Modeling heavy metal uptake by sludge particulates in the presence of dissolved organic matter

The uptake of the seven heavy metal ions Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II) by sludge particulates in single-metal systems was investigated. Results showed that under acidic and neutral pH conditions, the uptake of all heavy metals by sludge particulates increases with the increase of pH. However, in the alkaline pH region, the uptake of Cu(II), Ni(II), and Co(II) decreases with the increase of pH, primarily due to the high dissolved organic matter (DOM) concentration in high pH conditions. Based on chemical reactions among heavy metal, sludge solids, and DOM, a mathematical model describing metal uptake as functions of DOM and pH was developed. The stability constants of metal–sludge and metal–DOM complexes can be determined using this model in conjunction with experimental metal uptake data. Results showed that, for the secondary sludge sample collected from Baltimore Back River Wastewater Treatment plant on March 1997, the stability constants of Cu(II)–sludge complex (log K_S) and Cu(II)–DOM complex (log K_L) are 5.3±0.2 and 4.7±0.3, respectively; for Ni(II), they are 4.0±0.2 and 3.9±0.2, respectively. Results also showed that under neutral and low pH conditions (pH<8), the DOM effects on metal uptake for all heavy metals are insignificant. Therefore, the DOM term in the model can be ignored. Results showed that, for the secondary sludge sample collected from Baltimore Back River Wastewater Treatment plant on December 1996, the estimated log K_S values of metal–sludge complexes for Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II) are, respectively, 3.6±0.2, 3.0±0.1, 5.5±0.1, 4.8±0.1, 3.1±0.1, 5.1±0.1, and 4.4±0.3.     

The assessment of the state of pollution of the waters of the Trascarpathian rivers with heavy metals

The paper has given an assessment of the state of pollution of the Transcarpathian surface waters with heavy metals Pb(II), Cu(II), and Zn(II), which penetrate as a result of technogenic disasters, anthropogenic loads, with runoffs from floods in the basin of the Tisa River and as a result of natural anomalies caused by snow melting, shower rains in the Rika River over the period 2005–2009.     

The acute lethal toxicity of heavy metals to peracarid crustaceans (with particular reference to fresh-water asellids and gammarids)

In static tests on the acute toxicity of metal salts to two fresh-water peracarids, Asellus aquaticus (L.) (Isopoda) and Crangonyx pseudogracilis Bousfield (Amphipoda), 48 and 96 h LC₅₀ values were determined for Al(III), Cd(II), Cr(III), Cu(II), Fe(III), Hg(II), Mn(II), Ni (II), Pb(II) and Zn(II). Additional metals tested upon Crangonyx alone were Ag(I), Co(II), Cr(VI), Fe(II), Mn(VII), Mo(VI), Sn(II) and V(V). Of the metal salts tested on both species, Asellus was more sensitive to Al(III) and Mn(II) than Crangonyx, similarly sensitive to Cd(II), Fe(III) and Zn(II), and less sensitive to the remainder. Toxicity of metal salts which are unstable with respect to reduction or oxidation was found to be higher than that of the corresponding stable salts of the same metal.Previously published data on the acute toxicity of heavy metal salts to fresh-water, estuarine and marine amphipods and isopods are tabulated and discussed. Brief comparisons are also made between the relative tolerances of peracarids, Daphnia and fresh-water fish. Crangonyx pseudogracilis is recommended as worthy of further research, due to its widespread distribution and ease of culture.     

Removal of toxic metal ions with magnetic hydrogels

Hydrogels, based on 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) were synthesized via photopolymerization technique and used for the preparation of magnetic responsive composite hydrogels. These composite hydrogels with magnetic properties were further utilized for the removal of toxic metal ions such as Cd(II), Co(II), Fe(II), Pb(II), Ni(II), Cu(II) and Cr(III) from aqueous environments. It was revealed that hydrogel networks with magnetic properties can effectively be utilized in the removal of pollutants. The results verified that magnetic iron particle containing p(AMPS) hydrogel networks provide advantageous over conventional techniques. Langmuir and Freundlich adsorption isotherms were applied for toxic metal removal and both isotherms were fit reasonably well for the metal ion absorptions.     

Impact of complexing agents on the processes of sorption treatment of waters containing cobalt

We have investigated the impact on the Co(II) sorption by montmorrilonite of complexing agents: ethylenediaminetetraacetic acid disodium salts (EDTA) and nitrilotriacetic acids (NTA), and fulvic acids (FA). By the impact value of the latter on the Co(II) sorption process by montmorrilonite they can be arranged into a series: EDTA > NTA > FA.     

Enhanced adsorption of Cd (II) on a hydrous Al (III) floc in the presence of a modified form of polyethylenimine

A polymer modified with succinic anhydride has been investigated for the adsorption of cadmium (II) on a freshly precipitated aluminium (III) hydroxide floc. The proportion of chelate attached to the polymer is varied to determine the relationship between carboxyl and amino groups on the polyelectrolyte, in terms of enhanced adsorption of cadmium (II) on a hydrous aluminium floc. The presence of polyelectrolyte enhanced the adsorption of 3.3 ppm Cd (II) on a 333 ppm Al (III) floc at every concentration of polyelectrolyte investigated. The proportion of succinic anhydride attached to the polymer had an impact on the increased adsorption of Cd (II) on an Al (III) floc observed. A decreasing proportion of succinic anhydride to polymer resulted in a decrease in the amount of cadmium adsorbed on the floc. Above pH 8, a decrease in the % Cd (II) adsorbed on the floc and % Al (III) retained within the floc decreases with the presence of polyelectrolyte as a result of the formation of soluble Cd-Polyethylenimine-succinic acid (PEISA) complexes. When the Al-PEISA combination was applied to a complex matrix where Cd (II), Cu (II) and Ni (II) ions competed for adsorption, enhanced adsorption was observed for Cd (II) and Ni (II). At pH 7, dissolution of the floc observed with the addition of discrete chelates was not observed with the addition of polyelectrolytes.     

Study on the effect of <Emphasis Type="Italic">Artemia franciscana</Emphasis> on the uptake of Zn(II) and Cu(II)

The toxicokinetic study was used to assess the potential of an organism for Zn(II) and Cu(II) bioaccumulation and it was ascertained using a bicompartmental model. The effect of Zn(II) and Cu(II) concentration on the kinetics parameter in Artemia franciscana were determined. In the present investigation, the uptake rate seems to be high with the time period of 72 h for Zn(II) when compared to Cu(II) by the process of bioaccumulation. The bioconcentration factor (BCF) and metal influx rate (I) was also found higher in the Artemia which was exposed to Zn(II) when compared to Cu(II), whereas BCF was inversely related to the concentration. From these parameters, we may predict the effective bioaccumulation of Zn(II) and Cu(II) using Artemia franciscana and whose kinetic parameters were found to be suited to the bicompartmental model.     

Removal of copper,nickel, cobalt and manganese from aqueous solution by kaolinite

The removal of some heavy metals such as Mn(II), Co(II), Ni(II), and Cu(II) from aqueous solution is studied using a raw kaolinite. The sorption of these metals on kaolinite conformed to linear form of Langmuir adsorption equation. Langmuir C(m) constants for each metal were found as 0.446 mg/g (Mn), 0.919 mg/g (Co), 1.669 mg/g (Ni), 10787 mg/g (Cu) at 25 degrees C, respectively. Also, kinetic and thermodynamic parameters such as enthalpy (deltaH), free energy (deltaG) and entropy (deltaS) were calculated and these values show that adsorption of heavy metal on kaolinite was an endothermic process and the process of adsorption was favoured at high temperatures.     

Removal of metals by chemical treatment of municipal waste water

The reduction of the metal content of waste water by chemical treatment with aluminium sulfate or calcium hydroxide has been studied. p] Pb(II), Cu(II), Cr(III), Hg(II), Cd(II) and As(V) are reduced to low levels by both precipitants. Zn(II), Ni(II) and Co(II) are precipitated only at pH-values ≤ 9·5. The precipitation of Cu(II) and Pb(II) is greatly inhibited by the presence of nitrilotriacetate at pH ≤9.     

Adsorption of heavy metals by a sorbent based on pine bark

Sorption properties of the pine bark treated with a 5% urea solution have been studied with respect to heavy metals Cu(II), Ni(II), Zn(II), and Pb(II). The bark subjected to treatment has higher sorption properties and retains several times as many metals as the untreated bark. Parameters of the Langmuir and Freundlich sorption isotherms were obtained. The possible mechanisms of the bark interaction with urea and reasons for an enhanced metal adsorption on the bark treated with urea solution have been also discussed.     

Highly efficient removal of heavy metals by polymer-supported nanosized hydrated Fe(III) oxides: Behavior and XPS study

The present study developed a polymer-based hybrid sorbent (HFO-001) for highly efficient removal of heavy metals [e.g., Pb(II), Cd(II), and Cu(II)] by irreversibly impregnating hydrated Fe(III) oxide (HFO) nanoparticles within a cation-exchange resin D-001 (R-SO₃Na), and revealed the underlying mechanism based on X-ray photoelectron spectroscopy (XPS) study. HFO-001 combines the excellent handling, flow characteristics, and attrition resistance of conventional cation-exchange resins with the specific affinity of HFOs toward heavy metal cations. As compared to D-001, sorption selectivity of HFO-001 toward Pb(II), Cu(II), and Cd(II) was greatly improved from the Ca(II) competition at greater concentration. Column sorption results indicated that the working capacity of HFO-001 was about 4-6 times more than D-001 with respect to removal of three heavy metals from simulated electroplating water (pH ∼4.0). Also, HFO-001 is particularly effective in removing trace Pb(II) and Cd(II) from simulated natural waters to meet the drinking water standard, with treatment volume orders of magnitude higher than D-001. The superior performance of HFO-001 was attributed to the Donnan membrane effect exerted by the host D-001 as well as to the impregnated HFO nanoparticles of specific interaction toward heavy metal cations, as further confirmed by XPS study on lead sorption. More attractively, the exhausted HFO-001 beads can be effectively regenerated by HCl-NaCl solution (pH 3) for repeated use without any significant capacity loss.     

Comparisons of low-cost adsorbents for treating wastewaters laden with heavy metals

In this article, the removal performance and cost-effectiveness of various low-cost adsorbents derived from agricultural waste, industrial by-product or natural material are evaluated and compared to those of activated carbon for the removal of heavy metals (Cd(II), Cr(III), Cr(VI), Cu(II), Ni(II) and Zn(II)) from metals-contaminated wastewater. To highlight their technical applicability, selected information on pH, dose required, initial metal concentration, adsorption capacity and the price of the adsorbents is presented. It is evident from the survey of 102 published studies (1984-2005) that low cost adsorbents derived from agricultural waste have demonstrated outstanding capabilities for the removal of heavy metal (Cr(VI): 170 mg/g of hazelnut shell activated carbon, Ni(II): 158 mg/g of orange peel, Cu(II): 154.9 mg/g of soybean hull treated with NaOH and citric acid, Cd(II): 52.08 mg/g of jackfruit), compared to activated carbon (Cd(II): 146 mg/g, Cr(VI): 145 mg/g, Cr(III): 30 mg/g, Zn(II): 20 mg/g). Therefore, low-cost adsorbents can be viable alternatives to activated carbon for the treatment of metals-contaminated wastewater. It is important to note that the adsorption capacities presented in this paper vary, depending on the characteristics of the individual adsorbent, the extent of surface modification and the initial concentration of the adsorbate. In general, technical applicability and cost-effectiveness are the key factors that play major roles in the selection of the most suitable adsorbent to treat inorganic effluent.     

Removal of metal ions by modified Pinus radiata bark and tannins from water solutions

Pinus radiata bark and tannins, chemically modified with an acidified formaldehyde solution were used for removing metal ions from aqueous solutions and copper mine acidic residual waters. The adsorption ability to different metal ions [V(V), Re(VII), Mo(VI), Ge(IV), As(V), Cd(II), Hg(II), Al(III), Pb(II), Fe(II), Fe(III), Cu(II)] and the factors affecting their removal from solutions were investigated. Effect of pH on the adsorption, desorption, maximum adsorption capacity of the adsorbents, and selectivity experiments with metal ion solutions and waste waters from copper mine were carried out. The adsorbents considerably varied in the adsorption ability to each metal ion. The adsorption depends largely upon the pH of the solution. Modified tannins showed lower adsorption values than the modified bark. For the same adsorbent, the maximum capacity at pH 3 for the different ions were very different, ranging for modified bark from 6.8 meqg⁻¹ for V to 0.93 meqg⁻¹ for Hg. Waste waters were extracted with modified bark as adsorbent and at pH 2. The ions Cu(II) (35.2 mgL⁻¹), Fe(III) (198 mgL⁻¹), Al(III) (83.5 mgL⁻¹) and Cd(II) (0.15 mgL⁻¹) were removed in 15.6%, 46.9%, 83.7% and 3.3%, respectively, by using 1 g of adsorbent/10 mL of waste water. In general, a continuous adsorption on a packed column gave higher adsorbed values than those observed in the batchwise experiment.     

Application of sub-critical water technology for recovery of heavy metal ions from the wastes of Japanese scallop Patinopecten yessoensis

Sub-critical water (sub-CW) technology was used as a new technology with environmental and financial benefits for the recovery of harmful heavy metal ions Cd (II), Zn (II), Cu (II), Fe (II), Mn (II) and Ni (II) in the waste of Japanese scallop Patinopecten yessoensis. The metals are responsible for environmental problems owing to the large amount of the waste. This study proposes a new method using sub-CW treatment to recover the metal ions from scallop waste and simultaneously produce harmless and valuable materials. Reactions were conducted in a temperature range of 473-653 K and for reaction times of 1-60 min. After the sub-CW reaction, four phases existed: an oil phase, metal-soap phase, aqueous phase and solid residual. Some oil was hydrolyzed by the sub-CW reaction and converted to free fatty acids and glycerin. Free fatty acids reacted with metal ions and became metal-soap phase. Both the metal-soap phase and oil phase caught almost all metal ions at low and medium reaction temperatures (473-573 K) from original wastes, although the concentrations of the metal ions in the metal-soap phase were much higher than those in the oil phase. With increasing temperature, these two phases decomposed and the metal ions concentrated in solid residual (un-reacted waste). The binding mechanisms in the oil and metal-soap phases are discussed including the key functional groups involved. The maximum concentrations of metal ions in metal-soap phase were 7225 ppm (Fe), 862 ppm (Zn), and 800 ppm (Cd) at 573 K. The aqueous phase showed the lowest concentration of metal ions especially at temperatures above 550 K (~1.5 ppm).     

Uptake of heavy metals from synthetic aqueous solutions using modified PEI-silica gels

The decontamination of synthetic Pb(II), Zn(II), Cd(II), Ni(II) solutions was investigated, using silica gels chemically modified with poly(ethyleneimine) (PEI) as sorbents. Two families of sorbents, i.e. silica/PEI and crosslinked silica/PEI, were prepared and characterized. Then the removal of metal ions from synthetic aqueous solutions was studied by static tests. They revealed that the sorption capacities depend on the pH, the initial concentration and to some extent on the nature of the metal. The recovery of the metal cations from the saturated sorbents was possible with diluted acid, only for the crosslinked supports. In this case, the regeneration and reuse without sorption decrease, was demonstrated. The presence of other cations (as Na(+), Ca(2+)) and metals does not affect the sorption capacities.     

Desorption characteristics of Cr(III), Mn(II), and Ni(II) in contaminated soil using citric acid and citric acid-containing wastewater

Heavy metal-contaminated soil and wastewater have been attracting an increasing amount of attention due to the potential threat to the surrounding environment and human health. Thus, in this study, citric acid (CA) and citric acid-containing wastewater (CACW) were selected for an evaluation of the influence of the contamination level of the soil, the concentration of citric acid, the contact time, the soil pH, and the ionic interaction on the desorption characteristics of three heavy metals (i.e., Cr(III), Mn(II), and Ni(II)). According to the experimental results, a high concentration of citric acid, an acidic condition, a low level of contamination, and a lengthy contact time were found to be beneficial for desorbing the heavy metals from the contaminated soil. Based on the experimental and calculated results, the H⁺ ions and organic ligands made substantial contributions to the release and adsorption of the heavy metals. The metal ions on the low selectivity sorption sites were leached out earlier than those on the high selectivity sorption sites. The removal percentages of Cr(III), Mn(II), and Ni(II) using CA with a contact time of 6?h were 39.9%, 77.0%, and 62.8%, respectively. By using the CACW as a desorbent, the removal percentages of Cr(III), Mn(II), and Ni(II) with a contact time of 6?h reached 21.4%, 26.9%, and 63.4%, respectively. This suggests a promising practical application of CACW for removing heavy metals from contaminated soil.     

The impact of surface properties of modified pine bark on the mechanism of sorption of heavy metals from aqueous media

The surface properties of pine bark before and after the treatment with urea solution and the adsorption of Cu(II), Ni(II) and Zn(II) from aqueous solutions at different pH values have been studied. Types of active sorption sites, their surface concentration and change after the bark treatment with urea solution were determined. The results of potentiometric titration were processed by using ProtoFit and FITEQL software programs. The data obtained make it possible to conclude that in the extraction mechanism of heavy metals from water the share of ion exchange decreases and the share of complexation increases. The impact of alkaline and alkaline earth metals in the range of their concentrations up to 3000 mg/dm³ on Cu(II) extraction from model aqueous solutions was also investigated.     

Potential of zero-valent iron in remediation of Cd(II) contaminated soil: From laboratory experiment,mechanism study to field application

This study investigates the potential of ZVI on Cd(II) contaminated soil remediation through laboratory experiment, mechanism study and field application. The results show that the dosage of ZVI, the initial concentration level and the reaction time have significant impacts on Cd(II) adsorption and about 88% of aqueous Cd(II) can be removed from soils. The ZVI is observed to promote the increase of Cd(II) residual fraction in Cd(II) contaminated soils according to the sequential extraction procedure (SEP) results. Regression of the laboratory experimental data based on the Langmuir isotherm equation shows the adsorption capacity can reach 34.7 mg/g. Such a high value is attributed to physical and chemical adsorption, which is proved by X-ray diffraction patterns (XRD), scanning electron microscope images (SEM), and Brunner-Emmet-Teller & Barret–Joyner–Halenda (BET-BJH) analysis. The field application shows that the ZVI can reduce the Cd(II) content in soils and brown rice by 51% and alleviate soil acidification, resulting in a 9.4% increase in rice yields.     

Removal of toxic metals from aqueous solutions by layered double hydroxides

The article has investigated the possibility of using layered double hydroxide intercalated by diethylenetriaminepentaactetic acid for the removal of toxic metals from aqueous solutions. It has been shown that sorption of Ni(II), Co(II), and Pb(II) from aqueous solutions on the indicated sorbent is determined by several mechanisms of sorption: complexation, ionic exchange and precipitation of metal hydroxides. Comparative research of the efficiency of removing toxic metals by carbonate and chelate forms of sorbents was conducted.     

Effects of fulvic fractions on the pH-dependent sorption of Cu(II) to kaolinite

Sorption of copper on kaolinite in the absence and presence of four fulvic acid (FA) fractions fractionated using XAD-8 resin, including F4.8, F7.0, F11.0 and Feth fractions (eluted by pH4.8 buffer, pH7.0 buffer, pH11.0 buffer, and ethanol (95%), respectively, was investigated by batch experiments. Results showed that the binding of Cu(II) by pure kaolinite increased with an increase in pH values. The presence of each FA fraction significantly affects the sorption of Cu(II) to kaolinite. Below pH 6.3, Cu(II) sorption was pronouncedly promoted after adding FA fraction to binary systems, compared to that in pure kaolinite suspensions. Magnitude in enhancement of Cu(II) sorption to solid phase, which was caused by FA fractions, followed an order of F4.8>F7.0>11.0>Feth. Above pH 6.3, nearly all the Cu(II) were removed from solution in pure koalinte system, while a portion of Cu(II) left in aqueous phase via formation of dissolved Cu-FA complexes, was observed in systems in the presence of FA fractions. The largest Cu(II) distribution coefficients (K(d)) between solid phase and aqueous solution at pH 3.15-5.7, are obtained from the ternary system with F4.8 fraction. The smallest K(d) are from system in the presence of Feth fraction. Conversely, over a pH range from 5.7 to 7.0, the highest K(d) values are from system with Feth fraction. Overall, F4.8 fraction exhibited the greatest effect on Cu(II) pH-dependent sorption to kaolinite, and Feth fraction had the least. Functional groups such as carboxyl, phenolic moieties of FA played the vital role in Cu(II) sorption to kaolinite at lower pH conditions, and solubility under neutral conditions.