1
|
Song B, Liu Z, Li C, Zhou S, Yang L, Chen Z, Song M. Mechanistic insights into the leaching and environmental safety of arsenic in ceramsite prepared from fly ash. CHEMOSPHERE 2023; 344:140292. [PMID: 37769917 DOI: 10.1016/j.chemosphere.2023.140292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 09/11/2023] [Accepted: 09/25/2023] [Indexed: 10/03/2023]
Abstract
Utilizing fly ash to prepare ceramsite is a promising way to immobilize heavy metals and recycle industrial solid waste. However, traditional preparation method of fly ash ceramsite has the disadvantages of large ignition loss. Therefore, the present study applied the pressure molding method to enhance solid content and improve the strength of ceramsite. The optimal preparation conditions of ceramsite were suggested as preheating at 450 °C for 25 min followed by sintering at 1050 °C for 30 min. Under such conditions, ceramsite with high compressive strength of 10.8 Mpa, bulk density of 878 kg m-3, and 1-h water absorption of 18.5% was fabricated, in compliance with Chinese standard (GB/T 1743.1-2010). The arsenic leaching concentration from the resulting product was considerably lower than Chinese standard (GB 5085.3-2007). Moreover, arsenic volatilization during ceramsite calcination was insignificant, and the vast majority of arsenic remained in resulting ceramsite. A geochemical speciation model developed for the multiple component system in ceramsite suggested that FeAsO4, Ca5(OH) (AsO4)3, and hydrous ferric oxide adsorption are the primary mechanisms retaining arsenic in ceramsite. Additionally, based on density functional theory calculations and biotoxicity test, the binding site of arsenic atom on mineral components and the environmental safety of ceramsite was determined and evaluated.
Collapse
Affiliation(s)
- Bing Song
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu, 210096, China
| | - Zequan Liu
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu, 210096, China
| | - Chengming Li
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu, 210096, China
| | - Shiji Zhou
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu, 210096, China
| | - Linjun Yang
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu, 210096, China
| | - Zhiliang Chen
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, 400044, China; Department of Environmental Science, College of Environment and Ecology, Chongqing University, Chongqing, 400045, China.
| | - Min Song
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu, 210096, China; Jiangsu Province Engineering Research Center of Soil and Groundwater Pollution Prevention and Control, Nanjing, Jiangsu, 210036, China.
| |
Collapse
|
2
|
Chen Z, Zhang P, Brown KG, van der Sloot HA, Meeussen JCL, Garrabrants AC, Wang X, Delapp RC, Kosson DS. Impact of oxidation and carbonation on the release rates of iodine, selenium, technetium, and nitrogen from a cementitious waste form. JOURNAL OF HAZARDOUS MATERIALS 2023; 449:131004. [PMID: 36821900 DOI: 10.1016/j.jhazmat.2023.131004] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 01/24/2023] [Accepted: 02/12/2023] [Indexed: 06/18/2023]
Abstract
Evaluation of the long-term retention mechanisms and potential release rates for the primary constituents of potential concern (COPCs) (i.e., Tc, I, Se, and nitrate) is necessary to determine if Cast Stone, a radioactive waste form, can meet performance objectives under near-surface disposal scenarios. Herein, a mineral and parameter set accounting for the solubility of I and Se in Cast Stone was developed based on pH-dependent and monolithic diffusion leaching test results, to extend a geochemical speciation model previously developed. The impact of oxidation and carbonation as environmental aging processes on the retention properties of Cast Stone for primary COPCs was systematically estimated. Physically, the effective diffusion coefficients of 4 COPCs in Cast Stone were increased after carbonation and/or oxidation, reflecting an increase in permeability to diffusion. Chemically, i) pH & pe conditions in the original Cast Stone were favorable for the stabilization of Tc, but not for I, Se, and N; ii) oxidation (with/without carbonation) of Cast Stone changed the pe & pH conditions to be detrimental for Tc stabilization; and iii) carbonation (with/without oxidation) of Cast Stone modified the pH & pe conditions to be beneficial for the stabilization of I (in system with Ag added) and Se.
Collapse
Affiliation(s)
- Zhiliang Chen
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Peng Zhang
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States; Shanghai Shaanxi Coal Hi-tech Research Institute Co., Ltd., Shanghai 201613, China
| | - Kevin G Brown
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Hans A van der Sloot
- Hans van der Sloot Consultancy, Glenn Millerhof 29, 1628 TS Hoorn, the Netherlands
| | | | - Andrew C Garrabrants
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Xinyue Wang
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Rossane C Delapp
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - David S Kosson
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States.
| |
Collapse
|
3
|
Chen Z, Zhang P, Brown KG, van der Sloot HA, Meeussen JCL, Garrabrants AC, Delapp RC, Um W, Kosson DS. Evaluating the impact of drying on leaching from a solidified/stabilized waste using a monolithic diffusion model. WASTE MANAGEMENT (NEW YORK, N.Y.) 2023; 165:27-39. [PMID: 37080015 DOI: 10.1016/j.wasman.2023.04.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 03/06/2023] [Accepted: 04/04/2023] [Indexed: 05/03/2023]
Abstract
The release rates of constituents of potential concern from solidified/stabilized cementitious waste forms are potentially impacted by drying, which, however, is not well understood. This study aimed to identify the impacts of drying on subsequent leaching from Cast Stone as an example of a solidified cementitious waste form. The release fluxes of constituents from monoliths after aging under 100, 68, 40, and 15 % relative humidity for 16, 32, and 48 weeks, respectively, were derived from mass transfer tank leaching tests following EPA Method 1315. A monolithic diffusion model was calibrated based on the leaching test results to simulate the leaching of major and redox-sensitive constituents from monoliths after drying. The reduction in physical retention of constituents (tortuosity-factor) in the unsaturated zone was identified as the primary impact from drying on subsequent leaching. Fluxes of both major (i.e., OH-, Na, K, Ca, Si, and Al) and redox-sensitive constituents (i.e., Tc, Cr, Fe, and S) from monoliths during leaching were well described by the model. The drying-induced reduction of tortuosity-factor and concomitant changes in porewater pH and redox conditions can significantly change the subsequent release fluxes of pH- and redox- sensitive constituents.
Collapse
Affiliation(s)
- Zhiliang Chen
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Peng Zhang
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States; Shanghai Shaanxi Coal Hi-tech Research Institute Co., Ltd., Shanghai 201613, China
| | - Kevin G Brown
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Hans A van der Sloot
- Hans van der Sloot Consultancy, Glenn Millerhof 29, 1628 TS Hoorn, the Netherlands
| | | | - Andrew C Garrabrants
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Rossane C Delapp
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Wooyong Um
- Pacific Northwest National Lab., Richland, WA, United States; Pohang University of Science and Technology (POSTECH), Pohang, Korea
| | - David S Kosson
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States.
| |
Collapse
|
4
|
Wang Z, Cowan EA, Seramur KC, Dwyer GS, Wilson JC, Karcher R, Brachfeld S, Vengosh A. Legacy of Coal Combustion: Widespread Contamination of Lake Sediments and Implications for Chronic Risks to Aquatic Ecosystems. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:14723-14733. [PMID: 36190271 DOI: 10.1021/acs.est.2c04717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Elevated concentrations of toxic elements in coal ash pose human and ecological health risks upon release to the environment. Despite wide public concerns about water quality and human health risks from catastrophic coal ash spills and chronic leaking of coal ash ponds, coal ash disposal has only been partially regulated, and its impacts on aquatic sediment quality and ecological health have been overlooked. Here, we present a multiproxy approach of morphologic, magnetic, geochemical, and Sr isotopic analyses, revealing unmonitored coal ash releases over the past 40 to 70 years preserved in the sediment records of five freshwater lakes adjacent to coal-fired power plants across North Carolina. We detected significant sediment contamination and potential chronic ecological risks posed by the occurrence of hundreds of thousands of tons of coal ash solids mainly resulting from high-magnitude stormwater runoff/flooding and direct effluent discharge from coal ash disposal sites. The proximity of hundreds of disposal sites to natural waterways across the U.S. implies that such contamination is likely prevalent nationwide and expected to worsen with climate change.
Collapse
Affiliation(s)
- Zhen Wang
- Nicholas School of the Environment, Duke University, Durham, North Carolina 27708, United States
| | - Ellen A Cowan
- Department of Geological and Environmental Sciences, Appalachian State University, Boone, North Carolina 28608, United States
| | - Keith C Seramur
- Department of Geological and Environmental Sciences, Appalachian State University, Boone, North Carolina 28608, United States
| | - Gary S Dwyer
- Nicholas School of the Environment, Duke University, Durham, North Carolina 27708, United States
| | - Jessie C Wilson
- Department of Geological and Environmental Sciences, Appalachian State University, Boone, North Carolina 28608, United States
| | - Randall Karcher
- Department of Geological and Environmental Sciences, Appalachian State University, Boone, North Carolina 28608, United States
| | - Stefanie Brachfeld
- Earth and Environmental Studies, Montclair State University, Montclair, New Jersey 07043, United States
| | - Avner Vengosh
- Nicholas School of the Environment, Duke University, Durham, North Carolina 27708, United States
| |
Collapse
|
5
|
Wang X, van der Sloot HA, Brown KG, Garrabrants AC, Chen Z, Hensel B, Kosson DS. Application and uncertainty of a geochemical speciation model for predicting oxyanion leaching from coal fly ash under different controlling mechanisms. JOURNAL OF HAZARDOUS MATERIALS 2022; 438:129518. [PMID: 35999720 DOI: 10.1016/j.jhazmat.2022.129518] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 06/15/2022] [Accepted: 06/30/2022] [Indexed: 06/15/2023]
Abstract
Three primary mechanisms (adsorption to iron oxides or analogous surfaces, co-precipitation with Ca, and substitution in ettringite) controlling oxyanion retention in coal fly ashes (CFAs) were identified by differentiating the leaching behavior of As, B, Cr, Mo, Se, and V from 30 CFAs. Fidelity evaluation of geochemical speciation modeling focused on six reference CFAs representing a range of CFA compositions, whereby different leaching-controlling mechanisms of oxyanions were systematically considered. For three reference CFAs with low Ca and S content, calibration of adsorption reactions for the diffuse double-layer model for hydrous ferric oxides improved the simultaneous prediction of oxyanion leaching, which reduced uncertainties in Se and V predictions caused by nonideal adsorption surfaces and competitive adsorption effects. For two reference CFAs with intermediate Ca content, the solubility constants for Ca-arsenates from literature and postulated phases of B, Cr, Se, and V were used to describe co-precipitation of oxyanions with Ca-bearing minerals under alkaline conditions. For the reference CFA with high Ca and S content, an ettringite solid solution was used to capture the simultaneous retention of all oxyanions at pH> 9.5. Overall, the simultaneous leaching predictions of oxyanions from a wide range of CFAs were improved by calibration of adsorption reactions and controlling solid phases.
Collapse
Affiliation(s)
- Xinyue Wang
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Hans A van der Sloot
- Hans van der Sloot Consultancy, Glenn Millerhof 29, 1628 TS Hoorn, the Netherlands
| | - Kevin G Brown
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Andrew C Garrabrants
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Zhiliang Chen
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States
| | - Bruce Hensel
- Electric Power Research Institute (EPRI), 3420 Hillview Avenue, Palo Alto, CA 94304, United States
| | - David S Kosson
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235, United States.
| |
Collapse
|
6
|
Zhang P, Chen Z, Brown KG, Garrabrants AC, Delapp R, Meeussen JCL, van der Sloot HA, Kosson DS. Impact of carbonation on leaching of constituents from a cementitious waste form for treatment of low activity waste at the DOE Hanford site. WASTE MANAGEMENT (NEW YORK, N.Y.) 2022; 144:431-444. [PMID: 35461054 DOI: 10.1016/j.wasman.2022.04.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 02/04/2022] [Accepted: 04/08/2022] [Indexed: 06/14/2023]
Abstract
Carbonation can be a major aging process during disposal of alkaline cementitious waste forms and can impact constituent leaching by changes in material alkalinity, pore structure, and controlling mineral phases. The effect of carbonation on the leaching of major and trace constituents from Cast Stone, a cementitious waste form developed to treat high salt content low activity waste, was studied through a combination of leaching experiments and reactive transport simulations. Diffusive transport of constituents in the waste form was evaluated using reactive transport modeling of diffusion-controlled leaching test results and a geochemical speciation model derived from pH-dependent leaching. Comparisons between Cast Stone materials aged under nitrogen, air, and 2% carbon dioxide in nitrogen showed that carbonation impacts solubility, physical retention and observed diffusivity of major and trace constituents. Carbonation under 2% CO2 decreased the diffusion-controlled leaching of chromium by two orders of magnitude. Modeling results suggest that carbonation may also decrease solubility of technetium while changes to microstructure by carbonation increases effective diffusivity of constituents in Cast Stone.
Collapse
Affiliation(s)
- Peng Zhang
- Civil and Environmental Engineering, Vanderbilt University, Station B-351831, Nashville, TN 37235, USA
| | - Zhiliang Chen
- Civil and Environmental Engineering, Vanderbilt University, Station B-351831, Nashville, TN 37235, USA
| | - Kevin G Brown
- Civil and Environmental Engineering, Vanderbilt University, Station B-351831, Nashville, TN 37235, USA
| | - Andrew C Garrabrants
- Civil and Environmental Engineering, Vanderbilt University, Station B-351831, Nashville, TN 37235, USA
| | - Rossane Delapp
- Civil and Environmental Engineering, Vanderbilt University, Station B-351831, Nashville, TN 37235, USA
| | | | - Hans A van der Sloot
- Hans van der Sloot Consultancy, Glenn Millerhof 29, 1628 TS Hoorn, the Netherlands
| | - David S Kosson
- Civil and Environmental Engineering, Vanderbilt University, Station B-351831, Nashville, TN 37235, USA.
| |
Collapse
|