Toxicity Characteristic Leaching Procedure Results Research Articles

Investigation on solidified/stabilized behavior of marine soil slurry by lime-activated incinerated sewage sludge ash-ground granulated blast furnace slag under multifactor conditions

This study aims to evaluate the possibility of reusing treated marine clayey soils by stabilization/solidification (S/S) technology as geomaterial in reclamation projects from the aspects of engineering strength, chemical modification and environmental risk assessment. The lime-activated incinerated sewage sludge ash (ISSA) together with ground granulated blast furnace slag (GGBS) was employed as the binder. The multi-controlling factors including water content, curing time, salinity, and chemical compositions of mixing solution were taken account to identify the S/S treated Hong Kong marine deposit (HKMD) slurry based on the strength tests, pH measurement, thermo-gravimetric (TG) analysis, X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS) and toxicity characteristic leaching procedure (TCLP) tests, etc. The results show that the S/S treatment using lime-activated ISSA-GGBS can effectively enhance the strength of marine soil at initial water content of 110% and 200%. The water content and curing time have a significant impact on the S/S treated HKMD. The pH of treated soils is higher than 11.1, which proves an alkaline environment for the reactions in the treated soil. A special case is the treated HKMD at 200% water content hydrated by MgCl2 solution, which has a low pH of 10.23 and maintains a slurry state. Based on the TCLP results, the leaching concentration of heavy metals from S/S treated HKMD is environmentally safe and meets Hong Kong standard for reusing treated soil with a low level of <0.2 mg/L. The content of main products such as calcium/magnesium silicate hydrate, ettringite or Friedel's salt depends on the chemical additions (e.g. distilled water, seawater, NaCl and Na2SO4). The products in the specimens mixed with MgCl2 solutions are mainly composed of Mg(OH)2, M-S-H and MgCO3, which is distinct with the neoformations in the other cases. Therefore, this study proves that the S/S treated soil slurry could be reused as geomaterials in reclamation projects, and the S/S process is greatly affected by water content, curing time and solution compositions, etc.

Application of Cold Sintering Process for Stabilizing Heavy Metals in Municipal Solid Waste Incineration Fly Ash

Municipal solid waste incineration fly ash (MSWI FA) consists predominantly of compounds comprising elements such as calcium, aluminum, silicon, sodium, and others. Additionally, it encompasses a complex mixture of heavy metals, chlorides, sulfates, organic pollutants, and other constituents. The effective and economically viable treatment of MSWI FA poses a formidable challenge for resource cycling at the current stage. In this research report, we adopt a novel low-temperature sintering method called the “Cold Sintering Process” (CSP) as a means to immobilize heavy metals within the fly ash. By utilizing a Taguchi orthogonal array method, we will adjust five control factors in the CSP, including sintering temperature, uniaxial pressure, sintering time, initial water addition, and sodium carbonate dosage. The leaching of cadmium from the fly ash, as measured by the Toxicity Characteristic Leaching Procedure (TCLP), will serve as the quality indicator of products. Through the application of CSP, MSWI FA was transformed into structurally stable ceramic blocks, and the heavy metals within the blocks were effectively immobilized. The results of the experiments showed that MSWI FA under the conditions of a temperature of 300 °C, uniaxial pressure of 312 MPa, sintering time in 60 min, 25 wt% water addition, and 9 wt% Na2CO3 addition could effectively reduce the leaching of cadmium by 77.71%, lead by 21.14%, zinc by 42.37%, and chromium by 99.99%, as compared to the original MSWI FA TCLP results. The X-ray Diffraction (XRD) results indicate that during the CSP, fly ash forms phases such as calcium silicate, rankinite, hydrogrossular, anorthite, and marilite. These phase transformations are considered beneficial for preventing the leaching of internal heavy metals. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) results reveal that CSP is advantageous for compacting the overall structure, and EDS results further demonstrate that some of the Pb and Zn are carried out from the interior of the blocks, with uneven distribution on the surface of fly ash particles. The aforementioned experimental results serve as preliminary indications of CSP’s capability to stabilize detrimental components within high-purity fly ash. Future research endeavors may entail the refinement of material proportions, modification of experimental parameters, and other methodologies, thus facilitating potential scalability to industrial applications. Such developments align with the overarching goal of resource utilization.

The Synthesis of Lead-Bearing Jarosite and Its Occurrence Characteristic and Leaching Toxicity Evaluation

Lead is the main toxic factor in jarosite residue. It is important to study the release behavior of lead from simulated lead-bearing jarosite (SLBJ) for predicting the stability of jarosite residue and its secondary pollution to the environment. To identify the technical issues and limitations associated with its safe disposal, a comprehensive analysis of the chemical, structural, and morphological characteristics of SLBJ was conducted using various detection techniques including XRF, XRD, SEM-EDS, FTIR, XPS, etc. The environmental stability of SLBJ was assessed through the toxicity characteristic leaching procedure (TCLP), Chinese standard leaching tests (CSLT), and a long-term leaching experiment (LTLE). Phase composition analysis revealed that the primary components of SLBJ are sodium jarosite and lead sulfate. TCLP and CSLT results indicated that lead content surpassed the toxicity identification standard limit by more than 47 times. Furthermore, LTLE indicated that the lead concentration surpassed the standard limit about 15 times after prolonged contact time. This study is of great significance for predicting the stability of jarosite residue and its secondary pollution to the environment.

In-situ stabilization/solidification of lead/zinc mine tailings by cemented paste backfill modified with low-carbon bentonite alternative

The improper stockpiling of lead/zinc mine tailings results in significant toxic impurities releasing, which threatens both the surrounding environment and human health. Cemented paste backfill (CPB) is considered an effective in-situ remediation way for managing lead/zinc mine tailings. In this study, the mechanical performance and heavy metal retention of CPB were evaluated by comparing the different binder strategies of ordinary Portland cement (OPC), Ca-bentonite, and Na-bentonite. The engineering properties of the mixtures were verified by uniaxial compressive strength (UCS) tests. The phase composition and internal microstructure were obtained by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Toxicity characteristic leaching procedure (TCLP) was performed to ascertain the effectiveness of heavy metal retention capacity. The results showed that the use of bentonite effectively optimized the UCS at early ages. Despite the deterioration is observed at 28 days, the UCS values are still qualified for the engineering application. With XRD and SEM analysis, a great content of amorphous was quantitatively characterized, highlighting the importance of amorphous content in the regulation of mechanical properties. TCLP results indicate that all the Pb, Cd, and As are predominantly incorporated within the cementitious matrix, whereas the Zn is the only concern in which the leachability decreases with the Ca-bentonite proportion. The leachates met the regulation limits (0.1 mg/L) at the CPB samples with 1.28 wt% of Ca-bentonite. Overall, bentonite could be an attractive alternative for the in-situ remediation of lead/zinc mine tailings to revive the stockpile site and reduce the environmental influence of this solid waste.

Oxalic acid activated bone meal for immobilization of Pb and Cd contaminated soils.

Bone meal (BM) is a cost-effective and low-carbon material to remediate heavy metal contaminated soils. Moreover, its immobilization efficiency for heavy metals still requires improvement. This study aimed to assess the activation effect of oxalic acid on the BM to develop an oxalic acid-activated bone meal (ABM) for improving immobilization efficiency. Several series of tests, including the available phosphorus content test, toxicity characteristic leaching procedure (TCLP), modified European Community Bureau of Reference (BCR) sequential extraction procedure, and X-ray diffraction (XRD) analysis, are used to investigate the effect of activation on the immobilization ability and chemical speciation of lead (Pb) and cadmium (Cd) in soils and the different mechanisms of Pb/Cd immobilization using the ABM and BM. The results indicate that the ABM possesses a higher solubility than the BM. The activation of BM achieves optimal effect when using 1mol/L oxalic acid solution with a liquid-solid ratio of 2:1. The TCLP and BCR test results show that the ABM significantly outperforms the BM in terms of Pb immobilization. The leaching concentration of Pb from ABM immobilized soils can meet regulatory limits in China and the USA, and it is also 30 to 75% lower than that from BM immobilized soils. Regarding Cd immobilization, ABM outperforms BM after 90days of curing. The XRD analysis shows that heavy metal phosphates are the primary products of Pb and Cd immobilized by ABM, whereas heavy metal carbonates are the main products after the immobilization by BM.

Sustainable use of municipal solid waste incinerator bottom ash and the treated industrial wastewater in self-compacting concrete

The vast amount of solid waste landfilling and discharging of wastewater in surface water or groundwater increases water pollution. Therefore, reusing solid waste and wastewater is vital. We studied the feasibility of using different percentages of simultaneous municipal solid waste incineration bottom ash (MSWIBA) and the treated industrial wastewater in self-compacting concrete (SCC). Also, producing concrete using MSWIBA and tap water was performed. The workability (Slump flow, J-ring, T50, V-funnel, sieve segregation, and Visual Stability Index tests), mechanical property (compressive strength), durability (water adsorption and rapid chloride penetration tests), Scanning Electron Microscope (SEM) image, and Toxicity Characteristic Leaching Procedure (TCLP) of SCCs were carried out. The workability of different SCCs mixtures, including different percent of MSWIBA (replacing instead of natural aggregates) with tap water or the treated industrial wastewater, was reached the suitable level and satisfied European guidelines for SCCs and ASTM C1585 by adopting the rate of superplasticizer. The results indicated that the compressive strength decreased with increasing the MSWIBA content in concrete samples using tap water. However, using MSWIBA and the treated industrial wastewater led to increasing compressive strength compared to SCC using both MSWIBA and tap water. When it was used MSWIBA and the treated industrial wastewater simultaneously in SCCs, the water adsorption and rapid chloride permeability test (RCPT) results decreased compared to the concrete samples using MSWIBA and tap water. The SEM images present fewer pores and cracks while using the treated industrial wastewater in SCCs. The TCLP results of SCCs include concurrent MSWIBA, and the treated wastewater is below the U.S. Environmental Protection Agency (EPA) 1311.

A Screening Approach for the Selection of Drinking Water Treatment Residuals for Their Introduction to Marine Systems.

Drinking water treatment residuals (DWTRs) produced in large quantities worldwide show strong sorption capacities for several contaminants including metals. These by-products of the water-treatment process are primarily discharged as wastes, to either natural or engineered systems, based on the regulations in place in the country where they are produced. To assess how DWTRs can be repurposed to limit the mobility of metals in aquatic systems, we tested their propensity to release toxic metals and their potential ecotoxicity. To account for the wide variability in their physicochemical characteristics, DWTR samples were obtained from 15 water-treatment plants across the United States. A screening procedure based on a combination of 1) the toxicity characteristics leaching procedure (TCLP), 2) total metal contents and sediment quality guidelines, and 3) acute 10-d Americamysis bahia and chronic 28-d Neanthes arenaceodentata survival and growth bioassays was used. All tested samples were found to be nonhazardous based on TCLP results. However, the concentrations of As, Cu, and Ni exceeded the sediment quality guidelines in some samples, resulting in the exclusion of 7 DWTR samples. All of the DWTRs evaluated for toxicity were nontoxic to the tested organisms. The results of the present study suggest that certain DWTRs can be introduced safely into the marine environment and, therefore, used as potential amendments or capping materials to control the mobility of certain sediment contaminants. Environ Toxicol Chem 2021;40:1194-1203. © 2020 SETAC.

Physicochemical and environmental properties of arsenic sulfide sludge from copper and lead−zinc smelter

Abstract Physicochemical properties of arsenic sulfide sludge (ASS) from copper smelter (ASS-I) and lead−zinc smelter (ASS-II) were examined by XRD, Raman spectroscopy, SEM−EDS, TG−DTA, XPS and chemical phase analysis method. The toxicity characteristic leaching procedure (TCLP), Chinese standard leaching tests (CSLT), three-stage sequential extraction procedure (BCR) and batch leaching experiments (BLE) were used to investigate the environmental stability. The ASSs from different smelters had obviously different physicochemical and environmental properties. The phase composition and micrograph analysis indicate that ASS-I mainly consists of super refined flocculent particles including amorphous arsenic sulfide adhered with amorphous sulfur and that ASS-II mainly consists of amorphous arsenic sulfide. The valence state of arsenic in both sludges is trivalent, but the valence composition of sulfur is quite different. The ASSs have thermal instability properties. The results of TCLP and CSLT indicate that the concentrations of As and Pd in the leaching solution exceed the standard limits. More than 5% and 90% of arsenic are in the form of acid soluble and oxidizable fractions, respectively, which explains the high arsenic leaching toxicity and environmental activity of ASS. This research provides comprehensive information for the disposal of ASS from copper and lead−zinc smelter.

Utilization of color change and image processing to evaluate the Waste Foundry Sand reclamation level

Waste Foundry Sand (WFS) is the by-product of casting industries and is utilized to make molds. Some minerals, such as clay particles or chemical admixtures such as phenolic resins, are used to bond silica sand grains and shape the mold. Preventing environmental impacts such as WFS landfilling, many researches have been conducted to find an appropriate way for reclamation and evaluation of its cleaning. Due to the color changes during this process, image processing is helpful for an estimation of reclamation progress. In this paper, thermal reclamation method and Response Surface Methodology (RSM) are used as the most appropriate way of reclamation and design of experiments, respectively. Samples are heated at different temperatures for a variety of time durations. The color changes of samples are measured using image processing technique by detection of RGB (Red, Green, Blue) color coordinate system parameters changes (ΔRGB). The results of TCLP (Toxicity Characteristic Leaching Procedure) tests reveal that phenolic compounds are removed during the reclamation process, which causes WFS color changes from black to almost white. On this basis, a linear model is developed to predict RGB values relative to time or temperature variations. Results approve that an investigation on ΔRGB values provides a precise estimation of WFS grains reclamation level (less than 10 % error) to guide its reuse within the foundry industries.

In situ immobilization of heavy metals in contaminated sediments by composite additives of hydroxyapatite and oxides

The in situ immobilization performances of Zn, Mn, Pb, and Cd in the contaminated sediments using additives [hydroxyapatite (HAP), CaO, MgO, and HAP + CaO/MgO] were investigated by European Community Bureau of Reference (BCR) extraction test, toxicity characteristic leaching procedure (TCLP), and heavy metal releasing test. The results of immobilization test showed that 40.70% of Zn, 47.47% of Mn, 70.40% of Pb, and 61.86% of Cd were immobilized in forms of the oxidizable and residual speciation in the sediments applied by composite additives (HAP + CaO or MgO) with each additive’s dosage of 10% of the sediment. The results of TCLP indicated that, compared to the blank samples, nearly 80% of Zn, Pb, Cd, and 50% of Mn were reduced in the leaching solutions using the composite additives. In addition, the heavy metal releasing experiment demonstrated that the releasing amounts of heavy metals in the immobilized sediments were much lower than those in raw sediments, and the equilibrium of metal releasing cost 24–31 days. The results of this work demonstrated that 10% HAP coupled with 10% CaO or 10% MgO is feasible in immobilizing heavy metals and decreasing the releasing risk of heavy metals in sediments.

Inhibition of naphthalene leaching from municipal carbonaceous waste by a magnetic organophilic clay.

Municipal solid waste conversion into biofuels via gasification is one of the latest technologies to divert waste from landfills. The byproduct of the process is a carbonaceous material, which is often tainted with polycyclic aromatic hydrocarbons (PAH) such as naphthalene that can leach into the environment and have toxic effects on aquatic organisms. In this paper, we present a novel method to address the issue of leachable naphthalene in a carbonaceous waste produced from a gasification process, using a magnetic sorbent. The sorbent was fabricated by the coprecipitation of iron oxide nanoparticles on an organophilic clay under atmospheric conditions. The characterization results show that the intercalated nanoparticles are predominantly magnetite with a diameter of 15-20 nm, and increase the clay specific surface area from 0.4 to 17 m2 g-1. Toxicity characteristic leaching procedure results indicate that the magnetic composite has a high naphthalene inhibition efficiency comparable to that of the original clay. As opposed to the clay alone, the magnetic hybrid can be separated from the carbonaceous waste with a magnet, regenerated by heat treatment, and reused without compromising its naphthalene removal efficiency. Thus, these composites may provide a cost-effective method to curtail leaching of PAH from contaminated carbonaceous waste.

Concentrations and chemical fractions of Cu, Zn, Cd, and Pb at ten metallurgical sites in China.

Metal pollution in urban soils due to smelting and electroplating has become a severe problem in China. In this study, the concentration, chemical fraction, and leaching behavior of typical metals (Cu, Zn, Cd, and Pb) in soil samples from ten metallurgical sites were studied. The results show that some of the soils were polluted with Cu and most were heavily polluted with multiple metals, especially Zn, Cd, and Pb. The average concentration of Cu, Zn, Cd, and Pb was 498, 4145, 89, and 5091mg/kg, respectively. Chemical fractionation revealed that Cu, Zn, Cd, and Pb were mainly present in the acid-soluble fraction in polluted soils, but predominated in the residual fraction in unpolluted soils, demonstrating that allogenic metals in the soils were mostly present in the more labile fractions. Toxicity characteristic leaching procedure results were in agreement with the chemical fractionation study, indicating that the higher the total metal content, the higher the leachability, mobility, bioavailability, and potential toxicity to the environment, especially groundwater. Use of chemical fractionation results instead of total metal concentrations would provide better insight into the distribution and binding forms of metals for better assessment of their mobility and bioavailability. The study would provide much more important information for developing better remediation strategies for contaminated sites.

Characterization and Leachability Behaviour of Geopolymer Cement Synthesised from Municipal Solid Waste Incinerator Fly Ash and Volcanic Ash Blends

Municipal solid waste incinerator fly ash (MSWI-FA) was used synergistically with volcanic ash (VA) to synthesize Geopolymer cement. The effects of the incorporation of 0%, 30%, and 50% of VA and the alkalinity of activating solution on the structure and properties were studied by using the X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), field emission gun scanning electron microscopy (FEG-SEM), and mechanical testing. The encapsulation efficiency of the cements was carried out by using a toxicity characteristic leaching procedure (TCLP). The geopolymerization of MSWI-FA promoted the formation of new minerals such as Thernadite (Na2SO4), Hydrocalumite (Ca4Al2O6(CO3)0.67(SO3)0.33), C-S-H, and Faujasite-Na(Na2Ca)0.075(Al0.3Si0.7)O2(H2O)0.22. The Geopolymer cement synthesized with the addition of 50% of VA at 6M NaOH concentration, which exhibited the most compact microstructure. This was the highest strength with the best encapsulation ability. The microstructure analysis of the MSWI-FA-VA system revealed the coexistence of C-S-H and N-A-S-H phases as the main cementitious binders. The TCLP results of cement vis a vis raw MSWI-FA showed the leaching of metals reduced to a great extent. This was much lower than the permissible limit fixed by the United States Environmental Protection Agency (USEPA) for the toxicity characteristic. Furthermore, an attempt was made to correlate the microstructure with mechanical properties.

Utilization of graphene oxide for improving the environmental compatibility of cement-based materials containing waste cathode-ray tube glass

Abstract Utilization and processing of waste cathode ray tube (CRT) glass causes serious environmental damage due to its presence of lead and huge growing volume. The use of waste CRT glass in cement-based materials is an effective recycling method, whereas the huge amount of waste CRT glass usually results in severe lead leaching and weakened interfacial bonding. This paper presents an effective method for improving the lead immobilization and microstructure of the interfacial transition zone between cement paste and waste CRT glass (30 and 60 wt% of fine aggregates) using graphene oxide (GO) (up to 0.10 wt%). In order to investigate the environmental compatibility of the GO-waste CRT cement mortars, the standard toxicity characteristic leaching procedure (TCLP) was performed for lead leaching evaluation, and their mechanical properties were examined. Moreover, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) observation with backscattered electron mode were conducted. The results of TCLP indicate that the degrees of lead leaching from the waste CRT cement-based materials with both fine (0.075–0.15 mm) and coarse (8–9.5 mm) size containing 0.1 wt% GO were significantly lower than the regulatory limit specified by the United States Environmental Protection Agency and Chinese standard. The data obtained via mechanical testing revealed that the presence of 60 wt% waste CRT reduced its 28-day compressive and flexural strengths only slightly, whereas 0.1 wt% GO addition significantly increased their values. By analyzing the thermogravimetric and microstructural results, it was found that the increased formation of portlandite (CH) and calcium-silicate-hydrate (C S H) caused by GO addition reduced the number of interconnected cracks and pores and improved the properties of the interface between waste CRT glass and cement paste. This obtained improvement in environmental compatibility of the waste CRT cement mortars not only examines the reduced lead pollution caused by GO addition, but also sustainably promotes the industrial utilization of toxic waste CRT glass.

Toxicity characteristics and durability of concrete containing coal ash as substitute for cement and river sand

The main aim of this study was to investigate the toxicity characteristics and durability of concrete containing bottom ash (BA) and fly ash (FA), as partial or total replacement of fine aggregate and Ordinary Portland cement (OPC), respectively. Concrete mixtures were prepared containing 0, 20, 50, 75 and 100% of BA as a substitute for river sand and 20% of FA as a replacement for OPC. Tests carried out were Toxicity Characteristics Leaching Procedure (TCLP), sulfate and acid attack (change in compressive strength, microstructure and weight) and elevated temperature effects (loss in compressive strength and mass as well as change in pulse velocity). Results showed that submerging coal ash concrete (CAC) mixtures in 5% sulfuric acid solution resulted in less reduction of compressive strength and mass loss compare to that of the control concrete. Moreover, sulfate resistance tests on concrete mixtures indicated that there were no mass loss and no reduction in compressive strength of all the mixtures after submersion in 5% magnesium sulfate solution. CAC showed higher weight loss and greater compressive strength reduction at elevated temperatures. From TCLP results, it is concluded that none of the elements leached higher than the maximum concentration of contaminants for toxicity characteristics. It indicates that transportation, disposal and utilization of BA and FA as clean construction material’s replacement could be utilized to reduce their environmental problems, increase efficiency and reduced unit cost production of concrete.

Effectiveness of Single and Composited Stabilizers on Enhancing Stability of Multiple Metals in Mine Soil

The soil pollution is getting worse with the rapid development of industry in recent years, Heavy metals can ultimately affect human health through the food chain. So immobilization of heavy metals in soil is of great significance. Here, six single stabilizer and six composite stabilizers, including CaO, bone char (BC), Na2S, calcium superphosphate (SSP), sodium diethyldithiocarbamate (DDTC-Na) and FeSO4, were investigated to immobilize heavy metals and As in mine soil. Toxicity Characteristic Leaching Procedure (TCLP) was adopted to evaluate the stabilization effectiveness of the stabilizers on Pb, Zn, Cu, Cd and As, and the best stabilizers for simultaneously immobilizing Pb, Zn, Cu, Cd and As in soil were selected based on the TCLP results. The results in this study provide useful information for remediation of heavy metals contaminated soil.

Stabilization of Cadmium- and Lead-Contaminated Sites Using Sodium Tetraethylenepentamine-Multi Dithiocarbamate

Two soil amendments, KH2PO4 and sodium tetraethylenepentamine–multi dithiocarbamate (TEPA/CSSNa), were applied to heavy metal-contaminated sites, and their corresponding stabilization effects were compared. Three kinds of procedures, namely, sequential extraction procedure (SEP), toxicity characteristic leaching procedure (TCLP), and diethylenetriaminepentaacetic acid (DTPA) extraction procedure, were adopted to examine the potential of using TEPA/CSSNa to stabilize Cd and Pb in polluted sites. Simplified bioaccessibility extraction test (SBET) was used to investigate the bioaccessibility of Cd and Pb. TCLP and DTPA results showed that TEPA/CSSNa was more efficient than KH2PO4 in reducing the mobility of Cd and Pb. SBET results indicated that the bioaccessibility of Cd and Pb decreased with increasing dose of TEPA/CSSNa. The mobility rates of Cd and Pb decreased to 0.26 and 0 %, respectively, when using 3 % TEPA/CSSNa. The exchangeable and carbonate fractions of Cd and Pb were gradually converted into organic matter–sulfate compounds. After 1 year, natural aging tests revealed that organic matter–sulfate fractions of Cd and Pb increased and the labile fractions (exchangeable and carbonate fractions) decreased in the treated soil.

Performance evaluation of using electric arc furnace dust in asphalt binder

Electric arc furnace dust (EAFD) is one of the harmful by-products of steel manufacturing industry which contains elements such as Cr, Pb, Zn, Cu, and Cd. These elements are emitted after charge melting in an electric arc furnace. The results of leaching tests demonstrate that the amount of these elements in EAFD exceeds the established limits. To deal with this problem, EAFD can be used as an alternative material in asphalt mix production which improves fatigue life. A large amount of investments are spent on the road maintenance and a significant portion of these investments is assigned to repair cracks caused by iterative traffic load and freeze-thaw cycles. The potential of asphalt self-healing, the ability of recovering mechanical characteristics, aims in improving fatigue life of asphalt pavement as well as reducing energy consumption and environmental side effects. Mastic asphalt is a material with self-healing capability. This paper proposes an effective and efficient treatment which utilizes EAFD as filler in the asphalt mixture. Accordingly, the performance of the fatigue and self-healing potential in the mastic along with two common fillers including Granite and hydrated lime are compared through a time sweep test with/without rest period using a DSR device. Results show that asphalt mastic containing EAFD filler has much better self-healing and fatigue performance than those containing Granite filler. Consequently, using this filler in asphalt mixture decreases environmental side effects in addition to manufacturing cost reduction and improving economic aspects of asphalt production. Moreover, the environmental aspects of using EAFD in asphalt binder are investigated and the result of leaching test indicates that pavements constructed by EAFD has no threat for ground and surface waters. For monitoring the amount of pollution leaching from asphalt mixture containing EAFD into flowing water, Toxicity Characteristic Leaching Procedure (TCLP) was investigated. TCLP Results showed that the amount of heavy metals for all of these samples are lower than the regulatory levels.

Cadmium telluride leaching behavior: Discussion of

Zeng et al. (2015) evaluate the leaching behavior and surface chemistry of II–VI semiconductor materials, CdTe and CdSe, in response to pH and O2. Under agitation in acidic and aerobic conditions, the authors found approximately 3.6%–6.4% (w/w) solubility of Cd content in CdTe in the Toxicity Characteristic Leaching Procedure (TCLP), Waste Extraction Test (WET), and dissolution test, with lower solubility (0.56–0.58%) under agitation in acidic and anoxic conditions. This range is comparable with prior long-term transformation and dissolution testing and bio-elution testing of CdTe (2.3%–4.1% w/w solubility of Cd content in CdTe). The implications for potential leaching behavior of CdTe-containing devices require further data. Since CdTe PV modules contain approximately 0.05% Cd content by mass, the starting Cd content in the evaluation of CdTe-containing devices would be lower by three orders of magnitude than the starting Cd content in the authors’ study, and leaching potential would be further limited by the monolithic glass-adhesive laminate-glass structure of the device that encapsulates the semiconductor material. Experimental evaluation of leaching potential of CdTe PV modules crushed by landfill compactor has been conducted, with results of TCLP and WET tests on the crushed material below regulatory limits for Cd. CdTe PV recycling technology has been in commercial operation since 2005 with high yields for semiconductor (95%) and glass (90%) recovery.

Immobilization of copper ions laden kaolin waste: influence of thermal treatment on its immobilization in cement paste

This work aims to study the influence of thermal treatment of Cu2+ laden kaolin wastes on its immobilization efficiency in cement paste. Compressive strength and toxicity characteristic leaching procedure (TCLP) of 5–20 % kaolin waste blended cement pastes were tested. X-ray diffraction (XRD) results illustrate that adsorption of Cu2+ ions modify the crystal structure of kaolinite mineral. Fourier transform infrared (FTIR) results indicate that the adsorption sites on the kaolin surface that were occupied with free water molecules have been replaced with Cu2+ ions adsorbed from aqueous solutions. The thermal treatment of kaolin waste improves fixation ratio of Cu2+ in cement pastes containing up to 20 % of thermally treated waste. This is due to: pozzolanic activity of calcined kaolin, conversion of leachable adsorbed Cu2+ ions into encapsulated unleachable phase that does not retard the hydration of cement as well as adsorption of much of leachable Cu2+ ions on surfaces of hydration products and occlusion in its lattice structure as illustrated from XRD, FTIR, thermogravimetric, scanning electron microscopy and TCLP results. The fixation ratio of Cu2+ in cement paste blended with 20 % of thermally treated kaolin waste, reaches maximum value of about 97 % compared to 82 % for cement paste blended with 20 % of untreated kaolin waste.