibrium after 360 min; the equilibrium constant for copper and cadmium ions is more or less the same for the adsorption reaction.     

Biosorption of copper(II) from aqueous solutions by pre-treated biomass of marine algae Padina sp

Biosorption of heavy metals can be an effective process for the removal and recovery of heavy metal ions from aqueous solutions. The biomass of marine algae has been reported to have high uptake capacities for a number of heavy metal ions. In this paper, the adsorption properties of a pre-treated biomass of marine algae Padina sp. for copper(II) were investigated. Equilibrium isotherms and kinetics were obtained from batch adsorption experiments. The biosorption capacities were solution pH dependent and the maximum capacity obtained was 0.80 mmol/g at a solution pH of about 5. The biosorption kinetics was found to be fast, with 90% of adsorption within 15 min and equilibrium reached at 30 min. The effects of light metal ions on copper(II) uptake were studied and the presence of light metal ions did not affect copper(II) uptake significantly. Fixed-bed breakthrough curves for copper(II) removal were also obtained. This study demonstrated that the pre-treated biomass of Padina sp. could be used as an effective biosorbent for the treatment of copper(II) containing wastewater streams.     

黄河水中沉积物与锌、镉液-固界面的作用

研究了黄河水中沉积物与重金属污染物Zn^2 、Cd^ 的离子交换吸附作用。结果表明,Zn^2 、Cd^2 在黄河水中主要以M（OH）^ 的形式与沉积物进行－价阳离子交换反应;在天然黄河水pH范围内,Zn^2 、Cd^2 的离子交换率都大于70％;随温度升高,Zn^2 、Cd^2 与沉积物的交换率增加,E-pH曲线向pH值减小的方向位移。     

Polyelectrolyte enhanced ultrafiltration (PEUF) for the removal of Cd(II): effects of organic ligands and solution pH

This study focused on the effects of pH and organic ligands, namely ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and citric acids, on the removal and recovery of Cd(II) in polyelectrolyte enhanced ultrafiltration (PEUF). Polyethylenimine (PEI), which can bind with both positively charged metal ions by coordination bonding and negatively charged ligand-metal complexes by charge attraction, was employed as a chelating polymer. The removal and recovery of Cd species was greatly dependent on the chemistry of organic ligands according to solution pH, particularly being related to the distribution of Cd-ligand complexes at different pH levels. In the presence of EDTA, the dominant Cd species are negatively charged Cd(EDTA)(2-) and CdH(EDTA)(-) over the range of pH levels investigated, interacting with PEI via electrostatic attraction and being less pH dependent. On the other hand, the pH effects of both NTA and citric acid systems are similar to that for the system without organic ligands. This was associated with the fact that free Cd ions were predominant at the acidic pH range in both NTA and citric acid systems.     

改性玉米淀粉对Cu2＋、Pb2＋和Zn2＋的吸附特性研究

以玉米淀粉为原料,经过交联、醚化、胺化和亲核加成等步骤合成了一种新型重金属吸附剂——二硫代氨基甲酸改性淀粉（DTCS）。改性淀粉的结构采用红外光谱和扫描电镜进行表征。DTCS是一种性能优良的重金属吸附剂,对Cu2＋、Pb2＋和Zn2＋的饱和吸附容量随着pH（pH=2~6）的增加而增大。在有EDTA络合剂存在和酸性废水pH小于3的情况下,DTCS对Cu2＋、Pb2＋和Zn2＋仍有较高的去除率,分别达到90%、75%和50%以上,说明DTCS在含重金属离子的实际废水体系具有一定的实用价值。     

The sorption of heavy metal species by sediments in soakaways receiving urban road runoff

Infiltration facilities are designed for both the retention of non-point pollutants and the replenishment of groundwater in urban areas. In this study, sorption tests were conducted to evaluate the speciation of heavy metals and their behaviour in infiltration facilities receiving urban road runoff containing high DOC concentrations and stable heavy metal organic complexes. Road dust and three soakaway sediments were collected from heavy traffic areas and a residential area with an infiltration-type sewerage system in Tokyo, Japan. Sequential multiple batch tests were conducted by adding prepared road dust leachate (artificial road runoff) or deionised water to soakaway sediment to obtain soakaway sediment leachate (artificial percolating water from soakaway sediment), which mimicked the sorption by sediments in soakaways receiving urban road runoff. Heavy metal speciation was assessed by means of a combination of anion-exchange resin measurements and MINTEQA2 model calculations, and further validated by chelating resin measurements. In road dust leachates and soakaway sediment leachates, Cu predominantly existed as organic complexes and carbonates, whereas most Mn, Zn and Cd were found to exist in the form of free ions and carbonate complexes. Stable organic complexes of Cu in road dust leachates were strongly adsorbed by soakaway sediments despite the limited adsorption of DOC. On the other hand, desorption of free Mn, Zn and Cd ions from the sediment receiving road dust leachates was observed, indicating that heavy metals such as Mn, Zn and Cd may ultimately reach groundwater as free ions.