Heavy Metal Waste Research Articles

ELECTROLYTE-AS-CATHODE GLOW DISCHARGE (ELCAD)/GLOW DISCHARGE ELECTROLYSIS AT THE GAS-SOLUTION INTERFACE

ABSTRACT Electrolysis glow discharge (ELCAD), wherein an electrolyte serves as the cathode, is a potential new analytical source for on-line determination of trace heavy metals in waste and drinking waters, in addition to other liquid samples. The use of atomic emission spectrometry (AES) with ELCAD enhances the efficiency of the technique. Although possible applications of ELCAD-AES are widespread, the technique is currently unsuitable for the detection of toxic elements, such as mercury, at concentrations as low as the World Health Organization guideline level in drinking water (1 ng/mL). The aim of this contribution is to provide an overview of the brief history, development of instrumentation, fundamental mechanistic studies and applications of ELCAD. This review suggests that, whereas the scope of ELCAD-AES is diverse, it would benefit greatly from the involvement of more researchers to enhance the capabilities of the system, as otherwise this goal will not be achieved.

Preliminary assessment of metal toxicity in the middle tisza river (Hungary) flood plain

Cyanide and heavy metals were accidentally released from a mine waste lagoon in Romania into tributaries ultimately draining into the Tisza River. Within two months of the cyanide accident two subsequent heavy metal waste spills further contaminated the Tisza River, followed by severe spring flooding, which potentially spread the contamination to soils adjacent to the river. Flood plain soils and shoreline sediments were sampled from two locations on the middle Tisza River and a reference site to conduct a preliminary assessment of metal content and toxicity. Ten-day sediment toxicity tests were conducted with the amphipod,Hyalella azteca and 24 h soil toxicity tests were conducted with the nematode (Caenorhabditis elegans). High concentrations of cadmium, copper, zinc, lead and arsenic were detected in soil and sediment samples. However, no mortality was observed inHyalella exposed to Tisza River sediments and only up to 27% mortality of C.elegans was observed in flood plain soils. Low mortalities are attributed to reduced metal bioavailability caused by high soil cation exchange capacities and possible interactions with sediment organic matter or sulfides. Future studies should focus on factors that alter metal bioavailability and their relationship to potential toxicity of organisms exposed to Tisza River sediments and flood plain soils.

Determination of Heavy Metals in Waste Lubricating Oils by Inductively Coupled Plasma–Optical Emission Spectrometry

In accordance with EU strategy on waste, the utilization of waste oils as a fuel in local power plants has become an interesting choice in hazardous waste treatment planning. The present requirement in Finland is that all oil batches to be burned in power plants must be analyzed for six heavy metals. Thus rapid and cheap methods are needed for these analyses. We have studied and optimized the analytical conditions in the use of sequential inductively coupled plasma–optical emission spectroscopy (ICP-OES) for the quantitative determinations of heavy metals (Cd, Cr, Cu, Ni, Pb, V) in waste lubricating oils. The study showed that using that proposed kerosene dilution method, waste oils can easily be analyzed for heavy metals and the analytical performance of the method is good. In addition, the results suggest that, at least in the case of the Oulu Municipal Waste Management the use of a pair of indictor metals should be sufficient for required determination of heavy metals.

A systematic study of cement/PFA chemical stabilisation/solidification process for the treatment of heavy metal waste.

The aim of this study is to systematically quantify the physical and chemical properties of the cement based solidified/stabilised heavy metal waste with increasing replacement of cement by PFA. Bulk density and unconfined compressive strength are measured as the physical parameters. The equilibrium extraction tests, sequential chemical tests and dynamic leaching tests are reported as chemical characteristics. The results showed PFA-blended cement-based waste forms have higher porosity and lower strength than the pure cement-based waste forms at experimental curing time. The lower alkalinities of the PFA-blended cement-based waste forms, however, lead to higher leach rates of heavy metals when the waste is exposed to an acidic medium.

Thermodynamic Consideration on the Kiln Dust Generated from Eco-cement Production

Eco-cement is expected to provide a solution for both the municipal and industrial problems caused by limited availability of landfill sites. The heavy metals in wastes are vaporized through the sintering process and caught as kiln dust in the bag filter. For the purpose of recycling the metals, the usefulness of thermodynamic calculation in regard to the Eco-cement production process was confirmed, and the behavior of Zn, Cu and Pb components in Eco-cement production was analyzed by means of simulation. Consequently, the results can be summarized as follows: (1) As the volatilization ratio of metals at 1400°C, which is the sintering temperature of Portland cement type Eco-cement, Pb is the highest, followed by Cu and Zn is the lowest. (2) Each component reacts with CaCl2 and is vaporized mainly as ZnCl2, CuCl and PbCl2 in an oxidizing atmosphere of 1400°C. (3) It was found that the volatilization behavior of Cu and Zn are different depending on the employed atmosphere whether oxidizing or reducing. The volatilization ratio of the Cu component is higher than that of the Zn component under an oxidizing condition. On the other hand, that of Zn component is much higher under a reducing condition.

The effect of flow-through leaching on the diffusivity of heavy metals in stabilized/solidified wastes

The flow-through leaching test is a test method employed to study the leaching behavior of monolithic stabilized/solidified (S/S) hazardous wastes under the condition that the leachate flows through the sample. This method simulates the leaching process of the S/S hazardous waste disposed under a particular landfill condition when the S/S waste is more permeable than its surrounding materials or when the deterioration of the solidified waste form has reached a state that ground water can flow-through the waste via the porosity system of the S/S waste matrix. This paper describes a study on the long-term performance of the cement-based S/S heavy metal wastes using a flow-through leaching test method. Two series of leaching tests with different synthetic heavy metal waste samples were carried out. The S/S samples were made from five types of heavy metals with two kinds of binders. The metals were Pb 2+, Zn 2+, Cu 2+, Ni 2+ (positive ions as nitrates), and Cr 6+ (a negative ion as potassium dichromate), and the binders were type I ordinary portland cement (OPC) and pulverised fuel ash (PFA). The model developed by Godbee and Joy for simulating the leaching behavior was modified to estimate the diffusivity parameter in this study. The results obtained indicate that since the matrix of the solidified waste in a flow-through leaching tests is always being degraded, the values of diffusivities increase continuously during the leaching period. The diffusivity variation range was from 10 −13 to 10 −3 cm 2/s, and were normally higher than those obtained from other test methods such as ANS 16.1 test and other dynamic leaching tests.

Solidification/stabilization of lead with the aid of bagasse as an additive to Portland cement

Solidification/stabilization (S/S) of hazardous waste is a widely used technology; therefore, it is crucial to evaluate its effectiveness and make attempts to improve the technique. A better matrix for S/S of hazardous waste was designed that is effective and economically feasible. This was accomplished by adding bagasse (byproduct of milling or diffusing sugar cane) to the waste/cement matrix. Lead nitrate was used as the model heavy metal waste with a 10 or 15% lead by weight to cement loading. Samples were cured for 7, 14, and 28 days at 24°C. Samples containing bagasse typically resulted in TCLP (modified) extract lead concentrations of approximately 0.5 mg/l of lead for all samples, while samples containing no bagasse had lead extract concentrations of approximately 5 mg/l for 10% samples and 45 mg/l for 15%. Results indicate that using bagasse as an additive to cement effectively improved the S/S of lead.

Green, catalytic oxidation of alcohols in water

Alcohol oxidations are typically performed with stoichiometric reagents that generate heavy-metal waste and are usually run in chlorinated solvents. A water-soluble palladium(II) bathophenanthroline complex is a stable recyclable catalyst for the selective aerobic oxidation of a wide range of alcohols to aldehydes, ketones, and carboxylic acids in a biphasic water-alcohol system. The use of water as a solvent and air as the oxidant makes the reaction interesting from both an economic and environmental point of view.

Solidification of Hazardous Heavy Metal Ions with Soda-Lime Glass. Characterization of Iron and Zinc in the Waste Glass.

X-ray spectrometry and X-ray diffraction (XRD) studies indicate that yellow sludge containing hydroxides of several hazardous heavy metal ions, i.e., Cr, Fe, Cu, Zn and Pb, has an amorphous structure. The XRD and 57Fe Mossbauer studies of the yellow sludge indicate the formation of a small amount of γ-FeOOH particles. Heavy metal waste glass of a light green color could be prepared by melting the yellow sludge together with synthetic soda-lime silicate glass of a light brown color. Additional waste glass could be prepared from a glass bottle for commercial drinks. Leaching test for Zn and Fe with the acid rain simulant (pH 3.5), which was prepared from a nearly equal amount of HNO3 (pH 3.5) and H2SO4 solution (pH 3.5), proved that the waste glass has higher chemical durability than the sludge adsorbed on “diatomaceous earth.” These results indicate that soda-lime silicate glass is a very effective medium for stable solidification of heavy metal ions, and that the “glass wastes” can be reused for this purpose.

Microstructural study of carbonated cement-solidified synthetic heavy metal waste

Synthetic wastes have been widely employed to help elucidate the complex interactions between real wastes and hydraulic binders during solidification. In this work, a laboratory produced metal waste mixed with Portland cement and immediately carbonated it using an accelerated method. The microstructures of carbonated and non-carbonated control samples were distinct despite both being dominated by unusually large phenograins derived from the waste. In the carbonated sample waste phenograins remained unaltered, whereas cement grains were largely decalcified. As a consequence of decalcification, observable porosity was significantly reduced by the formation of precipitated carbonates.

Comparison of the characteristics of flow-through and flow-around leaching tests of solidified heavy metal wastes

This paper introduces a research work on studying the possibility of using a flow-through leaching test method to stimulate the leaching behaviour of the cement-based stabilized/solidified (S/S) hazardous wastes. Both the flow-through leaching and the more common flow-around (dynamic leaching) test methods were carried out in the study to compare the leaching behaviour of the solidified waste under different leaching environments. The solidified waste samples were prepared from five kinds of heavy metals with two kinds of binders. The metals were Pb 2+, Zn 2+, Cu 2+, Ni 2+ (positive ions as nitrate), and Cr 6+ (as a negative ion in potassium dichromate), and the binders were type I Ordinary Portland Cement (OPC) and Pulverised Fuel Ash (PFA). The results of two series of flow-through and flow-around leaching experiments are reported and compared in this paper. Mathematical models for simulating the leaching behaviour of the flow-through and flow-around leaching conditions were used to determine the diffusivities of the contaminants. The results show that, since the matrix of the solid waste in a flow-through leaching test is always being degraded, the diffusivities continuously increased during the leaching period. The range of the diffusivities was 10E-8 to 10E-3 cm 2/s, which corresponds to the case of liquid phase diffusion. But in the case of the flow-around (dynamic leaching) test, the range of the diffusivities was 10E-18 to 10E-9 cm 2/s which was similar to solid phase diffusion, and the variation of the diffusivity with time was not regular.

The limitation of the toxicity characteristic leaching procedure for evaluating cement-based stabilised/solidified waste forms

The United States Environmental Protection Agency's Toxicity Characteristic Leaching Procedure (TCLP) is commonly used as a regulatory tool to determine whether or not a waste can be classified as a hazardous waste. The validity of the test procedure for assessing cement-based stabilized/solidified heavy metal wastes is examined in this paper. Synthetic cement-based heavy metal waste forms with different ANC were prepared and subjected to TCLP to study the effect of waste acid neutralizing capacity (ANC) on metal leaching. A “real” waste was also obtained from a local commercial treatment facility and tested to verify the findings. The results showed that as long as the stabilized/solidified waste forms have sufficient ANC to neutralize the acidity of the leachant, the leaching of metals will be small and the performance of the different waste forms cannot be differentiated. The test therefore has limited use in comparing the performance of different cement-based waste forms. A modified test procedure is proposed.

96/06636 The Ion exchange properties of low rank coals on actinides and other heavy metals

The removal of heavy metal and low-level radioactive wastes from the environment and their subsequent immobilization in an appropriate repository is one of the major environmental challenges facing our nation. The scope and magnitude of the contamination at many DOE and Superfund sites are such that successful remediation will require the development of new, inexpensive technologies which remove, in an environmentally acceptable manner, the heavy metal and radioactive wastes from contaminated soil and water. In this paper, we will present the preliminary data on the viability of using low rank coals or lignites as a novel, inexpensive material to remove actinides and other metals from the aqueous system, and the effects of high radiation on ion-exchange properties of lignites.

The influence of mix parameters and binder choice on the carbonation of cement solidified wastes

This paper explores the kinetics of carbonation of cement-based solidified hazardous waste. This study is part of a wide investigation into the effects of carbonation on solidified waste forms. Two commercially produced heavy metal wastes were solidified with three different types of Portland cement and two mineral admixtures and carbonated under controlled conditions. Measurements of the uptake of carbon dioxide were made for the different mixes and areas showing the degree of carbonation for each cement system were defined. The effects of water/binder ratio, waste and binder type on both total uptake of carbon dioxide and rate of carbonation were investigated and are discussed.

Leaching of simulated heavy metal waste stabilized/solidified in different cement matrices

Leaching experiments have been carried out on samples of ordinary portland cement (OPC), sulphate-resistant portland cement (SRPC) with fly ash (FA) added and an alumina cement (AC), with each receiving various concentrations (0.1–1.0 M of chromium (Cr 6+), vanadium (V 5+) and cadmium (Cd 2+. The samples were prepared and evaluated with a statistical experimental matrix corresponding to a Box-Behnken fractional factorial design. Leaching was done in PTFE vessels using the standard TCLP (toxicity characteristic leaching procedure of the U.S. Environmental protection Agency). Analyses of the leachates were carried out for elements Cr, Cd, V, Si, Al, Ca and Fe by inductively coupled plasma spectroscopy. Selected solid samples were investigated before and after leaching by scanning electron microscopy, in conjunction with energy dispersive X-ray spectrometry, and by scanning transmission electron microscopy on thinned specimens. The normalized mass losses of chromium varied between 3.3 10 3-tand 3.5 10 1-t kg/m 2. Calculated maximum release was found for a hypothetical cement with approximately 20% alumina, while minimum release was found for AC with 36.7% alumina. The normalized mass losses of vanadium varied between 110 −3 and 810 −2 kg/m 2. Calculated maximum release was found for a hypothetical cement with approximately 25% alumina and minimum release was found for OPC. All samples of the cadmium series except three showed solution concentrations below the detection limit (0.1 ppm), suggesting very effective retention of this element by all three cement matrices investigated.

Evaluation of the leaching properties of solidified heavy metal wastes

Abstract The effects of three inorganic materials on the leaching properties of Type I Portland cement solidification matrix were studied. Also, possible effects on the cement chemistry were suggested. Cadnium nitrate and hydroxide sludges of cadmium and lead were used as the inorganic materials. Cure times of i, 7, and 28 days were studied. Leachability effects were determined by the Toxicity Characteristic Leaching Procedure (TCLP). Hydroxide sludges were added in hydroxide to cement weight percentages of 10% and 30%. A control group containing no additives were also prepared. A control group containing only hydroxide sludges was also tested by the TCLP to determine the amount of metal leached from the sludges alone. Cadmium (Cd+2), in hydroxide or nitrate form, was found by leaching results to be well contained in the cement matrix. All of the TCLP leaching results for Cd+2 were well below the 1.0 mg/L guideline established in the procedure. Lead (Pb+2) was found not to be readily contained as was seen by the high amounts of Pb+2 leached. Approximately ali of the Cd was immobilized by the addition of cement after a 1 day cure time, whereas a considerable amount of Pb+2 was still left in a leachable form after 28 days.

Electron microscopy of heavy metal waste in cement matrices

Ordinary Portland cements mixed with various amounts of chromium metal in the form of nitrates (Cr(NO3)3), to simulate industrial waste, have been studied by electron microscopy techniques, i.e. scanning electron and scanning transmission electron microscopy. Trivalent chromium was found to be chemically incorporated in all hydrated cement phases, and appeared to substitute for silicon in calcium silicate hydrate (C-S-H), which is the major product of hydration. Chromium was also concentrated in polycrystalline Ca-Cr-rich phases.

Recycling wastes in agriculture: heavy metal bioavailability

Recycling wastes in agriculture is an essential disposal method, and according to waste characteristics can produce supplementary organic-matter resources (sewage sludge, compost) for crop production, or valuable soil amendments (coal fly-ash). However, since heavy-metal content in waste materials is often higher than in the soil, application rates have to be carefully controlled, to obviate the possible accumulation of toxic metals in agricultural soils. The risk of the possible pollution of crops by heavy metals makes it necessary to use guidelines for waste utilization. Generally, guidelines and legislation refer to the total amounts of heavy metals in wastes and in soil. The total amount however, is of very low environmental importance and much international experimentation concerning these elements is actually engaged in determining the real availability of heavy metals to plants in relation to the chemical forms of heavy metals in the soil. This paper emphasizes the extractability of metals in relation to soil chemistry, and plant uptake bioassay as an important diagnostic tool for metal bioavailability.

Clustering of multiple sclerosis in Galion, Ohio, 1982-1985.

Epidemiologic evidence indicates that the outbreak of 30-40 cases of multiple sclerosis and other demyelinating syndromes in Galion, Ohio, USA, during 1982-1985 was related to an excess concentration of heavy-metal wastes, especially of cadmium and chromium in sewage and river water. Both multiple sclerosis and myasthenia gravis were diagnosed by board-certified neurologists.

A technique for preparing TEM specimens from cementitious materials

Transmission/scanning transmission electron microscopy (TEM/STEM) is a valuable analytical technique for studying the many phases present in cementitious materials. Specimen preparation is, however, a problem limiting the full exploitation of this technique. A relatively simple specimen preparation technique, combining dimpling and ion milling, has been presented here. Successful specimens have been prepared from ordinary Portland cement (OPC) and cement stabilized heavy metal waste samples.