Leaching mechanisms of heavy metals from fly ash stabilised soils

2018 ◽  
Vol 36 (7) ◽  
pp. 616-623 ◽  
Author(s):  
Kittitat Leelarungroj ◽  
Suched Likitlersuang ◽  
Thanakorn Chompoorat ◽  
Dao Janjaroen
Keyword(s):  
Heavy Metals ◽  
Fly Ash ◽  
Construction Projects ◽  
Ground Improvement ◽  
Chemical Compounds ◽  
Soil Improvement ◽  
Weak Soils ◽  
Lead And Zinc ◽  
Different Types ◽  
Ph Conditions

Fly ash is an industrial waste material that is repurposed as a soil stabiliser worldwide. In Thailand, many ground improvement projects utilise mixtures of cement and fly ash to stabilise weak soils. In this study, leaching mechanisms of arsenic, chromium, lead, and zinc from cement and fly ash stabilised soils were investigated in the laboratory. Leaching tests were performed, with different leachants and pH conditions, on cement and fly ash stabilised soils used for soil improvement in road embankment construction projects in Northern Thailand. The results suggested that chemical compounds (CaO and MgO) on fly ash surfaces can control the pH of the fly ash and soil leachant. The dissolution of chromium and zinc was found to be amphoteric and controlled by oxide minerals at a high or low pH. Arsenic leaching was found to be oxyanionic where AsO43- prevented the adsorption of arsenic onto the negatively charged fly ash surface. Different types of leachant also leached out in different amounts of heavy metals.

The Strength of Fly Ash-Bottom Ash (FA-BA) Mixtures as Backfill Material in Ground Improvement Works

2013 ◽  
Vol 465-466 ◽  
pp. 937-943
Author(s):  
Abd Rahim bin Hj. Awang ◽  
Wan Hilmi bin Wan Mansor ◽  
Ahmad Yusri Bin Mohamad
Keyword(s):  
Shear Strength ◽  
Fly Ash ◽  
Specific Gravity ◽  
Ground Improvement ◽  
Bottom Ash ◽  
Friction Angle ◽  
Soil Improvement ◽  
Geotechnical Properties ◽  
Raw Material ◽  
Fa Composition

In Malaysia, coal has been used as a raw material to generate electricity since 1988. In the past, most of the wastage of coal burning especially the bottom ash was not managed properly as it was dumped in the waste pond and accumulated drastically. This research has been conducted to explore the physical characteristic and geotechnical properties of fly ash-bottom ash (FA-BA) mixtures that consist of 30% FA, 50% FA, 70% FA and 90% FA by weight. The physical characteristics, that include the specific gravity, particle size distribution and compaction, were tested for each mixture without any curing. However, the geotechnical properties of the mixtures that include the permeability and shear strength had been studied at various curing periods (0, 14 and 28 days) to review the effect of time on the geotechnical properties of the mixtures. The results show that mixtures with higher FA composition have lower value of specific gravity, well-graded, and need less moisture to be compacted efficiently compared to those mixtures with lower FA composition. The results also show that mixtures with higher FA composition have less drainage characteristics but can be improved by prolonging the curing period. The maximum shear strength was obtained at mixture with 50%FA and the value increased with curing periods. The friction angle obtained ranged from 270to 370. It is also found that the mixtures with lower FA composition are more compressible compared to the mixtures with higher FA composition. The results obtained could be used by others to determine the suitability of different FA-BA mixtures for various usage in Geotechnical Engineering work such as for soil improvement work in weak soils or as backfill materials in embankment construction.

scholarly journals Compressibility of kaolinite treated with fly ash from fluidized bed combustion

2014 ◽  
Vol 13 (2) ◽  
pp. 033-038
Author(s):  
Karolina Knapik ◽  
Joanna Bzówka ◽  
Giacomo Russo
Keyword(s):  
Fly Ash ◽  
Fluidized Bed ◽  
Ground Improvement ◽  
Soil Improvement ◽  
Fluidized Bed Combustion ◽  
Waste Products ◽  
Current State ◽  
Combustion Technology ◽  
Engineering Projects ◽  
Compressibility Characteristics

Waste products such as fly ash can be an economically advantageous alternative for lime and cement in ground improvement techniques. Current state of knowledge indicates the possibility of using this material successfully in various engineering projects. However, the chemical composition of fly ash is related to the type of coal and combustion technology used in power plant. This fact indicates need for further studies aiming determination the effect of fly ash addition on soil properties. Rate of soil improvement considered in macro level includes designation of treated soil mechanical properties, inter alia compressibility characteristics. Presented results of laboratory tests are a part of a larger experimental work aiming to determine the suitability of fly ash from fluidized bed combustion for the purpose of soil strengthen with the use of selected ground improvement.

scholarly journals Rhizofiltration of Heavy Metals (Cadmium, Lead and Zinc) From Fly Ash Leachates Using Water Hyacinth (Eichhornia Crassipes)

2015 ◽  
Vol 4 (1) ◽  
pp. 179-196 ◽  
Author(s):  
Amit Kumar Yadav ◽  
Bhawana Pathak ◽  
M. H. Fulekar
Keyword(s):  
Heavy Metals ◽  
Fly Ash ◽  
Eichhornia Crassipes ◽  
Aquatic Macrophyte ◽  
Translocation Factor ◽  
Soil Surface ◽  
Toxic Heavy Metals ◽  
Lead And Zinc ◽  
Cadmium Lead ◽  
Maximum Removal

Fly ashes are usually contaminated with toxic heavy metals. These metals are leaching out aftercontact with water during wet disposal system, thus polluting the soil, surface and groundwater. In the present study, a hydroponics experiment was conducted to examine the removalof heavy metals Cd, Pb and Zn by Eichhornia crassipes grown at various concentration of fly ash ranging from 10, 20 and 40 percent over a period of 30 days.After 30 days, the plants were separately harvested, dried and weighedfor biomass of the roots and shoots. The uptake of each metalwas studied in the root and shoot separately, to determine the bioaccumulation of metals in Eichhornia crasspies.The translocation factor was calculated to study the efficiency of the plants forbioaccumulation of each metal in roots and shoot. The results showed that maximum uptake of metals Cd, Pb and Zn by plantwasfoundat the higher concentration (40%) of fly ash.The metals uptake found was 99.16, 166.52 and 741.04 μg g-1 tissues in the roots, respectively and 33.46, 41.33 and 255.90 μgg-1 tissues in the shoots, respectively and successfullyremoved up to 78% of Cd, 82% of Pb and 70% of Zn.The maximum removal efficiency by plant for Cd, Pb and Zn at lower concentration (10%) of fly ash was 84%, 86% and 75%, respectively.The heavy metals accumulated more in roots than in the shoots by Eichhornia crassipes. The maximum bioconcentration factor and translocation factor value of Eichhornia crappies for Cd, Pb and Zn were calculated as 705.55, 705.55 and 614.51 and 41.86, 47.18 and 34.53 respectively. The high removal efficiencies of heavy metals Cd, Pb and Zn was find without toxic effect by this aquatic macrophyte, thisplant can be recommended for the actual treatment of fly ash leachatesin ash pond to clean up the aquatic environment.DOI: http://dx.doi.org/10.3126/ije.v4i1.12187International Journal of Environment Volume-4, Issue-1, Dec-Feb 2014/15, page : 179-196   

Contaminant retention characteristics of fly ash–bentonite mixes

2016 ◽  
Vol 35 (1) ◽  
pp. 40-46 ◽  
Author(s):  
Abhijit Deka ◽  
Sreedeep Sekharan
Keyword(s):  
Fly Ash ◽  
Multiple Sources ◽  
Retention Capacity ◽  
Additional Advantage ◽  
Batch Tests ◽  
Landfill Sites ◽  
Different Types ◽  
Retention Characteristics ◽  
Ph Conditions ◽  
Chemical Retention

It is important to determine the contaminant retention characteristics of materials when assessing their suitability for use as liners in landfill sites. Sand–bentonite mixtures are commonly used as liners in the construction of landfill sites for industrial and hazardous wastes. Sand is considered to be a passive material with a negligible chemical retention capacity; fly ash, however, offers the additional advantage of adsorbing the heavy metals present in landfill leachates. There have been few studies of the contaminant retention characteristics of fly ash–bentonite mixes. The study reported here determined the contaminant retention characteristics of different fly ashes, bentonite and selected fly ash–bentonite mixes for Pb2+ using 24 h batch tests. The tests were conducted by varying the initial concentrations of metal ions under uncontrolled pH conditions. The efficiency of the removal of Pb2+ by the different types of fly ash and fly ash–bentonite mixes was studied. The influence of multiple sources of fly ash on the retention characteristics of fly ash–bentonite mixes was investigated.

Conditioning of oily sludges with municipal solid wastes incinerator fly ash

1997 ◽  
Vol 35 (8) ◽  
pp. 231-238 ◽  
Author(s):  
Tay Joo Hwa ◽  
S. Jeyaseelan
Keyword(s):  
Heavy Metals ◽  
Fly Ash ◽  
Specific Resistance ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Solid Wastes ◽  
Municipal Solid Wastes ◽  
Capillary Suction ◽  
Optimum Dosage

Conditioning of sludges improves dewatering characteristics and reduces the quantity of sludge to be handled. Anaerobic digested sludge collected from a sewage treatment plant contained 1.8% to 8% oil. The increase of specific resistance and capillary suction time (CST) with increasing oil content observed in these samples indicates the interference of oil in dewatering. It has been found that addition of municipal solid wastes incinerator fly ash decreases the specific resistances and capillary suction times of oily sludges rapidly up to 3% dosage. Beyond 3% fly ash, the decrease is less significant and the solids content in the sludge cake increases. This optimum dosage remains the same for sludges with varying oil contents from 1.8% to 12%. The total suspended solids of filtrate decreases with fly ash dosage but the toxic concentrations of heavy metals increases considerably. However at the optimum dosage of 3%, concentrations of heavy metals are within the limits for discharging into the sewers. The correlations of CST with the dewatering characteristics such as specific resistance, filter yield and corrected filter yield are established. These correlations can be used to obtain a quick prediction on dewaterability.

scholarly journals A Review of Photoelectrocatalytic Reactors for Water and Wastewater Treatment

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1198
Author(s):  
Stuart McMichael ◽  
Pilar Fernández-Ibáñez ◽  
John Anthony Byrne
Keyword(s):  
Chemical Compounds ◽  
Research Area ◽  
Heterogeneous Photocatalysis ◽  
Semiconducting Materials ◽  
Electron Hole ◽  
Water And Wastewater Treatment ◽  
Aqueous Environments ◽  
Different Types ◽  
Water And Wastewater ◽  
Electrical Bias

The photoexcitation of suitable semiconducting materials in aqueous environments can lead to the production of reactive oxygen species (ROS). ROS can inactivate microorganisms and degrade a range of chemical compounds. In the case of heterogeneous photocatalysis, semiconducting materials may suffer from fast recombination of electron–hole pairs and require post-treatment to separate the photocatalyst when a suspension system is used. To reduce recombination and improve the rate of degradation, an externally applied electrical bias can be used where the semiconducting material is immobilised onto an electrically conducive support and connected to a counter electrode. These electrochemically assisted photocatalytic systems have been termed “photoelectrocatalytic” (PEC). This review will explain the fundamental mechanism of PECs, photoelectrodes, the different types of PEC reactors reported in the literature, the (photo)electrodes used, the contaminants degraded, the key findings and prospects in the research area.

scholarly journals Cements with calcareous fly ash as component of low clinker eco-self compacting concrete

2019 ◽  
Vol 9 (1) ◽  
pp. 196-201
Author(s):  
Jacek Gołaszewski ◽  
Grzegorz Cygan ◽  
Tomasz Ponikiewski ◽  
Małgorzata Gołaszewska
Keyword(s):  
Fly Ash ◽  
Hardened Concrete ◽  
Self Compacting Concrete ◽  
Basic Properties ◽  
Ecological Self ◽  
Different Types ◽  
Hardened State ◽  
Main Component ◽  
New Generation ◽  
Good Workability

AbstractThe main goal of the presented research was to verify the possibility of obtaining ecological self-compacting concrete of low hardening temperature, containing different types of cements with calcareous fly ash W as main component and the influence of these cements on basic properties of fresh and hardened concrete. Cements CEM II containing calcareous fly ash W make it possible to obtain self-compacting concrete (SCC) with similar initial flowability to analogous mixtures with reference cement CEM I and CEM III/B, and slightly higher, but still acceptable, flowability loss. Properties of hardened concretes with these cements are similar in comparison to CEM I and CEM III concretes. By using cement nonstandard, new generation multi-component cement CEM “X”/A (S-W), self-compacting concrete was obtained with good workability and properties in hardened state.

scholarly journals Enhanced Electrokinetic Remediation for the Removal of Heavy Metals from Contaminated Soils

2021 ◽  
Vol 11 (4) ◽  
pp. 1799
Author(s):  
Claudio Cameselle ◽  
Susana Gouveia ◽  
Adrian Cabo
Keyword(s):  
Heavy Metals ◽  
Citric Acid ◽  
Organic Acids ◽  
Contaminated Soils ◽  
Electrokinetic Remediation ◽  
Deionized Water ◽  
Soil Specimen ◽  
Removal Of Heavy Metals ◽  
Ph Conditions ◽  
Neutral Metal

The electrokinetic remediation of an agricultural soil contaminated with heavy metals was studied using organic acids as facilitating agents. The unenhanced electrokinetic treatment using deionized water as processing fluid did not show any significant mobilization and removal of heavy metals due to the low solubilization of metals and precipitation at high pH conditions close to the cathode. EDTA and citric acid 0.1 M were used as facilitating agents to favor the dissolution and transportation of metals. The organic acids were added to the catholyte and penetrated into the soil specimen by electromigration. EDTA formed negatively charged complexes. Citric acid formed neutral metal complexes in the soil pH conditions (pH = 2–4). Citric acid was much more effective in the dissolution and transportation out of the soil specimen of complexed metals. In order to enhance the removal of metals, the concentration of citric acid was increased up to 0.5 M, resulting in the removal of 78.7% of Cd, 78.6% of Co, 72.5% of Cu, 73.3% of Zn, 11.8% of Cr and 9.8% of Pb.

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