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Chen Q, Sun S, Wang Y, Zhang Q, Zhu L, Liu Y. In-situ remediation of phosphogypsum in a cement-free pathway: Utilization of ground granulated blast furnace slag and NaOH pretreatment. CHEMOSPHERE 2023; 313:137412. [PMID: 36455381 DOI: 10.1016/j.chemosphere.2022.137412] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 11/25/2022] [Accepted: 11/26/2022] [Indexed: 06/17/2023]
Abstract
In-situ remediating phosphogypsum (PG) for cemented paste backfill (CPB) in the contaminated site is economic management for promoting sustainable developments in the phosphate industry. This study concerns the combined use of NaOH pretreatment and ground-granulated blast furnace slag (GGBFS) additives to promote the solidification/stabilization of PG with a lower carbon footprint pathway. According to physico-chemical analyses, the NaOH pretreatment effectively removed approximately 95% of F within the PG, which may originally be present as sparingly soluble fluorides or coexisting with silicates. The micro mineralogical characterization illustrates that the pretreatment can accelerate the early age hydration, with more hydration products observed, including calcium silicate hydrates and ettringite, effective F and P retention candidates. Whereas the incorporation of GGBFS plays an essential role in promoting the generation of additional cement hydrates at the following stages. The macro mechanical performance analysis indicates that the mixtures of pretreated-PG-OPC-GGBFS exhibit an excellent mechanical performance satisfying the design criteria. Subsequent elemental mapping and toxicity characteristic leaching procedures demonstrate that this combined approach has a competitive F and P immobilization ability compared to the typical OPC binder and individual GGBFS addition. The newly formed phases effectively controlled the concentration of F and P through adsorption, incorporation, or encapsulation. Objectively, the proposed methodology can be a promising candidate pathway for extrapolating the in-situ immobilization of PG. This study opens up new perspectives for synergetically recycling PG and GGBFS in a profitable and low carbon footprint way.
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Affiliation(s)
- Qiusong Chen
- School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China; Sinosteel Maanshan General Institute of Mining Research Co., Ltd., Maanshan, 243000, China
| | - Shiyuan Sun
- School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China
| | - Yunmin Wang
- School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China
| | - Qinli Zhang
- School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China
| | - Liming Zhu
- School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China
| | - Yikai Liu
- Department of Geosciences and CIRCe Centre, University of Padua, Via G. Gradenigo 6, 35129, Padua, Italy.
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A Review on Pollution Treatment in Cement Industrial Areas: From Prevention Techniques to Python-Based Monitoring and Controlling Models. Processes (Basel) 2022. [DOI: 10.3390/pr10122682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Anthropogenic climate change, global warming, environmental pollution, and fossil fuel depletion have been identified as critical current scenarios and future challenges. Cement plants are one of the most impressive zones, emitting 15% of the worldwide contaminations into the environment among various industries. These contaminants adversely affect human well-being, flora, and fauna. Meanwhile, the use of cement-based substances in various fields, such as civil engineering, medical applications, etc., is inevitable due to the continuous increment of population and urbanization. To cope with this challenge, numerous filtering methods, recycling techniques, and modeling approaches have been introduced. Among the various statistical, mathematical, and computational modeling solutions, Python has received tremendous attention because of the benefit of smart libraries, heterogeneous data integration, and meta-models. The Python-based models are able to optimize the raw material contents and monitor the released pollutants in cement complex outputs with intelligent predictions. Correspondingly, this paper aims to summarize the performed studies to illuminate the resultant emissions from the cement complexes, their treatment methods, and the crucial role of Python modeling toward the high-efficient production of cement via a green and eco-friendly procedure. This comprehensive review sheds light on applying smart modeling techniques rather than experimental analysis for fundamental and applied research and developing future opportunities.
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Liu Y, Chen Q, Dalconi MC, Molinari S, Valentini L, Wang Y, Sun S, Wang P, Artioli G. Retention of phosphorus and fluorine in phosphogypsum for cemented paste backfill: Experimental and numerical simulation studies. ENVIRONMENTAL RESEARCH 2022; 214:113775. [PMID: 35830912 DOI: 10.1016/j.envres.2022.113775] [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: 12/20/2021] [Revised: 06/16/2022] [Accepted: 06/27/2022] [Indexed: 06/15/2023]
Abstract
The solidification/stabilization of phosphogypsum using cemented paste backfill (OCPB) provides a low-cost and alternative in-situ technique for recycling phosphogypsum stockpiles. But the OCPB is far from obtaining steady states in which the pollutants would redistribute as a response to dynamic environmental conditions. Further, the associated chemical interactions and the mineralogy information of the solubility-controlling phases of contaminants (fluorine and phosphorus) have not been thoroughly studied or fully understood. In this study, a framework coupling the chemical, mineralogical, and morphological analyses is used to determine the fluoride and phosphate retention mechanisms of immobilized OCPB. Then the pH-dependent leaching tests and numerical simulation is applied as a useful tool to identify the minerals controlling stabilized OCPB leaching behavior. The overall findings proved that aluminate-rich calcium silicate hydrates play an essential role in fluoride and phosphate retention. Both experimental and simulational acid neutralization and leaching curves indicate that the cementitious matrix works as a strong buffering material ensuring high pH conditions that are necessary for fluorine and phosphorus retention. Although discrepancies were observed in absolute fluorine and phosphorus leaching values at highly acidic conditions, the simulations are able to describe highly amphoteric leaching behavior. The simulation suggests that the aluminum species and calcium phosphates governed the solubility of fluorine and phosphorus, respectively. The results of this work would have implications for predicting the leaching behavior of OCPB in detrimental and multiple environments.
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Affiliation(s)
- Yikai Liu
- Department of Geosciences and CIRCe Centre, University of Padua, via G. Gradenigo 6, 35129, Padua, Italy
| | - Qiusong Chen
- Sinosteel Maanshan General Institute of Mining Research Co., Ltd., Maanshan, 24300, China; School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China.
| | - Maria Chiara Dalconi
- Department of Geosciences and CIRCe Centre, University of Padua, via G. Gradenigo 6, 35129, Padua, Italy
| | - Simone Molinari
- Department of Geosciences and CIRCe Centre, University of Padua, via G. Gradenigo 6, 35129, Padua, Italy
| | - Luca Valentini
- Department of Geosciences and CIRCe Centre, University of Padua, via G. Gradenigo 6, 35129, Padua, Italy
| | - Yunmin Wang
- Sinosteel Maanshan General Institute of Mining Research Co., Ltd., Maanshan, 24300, China; School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China
| | - Shiyuan Sun
- School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China
| | - Peishen Wang
- School of Resources and Safety Engineering, Central South University, Lushan South Road 932, 410083, Hunan, China
| | - Gilberto Artioli
- Department of Geosciences and CIRCe Centre, University of Padua, via G. Gradenigo 6, 35129, Padua, Italy
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Chemical Stabilization Used to Reduce Geogenic Selenium, Molybdenum, Sulfates and Fluorides Mobility in Rocks and Soils from the Parisian Basin. ENVIRONMENTS 2022. [DOI: 10.3390/environments9070078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Rocks and soils excavated from civil works frequently present high concentrations of naturally occurring leachable (oxy-)anions. This situation raises concerns regarding the potential transfer of contaminants to groundwater in a storage scenario. This study was carried out to give practical insights on the ability of various stabilizing agents to reduce molybdenum (Mo), selenium (Se), fluorides and sulfates mobility in four types of naturally contaminated excavated materials. Based on standardized leaching tests results, Mo and Se were effectively immobilized after zero valent iron or iron salts additions. Although alkaline materials were found to effectively reduce fluorides and sulfates mobility, their addition occasionally caused a subsequent increase in Mo and Se leaching due to pH increase. None of the reagents tested allowed a simultaneous immobilization of all (oxy-)anions sufficient to reach regulatory threshold values. The remaining difficulties were related to: (i) sulfates leaching from gypsum-rich samples, (ii) fluorides leaching from clayey samples and (iii) Mo and sulfates mobility from tunnel muck. Altogether, the study revealed that the choice of stabilizing agents should be made depending on the speciation of the contaminant or else an opposite impact (i.e., increase in contaminant mobility) might be triggered.
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