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Toxic Metal Remediation: Recent Advances in the Development of a Green and Sustainable Environment

A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Environmental Sustainability and Applications".

Deadline for manuscript submissions: 31 May 2024 | Viewed by 10451

Special Issue Editors

College of Environmental Science and Engineering, Hunan University, Changsha 410005, China
Interests: heavy metals; functional materials; water treatment; soil remediation; health risk assessment

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Guest Editor
College of Environmental Science and Engineering, Hunan University, Changsha 410005, China
Interests: waste resource management; functional biochar; heavy metals; environmental self-cleaning materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

For centuries, toxic metals (e.g., Cd, As, Hg, Cr, and Pb) have been considered hazardous to humans and ecotopes due to their toxicity, persistence, and biological accumulation, with damage to human health occurring through complex multi-pathways. Unfortunately, the industrialization and urbanization of the developing world and the rising demand for resources have increased the risk of exposure to these toxic metals. The continuous increase in new substances and the advent of new technologies in the modern world have also altered the transport and transformation of toxic metals through different media. In particular, water and soil are the top two media for which pollution cases are reported and require the most attention because of their direct relation to daily human life. The chemical behavior and fate of toxic metals in aquatic and soil systems, the interaction of toxic metals with various environmental elements, and the risk of their exposure to human beings through different pathways must be well understood, along with the implementation and development of remediation.

Thus, to encourage progress in the assessment and remediation of toxic metals, this Special Issue aims to highlight the application and/or development of new and/or improved approaches, models, materials, and techniques. We welcome contributions on any aspect of remediation strategies for toxic metals and their corresponding behavior and fate in water and soil systems. Contributions embracing interdisciplinary and multidisciplinary approaches are especially welcome, as are research papers, analytical reviews, case studies, conceptual frameworks, and policy-relevant articles. The goal of the Special Issue is to provide information to research fellows, policymakers, and professionals to assist in resolving toxic metal assessment and pollution control problems.

Dr. Jia Wen
Dr. Xiaofei Tan
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • toxic metals
  • distribution, transportation, and transformation
  • enrichment and bioavailability
  • functional materials
  • remediation technologies
  • soil and water systems
  • risk assessment

Published Papers (5 papers)

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Research

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26 pages, 6547 KiB  
Article
Long Short-Term Memory and Bidirectional Long Short-Term Memory Modeling and Prediction of Hexavalent and Total Chromium Removal Capacity Kinetics of Cupressus lusitanica Bark
by Juan Crescenciano Cruz-Victoria, Alma Rosa Netzahuatl-Muñoz and Eliseo Cristiani-Urbina
Sustainability 2024, 16(7), 2874; https://doi.org/10.3390/su16072874 - 29 Mar 2024
Viewed by 676
Abstract
Hexavalent chromium [Cr(VI)] is a high-priority environmental pollutant because of its toxicity and potential to contaminate water sources. Biosorption, using low-cost biomaterials, is an emerging technology for removing pollutants from water. In this study, Long Short-Term Memory (LSTM) and bidirectional LSTM (Bi-LSTM) neural [...] Read more.
Hexavalent chromium [Cr(VI)] is a high-priority environmental pollutant because of its toxicity and potential to contaminate water sources. Biosorption, using low-cost biomaterials, is an emerging technology for removing pollutants from water. In this study, Long Short-Term Memory (LSTM) and bidirectional LSTM (Bi-LSTM) neural networks were used to model and predict the kinetics of the removal capacity of Cr(VI) and total chromium [Cr(T)] using Cupressus lusitanica bark (CLB) particles. The models were developed using 34 experimental kinetics datasets under various temperature, pH, particle size, and initial Cr(VI) concentration conditions. Data preprocessing via interpolation was implemented to augment the sparse time-series data. Early stopping regularization prevented overfitting, and dropout techniques enhanced model robustness. The Bi-LSTM models demonstrated a superior performance compared to the LSTM models. The inherent complexities of the process and data limitations resulted in a heavy-tailed and left-skewed residual distribution, indicating occasional deviations in the predictions of capacities obtained under extreme conditions. K-fold cross-validation demonstrated the stability of Bi-LSTM models 38 and 43, while response surfaces and validation with unseen datasets assessed their predictive accuracy and generalization capabilities. Shapley additive explanations analysis (SHAP) identified the initial Cr(VI) concentration and time as the most influential input features for the models. This study highlights the capabilities of deep recurrent neural networks in comprehending and predicting complex pollutant removal kinetic phenomena for environmental applications. Full article
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20 pages, 8203 KiB  
Article
Research on the Closure and Remediation Processes of Mining Areas in Romania and Approaches to the Strategy for Heavy Metal Pollution Remediation
by Violeta Monica Radu, Anca Marina Vîjdea, Alexandru Anton Ivanov, Veronica Elena Alexe, George Dincă, Valentina Maria Cetean and Andra Elena Filiuță
Sustainability 2023, 15(21), 15293; https://doi.org/10.3390/su152115293 - 26 Oct 2023
Cited by 1 | Viewed by 1343
Abstract
Mining activities often generate important amounts of extractive waste, and, as a consequence, environmental impacts that affect all factors to a greater or lesser extent. Depending on a variety of variables, the impact can be permanent or temporary, reversible or irreversible, negative or [...] Read more.
Mining activities often generate important amounts of extractive waste, and, as a consequence, environmental impacts that affect all factors to a greater or lesser extent. Depending on a variety of variables, the impact can be permanent or temporary, reversible or irreversible, negative or positive. This study conducted research on the status of closure and remediation processes of mining areas in Romania, specifically in the counties of Maramureș, Suceava, Harghita, Alba, Hunedoara and Caraș-Severin. Furthermore, based on the type and level of pollution, the degree of application of remediation techniques for water and soil pollution in the investigated mining areas was studied. From the analysed information, it is evident that although the closure and remediation process started in Romania over 20 years ago, unfortunately, to this day, the technical projects, technical assistance, and execution of closure and remediation works have not yet completely solved the complex environmental issues in the mining sector. Most of the tailing ponds and waste piles of former mines continue to pose permanent specific risks to the environment and the population. This study concludes that the mining sector in Romania, although it has the necessary techniques and technologies for the ecological rehabilitation of degraded lands related to the Extractive Waste Facilities and the elimination of negative impacts on the environment and public health, has not yet been able to fully concretize its remediation efforts. Full article
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16 pages, 8282 KiB  
Article
Adsorption of Zn(II), Pb(II), and Cu(II) by Residual Soil-Derived Zeolite in Single-Component and Competitive Systems
by Zhe Wang, Wen Li, Liling Wang, Yi Zhang, Jiake Li and Yuling Liu
Sustainability 2023, 15(18), 13515; https://doi.org/10.3390/su151813515 - 9 Sep 2023
Viewed by 973
Abstract
Using construction residual soil (RS) as the raw material, RS-derived zeolite (RSDZ) was prepared through a fusion-hydrothermal process. The adsorption performance and mechanisms of RSDZ for Pb2+, Zn2+, and Cu2+ were investigated in single-component and competitive systems. The [...] Read more.
Using construction residual soil (RS) as the raw material, RS-derived zeolite (RSDZ) was prepared through a fusion-hydrothermal process. The adsorption performance and mechanisms of RSDZ for Pb2+, Zn2+, and Cu2+ were investigated in single-component and competitive systems. The strong RSDZ X-ray diffraction peaks at 2θ = 12.47, 17.73, 21.65, 28.18, and 33.44°, together with the results of scanning electron microscopy and Fourier transform-infrared spectroscopy (FT-IR) indicated that NaP1 zeolite (Na6Al6SiO32∙12H2O) was successfully synthesised. The Brunauer–Emmett–Teller surface area, average pore size, and cation exchange capacity increased from 9.03 m2∙g−1, 18.85 nm, and 0.12 meq∙g−1 to 47.77 m2∙g−1, 41.60 nm, and 0.61 meq∙g−1, respectively, after the fusion-hydrothermal process. The maximum Langmuir adsorption capacity of RSDZ for Zn2+, Pb2+, and Cu2+ in the unary systems was 0.37, 0.38, and 0.40 mmol·g−1, respectively. Increasing the initial solution pH facilitated the adsorption reaction, and the adsorption performance was stable when pH > 3. The distribution coefficients in the binary and ternary systems indicated that RSDZ had greater affinity for Pb2+ and Zn2+ than for Cu2+ due to the larger ionic radius and relative atomic weight of the former two cations. The relative affinity to Pb2+ and Zn2+ was related to their concentration, with more competitive adsorption of Pb2+ at concentrations higher than 0.4 mmol·L−1 in binary systems and 0.25 mmol·L−1 in ternary systems. X-ray photoelectron spectroscopy and FT-IR analyses indicated that ion exchange was the main mechanism involved in the adsorption of heavy metal ions by RSDZ, accompanied by ligand exchange. Full article
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Review

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20 pages, 3525 KiB  
Review
Bio-Remediation of Heavy Metal-Contaminated Soil by Microbial-Induced Carbonate Precipitation (MICP)—A Critical Review
by Sheng Wang, Longyang Fang, Malcom Frimpong Dapaah, Qijian Niu and Liang Cheng
Sustainability 2023, 15(9), 7622; https://doi.org/10.3390/su15097622 - 6 May 2023
Cited by 5 | Viewed by 3670
Abstract
Biomineralization processes utilizing microbial-induced carbonate precipitation (MICP) have recently shown promise as an effective approach for remediating heavy metal contamination. This article offers a comprehensive review of the latest research on MICP-mediated heavy metal remediation, with a focus on the characteristics of heavy [...] Read more.
Biomineralization processes utilizing microbial-induced carbonate precipitation (MICP) have recently shown promise as an effective approach for remediating heavy metal contamination. This article offers a comprehensive review of the latest research on MICP-mediated heavy metal remediation, with a focus on the characteristics of heavy metals in the treated environment, such as copper, cadmium, lead, nickel, zinc, chromium, and mixed heavy metals. The review summarizes experimental results from various heavy metals treated by MICP, including the enrichment and screening of new urease-positive bacteria, the mineral structure of different heavy metal precipitates, and the efficiency of the MICP technology. Recent advancements in the MICP technology regarding heavy metal removal, long-term stability, and practical applications are also discussed. Additionally, the limitations of the technique and existing solutions are reviewed. In addition, it provides insights on future directions for further research and development of the MICP approach for heavy metal remediation, in order to optimize the technique and improve its efficiency. Overall, the review highlights the potential of MICP as a viable method for heavy metal remediation, offering promising results for the removal of a variety of heavy metal contaminants from contaminated environments. Full article
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45 pages, 5304 KiB  
Review
Recent Advances in MOF-Based Materials for Remediation of Heavy Metals and Organic Pollutants: Insights into Performance, Mechanisms, and Future Opportunities
by Cuilian Yang, Zhuangzhuang Xue and Jia Wen
Sustainability 2023, 15(8), 6686; https://doi.org/10.3390/su15086686 - 14 Apr 2023
Cited by 9 | Viewed by 2963
Abstract
In recent years, heavy metals and organic pollutants have become two major obstacles to maintaining the ecological environment. Thus, choosing efficient and environmentally friendly methods and materials to remediate heavy metals and organic pollution has become a hot research topic. Porous metal–organic frameworks [...] Read more.
In recent years, heavy metals and organic pollutants have become two major obstacles to maintaining the ecological environment. Thus, choosing efficient and environmentally friendly methods and materials to remediate heavy metals and organic pollution has become a hot research topic. Porous metal–organic frameworks (MOFs) and their composites or derivatives can be used as ideal adsorbents and catalytic materials because of their unique structures and functions. This work reviews the research progress on MOF-based materials in the remediation of the water environment in the past decade. The MOF-based materials discussed here mainly include MOF composites obtained by fabrication and MOF derivatives obtained by pyrolysis. Both MOF composites and MOF derivatives are optimized materials that exhibit adsorption or catalytic performance superior to the pristine MOFs. Additionally, the interactions and mechanisms between the MOF-based materials and different heavy metals or organic pollutants are discussed in detail. Finally, some problems or defects of the MOF-based materials are also proposed considering the materials’ economic efficiency, stability and safety. There is still a long way forward for the real application of MOF-based materials. Further efforts are also needed to explore and expand the environmental remediation scope of MOF-based materials. Full article
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