Use of fly ash for remediation of metals polluted sediment – Green remediation (original) (raw)
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Water, Air, & Soil Pollution, 2020
Raw and activated dolomite or wood ash were comparatively evaluated in column reactors for the simultaneous removal of Ni and Zn in synthetic contaminated neutral drainage (CND) over 119 days. Dolomite was thermally activated by charring, while wood ash was subject to alkaline fusion followed by hydrothermal treatment. Column testing was performed using CND with 51.5 mg/L Ni and 46.5 mg/L Zn, at pH 6. Testing was considered complete when metal concentrations in the final effluent reached 0.5 mg/L to meet Canadian regulations on discharge. Results showed that thermally activated wood ash was the most efficient among all tested materials as it removed 64 mg/ g Ni and 61.6 mg/g Zn. Based on these results, thermally activated wood ash could be considered a promising option for Ni and Zn treatment in CND, although final pH correction of treated effluent might be necessary. At the end of the testing period, metals could be recovered by dissolution with concentrated acid and by hydrometallurgical processes from spent activated dolomite and wood ash, respectively. As spent material could be used for recovery of treated metals, sludge management issues could be alleviated.
Leaching behavior and immobilization of heavy metals in solidified/stabilized products
Journal of Hazardous Materials, 2006
The aim of the present study was to investigate the metal leaching behavior of the hazardous waste of zinc industry before and after thermal treatment. Samples were subjected to the TCLP (Toxicity Characteristic Leaching Procedure) and ASTM (American Society of Testing and Materials) methods. The results of TCLP and ASTM leaching methods demonstrate that addition of clinoptilolite, blast furnace slag, and red mud to the zinc leach residue reduces the heavy metal content in the effluent and the red mud performs better than clinoptilolite and blast furnace slag. The leaching tests showed that the content of some elements in the waste before thermal treatment exceeded the regulatory limits and cannot be disposed of in the present form. Metal releases decreased at higher temperatures from 6008C and 8008C and reached to minimum levels at 12008C because of heat-induced formation of a glassy matrix. The levels of Zn 21 released for 12008C was 0.025 mmol/L. Therefore, a stabilization or inertization treatment is necessary prior to disposal. Thermal treatment can be an acceptable method for disposal of zinc leach residue. 2008 American Institute
Removal of Ni and Zn in contaminated neutral drainage by raw and modified wood ash
Journal of Environmental Science and Health, Part A, 2016
In the present study, wood ash was modified by alkaline fusion, prior to hydrothermal synthesis, for potential application in the treatment of mine drainage impacted water. With this objective, two types of wood ash (both raw and modified) were evaluated for the treatment of Ni and Zn in contaminated neutral drainage (CND). Batch adsorption experiments were initially conducted on synthetic CND, and then on two real CND, sampled on two active mine sites, contaminated by either Ni (3.7 mg/L) or Zn (9.1 mg/L). Leaching of Zn was observed during the kinetic tests for the raw wood ash, whereas its modification suppressed the leaching. The cation exchange capacity acquired by modification of the two samples of wood ash exceeded 300 meq/100 g (which is two to fourfold higher than those of the raw ash), while sorption capacity for Ni and Zn tripled relative to the raw material. The Langmuir model best described the sorption process for all materials, while potential mechanisms of metal removal include adsorption, precipitation and ion exchange, following pseudo second-order kinetics. Results also showed that within 2 h of contact of mine effluents with one modified wood ash, Ni and Zn concentrations decreased below the maximum authorized monthly mean concentration allowed by the Canadian law (0.5 mg/L), whereas the other modified wood ash allowed reaching the regulatory conformity after 2 h for Ni but 7 days for Zn (although 93% removed after 2 h). Nonetheless, the pH was raised (10.9-11.8) above the legally allowed limits (6-9.5). Based on these findings, modified wood ash could be considered as a promising option for the treatment of Ni and Zn in CND, but the pH correction of final effluent might be necessary.
Bio-immobilization of Cu and Zn in recirculated bioreactor landfill
Environmental Science and Pollution Research, 2010
Purpose To protect the environmental quality of soil, groundwater, and surface water near the landfill site, it is necessary to make an accurate assessment of the heavy metal mobility. This study aims to present the bio-immobilization behavior of heavy metals in landfill and provide some reference suggestion for the manipulation of heavy metal pollution control after closure. Materials and methods Two simulated bioreactor landfill system loaded with real municipal solid waste (MSW), namely, conventional bioreactor landfill (CL) and leachate recirculated bioreactor landfill (RL), were operated. Cu and Zn, the two conventional heavy metals with the highest contents in MSW, were chosen to track the heavy metal bio-immobilization behavior in landfill. Results The MSW in landfill is a great threat to environment because much of the heavy metal is “hidden” in different components. The weight ratio of Cu and Zn in landfill amounts to 0.00427% and 0.00437%, respectively. The accumulated effluent masses of Cu and Zn in CL increased all along, while they still kept at a stable level after day 105 in RL. Conclusions The microbes like sulfate-reducing bacteria mediate the behavior of Cu and Zn in bioreactor landfill system. Cu and Zn can be bio-immobilized in bioreactor landfill system with leachate recirculation like RL.
Assessment of leaching characteristics of heavy metals from industrial leach waste
International Journal of Mineral Processing, 2013
Leaching of valuable metals from residues generated by pyrometallurgical or hydrometallurgical process usually results in a large amount of wastes. In the present study, the leaching behavior of the zinc leach waste was investigated by utilizing a regression model with dummy variables. The results of different leaching methods indicate that addition of fly ash and blast furnace slag to the zinc leach waste reduces the heavy metal content in the effluent and that fly ash performs better than blast furnace slag. The results of thermal treatment showed that the zinc leach waste cannot be disposed of in the present form. The metal release from the zinc leach waste decreased in relation to increasing treatment temperature. Metal releases for residues treated at 1000-1200°C decreased because of heat-induced formation of a glassy matrix. The levels of Zn, Pb and Mn released for 1200°C treatment temperature were 1.05, 0.08, 0.07 mg/l, respectively. Therefore an immobilization treatment is necessary prior to disposal.
Immobilization of Zn(II) ions from contaminated biomass using ceramic matrices
Journal of Hazardous Materials, 2019
This article describes the adsorption of zinc ions from synthetic solutions using residual pine sawdust as an adsorbent and, subsequently, the use of clay ceramic pieces and contaminated biomass as metal immobilizers. The process of adsorption was carried out with a synthetic solution of ZnCl 2 in contact with sawdust for a fixed time of 24 h. The mixture was stirred continually. The mixture was then filtered, and the metal ions not adsorbed by the biomass and present in the liquid phase were quantified. The physicochemical characteristics of the sawdust were determined by thermogravimetric and differential thermal analysis, infrared Fourier transform spectroscopy, fluorescence and X-ray diffraction, among others. The adsorption kinetics shows that the equilibrium was reached at 24 h. The most efficient ratio of the amount of biomass and the concentration of Zn(II) was 10 g/L of sawdust and 6.5 × 10 4 mg/L of metal, which was used to analyse the capacity of metal immobilization in the designed bricks. The values obtained for the apparent porosity, the loss of weight by ignition, the mechanical properties and the efficiency of retention, indicate that these bricks are suitable for use in civil construction.
Chemical Speciation & Bioavailability, 2001
In the present study, a five step sequential chemical extraction (SCE) procedure was employed to investigate the binding mechanisms and chemical partitioning of zinc in cement-based stabilised waste materials. After each step of SCE, scanning electronic microscope with energy dispersive spectrometer (SEM/EDS) and X-ray diffraction (XRD) were used to assess the microstructural and chemical changes of the waste materials. The results showed that the leaching of Zn from the cement based stabilised waste mainly took place at the second and the third extraction steps at pH 5.0 and 2.0, respectively. The addition of pulverised fly ash (PFA) increased the leachability of Zn at the second extraction step. The SCE results also indicated the hydration of cement was greatly retarded by the incorporation of zinc waste. The SEM and XRD analysis of the samples after each extraction step demonstrated that zinc leached at the second step extraction was partially due to the dissolution of the new crystalline phase (ZnO) in the waste materials. Since large amounts of zinc were leached out only at the third extraction step at pH 2.0, these stablised waste materials may be relatively stable under a normal disposal environment.
Comparative Study of Different Leaching Procedures
2014
ABSTRACT- Leaching is a natural process by which water soluble substances, (such as Ca, fertilizers, pesticides) are washed out from soil or wastes. These leached out chemicals, called leachate(s), cause pollution of surface and subsurface water. Experts in Municipal Solid Waste Management often require conceptualization of the leachability of metals in order to assess the risk of landfills to human health and environment. Literature identifies more than 100 leaching methods to remove soluble components from a solid matrix. In this study four potential leaching procedures used for municipal solid wastes are studied and compared to suggest the effects of these metals to the environment
Environmental Geochemistry and Health, 2011
"Various analyses of physico-chemical characteristics and batch tests were conducted with the sludge obtained from a full-scale electrolysis facility for treating coal mine drainage in order to find the applicability of sludge as a material for removing Zn(II) in an aqueous phase. The physico-chemical analysis results indicated that coal mine drainage sludge (CMDS) had a high specific surface area and also satisfied the standard of toxicity characteristic leaching procedure (TCLP) because the extracted concentrations of certain toxic elements such as Pb, Cu, As, Hg, Zn, and Ni were much less than their regulatory limits. The results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the CMDS mainly consists of goethite (70%) and calcite (30%) as a weight basis. However, the zeta potential analysis represented that the CMDS had a lower isoelectric point of pH (pHIEP) than that of goethite or calcite. This might have been caused by the complexation of negatively charged anions, especially sulfate, which usually exists with a high concentration in coal mine drainage. The results of Fourier transform infrared (FT-IR) spectrometry analysis revealed that Zn(II) was dominantly removed as a form of precipitation by calcite, such as smithsonite [ZnCO3] or hydrozincite [Zn5(CO3)2(OH)6]. Recycling sludge, originally a waste material, for the removal process of Zn(II), as well as other heavy metals, could be beneficial due to its high and speedy removal capability and low economic costs. © 2010 Springer Science+Business Media B.V. http://www.ncbi.nlm.nih.gov/pubmed/21063752 http://link.springer.com/article/10.1007/s10653-010-9348-0 "
Journal of Environmental Engineering and Landscape Management, 2009
Nowadays, with the environmental regulations becoming more and more stringent and growing pressure on the conservation of mineral resources, recycling has been gaining interest to develop economically-viable refining technology. As the costs of the wastewater disposal increase (especially in the metal finishing industry) more emphasis is being placed on the recovery and recycling of valuable chemicals contained within these streams. In this study, a commercial plating plant filter waste (PPFW) was examined as an alternative source for the recovery of Ni as a nickel rich precipitate. The treatment tests performed by H 2 SO 4 leaching method showed that dissolution amounts of metals such as Ni, Cu, Zn and Cr were affected by leaching time, temperature and acid concentration. Although the dissolution of metallic compounds almost was completed within the one hour of the extraction time, a rapid and higher dissolution amounts of Ni within the first minute of the leaching process (approximately 81% of the total extractable amount of Ni is extracted at the beginning period for 24 °C) indicated that the usage of this waste as a source of Ni has an advantage compared to Ni recovery from natural ores. A kinetic study carried out to clarify the dissolution of Ni, showed that a series of rate controlling steps, both chemical and diffusion reactions, was involved in the observed kinetic. After leaching, the filtered solution was subjected to two stages of controlled precipitation carried out at a pH of about 4-5.5 and about 8 to produce the solids containing non-nickel and nickel respectively. The precipitation test performed by NaOH or MgO showed that almost all of the dissolved Ni ions were seperated from the solution. Based on the XRD and IR analysis, it was found out that a final precipitate, obtained by the use of NaOH, could be characterized as a disordered α-Ni(OH) or as a blend of α and β-Ni(OH) 2 , as for the MgO, the precipitate composed of mainly β-(Ni(OH) 2) phase and/or α-(Ni(OH) 2) phases.