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Toxics
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Integrated Remediation Processes toward Heavy Metal-Contaminated Environment
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Integrated Remediation Processes toward Heavy Metal-Contaminated Environment

A special issue of Toxics (ISSN 2305-6304). This special issue belongs to the section "Toxicity Reduction and Environmental Remediation".

Deadline for manuscript submissions: closed (15 September 2024) | Viewed by 10230

Special Issue Editors

Dr. Liang Hu

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Guest Editor
School of Minerals Processing and Bioengineering, Central South University, Changsha, China
Interests: environmental microbial technology; heavy metals removal; environmental remediation
Special Issues, Collections and Topics in MDPI journals
Dr. Luhua Jiang

E-Mail Website
Guest Editor
School of Minerals Processing and Bioengineering, Central South University, Changsha, China
Interests: microbial–mineral interaction; mine restoration; paddy soil bioremediation; metal(loid) transformation
Special Issues, Collections and Topics in MDPI journals
Dr. Zhigang Yu

E-Mail
Guest Editor
Australian Centre for Water and Environmental Biotechnology, St Lucia QLD 4072, Australia
Interests: heavy metal removal; soil remediation; antimicrobial resistance; antibiotic resistance gene

Special Issue Information

Dear Colleagues,

With the development of urban industrialization and the utilization of mineral resources, a lot of toxic pollutants (especially heavy metals) enter the water ecosystem, agricultural soil and atmosphere, which cause a serious threat to human health. Under the national dual carbon target, researchers are trying to exploit the integrated technologies for pollution removal and carbon reduction. To date, various remediation technologies (e.g., environmental microorganism, hyperaccumulator, functional materials, and multi-technology combination strategies) have been developed worldwide to deal with the contaminated water, soil, or even groundwater. It is expected that the dual carbon target associated with heavy metal remediation can be concurrently achieved by removing or stabilizing heavy metal in the environment, thus reducing their ecological risks. This Special Issue aims to receive submissions of high-quality, original, and previously unpublished research on the fundamental theory and engineering practice of the heavy metal remediation technologies, including, but not limited to, the following topics:

  • Biogeochemical processes of heavy metal, including migration, transformation, fate, oxidation, reduction;
  • Advanced heavy metal remediation technology (targeting, persistence, mechanism);
  • Ecological safety assessment methods of remediation technology.

Dr. Liang Hu
Dr. Luhua Jiang
Dr. Zhigang Yu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 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

  • heavy metals
  • soil remediation
  • phytoremediation
  • microbial technology
  • bioavailability
  • biochar
  • risk assessment
  • contaminated site

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Related Special Issue

Published Papers (7 papers)

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Research

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20 pages, 4197 KiB  
Article
Removal of Lead Cations by Novel Organoclays Derived from Bentonite and Amphoteric and Nonionic Surfactants
by Maria Gertsen, Leonid Perelomov, Anna Kharkova, Marina Burachevskaya, S. Hemalatha and Yury Atroshchenko
Toxics 2024, 12(10), 713; https://doi.org/10.3390/toxics12100713 - 30 Sep 2024
Viewed by 997
Abstract
For many decades, natural and modified clay minerals have been used as adsorbents to clean up aquatic and soil ecosystems contaminated with organic and inorganic pollutants. In this study, organoclays based on bentonite and various amphoteric and nonionic surfactants were synthesized and tested [...] Read more.
For many decades, natural and modified clay minerals have been used as adsorbents to clean up aquatic and soil ecosystems contaminated with organic and inorganic pollutants. In this study, organoclays based on bentonite and various amphoteric and nonionic surfactants were synthesized and tested as effective sorbents for lead ions. The maximum values of R were obtained when describing the sorption processes using the Langmuir model, which ranged from 0.97 to 0.99. The adsorption of lead ions by these organoclays was investigated using different sorption models including the Langmuir, Freundlich, and BET. It was found that, according to the values of limiting adsorption to the Langmuir equation, the synthesized organoclays formed an increasing series: organoclay with cocamide diethanolamine < bentonite < organoclay with lauramine oxide < organoclay with sodium cocoiminodipropionate < organoclay with disodium cocoamphodiacetate < organoclay with alkyl polyglucoside. The Gibbs energy for all of the analyzed samples was calculated and found to be negative, indicating the spontaneity of the cation adsorption process in the forward direction. The maximum value of the adsorption capacity of lead cations on organoclay-based bentonite with alkyl polyglucoside was 1.49 ± 0.05 mmol/g according to the Langmuir model, and 0.523 ± 0.003 mmol/g as determined by the BET model. In the process of modifying bentonite, there was an increase in negative values of the zeta potential for organoclays compared to the initial mineral, which clearly enhanced their electrostatic interactions with the positively charged lead ions. It was hypothesized, based on the physicochemical principles, that exchange adsorption is the main mechanism for lead absorption. Based on chemical approaches, organoclays based on amphoteric surfactants absorb lead mainly through the mechanisms of electrostatic attraction, ion exchange, and complexation as well as the formation of insoluble precipitates. Organoclays based on nonionic surfactants, on the other hand, absorb lead through mechanisms of complexation (including chelation) and the formation of insoluble chemical precipitates. The comparison of isotherms from different models allows us to find the most accurate match between the model and the experimental data, and to better understand the nature of the processes involved. Full article
(This article belongs to the Special Issue Integrated Remediation Processes toward Heavy Metal-Contaminated Environment)
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15 pages, 2971 KiB  
Article
Bioreactor Expansion Affects Microbial Succession of Mixotrophic Acidophiles and Bioremediation of Cadmium-Contaminated Soils
by Xiaodong Hao, Ping Zhu, Xueduan Liu, Luhua Jiang, Huidan Jiang, Hongwei Liu and Zhiqun Chen
Toxics 2024, 12(5), 362; https://doi.org/10.3390/toxics12050362 - 13 May 2024
Viewed by 1149
Abstract
Microbial scale-up cultivation is the first step to bioremediating cadmium (Cd)-contaminated soils at the industrial scale. However, the changes in the microbial community as the bioreactor volume expands and their associations with soil Cd removal remain unclear. Herein, a six-stage scale-up cultivation process [...] Read more.
Microbial scale-up cultivation is the first step to bioremediating cadmium (Cd)-contaminated soils at the industrial scale. However, the changes in the microbial community as the bioreactor volume expands and their associations with soil Cd removal remain unclear. Herein, a six-stage scale-up cultivation process of mixotrophic acidophiles was conducted, scaling from 0.1 L to 10 m3, to remediate Cd-contaminated soils. The findings showed that bioreactor expansion led to a delay in sulfur and glucose oxidations, resulting in a reduced decline in solution pH and cell density. There were minimal differences observed in bacterial alpha-diversity and community structure as the bioreactor volume increased, except for the 10 m3 scale. However, bioreactor expansion decreased fungal alpha-diversity, changed the community structure, and simplified fungal community compositions. At the family level, Acidithiobacillaceae and Debaryomycetaceae dominated the bacterial and fungal communities throughout the scale-up process, respectively. Correlation analysis indicated that the indirect effect of mixotrophic acidophiles played a significant role in soil Cd removal. Bacterial community shifts, driven by changes in bioreactor volume, decreased the pH value through sulfur oxidation, thereby indirectly enhancing Cd removal efficiency. This study will contribute to the potential industrial application of mixotrophic acidophiles in bioremediating Cd-contaminated soils. Full article
(This article belongs to the Special Issue Integrated Remediation Processes toward Heavy Metal-Contaminated Environment)
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18 pages, 3653 KiB  
Article
Oxidative Dissolution Process of Sphalerite in Fe2(SO4)3-O3 System: Implications for Heavy Metals Removal and Recovery
by Mingtong Zhang, Hongbo Zhao, Yisheng Zhang, Xin Lv, Luyuan Zhang, Li Shen, Liang Hu, Jiankang Wen, Louyan Shen and Xianping Luo
Toxics 2024, 12(4), 275; https://doi.org/10.3390/toxics12040275 - 8 Apr 2024
Cited by 1 | Viewed by 1401
Abstract
Metal sulfides in waste rocks and tailings are susceptible to serious soil and water contamination due to the generation of acid mine drainage (AMD) during stockpiling. The hydrometallurgical process is one of the most essential heavy metal remediation technologies through harmless disposal and [...] Read more.
Metal sulfides in waste rocks and tailings are susceptible to serious soil and water contamination due to the generation of acid mine drainage (AMD) during stockpiling. The hydrometallurgical process is one of the most essential heavy metal remediation technologies through harmless disposal and resource utilization of the waste sulfides. However, atmospheric hydrometallurgy of sulfides still faces great challenges due to low leaching efficiency and high cost. In this work, we proposed a cooperative leaching system (Fe2(SO4)3-O3) and investigated the oxidative dissolution process of sphalerite (ZnS). Under the optimal conditions, the extracted zinc reached 97.8%. Reactive oxygen species (ROS) (·OH, 1O2 and ·O2−) were identified in the radical quenching experiments. The dissolution of sphalerite did not show passivation due to the ozone’s capability to oxidize the sulfur in sphalerite to sulfate. In addition, stirring rate, O3 inlet concentration, and Fe2(SO4)3 concentration had a significant effect on the dissolution of sphalerite. Meanwhile, the apparent activation energy was 24.11 kJ/mol based on kinetic fitting, which indicated that the controlling step of the reaction was mainly a diffusion process. This work demonstrated the cooperative effect of sphalerite leaching in the O3-Fe2(SO4)3 system and provided a theoretical reference for efficient and atmospheric dissolution of sphalerite. Full article
(This article belongs to the Special Issue Integrated Remediation Processes toward Heavy Metal-Contaminated Environment)
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17 pages, 4662 KiB  
Article
Removal of Pb from Contaminated Kaolin by Pulsed Electrochemical Treatment Coupled with a Permeable Reactive Barrier: Tuning Removal Efficiency and Energy Consumption
by Yinyin Zhang, Libin Zang, Yuyan Zhao, Qiaoqiao Wei and Jiangtao Han
Toxics 2023, 11(12), 961; https://doi.org/10.3390/toxics11120961 - 27 Nov 2023
Cited by 2 | Viewed by 1349
Abstract
Lead contamination in soil has emerged as a significant environmental concern. Recently, pulse electrochemical treatment (PECT) has garnered substantial attention as an effective method for mitigating lead ions in low-permeability soils. However, the impact of varying pulse time gradients, ranging from seconds to [...] Read more.
Lead contamination in soil has emerged as a significant environmental concern. Recently, pulse electrochemical treatment (PECT) has garnered substantial attention as an effective method for mitigating lead ions in low-permeability soils. However, the impact of varying pulse time gradients, ranging from seconds to hours, under the same pulse duty cycle on lead removal efficiency (LRE) and energy consumption in PECT has not been thoroughly investigated. In this study, a novel, modified PECT method is proposed, which couples PECT with a permeable reaction barrier (PRB) and adds acetic acid to the catholyte. A comprehensive analysis of LRE and energy consumption is conducted by transforming pulse time. The results show that the LREs achieved in these experiments were as follows: PCb-3 s (89.5%), PCb-1 m (91%), PCb-30 m (92.9%), and PCb-6 h (91.9%). Importantly, these experiments resulted in significant reductions in energy consumption, with decreases of 68.5%, 64.9%, 51.8%, and 47.4% compared to constant voltage treatments, respectively. It was observed that LRE improved with an increase in both pulse duration and voltage gradient, albeit with a corresponding rise in energy consumption. The results also revealed that corn straw biochar as a PRB could enhance LRE by 6.1% while adsorbing migrating lead ions. Taken together, the present data highlights the potential of modified PECT technology for remediation of lead-contaminated soil, which provides an optimal approach to achieve high LRE while minimizing energy consumption. Full article
(This article belongs to the Special Issue Integrated Remediation Processes toward Heavy Metal-Contaminated Environment)
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20 pages, 14427 KiB  
Article
Leaching Behavior of As and Pb in Lead–Zinc Mining Waste Rock under Mine Drainage and Rainwater
by Ziwen Guo, Jiejie Yang, Kewei Li, Jiaxin Shi, Yulong Peng, Emmanuel Konadu Sarkodie, Bo Miao, Hongwei Liu, Xueduan Liu and Luhua Jiang
Toxics 2023, 11(11), 943; https://doi.org/10.3390/toxics11110943 - 20 Nov 2023
Cited by 4 | Viewed by 1758
Abstract
At present, the pollution of arsenic (As) and lead (Pb) is becoming increasingly serious. The pollution caused by the release of As and Pb from lead–zinc mines has seriously affected the water and soil environment and threatened human health. It is necessary to [...] Read more.
At present, the pollution of arsenic (As) and lead (Pb) is becoming increasingly serious. The pollution caused by the release of As and Pb from lead–zinc mines has seriously affected the water and soil environment and threatened human health. It is necessary to reveal the release characteristics of As and Pb. The actual scene of mine drainage (MD) and rainwater (RW) leaching waste rocks is the one of the main reasons for the release of As and Pb. However, the leaching behavior of As and Pb in these waste rocks under MD and RW suffered from a lack of in-depth research. In this study, we investigated the occurrence of As and Pb in waste rocks (S1–S6) by using X-ray diffraction (XRD) and time-of-flight secondary ion mass spectrometry (TOF-SIMS), and then, the changes in As and Pb concentration and the hydrochemical parameter in leaching solution were systematically studied. Furthermore, the correlation between the release of As and Pb and mineral composition was also evaluated. Results showed that these waste rocks were mainly composed of carbonate and sulfide minerals. As and Pb were mainly bounded or associated with sulfide minerals such as arsenopyrite, pyrite, chalcopyrite, and galena in these waste rocks, and small parts of As and Pb were absorbed or encased by clay minerals such as kaolinite and chlorite. Under MD and RW leaching, the pH, redox potential (Eh), and electric conductivity (EC) of each waste rock tended to be consistent due to their buffering ability; the leachate pH of waste rocks with more carbonate minerals was higher than that of sulfide minerals. Both As and Pb were released most under MD leaching in comparison to RW, reaching 6.57 and 60.32 mg/kg, respectively, due to MD’s low pH and high Eh value. However, As in waste rock released more under alkaline conditions because part of the arsenic was in the form of arsenate. As and Pb release were mainly positively correlated with the proportions of sulfide minerals in these waste rocks. MD leaching significantly promoted the release of As and Pb from waste rocks, which would cause a great threat to the surrounding environment, and control measures were imperative. This paper not only reveals the As and Pb pollution mechanism around the lead–zinc mining area but also provides a theoretical basis for the prevention and control of As and Pb pollution in the future. Full article
(This article belongs to the Special Issue Integrated Remediation Processes toward Heavy Metal-Contaminated Environment)
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14 pages, 2926 KiB  
Article
Mathematical Estimation of Endogenous Proline as a Bioindicator to Regulate the Stress of Trivalent Chromium on Rice Plants Grown in Different Nitrogenous Conditions
by Chengzhi Li, Yuxi Feng, Peng Tian and Xiaozhang Yu
Toxics 2023, 11(10), 803; https://doi.org/10.3390/toxics11100803 - 22 Sep 2023
Cited by 4 | Viewed by 1177
Abstract
The accumulation of proline impacts the defense mechanisms of plants against the harmful effects of adverse environmental conditions; however, its concentration in plants is associated with the metabolism of N. Therefore, the effects of exogenous organic [glutamate (Glu)/arginine (Arg)] and inorganic [nitrate (NO [...] Read more.
The accumulation of proline impacts the defense mechanisms of plants against the harmful effects of adverse environmental conditions; however, its concentration in plants is associated with the metabolism of N. Therefore, the effects of exogenous organic [glutamate (Glu)/arginine (Arg)] and inorganic [nitrate (NO3−)/ammonium (NH4+)] N on the accumulation of proline (Pro) in rice plants under trivalent chromium [Cr(III)] stress were studied through using the mass balance matrix model (MBMM). Application of ‘NH4+’ showed the largest contribution to the Pro content in rice shoots under different concentrations of Cr(III), followed by ‘NO3−’, ‘Arg’, and ‘Glu’ applications. On the other hand, ‘Arg’ application displayed the largest contribution to the Pro content in roots under Cr(III) stress, followed by ‘NH4+’, ‘Glu’, and ‘NO3−’ applications. The combined application of ‘NH4++Arg’ showed the greatest contribution to the Pro content in both roots and shoots of Cr(III)-treated rice seedlings, while the application of ‘NO3−+Glu’ showed the least contribution to the Pro content in rice seedlings. The current study indicated that the endogenous level of Pro in rice seedlings is quite sensitive to Cr(III) stress under different N sources, and the mathematical modeling showed a reliable result while estimating the relationship between Pro content and N source application. Full article
(This article belongs to the Special Issue Integrated Remediation Processes toward Heavy Metal-Contaminated Environment)
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Review

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43 pages, 10551 KiB  
Review
Biochar-Derived Persistent Free Radicals: A Plethora of Environmental Applications in a Light and Shadows Scenario
by Silvana Alfei and Omar Ginoble Pandoli
Toxics 2024, 12(4), 245; https://doi.org/10.3390/toxics12040245 - 27 Mar 2024
Cited by 2 | Viewed by 1585
Abstract
Biochar (BC) is a carbonaceous material obtained by pyrolysis at 200–1000 °C in the limited presence of O2 from different vegetable and animal biomass feedstocks. BC has demonstrated great potential, mainly in environmental applications, due to its high sorption ability and persistent [...] Read more.
Biochar (BC) is a carbonaceous material obtained by pyrolysis at 200–1000 °C in the limited presence of O2 from different vegetable and animal biomass feedstocks. BC has demonstrated great potential, mainly in environmental applications, due to its high sorption ability and persistent free radicals (PFRs) content. These characteristics enable BC to carry out the direct and PFRs-mediated removal/degradation of environmental organic and inorganic contaminants. The types of PFRs that are possibly present in BC depend mainly on the pyrolysis temperature and the kind of pristine biomass. Since they can also cause ecological and human damage, a systematic evaluation of the environmental behavior, risks, or management techniques of BC-derived PFRs is urgent. PFRs generally consist of a mixture of carbon- and oxygen-centered radicals and of oxygenated carbon-centered radicals, depending on the pyrolytic conditions. Here, to promote the more productive and beneficial use of BC and the related PFRs and to stimulate further studies to make them environmentally safer and less hazardous to humans, we have first reviewed the most common methods used to produce BC, its main environmental applications, and the primary mechanisms by which BC remove xenobiotics, as well as the reported mechanisms for PFR formation in BC. Secondly, we have discussed the environmental migration and transformation of PFRs; we have reported the main PFR-mediated application of BC to degrade inorganic and organic pollutants, the potential correlated environmental risks, and the possible strategies to limit them. Full article
(This article belongs to the Special Issue Integrated Remediation Processes toward Heavy Metal-Contaminated Environment)
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