Toxicity Characteristic Leaching Procedure Limits Research Articles

Valorization of secondary copper slag as aggregate and cement replacement in ultra-high performance concrete

This study aims to examine the influence of quickly cooled granulated copper slag (QCS) and finely ground slowly cooled broken copper slag (SCS) as basalt aggregate and cement replacement, respectively, in ultra-high performance concrete (UHPC). The UHPC mixtures and cement pastes having a water-to-binder ratio of 0.18 were produced with different proportions of QCS-aggregate (up to 60% aggregate replacement) and SCS-binder (up to 20% cement replacement) and intensive vacuum mixing and heat curing were applied to the mixtures. The pozzolanic activity of SCS-binder was determined by bound water test. The evolution of the UHPC porosity was investigated by mercury intrusion porosimetry. A leaching test was performed on concrete containing copper slag to monitor the heavy metals release.The results obtained, revealed that the mechanical strength of UHPC containing QCS-aggregate and SCS-binder were comparable to or even better than for the reference mixture. The use of vacuum mixing combined with heat curing had a limited effect on strength and porosity reduction of concrete. The chemically bound water of cement pastes decreased as the SCS-binder content increased, indicating low pozzolanic activity of the SCS-binder used in this study. However, the relative contribution of SCS-binder increased with time, as the pozzolanic reaction of this SCS-binder continues for the longer curing ages. The UHPC made with copper slag meets the specific technical and health and safety requirements as construction material since the leachability results were below the Toxicity Characteristic Leaching Procedure limit values.

Buyer beware: Inexpensive, high cadmium jewelry can pose severe health risks

The use of cadmium to produce inexpensive jewelry has recently been documented. Governments have adopted varying standards, with US states focused on either total cadmium content or extractable cadmium from children's jewelry, while the European Union has adopted a limit of 100 mg/kg cadmium for all jewelry. This study evaluated 80 items purchased at a discount jewelry store. The objective was to determine prevalence of cadmium in this jewelry, the amount of cadmium released by simulated mouthing or ingestion, and to confirm previous reports that damage to jewelry can increase cadmium release. Finally, a modified toxicity characteristic leaching procedure (TCLP) assessed the potential for jewelry to release cadmium after disposal. Thirty-two (40%) items showed detectable cadmium by X-ray fluorescence. Nine high‑cadmium pendants and rings with cadmium content ranging from 31.3 to 89.2% were subjected to extractions simulating mouthing or ingestion. Seven of nine items extracted in dilute saline to simulate mouthing released more than the US recommended maximum of 18 micrograms. Damaged jewelry released more cadmium for most items tested, with one ring yielding an average of 10,600 micrograms. Two pendants small enough to be swallowed were tested using dilute HCl to simulate ingestion. While one pendant did not release cadmium in excess of the US recommended maximum of 200 micrograms even when damaged, the other released an average of 63,100 micrograms after being damaged. Fourteen of fifteen samples of two high cadmium charms extracted using a modified TCLP extraction exceeded the 1.0 mg/L TCLP limit for cadmium, averaging 13.1 and 9.6 mg/L respectively for the two charms. These results demonstrate that high‑cadmium jewelry may pose a serious hazard if mouthed or ingested, and that regulatory standards that do not take into account the potential for increased release of cadmium resulting from damage to jewelry electroplating are inadequate.

Cotreatment of MSWI Fly Ash and Granulated Lead Smelting Slag Using a Geopolymer System.

Municipal solid waste incineration fly ash (MSWI FA) and granulated lead smelting slag (GLSS) are toxic industrial wastes. In the present study, granulated lead smelting slag (GLSS) was pretreated as a geopolymer precursor through the high-energy ball milling activation process, which could be used as a geopolymeric solidification/stabilization (S/S) reagent for MSWI FA. The S/S process has been estimated through the physical properties and heavy metals leachability of the S/S matrices. The results show that the compressive strength of the geopolymer matrix reaches 15.32 MPa after curing for 28 days under the best parameters, and the physical properties meet the requirement of MU10 grade fly ash brick. In addition, the toxicity characteristic leaching procedure (TCLP) test results show that arsenic and heavy metals are immobilized effectively in the geopolymer matrix, and their concentrations in the leachate are far below the US EPA TCLP limits. The hydration products of the geopolymer binder are characterized by X-ray diffraction and Fourier transform infrared methods. The results show that the geopolymer gel and Friedel’s salt are the main hydration products. The S/S mechanism of the arsenic and heavy metals in the geopolymer matrix mainly involves physical encapsulation of the geopolymer gel, geopolymer adsorption and ion exchange of Friedel’s salt.

Preliminary Evaluation of Animal Bone Char as Potential Metal Stabilization Agent in Metal Contaminated Soil.

The aim of this study was to evaluate the potential effect of animal bone char (ABC) addition on metal mobility in mine tailings. The mobility of metals after addition of ABC to tailings at four different application rates (0.6 g, 1.2 g, 1.8 g and 3.6 g ABC per 100 g of tailings) was evaluated by Toxicity Characteristic Leaching Procedure (TCLP) one step extraction. The obtained results indicated that the mobility of Pb, Cr and Cd gradually decreased with increasing quantity of added ABC. According to the TCLP, mobile concentrations of Pb in tailings exceeded threshold values for almost eight times. After ABC addition, Pb TCLP-extractable concentrations decreased from 39 mg L-1 in tailings to lower than the TCLP limit values of 5 mg L-1 at all ABC application rates, except in mixtures with the lowest addition of ABC. We concluded that ABC could be a successful metal stabilization agent for multi-metal contaminated soil, although attention should be paid at highly As contaminated soil.

Leaching of cadmium and tellurium from cadmium telluride (CdTe) thin-film solar panels under simulated landfill conditions

A crushed non-encapsulated CdTe thin-film solar cell was subjected to two standardized batch leaching tests (i.e., Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET)) and to a continuous-flow column test to assess cadmium (Cd) and tellurium (Te) dissolution under conditions simulating the acidic- and the methanogenic phases of municipal solid waste landfills. Low levels of Cd and Te were solubilized in both batch leaching tests (<8.2% and <3.6% of added Cd and Te, respectively). On the other hand, over the course of 30days, 73% of the Cd and 21% of the Te were released to the synthetic leachate of a continuous-flow column simulating the acidic landfill phase. The dissolved Cd concentration was 3.24-fold higher than the TCLP limit (1mgL−1), and 650-fold higher than the maximum contaminant level established by the US-EPA for this metal in drinking water (0.005mgL−1). In contrast, the release of Cd and Te to the effluent of the continuous-flow column simulating the methanogenic phase of a landfill was negligible. The remarkable difference in the leaching behavior of CdTe in the columns is related to different aqueous pH and redox conditions promoted by the microbial communities in the columns, and is in agreement with thermodynamic predictions.

Leaching Behavior and Risk Control of Waste Mercury Chloride Catalyst Through Mechanochemical Reaction Using Sulfur

Abstract A large volume of waste mercury chloride catalyst (HgCl2) is generated by calcium carbide-based polyvinyl chloride production in China, which accounts for 30% of global mercury consumption. However, there are few studies on the leaching behavior and risk control of waste catalyst where mercury is in the form of HgCl2, which is more soluble than metal mercury and poses great threat to human health and environment. This study investigated mechanochemical stabilization and leaching behavior of waste mercury catalyst using sulfur as additive. We found that mercuric sulfide (HgS) formed through mechanical milling, although the reaction between HgCl2 and S is not thermodynamically favored. Moreover, toxicity characteristic leaching procedure (TCLP) results showed mercury leaching values are lower than the TCLP limit value of 0.2 mg/L after mechanochemical treatment. Results of sequential extraction procedure showed that ball mill could transfer more than 99.9% of the Hg in the catalyst to the least mob...

The enhancement effect of pre-reduction using zero-valent iron on the solidification of chromite ore processing residue by blast furnace slag and calcium hydroxide

A bench scale study was performed to assess the effectiveness of the solidification of chromite ore processing residue (COPR) by blast furnace slag and calcium hydroxide, and investigate the enhancement effect of pre-reduction using zero-valent iron (ZVI) on the solidification treatment. The degree of Cr immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as the solid waste-extraction procedure for leaching toxicity–sulfuric acid & nitric acid method (Chinese standard HJ/T299-2007). Strength tests and semi-dynamic leaching tests were implemented to investigate the potential for reusing the final treatment product as a readily available construction material. The experimental results showed that the performance of pre-reduction/solidification (S/S) was superior to that of solidification alone. After pre-reduction, all of the S/S treated COPR samples met the TCLP limit for total Cr (5mgL−1), whereas the samples with a COPR content below 40% met the pollution control limit of bricks and building block products (Chinese standard HJ/T 301-2007) produced with COPR for total Cr (0.3mgL−1). At the same time, all of the S/S treated specimens tested were suitable for utilization at certain levels.

Mineral phases and metals in baghouse dust from secondary aluminum production

Baghouse dust (BHD) is a solid waste generated by air pollution control systems during secondary aluminum processing (SAP). Management and disposal of BHD can be challenging in the U.S. and elsewhere. In this study, the mineral phases, metal content and metal leachability of 78 BHD samples collected from 13 different SAP facilities across the U.S. were investigated. The XRD semi-quantitative analysis of BHD samples suggests the presence of metallic aluminum, aluminum oxide, aluminum nitride and its oxides, spinel, elpasolite as well as diaspora. BHD also contains halite, sylvite and fluorite, which are used as fluxes in SAP activities. Total aluminum (Al) in the BHD samples averaged 18% by weight. Elevated concentrations of trace metals (>100μgL−1 As; >1000μgL−1 Cu, Mn, Se, Pb, Mn and Zn) were also detected in the leachate. The U.S. toxicity characteristic leaching procedure (TCLP) results showed that some samples leached above the toxicity limit for Cd, Pb and Se. Exceeding the TCLP limits in all sample is independent of facilities generating the BHD. From the metal content perspective only, it appears that BHD has a higher potential to exhibit toxicity characteristics than salt cake (the largest waste stream generated by SAP facilities).

Improvement of zeolites on solidification/stabilization of mercury‐contaminated wastes in chemically bonded phosphate ceramics: stabilization effect and mechanism study

AbstractIn this study, two kinds of zeolites materials [natural zeolite (NZ) and thiol‐functionalized zeolite] were added to the chemically bonded phosphate ceramics (CBPCs) processes for the stabilization/solidification (S/S) of mercury‐contaminated hazardous wastes. The stabilization effect of the process and the stabilization mechanism are investigated in detail. Strong promotion effects of zeolites on the stability of mercury in the hazardous wastes were obtained, and the technology showed great advantages toward traditional Portland cement process. Not only high stabilization efficiency is obtained but also lower dosage of solidification and stabilization agents were used compared with Portland cement process. Treated by thiol‐functionalized zeolite (TFZ) and CBPC under optimum parameters, the waste containing 1500 mg Hg/kg could successfully pass the Toxicity Characteristic Leaching Procedure (TCLP) test. The S/S technology using NZ and CBPC could effectively reduce the mercury waste containing 625 mg Hg/kg pass the TCLP limit. The functions of NZ for reinforcing S/S of Hg‐containing CBPC matrixes could be assumed as physical filling by fine zeolites particles and microencapsulation by cementing gel formed by zeolites and phosphate; while for CBPC and TFZ processes, the reaction of SH with Hg to form HgS may play a major role in the stabilization of mercury. © 2015 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Arsenic leaching characteristics of the sludges from iron based removal process

This paper examines the arsenic (As) leaching from the iron rich sludges. The sludges (S1, S2 and S3) were taken from laboratory scale As removal columns and were tested by sequential extraction procedure, toxicity characteristic leaching procedure (TCLP) and pH leaching test. The sludges were observed to have 1270 mg/kg, 705 mg/kg and 313 mg/kg of As for S1, S2 and S3, respectively. About 50–60% of the total As in the sludges was strongly bound with amorphous iron hydroxides. TCLP extraction results showed that concentrations of As leached were below the TCLP limit. At high alkaline conditions (pH 11) the dissolved As concentrations were as much as 35–45 times higher than at lower pH (pH 3) indicating that strongly bounded As would be released in the environment at high alkaline and low redox conditions. These laboratory experiments suggested maintaining non-alkaline and high redox conditions for minimum As solubility and mobilization from the sludges.

Evaluation of Heavy Metal Release from the Disposal of Waste Computer Monitors at an Open Dump

Large quantities of waste computer monitors are presently being disposed in Nigeria. As much as 2.4 million units of 'used' computer monitors are imported annually into the country. Significant proportions of these imported devices are non-functioning and are never reused, but rather disposed of at open dumps. This study simulated the breaking of cathode ray tubes at open dumps and assessed the total available metals in the cathode ray tube glass; the printed wiring board and plastic components as well as the ability of rainwater to leach and mobilize the metals through batch extraction using weak electrolytes (CaCl2, Ca(NO3)2, and H2O). The total lead concentration (mg/kg) of the monitor components ranged from 645-2892 (mean 1271±918); 11.1-117 (45.6±44.2) and 3860-4581 (4129±290) in cathode ray tubes, plastic and printed wiring board samples respectively. The chromium concentrations in the components were generally <115mg/kg. The extractable Pb from the cathode ray tubes and printed wiring board failed to pass the established limit for leaching tests such as the toxicity characteristic leaching procedure limits used in toxicity characterization of solid waste (5mg/l). High Pb concentrations, 1.3-12% of the total lead, were leached by the weak electrolytes (53.7±7.74 - 248±33.3mg/l), and this is between 10-50 times the toxicity characteristic leaching procedure limit. The results of this study reveal the dangers of inappropriate management of computer monitors, especially the disposal at open dumps or with municipal solid waste.

Surface Runoff from Full-Scale Coal Combustion Product Pavements during Accelerated Loading

In this study, the release of metals and metalloids from full-scale portland cement concrete pavements containing coal combustion products (CCPs) was evaluated by laboratory leaching tests and accelerated loading of full-scale pavement sections under well-controlled conditions. An equivalent of 20 years of highway traffic loading was simulated at the OSU/OU Accelerated Pavement Load Facility (APLF). Three types of portland cement concrete driving surface layers were tested, including a control section [i.e., ordinary portland cement (PC) concrete] containing no fly ash and two sections in which fly ash was substituted for a fraction of the cement; i.e., 30% fly ash (FA30) and 50% fly ash (FA50). In general, the concentrations of minor and trace elements were higher in the toxicity characteristic leaching procedure (TCLP) leachates than in the leachates obtained from synthetic precipitation leaching procedure and ASTM leaching procedures. Importantly, none of the leachate concentrations exceeded the TCLP limits or primary drinking water standards. Surface runoff monitoring results showed the highest release rates of inorganic elements from the FA50 concrete pavement, whereas there were little differences in release rates between PC and FA30 concretes. The release of elements generally decreased with increasing pavement loading. Except for Cr, elements were released as particulates (>0.45 μm) rather than dissolved constituents. The incorporation of fly ash in the PC cement concrete pavements examined in this study resulted in little or no deleterious environmental impact from the leaching of inorganic elements over the lifetime of the pavement system.

English

Granular mine waste are generated from the extraction and beneficiation of lead/zinc minerals. The fine gravel waste, commonly known as chat, contains elevated levels of lead, zinc and cadmium which can result in potentially serious human health and ecological concerns. With the use of chat in a variety of applications such as road construction, there is an increased environmental concern due to the potential leachability of lead (Pb), cadmium (Cd) and zinc (Zn) at high concentrations. In this study, we examine the release of these three metals from raw chat and its reuse products, mainly cold-mix asphalt (CMA) and hot-mix asphalt (HMA), to determine the environmental stability of the materials under different environmental conditions. The leachability of metals was evaluated using extraction tests including the toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP) and deionized water extraction procedure (DWEP). In addition, the relative bioaccessability of the metals was determined by the relative bioaccessability leaching procedure (RBLP) tests. Based on the conducted leaching tests, it was observed that all the three samples failed the TCLP test. The Cd and Pb concentrations in the TCLP extracts were higher than the mandated TCLP limits for leaching from wastes. The TCLP extracts of CMA and HMA samples were found to be less than the limit for Cd, but higher for Pb. The experimental data also showed that the concentrations of Cd and Pb in the SPLP extracts were less than the National Drinking Water Primary Standards of 0.005 mg/L and 0.015 mg/L, respectively. This indicated the suitability of the mine tailing and its reuse products for beneficial applications. The percent bioaccessible metal followed the order: raw chat < HMA < CMA, probably due to its smaller particle size (< 250 µm), compared to the particle sizes of CMA and HMA tested (< 2 mm). The data indicated that while the use of chat in asphalt is environmentally safe, care should be taken as metals could leach in significant concentrations when placed in moist environments for longer duration.

Chromium Leaching and Immobilization in Treated Soils

The purpose of this study is to investigate the effectiveness of a quicklime-based stabilization/solidification (s/s) technique to reduce the leachability of Cr(III) and Cr(VI) in laboratory-prepared soil. The soils were prepared by mixing kaolinite or montmorillonite with fine quartz sand and then subjecting the samples to s/s treatment. Treatment included quicklime, fly ash, and quicklime–fly ash additions. The effectiveness of the treatment was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) test. To elucidate the controlling Cr(VI) immobilization mechanisms, slurry mixtures were prepared with potassium chromate (K2CrO4), quicklime, and fly ash. X-ray diffraction (XRD) analyses were performed to investigate the reaction products responsible for Cr(VI) immobilization. Experimental results indicate very low Cr(III) leachability upon quicklime treatment. All samples treated with quicklime and quicklime–fly ash show TCLP Cr(III) concentrations below the U.S. EPA TCLP limit of 5 ppm. However, neither quicklime nor fly ash treatment alone was effective in reducing Cr(VI) leachability. An effective reduction in Cr(VI) leachability was achieved only when both quicklime and fly ash were added to the laboratory-prepared soils. Previous research has attributed this reduction in Cr(VI) leachability to the fly ash-induced chemical reduction of Cr(VI) to Cr(III). However, in this study, fly ash was found to be an ineffective reducing agent. XRD analyses results for quicklime–fly ash slurries do not indicate the formation of CaCrO4 or CaCrO4 · 2H2O, which were identified in previous research as the reaction products responsible for Cr(VI) immobilization. A hypothesis is presented in this paper to explain these results and the effectiveness of quicklime-fly ash mixtures in reducing the leachability of Cr(VI). XRD analyses have also identified the pozzolanic compound 3CaOAl2O30.5CaCrO40.5CaSO4 · nH2O as the precipitate most likely responsible for Cr(VI) immobilization.

Assessment of Fossil Fuel Fly Ash Formulations in the Immobilization of Hazardous Wastes

In this work, a simple and inexpensive method is introduced for the immobilization of the hazardous elements Cd, Pb, and Fe from their aqueous solutions in compressed fossil fuel fly ash formulations, as candidates for waste forms. The molded formulations were prepared by initially mixing the hazardous waste solutions with the fossil fuel fly ash material at a constant ratio (17%). Then the resulting pastes were pressed at the appropriate pressure using a manual hydraulic press. The compressed formulations revealed good water resistance, compression strength, and radiation resistance. Leachability investigations of the molded matrices were performed in terms of the accelerated leach test, the toxicity characteristic leaching procedure (TCLP), and long-term leach tests. The TCLP results obtained for Cd and Pb were well below their TCLP limits. On the other hand, the accelerated and long-term leach tests showed a similar behavior. The properties of the compressed formulations revealed their high performance...

Stabilization and Solidification of Metal-Laden Wastes by Compaction and Magnesium Phosphate-Based Binder

ABSTRACT Bench-scale and full-scale investigations of waste stabilization and volume reduction were conducted using spiked soil and ash wastes containing heavy metals such as Cd, Cr, Pb, Ni, and Hg. The waste streams were stabilized and solidified using chemically bonded phosphate ceramic (CBPC) binder, and then compacted by either uniaxial or harmonic press for volume reduction. The physical properties of the final waste forms were determined by measuring volume reduction, density, porosity, and compressive strength. The leachability of heavy metals in the final waste forms was determined by a toxicity characteristic leaching procedure (TCLP) test and a 90-day immersion test (ANS 16.1). The structural composition and nature of waste forms were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. CBPC binder and compaction can achieve 80-wt % waste loading and 39-47% reduction in waste volume. Compressive strength of final waste forms ranged from 1500 to 2000 psi. TCLP testing of waste forms showed that all heavy metals except Hg passed the TCLP limits using the phosphate-based binder. When Na2S was added to the binder, the waste forms also passed TCLP limits for Hg. Long-term leachability resistance of the final waste forms was achieved for all metals in both soil and ash wastes, and the leachability index was ~14. XRD patterns of waste forms indicated vermiculite in the ash waste was chemically incorporated into the CBPC matrix. SEM showed that waste forms are layered when compacted by uniaxial press and are homogeneous when compacted by harmonic press.

The effect of particle size reduction of fibrous materials on TCLP results

The TCLP (toxicity characteristic leaching procedure) test is used to determine the mobility of toxic contaminants present in waste materials and to define hazardous wastes under RCRA. The test requires particle size reduction for solids > 9.5 mm. Filamentous wastes do not need particle size reduction if they have a surface area greater than 3.1 cm2/g. However, guidance in this area is open to interpretation, and specific recommendations regarding the testing of carpeting are not available. This paper describes the effect on TCLP test results of three particle size reduction techniques for three types of carpets that were contaminated with lead in a laboratory experiment. Lead levels applied to the carpets ranged from 1–4 g/kg with lead loadings from 53.8–516.7 mg/m2. The carpets were vacuumed for 18.5 min/m2 prior to testing. The particle size reduction techniques tested include grinding, cutting into strips, and no reduction. The results indicated no significant difference between the particle size reduction methods, but significant differences were seen between the carpet types. No result was greater than the 5 mg/L TCLP limit for lead. However, some were close, indicating that the carpet type and predisposal remediation method may be important factors when disposal of contaminated carpeting is required. Examples are during lead-based paint abatement or home interior cleanups where lead dust is present.