Sorption kinetics of Fe(II), Zn(II), Co(II), Ni(II), Cd(II), and Fe(II)/Me(II) onto hematite

The reactions of Fe(II) and other divalent metal ions including Zn, Co, Ni, and Cd on hematite were studied in single and competitive binary systems with high sorbate/sorbent ratios in 10 mM PIPES (pH 6.8) solution under strict anoxic conditions. Adsorbed Me(II) was defined as extractable by 0.5 N HCl within 20 h, and fixed Me(II) was defined as the additional amount that was extracted by 3.0 N HCl within 7 days. Binary systems contained Fe(II) plus a second metal ion. The extent of uptake of divalent metal ions by hematite was in order of Fe> or =Zn>Co> or =Ni>Cd. For all metals tested, there was an instantaneous adsorption followed by a relatively slow stage that continued for the next 1-5 days. This sequence occurred in both single and binary systems, and could have been due to a variety of sorption site types or due to slow conversion from outer- to inner-sphere surface complexes due to increasing surface charge. Sorption competition was observed between Fe(II) and the other metal ions. The displacement of Fe(II) by Me(II) was in order of Ni approximately Zn>Cd, and the displacement of Me(II) by Fe(II) was in order of Cd>Zn approximately Ni>Co. Fixed Fe(II) was in order of Fe+Co (20%)>Fe+Cd (6%)>Fe approximately Zn (4%)>Fe approximately Ni (4%) after 30 days. There was no fixation for the other metals in single or binary systems.     

Influence of fulvic acid on the removal of trace concentrations of cadmium(II), copper(II), and zinc(II) from water by alum coagulation

The effectiveness of Cu²⁺, Cd²⁺ and Zn²⁺ removal from solution by alum coagulation was measured with fulvic acid present and absent. A factorial experimental design and analysis of variance were used to determine the effect on metal ion removal of the individual variables pH, metal ion concentration, alum concentration and fulvic acid concentration and their combinations. The variable levels model water treatment plant conditions. Metal ion losses up to 96% for Cu²⁺. 59% for Cd²⁺ and 82% for Zn^z+ were measured in the presence of fulvic acid. In its absence the maximum metal ion losses observed were 93%, 14% and 53% for Cu²⁺, Cd²⁺ and Zn²⁺ respectively. Fulvic acid enhances metal ion removal under most experimental conditions. The practical implication of the results is that strong complexes between natural water organic matter and metal ions enhance their removal by the alum coagulation process.     

Iron, zinc, copper, manganese and magnesium in malignant lymphomas

Lymph node and spleen tissues involved in malignant lymphomas were analysed for iron, manganese, copper, zinc and magnesium by atomic absorption spectrophotometry. The levels of iron are found to be significantly lower in the case of Hodgkin's lymphoma compared with non-Hodgkin's lymphoma and normal lymph nodes. However, they are elevated in Hodgkin's lymphoma when compared with the normal value for spleen tissues. Magnesium is significantly higher in lymph nodes of non-Hodgkin's lymphoma compared with Hodgkin's lymphoma and normal values, but is not altered significantly in spleen tissues. The distribution of the other elements examined is not altered significantly in malignant lymphomas. The importance of the in situ levels of these elements to NMR imaging is discussed.     

Hybrid adsorbents based on hydrated oxides of Zr(IV), Ti(IV), Sn(IV), and Fe(III) for arsenic removal

Synthesized are hybrid organoinoragnic adsorbents based on organic resins Dowex SBR-P, Dowex Marathon II and hydrated oxides Zn(IV), Ti(IV), Sn(IV) and Fe(III). Specific conductivity was measured of the specified resins and hybrid organoinorganic adsorbents in the initial form and after absorption of ions As(V) from 10^–2 M aqueous solution of NaH₂AsO₄. Introduction of hydrated tin oxide increases ionic conductivity of organic resin Dowex SBR-P by 2.5 times. During the conversion to the arsenate form the conductivity of hybrid adsorbents changes insufficiently at the adsorption from the solution with pH 7 and increased by 2–10 times at adsorption from the solution with pH 2.     

Removal of arsenic (III) and arsenic (V) from aqueous medium using chitosan-coated biosorbent

A biosorbent was prepared by coating ceramic alumina with the natural biopolymer, chitosan, using a dip-coating process. Removal of arsenic (III) (As(III)) and arsenic (V) (As(V)) was studied through adsorption on the biosorbent at pH 4.0 under equilibrium and dynamic conditions. The equilibrium adsorption data were fitted to Langmuir, Freundlich, and Redlich-Peterson adsorption models, and the model parameters were evaluated. All three models represented the experimental data well. The monolayer adsorption capacity of the sorbent, as obtained from the Langmuir isotherm, is 56.50 and 96.46 mg/g of chitosan for As(III) and As(V), respectively. The difference in adsorption capacity for As(III) and As(V) was explained on the basis of speciation of arsenic at pH 4.0. Column adsorption results indicated that no arsenic was found in the effluent solution up to about 40 and 120 bed volumes of As(III) and As(V), respectively. Sodium hydroxide solution (0.1M) was found to be capable of regenerating the column bed.     

Daily intakes of copper, zinc and arsenic in drinking water by population of Shanghai, China

Daily intakes of metals in drinking water are of extreme importance in risk assessment to human health. Some papers focused on this topic, but most of them did not consider the effect of age, gender and work location on daily intakes of metals in drinking water. The objective of present paper is to estimate the levels of Cu, Zn and As ingestion in drinking water in Shanghai, China and the effect of age, gender and work location on daily intakes of these metals. It was also the first time that such a detailed investigation on daily intakes of metals in drinking water was carried out in China in recent years. Drink/Sample (D/S) method was used to estimate the daily intakes of Cu, Zn and As in drinking water. The mean concentrations of Cu, Zn and As in drinking water were 10.8 microg/l, 0.29 mg/l and 0.91 microg/l, which were lower than U.S. EPA's Drinking Water Equivalent Level (DWEL) and WHO guideline values. The average daily intakes of Cu, Zn and As in drinking water was 21.12 microg/d, 0.65 mg/d, and 1.83 microg/d, which were on average 0.01%, 1.1% and 1.5% of the provisional maximum tolerable daily intake (PMTDI) set by the Joint FAO/WHO Expert Committee. There was a significant difference in daily intake of Zn for different work locations (P=0.04). But no other significant differences in daily intakes of metals in drinking water were found according to age, gender and work location.     

The effect of groundwater composition on uranium(VI) sorption onto bacteriogenic iron oxides

In this study, we investigated the effect of groundwater composition on the sorption of U(VI) onto bacteriogenic iron oxides (BIOS) and synthetic ferrihydrite (HFO). The concentration of carbonate was found to be the key factor controlling U(VI) sorption onto both BIOS and HFO. However, the efficiency of HFO to adsorb uranium(VI) was higher than that of BIOS at pH 7.0. The pH value also played an important role on the U(VI) sorption onto iron oxides. U(VI) sorption onto BIOS was optimum in the pH range 3-4.5, whereas in the same pH range, the ability of HFO to adsorb U(VI) was very low. HFO was very efficient in adsorbing U(VI) in the pH range 4.5-6.5. Zeta potential measurements have been employed to understand the different removal trends between BIOS and HFO. BIOS had a negative surface charge across the whole pH range examined, in contrast to HFO, which had point of zero charge 7.6. The sorption results have been incorporated in a surface complexation model, which predicted adequately the pH-dependent sorption of U(VI) onto both types of iron oxides.     

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.     

Transport of iron, manganese, cadmium, copper and zinc by magela creek, Northern territory, Australia

Five major flood events occurring in Magela Creek during the 1978–1979 tropical wet season were sampled for conductivity, suspended solids and the trace metals iron, manganese, cadmium, copper and zinc. All concentrations were found to be very low, as were the denudation rates for trace metals and suspended materials. These results are as expected since the catchment is highly weathered, and is relatively undisturbed by man. The variations in conductivity, suspended solids and trace metal concentrations during individual flood events are also discussed.     

Film-pore diffusion model for the fixed-bed sorption of copper and cadmium ions onto bone char

The sorption of copper and cadmium ions onto bone char in single component systems has been studied using fixed-bed column adsorbers. The effects of solution flowrate, initial metal ion concentration and bone char particle size have been studied. A film-pore diffusion model has been developed to predict the fixed-bed breakthrough curves for the two metal ions. A sensitivity analysis has been carried out to investigate the influence of the external mass transfer coefficient (film resistance), the effective diffusion coefficient (pore diffusion) and the solid phase loading capacity. It is found that under the experimental conditions employed in the study, film diffusional resistance was low and the Biot numbers were relatively high. Furthermore, a constant effective pore diffusivity was not sufficient to correlate the breakthrough curves accurately and a variable dependent effective diffusivity was required; suggesting a possible contribution from surface diffusion. Since the metal ion-bone char systems take a long time to reach equilibrium, the solid phase loading capacity, as predicted by the "best-fit" equilibrium isotherm, was not suitable for use in the diffusional mass transport model and the mass balance solid phase loading was utilised instead.     

Sonochemical oxidation of arsenic(III) to arsenic(V) using potassium peroxydisulfate as an oxidizing agent

The sonochemical oxidation of As(III) in the presence of peroxydisulfate ion (PDS) has been investigated. Sulfate anion radicals and OH radicals produced during acoustic cavitation readily oxidized As(III) to As(V) in an aqueous environment. The rate of oxidation of As(III) was remarkably high (～10 times) with respect to the concentration of PDS. The As(III) oxidation was found to be independent of the initial pH of the solution in the range 3–8. It was relatively low at pH above 8, however, this could be circumvented by increasing the concentration of PDS. The presence of oxygen in solution played a significant role in the rate of oxidation of As(III). Around 40% oxidation of As(III) was observed in the absence of oxygen compared to 80% oxidation in the presence of dissolved oxygen (10 mg/L) over a sonication time of 5 min. The addition of humic acid (HA) retarded the oxidation rate of As(III), but the effect could be offset by using larger amounts of PDS. The effects of ultrasound intensity, and frequency on the rate of the oxidation of As(III) were also studied. The rate of the oxidation of As(III) was not significantly dependent on the acoustic power applied, for the concentrations of As(III) used in this study. At an ultrasound frequency of 211 kHz, the rate of oxidation of As(III) was lower than that observed at 20 kHz. It is concluded that the sonochemical treatment of As(III) solutions in the presence of PDS is a simple and viable technique for the oxidation of As(III) to As(V).     

Determination of the complexing properties of drinking waters toward copper(II) and aluminium(III) by ligand titration

The complexing capacity of some drinking waters for aluminium(III) and copper(II) is determined by a ligand titration with metal ions based on the use of complexing resins. The resins used in the titration are the iminodiacetic resin Chelex 100, the carboxylic resin Amberlite CG50 and the anionic exchange resin AG1X8. They allow the detection of ligands forming complexes of different stability with the metal ions used for the titration, since they have different sorbing properties. After equilibration with the resin, the concentration of the free metal ion in solution is evaluated from the concentration of sorbed metal ion and from the quantity K^*, which is the ratio of the concentration of the metal ion sorbed on the resin to the free metal ion in solution. It strongly depends on the conditions, but it can be evaluated, at the considered conditions, from the sorption equilibria of the metal ion on the resin. The concentration of the ligands in solution and the conditional stability constant are obtained from the Ruzik linearization procedure. Very strong ligands of copper(II) and aluminium(III) were detected in a tap water sample at concentrations ranging from 10⁻⁷ to 10⁻⁶ mol kg⁻¹, and forming complexes having conditional complexation constants K_cI=2.3×10¹⁷ (pH=6.77) and 4.5×10¹⁶ (pH=6.24), respectively, for copper(II) and aluminium(III). Weaker ligands were detected using the less strongly sorbing resins Amberlite CG50 and AG1X8, but at a concentration equal to that of the strong ligands. This was ascribed to the presence of competing metals in solution, not sorbed by the weak resins. Two other drinking waters had completely different complexing properties both towards copper(II) and aluminium(III), containing much weaker ligands.     

A 1500-year record of lead, copper, arsenic, cadmium, zinc level in Antarctic seal hairs and sediments

To reconstruct the profiles of heavy metal levels in the South Ocean ecosystem of Antarctica, the concentrations of lead (Pb), copper (Cu), arsenic (As), cadmium (Cd), and zinc (Zn) in seal hairs and lake sediments spanning the past 1500 years from Fildes Peninsula of King George Island and in weathering lake sediments from Nelson Island of West Antarctica were determined. The lead contents in the seal hairs and the weathering sediments show a sharp increase since the late 1800s, very likely due to anthropogenic contamination from modern industries. After the 1980s, the Pb content in seal hairs dropped by one-third, apparently due to the reduced usage of leaded gasoline in the Southern Hemisphere. Copper arises mainly from the weathering process, and its level may be substantially affected by climatic conditions. The concentrations of Cd, As, and Zn do not show any clear temporal trends.     

Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH)

Relatively limited information is available regarding the impacts of temperature on the adsorption kinetics and equilibrium capacities of granular ferric hydroxide (GFH) for arsenic (V) and arsenic (III) in an aqueous solution. In general, very little information is available on the kinetics and thermodynamic aspects of adsorption of arsenic compounds onto other iron oxide-based adsorbents as well. In order to gain an understanding of the adsorption process kinetics, a detailed study was conducted in a controlled batch system. The effects of temperature and pH on the adsorption rates of arsenic (V) and arsenic (III) were investigated. Reaction rate constants were calculated at pH levels of 6.5 and 7.5. Rate data are best described by a pseudo first-order kinetic model at each temperature and pH condition studied. At lower pH values, arsenic (V) exhibits greater removal rates than arsenic (III). An increase in temperature increases the overall adsorption reaction rate constant values for both arsenic (V) and arsenic (III). An examination of thermodynamic parameters shows that the adsorption of arsenic (V) as well as arsenic (III) by GFH is an endothermic process and is spontaneous at the specific temperatures investigated.     

Lead, cadmium, iron, zinc, copper, manganese, calcium and magnesium in SPF male rats exposed to a dilution of automotive exhaust gas throughout their lives

Male pathogen free CFE albino Sprague Dawley rats were exposed 8 h per day, 5 days per week, for three years to a 1/1000 dilution of automotive exhaust gas, containing 58 ppm carbon monoxide, 0.37% carbon dioxide, 23 ppm nitrogen oxides, 2 ppm aldehydes, less than 5 mg/l hydrocarbons and 8.5 micrograms/m3 lead. Lead, cadmium, iron, zinc, calcium and magnesium were measured by atomic absorption in the femurs and tibias of the rats which died during the experiment. A comparison with two control groups revealed that the only significant difference in the elements measured in the bones was a 500% increase in lead concentration. The calculations of the correlations between the percentages of the elements in bones, the ages and the body weights of the rats, as well as cluster analysis, did not show consistent variations of the water, calcium, magnesium concentrations nor of the other studied metals related to this increase in lead concentration. Moreover, longevity was the same in the 3 groups of rats, but the body weight was statistically smaller (4%) in the group exposed to the auto exhaust dilution.     

Adsorption and desorption of polydimethylsiloxane, PCBs, cadmium nitrate, copper sulfate, nickel sulfate and zinc nitrate by river surface sediments

An investigation into the adsorption and desorption of polydimethylsiloxane, PCBs, cadmium nitrate, copper sulfate, nickel nitrate and zinc nitrate by river sediments was carried out using either a flow-through system or a semi-static system. The material balance in the sediment compartment could be explained by the equation, dCs/dT= K1Cw-K2Cs. The adsorption rate constants (K1), desorption rate constants (K2) and concentration factors (K1/K2) were calculated. For hydrophobic chemicals, the K1's were independent of water solubility, but the K2's were relatively related to water solubility. For both hydrophobic chemicals and heavy metals, the concentration factors per fraction organic carbon were similar to the soil sorption coefficients (Koc), expressed on a organic carbon basis.     

The environmental chemistry of copper (II) in aquatic systems

The speciation of copper(II) in fresh water has been examined by considering inorganic and organic complexation and adsorption and precipitation processes. It is concluded that in most aquatic systems these processes are capable of reducing free copper levels to very low values even in the presence of high levels of total copper.     

The influence of subcutaneously administered lead(II) acetate on the concentrations of copper, iron, and zinc in the blood, kidney, liver, and spleen of rats

The concentrations of copper, iron, lead, and zinc in the blood, kidney, liver and spleen were determined before and after subcutaneous administration of lead(II) acetate (100 mg Pb kg-1 body weight) to male albino Wistar rats. The control rats had the following concentrations (microgram g-1 dry weight) of Cu, Fe, Pb and Zn: blood, 4.5, 3200, 2.1, 182; kidney, 36, 585, 120, 92; liver, 11.1, 720, 14.3, 124; spleen, 4.5, 420, 7.0, 76. After administration of lead, rats were sacrificed after 12, 24, 48, 72 and 96 h. The Pb concentration in the blood remained constant for the first 24 h at the level of the control group (2.1 micrograms g-1) and had decreased to half that level at 96 h. The lead concentrations peaked in the organs at 110-142% of those in the control group and had decreased at 96 h to levels considerably below those in the control group. The concentrations of Cu, Fe and Zn increased in the three organs to values 117-161% found for the control group. At 96 h the concentrations of Cu, Fe and Zn in the spleen had returned to levels of the control group; the concentrations in the liver were 112-153%, and in the blood 89-93% of those of the control group. In the kidney the iron (110%) and the zinc (126%) concentrations at 96 h were higher than the control values, whereas the copper concentration was the same as the control value. The concentrations in the blood were least affected. The most drastic changes were observed in the liver.(ABSTRACT TRUNCATED AT 250 WORDS)     

Monitoring of cadmium, copper, lead and zinc status in young children using toenails: comparison with scalp hair

Cadmium, copper, lead and zinc concentrations were determined (atomic absorption spectrometry) in the proximal end of scalp hair (n = 474) and in toenail clippings (n = 461) of children, aged 3-7 years, living in an industrialized and in a rural area of the Federal Republic of Germany. With the exception of Zn in hair, levels of the elements were log-normally distributed. Data are presented as geometric means. Toenail Cd and Pb levels were much higher than those in hair (Cd, 457 vs 90 ng g-1; Pb, 8.5 vs 2.7 micrograms g-1), while Cu and Zn values were similar in both biological media (toenail vs hair: Cu, 7.5 vs 10.6 micrograms g-1; Zn, 129 vs 108 micrograms g-1). In toenails, all elements were positively correlated with each other. In hair, there was a close relationship only between Cd and Pb; Cd and Pb were inversely related to Zn. With the exception of Zn (no correlation), there was a minor relationship between metal levels in hair and those in toenails. Using stepwise regression analysis, seasonal variation was found to be the main factor influencing hair metal levels, while nail metal levels were mainly influenced by place of residence (with the exception of Cu concentrations, for which there were no significant predictors). Multiple correlation coefficient was higher for hair than for nails. It is concluded that, for biological monitoring, toenail clippings are less suitable than hair samples.     

Characterization of PEI-modified biomass and biosorption of Cu(II), Pb(II) and Ni(II)

The objective of this work is to develop a surface-modified biosorbent with enhanced sorption capacity for heavy metal ions. The biomass of Penicillium chrysogenum was modified with polyethylenimine (PEI) and then crosslinked with glutaraldehyde. The crosslinked PEI was chemically bonded on the biomass surface through the amine and carboxylate groups on the pristine biomass. The presence of the amine group was confirmed by X-ray photon spectroscopy (XPS) and Fourier transform infrared (FTIR) analysis, and the concentration of the amine groups on the biomass surface was found to be 2 mmol/g through potentiometric titration. The rugged morphology of the biomass surface after the modification was observed by scanning electron microscope (SEM). Compared with the pristine biomass, the modified biomass with amine groups showed a significant increase in sorption capacity for three metal ions, namely, copper, lead and nickel. The sorption isotherms of the biomass for three metals were well described by Langmuir equation, with a maximum sorption at 92 mg copper, 204 mg lead and 55 mg nickel per g biomass. The binding sites for the three metals attributed to the amine groups on the biomass surface were verified by FTIR analysis.