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Liu R, Liu S, Sun S, Cao X, Lin J, Peng J, Ji F, Ma R. Medical waste incineration fly ash-based magnesium potassium phosphate cement: Calcium-reinforced chlorine solidification/stabilization mechanism and optimized carbon reduction process strategy. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 357:120749. [PMID: 38552517 DOI: 10.1016/j.jenvman.2024.120749] [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: 11/30/2023] [Revised: 02/28/2024] [Accepted: 03/20/2024] [Indexed: 04/14/2024]
Abstract
The traditional solidification/stabilization (S/S) technology, Ordinary Portland Cement (OPC), has been widely criticized due to its poor resistance to chloride and significant carbon emissions. Herein, a S/S strategy based on magnesium potassium phosphate cement (MKPC) was developed for the medical waste incineration fly ash (MFA) disposal, which harmonized the chlorine stabilization rate and potential carbon emissions. The in-situ XRD results indicated that the Cl- was efficiently immobilized in the MKPC system with coexisting Ca2+ by the formation of stable Ca5(PO4)3Cl through direct precipitation or intermediate transformation (the Cl- immobilization rate was up to 77.29%). Additionally, the MFA-based MKPC also demonstrated a compressive strength of up to 39.6 MPa, along with an immobilization rate exceeding 90% for heavy metals. Notably, despite the deterioration of the aforementioned S/S performances with increasing MFA incorporation, the potential carbon emissions associated with the entire S/S process were significantly reduced. According to the Life Cycle Assessment, the potential carbon emissions decreased to 8.35 × 102 kg CO2-eq when the MFA reached the blending equilibrium point (17.68 wt.%), while the Cl- immobilization rate still remained above 65%, achieving an acceptable equilibrium. This work proposes a low-carbon preparation strategy for MKPC that realizes chlorine stabilization, which is instructive for the design of S/S materials.
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Affiliation(s)
- Runjie Liu
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Shiwei Liu
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Shichang Sun
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Xing Cao
- Shenzhen Engineering Lab of Flexible Transparent Conductive Films, School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China
| | - Junhao Lin
- Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Juan Peng
- Shenzhen Environmental Technology Group Co. LTD, Shenzhen, 518010, China
| | - Fei Ji
- Shenzhen Environmental Technology Group Co. LTD, Shenzhen, 518010, China
| | - Rui Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, China.
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Li Y, Zhou W, Huang X, Wang Y, Liang J, Liu Y, Tong M. Is crystalline chromium phosphate environmentally stable? A study on the formation, dissolution and oxidation risk of CrPO 4·6H 2O. JOURNAL OF HAZARDOUS MATERIALS 2024; 465:133112. [PMID: 38043420 DOI: 10.1016/j.jhazmat.2023.133112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Revised: 11/22/2023] [Accepted: 11/26/2023] [Indexed: 12/05/2023]
Abstract
Hexavalent chromium (Cr(VI)) contamination in soil and groundwater is usually remediated via reduction techniques. The formation of crystalline chromium phosphate (CrPO4·6 H2O) occurs as a byproduct during Cr(VI) remediation processes in the presence of phosphate, yet its stability in the environment has received limited attention. In this study, the formation conditions, structure, properties, and risks associated with the dissolution and oxidation of CrPO4·6 H2O were comprehensively assessed. Results showed that crystalline CrPO4·6 H2O was formed under pH 5 - 7 at room temperature. CrPO4·6 H2O exhibits higher dissolution risk compared to Cr(OH)3·3 H2O due to a long Cr-P bond (4.2 Å). H+ and OH- increased the risk of dissolution at pH 5 and 11, respectively, owing to the formation of CrH2PO42+ and Cr(OH)4-. In addition, under faintly acidic conditions, the high solubility of CrPO4·6 H2O increases the risk of oxidation; under neutral and weakly alkaline conditions, the presence of positively charged Cr(H2O)63+ structures on the surface elevates its susceptibility to contact and oxidation by δ-MnO2 compared to Cr(OH)3·3 H2O. Specifically, at pH 11, the conversion of CrPO4·6 H2O to Cr(OH)3·3 H2O results in similar oxidation risks for both Cr(III) precipitates.
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Affiliation(s)
- Yunyi Li
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China.
| | - Wenshuai Zhou
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China
| | - Xinmiao Huang
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China
| | - Yutong Wang
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China
| | - Jialiang Liang
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China
| | - Yangsheng Liu
- College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China
| | - Meiping Tong
- College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China
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Han L, Li J, Fei X, Wang M, Liu S, Zhang X, Xue Q. Stabilization and strengthening of chromium(VI)-contaminated soil via magnesium ascorbyl phosphate (MAP) and phytase addition. JOURNAL OF HAZARDOUS MATERIALS 2023; 448:130860. [PMID: 36709739 DOI: 10.1016/j.jhazmat.2023.130860] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/27/2022] [Accepted: 01/22/2023] [Indexed: 06/18/2023]
Abstract
Cr(VI) contamination of soil threatens the environment and reduces soil strength. Therefore, both Cr(VI) stabilization and soil reinforcement should be considered in site remediation for future construction. This study investigated a biochemical treatment process using magnesium ascorbyl phosphate (MAP) and phytase. MAP was hydrolyzed via phytase catalysis to produce ascorbic acid (AA) and MgHPO4·3H2O precipitation. The AA reduced Cr(VI) into low-toxic Cr(III), which precipitated as Cr(OH)3 and CrPO4. More than 90% of the 500 mg/kg Cr(VI) in soil was reduced by 5% MAP (wt% of soil) and 1% phytase (vol/vol of soil water) doses at the geotechnically optimal soil moisture content of 16.8%. The MgHPO4·3H2O precipitates filled soil pores and enhanced the unconfined compression strength of treated soil by more than two times. This research reports a novel and practical enzymatically induced phosphate precipitation process for the remediation of Cr(VI)-contaminated soil.
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Affiliation(s)
- Lijun Han
- State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Science, Beijing 100049, China; School of Civil and Environmental Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore
| | - Jiangshan Li
- State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China; IRSM-CAS/HK PolyU Joint Laboratory on Solid Waste Science, Wuhan 430071, China.
| | - Xunchang Fei
- State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China; School of Civil and Environmental Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore; Residues and Resource Reclamation Centre, Nanyang Environment and Water Research Institute, 1 Cleantech Loop, 637141, Singapore
| | - Mengqi Wang
- School of Urban Construction, Wuhan University of Science and Technology, Wuhan 430065, China
| | - Shiyu Liu
- School of Urban Construction, Wuhan University of Science and Technology, Wuhan 430065, China
| | - Xianwei Zhang
- School of Urban Construction, Wuhan University of Science and Technology, Wuhan 430065, China
| | - Qiang Xue
- State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China; IRSM-CAS/HK PolyU Joint Laboratory on Solid Waste Science, Wuhan 430071, China.
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