Recovery Of Cadmium Research Articles

Effect of phosphate fertiliser type on the accumulation and plant availability of cadmium in grassland soils

Cadmium (Cd), a potentially toxic heavy metal for humans and animals, accumulates in the liver and kidneys of older animals grazing New Zealand and Australian pastoral soils. Phosphorus (P) fertiliser is the major input of Cd into these farming systems. A study was conducted to evaluate the effects, over 10 years, of annual application (30 kg P ha−1 yr−1) of four forms of P fertilisers having different solubilities and Cd contents [41, 32, 10 and 5 μg Cd g−1 for North Carolina phosphate rock (NCPR), single superphosphate (SSP), diammonium phosphate (DAP) made from low Cd phosphate rocks and Jordan phosphate rock (JPR) respectively] on soil and herbage Cd concentrations. Ten years of fertiliser application caused a marked increase in surface soil Cd concentrations. Total soil Cd was significantly higher in SSP and NCPR treatments compared to control (no P fertiliser), JPR and DAP treatments in the 0–30 and 30–75 mm soil depths. Plant-available Cd (0.01 M CaCl2 extractable Cd) was higher in SSP treatments than in control and other fertiliser treatments. Chemical analysis of herbage samples showed that there was no significant difference in Cd concentration in pasture grasses between treatments in the second year of the trial but in the eighth and tenth year, plots fertilised with SSP and NCPR had significantly higher Cd in pasture grasses in most of the seasonal cuts compared to control, JPR and DAP. Cadmium recovery by both grasses and clover was less than 5% of Cd applied in fertiliser. Clover Cd concentration and yield were much lower than those for grass and therefore its contribution to pasture Cd uptake was very low (< 7%). A strong seasonal effect on grass Cd concentration, which is inversely related to pasture growth rate, was observed in all three sampling years — Cd concentration was highest during autumn and lowest in spring. Total Cd contents of the fertilisers and their rate of dissolution rather than soil pH [pH (H2O) at 30–75 mm depth of 5.39, 5.20, 5.11 and 5.36 for NCPR, SSP, DAP and JPR treatments respectively]influenced soil and herbage Cd. These results showed that the use of P fertilisers with low Cd contents will reduce herbage Cd levels and has the potential of reducing Cd levels in grazing animals and their products.

Solubilization of plant tissue with nitric acid‐hydrofluoric acid‐hydrogen peroxide in a closed‐system microwave digestor

Abstract Application of a microwave dissolution technique for plant tissues using hydrofluoric acid (HF), nitric acid (HNO3), and hydrogen peroxide (H2O2) as reagents was studied. It was found that the use of all reagents in the mixture followed by the microwave heating in many cases does not lead to complete dissolution. The solid, remaining after the reaction, was found to contain fluoride (F), calcium (Ca), magnesium (Mg), aluminum (Al), and silicon (Si) as major components. However, when HF was allowed to react first and evaporated prior to the addition of H2O2+HNO3 with subsequent microwave heating in a closed system, complete dissolution with high degree of mineralization was achieved. The procedure was applied to a number of plant Certified Reference Materials (CRM's) with very good recoveries of Ca, Mg, iron (Fe), lead (Pb), zinc (Zn), copper (Cu), Al, manganese (Mn), cadmium (Cd), potassium (K), sodium (Na), sulfur (S), and phosphorus (P).

Chelating extraction and recovery of cadmium from soil using pyridine-2,6-dicarboxylic acid

Heavy metal contamination of soil frequently occurs at hazardous waste sites in many countries of the industrialized world. The use of chelating agents to extract heavy metals from contaminated soils is seen as a treatment method. This research investigated the use of chelator pyridine-2,6-dicarboxylic acid (PDA) to extract cadmium from a spiked soil. Batch equilibration experiments over 24-hr periods were performed to test hypotheses that through a proper choice of chelator: (1) extraction could be made selective toward heavy metals, and (2) extracted metals could be, by simply raising the solution pH, recovered and the chelator reclaimed and reused. The results have shown that PDA extracts and releases cadmium reversibly, and that PDA preferentially complexes with cadmium over competing Fe and Ca ions. Chemical equilibrium modeling was found to be useful for selecting suitable chelating agents and treatment conditions for the extraction and subsequent recovery of metals.

An Integrated Chemical-Microbiological Approach for the Disposal of Waste thin Film Cadmium Telluride Photovoltaic Modules

AbstractThe paper describes a novel chemical-microbiological method for the selective removal of cadmium, tellurium and silver from the thin film CdTe photovoltaic modules. The chemical component of the process utilizes dissolution of metals with nitric acid. The metal solution is subjected to selective biosorption of silver and cadmium by passing through biosorbent columns. The adsorbed cadmium and silver are desorbed and recovered by chemical precipitation. Tellurium in solution coming out of the biosorbent columns is converted microbiologically to its metallic form in a bioreactor. The combined chemical-microbiological treatment ensures recovery of silver, cadmium and tellurium with 86%, 80% and 99% efficiency, respectively. The treated waste can be discharged safely in the environment.

Adsorption of Heavy Metal Ions onto Insolubilized Humic Acid

A fundamental study of the application of humic acid (HA) to the recovery of cadmium and lead from dilute solutions was carried out. HA, which has an excellent complexing ability with heavy metals, was insolubilized by heating at 330°C for 1 h and was used as an adsorbent. A metal-complexation model was used to compare the adsorption characteristics of insolubilized humic acid (IHA) with those of HA. The results showed that two different types of acidic groups were present on HA and the insolubilization process scarcely influenced the metal-complexation constant of acidic groups; however, the number of available metal binding sites on IHA was decreased to some extent.

The atomization of cadmium in graphite furnaces

The effect of the atomization temperature on the analysis of cadmium in graphite furnaces has been studied. A comparison of the electrothermal atomic absorption spectrometry (ETAAS) determination of total Cd in animal tissues was carried out with Zeeman effect and deuterium background corrections. A detailed study of the atomic absorption profile and background correction of cadmium, as well as the variation of absorbance values at different atomization temperatures, in both peak-height and integrated modes, has been made. The accuracy of the ETAAS determination of Cd in tissue samples, using various atomization temperatures, has also been evaluated, having found that an atomization temperature equal or higher than 1600 °C is necessary in order to obtain accurate and reproducible results. The use of low atomization temperatures, suggested in some published works, makes it possible to obtain accurate results, but the slow production of gaseous atoms of cadmium can affect the precision of the absorbance measurements and strongly affects the peak area values. On the other hand, the use of atomization temperatures higher than 2000 °C produces bad recoveries of cadmium in the analysis of certified tissue samples.

Thermally activated recovery of polycrystalline cadmium deformed by anisotropic thermal expansion

The recovery of polycrystalline cadmium plates, after being deformed by internal stresses due to anisotropic thermal expansion during cooling, has been investigated by measuring the increase in the vibration frequency of the plate with time and varying the temperature as a parameter. The recovery of frequency with time was shown to follow an exponential law with a characteristic time of the order of few hours, thus reaching a limiting frequency after sufficiently long time. This limiting frequency is found to increase with the increase in the annealing temperature. The activation enthalpy controlling the recovery process is about 0.12 eV. The recovery is explained in terms of elimination of dislocations kinks produced during the deformation.

Process Development for Removal and Recovery of Cadmium from Wastewater by a Low-Cost Adsorbent: Adsorption Rates and Equilibrium Studies

Activated carbon prepared from peanut hulls (PHC), an agricultural waste by-product, has been used for the adsorption of Cd(II) from synthetic wastewater. The adsorption data fit better with the Freundlich adsorption isotherm. The applicability of the Lagergren kinetic model has also been investigated. An almost quantitative removal of 20 mg/L Cd(II) by 0.7 g of PHC/L of aqueous solution was observed in the pH range 3.5--9.5. A comparative study with a commercial granular activated carbon (CAC) showed that the adsorption capacity (K[sub f]) of PHC was 31 times larger than that of CAC.

Lung cancer findings from the NIOSH study of United States cadmium recovery workers: a cautionary note.

Lung cancer findings from the NIOSH study of United States cadmium recovery workers: a cautionary note.

Process for recycling spent potliner and electric arc furnace dust into commercial products using oxygen enrichment

This paper discusses the Enviroscience, Inc (ESI) process for recycling hazardous wastes by extractive metallurgy followed by vitrification of non-reducible metal oxides. In this process, volatile and reducible metals are reclaimed as their respective oxides and elements. Non-reducible metal oxides are converted into a man-made vitreous fiber identical in chemical content to mineral wool fiber known as rock or slag wool. The project discussed here involved aluminum plant and steel plant recycling of potliner and EAF dust into commercial products. Potliner (K088) is produced by primary aluminum plants. The annual waste generation rate is 130,000 tons/year. Electric Arc furnace dust (K061) is produced by 76 steel companies and the annual generation rate is estimated to be 600,000 tons/year. An 18-inch I.D. (pilot plant scale) countercurrent mineral wool type shaft furnace was used in the project. The feed was spent potliner and electric arc furnace dust. The pilot plant results were 1) cyanide consumption as a reductant: 96.89% to 99.55%, 2) fluoride utilization: 69.2% to 89.50%, 3) zinc recovery: 96.54% to 97.76%, 4) cadmium recovery: 99.47% to 99.99%, 5) lead recovery: 97.98% to 99.41%, 6) slag (fiber) recovery: 49.33% to 64.31%, 7) iron recovery: 95.12% to 96.93% in the iron and slag (fiber) products. Oxygen enrichment tests conducted by Airco increased the furnace melt rate by 44.8% and reduced coke consumption (energy use) by 41.4%. No detectable levels of NO 2, N 2O 3, H 2S, SO, or SO 2 were found in limited emissions test. Oxygen enrichment resulted in 66.3% fiber production. Analytical results on the enriched zinc oxide iron and fiber products are comparable to prior tests conducted by Enviroscience. As a result of these tests, extractive metallurgy combined with fiber production (vitrification) has now been proven to be a cost-effective recycle process when compared to thermal treatment, secure landfill disposal or standard HTMR processes. The process provides for the production of commercial products from select inorganic liquid, semi-solid, and solid hazardous wastes.

Low-volume microwave digestion of marine biological tissues for the measurement of trace elements.

The use of low-volume (7 ml) Teflon vessels and microwave heating is described for the digestion of three marine biological tissues representing a mollusc, a fish and a crustacean. Freeze-dried samples (< 0.1 g dry mass) and 1 ml of nitric acid were placed in 7 ml screw-topped Teflon vessels and treated using a programmed three-stage digestion. The first two stages were kept consistent (600 W, 2 min; 0 W, 2 min) and the third stage was varied from 150 to 450 W over 15-60 min to find the optimum microwave digestion conditions. Trace elements were determined using flame atomic absorption spectrometry, or electrothermal atomic absorption spectrometry when analysing samples containing very low concentrations of cadmium. Quantitative recoveries of copper, zinc and cadmium were obtained from the five marine reference materials under the following conditions: 600 W, 2 mins; 0 W, 2 min; 450 W, 45 mins.

Application of Chelating Ion Exchanger Ostsorb DTTA to Determination of Lead and Cadmium in Soils, Plants, and Fertilizers

The paper investigates a possible application of chelating cellulose ion exchanger with the functional groups of diethylenetriaminetetraacetic acid to concentrating lead and cadmium in extracts from soils and industrial fertilizers or mineralizates of plant materials. A favourable recovery of the metals needs the knowledge of the approximate content of the complex forming cations in the solutions and the suppression of formation of iron and aluminium hydroxides during modification of acidity of extracts to the value of pH 4 which is the optimum for the formation of chelates. The degree of concentrating reached the values of fE = 10 - 50, the recovery of lead and cadmium depended on the nature of sample and was in the range of R = 60 - 100%.

Recovery of Zinc, Cadmium, and Lanthanum by Biopolymer Gel Particles of Alginic Acid

Abstract Biopolymer gel particles of alginic acid were found to be a useful material for recovering zinc, cadmium, and lanthanum from aqueous solutions. The metals sorbed by the gel particles could be completely eluted by using dilute HCl solution of 0.1 kmol/m3. The distribution ratios of the individual metals between the gel and liquid phases were measured by using a batch method. The equilibrium data were consistent with predictions made assuming that sorption takes place with the ion-exchange reaction between metal ions and alginic acid. The maximum sorption capacity of the gel particles and the distribution equilibrium constants for the metals were determined by comparing the experimental data with the theoretical predictions. The observed effect of temperature on the distribution equilibrium was insignificant in the range from 15 to 35°C.

Extraction and enrichment of cadmium and manganese from aqueous solution using a liquid membrane

A liquid membrane containing 4% di-2-ethylhexyl phosphoric acid and 5% sorbitan monooleate in kerosene is used in the form of an emulsion for the simultaneous extraction and concentration of cadmium and manganese from aqueous solutions. When 4% tri-n-octylamine is included in the membrane composition, only manganese is extracted while cadmium remains in the sample solution. The extracted elements in the concentrate are recovered by breaking the emulsion with n-butanol. Recoveries of cadmium and manganese range from 92–104% for 60-ml samples containing 2–9 μg of each element.

Chronic renal effects in three studies of men and women occupationally exposed to cadmium.

We measured sensitive indicators of renal damage in three different populations occupationally exposed to cadmium, and examined the degree of variation in damage and the relative sensitivity of different types of indicators. The three studies included (1) men exposed in a cadmium recovery plant, (2) men exposed in a nickel/cadmium battery plant, and (3) women exposed in the latter plant. The indicators of renal damage were urinary proteins in three categories: (1) the high molecular weight enzymes alanine aminopeptidase (AAP) and N-acetyl-beta-D-glucosaminidase (NAG), (2) the intermediate molecular weight protein albumin (ALB), and (3) the low molecular weight proteins retinol-binding protein (RBP) and beta 2-microglobulin (B2M). These tests indicate that exposed groups with higher urine cadmium levels had varying degrees of renal damage. All exposed groups showed evidence of renal damage when compared with their respective control groups. A higher percentage of elevated protein levels was noted in the exposed group of Study 1 than in the exposed groups of Studies 2 and 3. In Study 1, the means of all five protein levels and ALB, RBP, and B2M fractional clearances were significantly elevated in the group with higher urine cadmium concentrations when compared with the groups with lower urine cadmium concentrations. Highly significant dose-response relationships for all of the urinary protein tests, including fractional clearances, were found. All of the tests were more sensitive in detecting evidence of subclinical renal damage than serum creatinine, a commonly used indicator of renal function. The order of test sensitivity in men was determined by considering three factors: (1) the magnitude of the correlation coefficient between the test and the urine cadmium concentration in the study with the most advanced damage, (2) the relative cadmium level predicted by the dose-response model at which there is a 10% chance of observing an elevated test value, and (3) the ability of the tests to detect renal effects in the population with less advanced damage. The tests in order of decreasing sensitivity in men are ALB, AAP, NAG, RBP approximately B2M. The women with higher urine cadmium levels in Study 3 had a higher percentage of elevated AAP and NAG values when compared with the control group.

Novel uses for thiophosphinic acids in solvent extraction

American Cyanamid’s Cyanex® 301 and 302 extractants were originally developed for use in the selective recovery of zinc from solutions also containing magnesium and, particularly, calcium. Since their introduction in 1985 and 1988, respectively, several more potential applications for these reagents have been examined. Two of those—the recovery of cadmium from wet process phosphoric acid and the separation of cobalt from nickeliferous solutions that also contain manganese—are described in this article.

Determinants of lung cancer risk among cadmium-exposed workers.

Workers at a cadmium recovery plant in Globe, Colorado, showed an increased risk of lung cancer, which some investigators have attributed to cadmium exposure. We conducted a cohort mortality analysis of this work force and a case-control analysis of the lung cancer cases within this work force in order to assess the probable causes of the lung cancer excess. The Globe plant began as a lead smelter about 1886, switched to arsenic production in 1920, and became a cadmium metal production facility in 1926. Cadmium, arsenic, and cigarette smoking are three potential lung carcinogens found in this workplace. Industrial hygiene data collected from 1943 onward served as the basis for the National Institute for Occupational Safety and Health (NIOSH)-derived exposure algorithm that assigned cadmium exposure estimates to employees based on their work area in the plant and calendar time. Few exposure data existed for substances other than cadmium. Feedstock ore concentrations were used as a surrogate measure of air arsenic levels. The arsenic content of the fines used as feedstock prior to 1940 was considerably higher than that of the fines used after 1940. Smoking histories had been obtained previously for 45% of the workers. A case-control analysis of the 25 cases of lung cancer known to have occurred among these workers through 1982 was conducted using three controls per case, matched by closest data of hire and age at hire. Potential causal agents for lung cancer included cadmium exposure, cigarette smoking, and arsenic exposure. Exposure variables for each case and control included estimated cumulative cadmium exposure in milligram-years per cubic meter, cigarette smoking history, and plant arsenic exposure status at the time of hire. Estimated cumulative cadmium exposures of cases and controls did not differ overall or within the date-of-hire strata. Cases were more than eight times more likely to have been cigarette smokers than were controls. Lung cancer risk in this workplace was more closely related to the period of hire, not to the cumulative cadmium exposure. The period of hire appears to be a surrogate for arsenic exposure as related to feedstock. The measures used here seem to indicate that exposure to arsenic and cigarette particulates, rather than to cadmium particulates, may have caused the increased rate of lung cancer of these workers.

Separation and Recovery of Nickel and Cadmium from Spent Cd—Ni Storage Batteries and Their Process Wastes

Abstract Several typical methods for the recovery and separation of cadmium and nickel from Ni- and Cd-bearing wastes are briefly described. Laboratory- and large-scale experiments were respectively developed to improve the processes for the recovery and treatment of cadmium and nickel. A high degree of purity of recovered cadmium was obtained. Yields of >95% for nickel and >99.66% for cadmium were obtained. The large-scale experimental process involves no secondary pollution, and it decreases and sometimes eliminates the disposal of spent process streams. A plant in China has established a production line based on the large-scale process, and a large number of benefits in cadmium recovery from spent alkaline Ni—Cd storage batteries and their process wastes have resulted.

Flow injection on-line coprecipitation preconcentration for electrothermal atomic absorption spectrometry

A flow injection on-line coprecipitation system has been synchronously coupled to an electrothermal atomic absorption spectrometric system for the determination of trace amounts of heavy metals in whole blood digests. Cadmium and nickel in the digest were coprecipitated with the iron(II)–hexamethylenedithiocarbamate (HMDTC) complex on the walls of a knotted reactor without using a filter. The precipitate was dissolved in 60 µl of isobutyl methyl ketone and stored in a poly(tetrafluoroethylene) tube before introduction onto the platform of a graphite furnace carried by a stream of HMDTC reagent. Electrothermal atomic absorption spectrometric determination of the analyte was performed in parallel with the preconcentration of the next sample. Enrichment factors of 16 and 8 were obtained for cadmium and nickel, respectively, using 20 and 40 s precipitate collection times, at a sample flow-rate of 3 ml min–1 for cadmium and 2 ml min–1 for nickel. The detection limits (3σ) were 0.003 and 0.02 µg l–1 for cadmium and nickel, respectively, and the precisions were 5.9% relative standard deviation (RSD) at the 0.02 µg l–1 level for cadmium, and 6.0% RSD at the 1.5 µg l–1 level for nickel. Recoveries of cadmium and nickel in blood digests were 103 and 106%, respectively.

Stabilization and hydrometallurgical treatment of flyash from a municipal incinerator

Flyash from municipal solid-waste (MSW) incinerators is frequently classified as a characteristic hazardous waste due to lead and cadmium content. Two alternate processing schemes for the treatment of flyash obtained from the MSW incinerator in Tuscaloosa, AL have been investigated; one involves stabilization of the flyash with portland cement, and the other involves the recovery and recycling of metal values by leaching and subsequent precipitation. Results indicate that flyash can be successfully stabilized in a 1:1 mixture of flyash and portland cement which meets environmental requirements. It has also been demonstrated that extraction of the metal content from flyash, specifically lead, cadmium and zinc, can be accomplished quickly and efficiently by leaching in hydrochloric acid solutions. Preliminary experiments on the subsequent recovery or precipitation of metallic lead and cadmium from these leaching solutions by cementation with zinc dust appear to be promising. Various means were used for characterization of the as-received material and several leaching residues including X-ray diffraction, particle size analysis, inductively coupled plasma spectroscopy, and atomic absorption spectroscopy. Results indicated that at least some of the lead in the flyash is present in the form of PbSO 4, with smaller amounts of PbCl 2.