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Solid Waste and Fly Ash Chemical Treatment Methods
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Solid Waste and Fly Ash Chemical Treatment Methods

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: 31 May 2025 | Viewed by 8693

Special Issue Editors

Dr. Lu Dong

E-Mail Website
Guest Editor
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: solid waste; fly ash; chemical treatment; waste management; thermal treatment; heavy metal
Special Issues, Collections and Topics in MDPI journals
Dr. Xinye Wang

E-Mail Website
Guest Editor
Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, School of Energy and Mechanical Engineering, Nanjing Normal University, Nanjing 210042, China
Interests: solid waste; fly ash; chemical treatment; waste management; thermal treatment; heavy metal
Special Issues, Collections and Topics in MDPI journals
Dr. Huimin Liu

E-Mail Website
Guest Editor
School of Naval Architecture, Ocean and Energy Power Engineering, Wuhan University of Technology, Wuhan, China
Interests: solid waste; fly ash; chemical treatment; waste management; thermal treatment; heavy metal

Special Issue Information

Dear Colleagues,

In recent years, the ever-increasing generation of solid waste, predominantly comprising municipal and industrial waste, has emerged as a pressing environmental concern. These solid wastes often contain a significant concentration of hazardous pollutants, necessitating the adoption of thermochemical treatment methods such as combustion and pyrolysis to achieve energy recovery, resource utilization, and safe disposal. However, the thermal treatment processes are confronted with challenges related to pollution emissions and energy consumption.

Furthermore, during thermal treatment, the hazardous constituents of solid waste are transferred to the resulting solid residues, commonly known as fly ash. These fly ash residues are enriched with heavy metals, dioxins, and high concentrations of inorganic salts, often classified as hazardous waste. The efficient and cost-effective management of such hazardous waste has become a pivotal research focus and a formidable challenge in contemporary waste management practices.

This Special Issue aims to present recent advancements in research related to the safe and resourceful treatment of solid waste and fly ash through appropriate chemical treatment methods. We welcome original research papers, comprehensive review articles, and short communication letters that contribute to addressing these critical issues. 

Dr. Lu Dong
Dr. Xinye Wang
Dr. Huimin Liu
Guest Editors

Manuscript Submission Information

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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. Molecules is an international peer-reviewed open access semimonthly 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 2700 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

  • solid waste
  • fly ash
  • chemical treatment
  • waste management
  • thermal treatment
  • resource recovery
  • waste-to-energy
  • environmental chemistry

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Published Papers (7 papers)

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Research

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12 pages, 4143 KiB  
Article
Efficient Extraction and Separation of Scandium from Scandium-Bearing Solid Waste and Acid by Synergistically Leaching Followed by Solvent Extraction
by Wen Cao, Jinmao Hua, Xi Jin, Minyu He, Yuntao Xin and Weizao Liu
Molecules 2024, 29(19), 4766; https://doi.org/10.3390/molecules29194766 - 9 Oct 2024
Viewed by 575
Abstract
The solid waste and waste acid generated during the production of titanium dioxide contain considerable amount of scandium, which are valuable secondary resources. In this study, the titanium dioxide waste acid was used to leach the scandium-containing solid waste, and the leached solution [...] Read more.
The solid waste and waste acid generated during the production of titanium dioxide contain considerable amount of scandium, which are valuable secondary resources. In this study, the titanium dioxide waste acid was used to leach the scandium-containing solid waste, and the leached solution was pretreated for iron removal by reduction-crystallization process. After that, scandium was recovered from the leached solution by using the P204-TBP co-extraction system. The process parameters were investigated systematically. The results showed that iron powder reduction-crystallization for iron removal at molar ratio of Fe:Fe3+ = 0.25 was most suitable for subsequent extraction, and the scandium extraction efficiency could reach 100% using 15% P204-5% TBP at 25 °C with A/O = 8. This study provided a novel process for treating scandium-bearing solid waste with scandium-bearing waste acid, showing great potential for industrial application. Full article
(This article belongs to the Special Issue Solid Waste and Fly Ash Chemical Treatment Methods)
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14 pages, 2283 KiB  
Article
Enhancing the High-Solid Anaerobic Digestion of Horticultural Waste by Adding Surfactants
by Wangliang Li, Zhikai Zhang, Shuzhen Mi and Shengyong Zhao
Molecules 2024, 29(17), 4061; https://doi.org/10.3390/molecules29174061 - 27 Aug 2024
Viewed by 668
Abstract
The influence of adding surfactants on the performance of high-solid anaerobic digestion of horticultural waste was extensively investigated in batch systems. Adding Tween series and polyethylene glycol series non-ionic surfactants had positive effects on biogas production, resulting in 370.1 mL/g VS and 256.6 [...] Read more.
The influence of adding surfactants on the performance of high-solid anaerobic digestion of horticultural waste was extensively investigated in batch systems. Adding Tween series and polyethylene glycol series non-ionic surfactants had positive effects on biogas production, resulting in 370.1 mL/g VS and 256.6 mL/g VS with Tween 60 and polyethylene glycol 300 at a surfactant-to-grass mass ratio of 0.20, while the biogas production of anaerobic digestion without surfactants was 107.54 mL/g VS. The optimal and economically feasible choice was adding Tween 20 at a ratio of 0.08 g/g grass in high-solid anaerobic digestion. A kinetics model reliably represented the relationship between surfactant concentration and biogas production. The mechanism of surfactants working on lignocellulose was investigated. The improvement in high-solid anaerobic digestion by adding surfactants was attributed to the interaction between lignocelluloses and surfactants and the extraction of biodegradable fractions from the porous structure. An economic analysis showed that adding Tween 20 was likely to make a profit and be more feasible than adding Tween 60 and polyethylene glycol 300. This study confirms the enhancement in biogas production from horticultural waste by adding non-ionic surfactants. Full article
(This article belongs to the Special Issue Solid Waste and Fly Ash Chemical Treatment Methods)
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17 pages, 3616 KiB  
Article
Synergistic Leaching of Titanium, Aluminum, and Magnesium Components during Dilute Acid Pressure Treatment of High-Titanium Blast Furnace Slag
by Ke Yuan, Siqi He, Bo Yu, Shiyi Qian, Xueyu Wu, Wenyi Li and Chunmeng Zhao
Molecules 2024, 29(14), 3336; https://doi.org/10.3390/molecules29143336 - 16 Jul 2024
Viewed by 907
Abstract
This study focuses on an improved leaching process through the combination of pressurized conditions and direct filtration of acid leaching slurry, which is conductive to improving the filterability of acid leaching systems and the extraction rates of Ti, Al, and Mg components. The [...] Read more.
This study focuses on an improved leaching process through the combination of pressurized conditions and direct filtration of acid leaching slurry, which is conductive to improving the filterability of acid leaching systems and the extraction rates of Ti, Al, and Mg components. The effects of sulfuric acid concentration, reaction temperature, particle size of materials, acid–slag ratio, and reaction time on the leaching efficiency were systematically investigated. The results showed that pressurization significantly enhances the filtration efficiency of the reaction slurry. Under the same filtration time, the filtration efficiency increased from 46% under ordinary pressure to 78% under pressurized conditions. Moreover, under the optimal reaction conditions, the extraction rates of Ti, Al, and Mg components were more than 88.21%, 97.8%, and 96.31%, respectively. Additionally, XRD and FTIR showed that titanium oxide sulfate hydrate crystals were produced in the acid-leached residues when the reaction temperature exceeded 190 °C, thereby reducing the extraction rate of Ti component. And the XRD pattern shows that when the reaction temperature is maintained at 190 °C and the reaction time is extended to 150 min, titanium oxide sulfate hydrate crystals will be formed to reduce the extraction rate of the Ti component. In summary, this study not only provides important theoretical support for the resource utilization of high-titanium blast furnace slag but also offers a feasible solution for efficient extraction and convenient filtration, thus holding significant academic and practical implications. Full article
(This article belongs to the Special Issue Solid Waste and Fly Ash Chemical Treatment Methods)
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16 pages, 1518 KiB  
Article
The Development of Innovated Complex Process for Treatment of Old Flotation Tailings of Copper-Zinc Sulfide Ore
by Khussain Valiyev, Aliya Bugubaeva, Aleksandra Nechaeva, Alena Artykova, Vitaliy Melamud, Devard Stom, Anna Boduen and Aleksandr Bulaev
Molecules 2024, 29(7), 1550; https://doi.org/10.3390/molecules29071550 - 29 Mar 2024
Viewed by 1093
Abstract
The possibility of selective Cu and Zn leaching from the sample of old pyrite tailings, which is one of the most widespread types of solid waste forming during non-ferrous metal production, using sulfuric acid solutions and water was studied. It was shown that [...] Read more.
The possibility of selective Cu and Zn leaching from the sample of old pyrite tailings, which is one of the most widespread types of solid waste forming during non-ferrous metal production, using sulfuric acid solutions and water was studied. It was shown that water leaching provided selective extraction of Cu and Zn and comparatively low iron ion extraction. At the same time, acid leaching provided the obtainment of pregnant solutions with high ferric ion concentration, which can be used for oxidative leaching of substandard copper concentrates. Water and acid leaching also provided increased Au recovery by cyanidation. The results suggest that acid leaching can be an effective approach for processing old flotation tailings, which allows the extraction of base metals from these wastes and treating flotation tailings for subsequent cyanidation. Effective flotation treatment methods should also provide environmental load reduction, which is caused by the long-term storage of metal-bearing wastes. Full article
(This article belongs to the Special Issue Solid Waste and Fly Ash Chemical Treatment Methods)
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13 pages, 5186 KiB  
Article
The Effect of Nitrogen Functional Groups on Pb0, PbO, and PbCl2 Adsorption over a Carbonaceous Surface
by Liang Wang, Huaizhou Wen, Lei Guo, Ancheng Liang, Tingan Liu, Dongxu Zhao and Lu Dong
Molecules 2024, 29(2), 511; https://doi.org/10.3390/molecules29020511 - 19 Jan 2024
Cited by 2 | Viewed by 1234
Abstract
Lead (Pb) pollution, especially from the incineration of municipal solid waste (MSW), poses a significant threat to the environment. Among all the effective methods, activated carbon (AC) injection serves as an effective approach for lead removal from flue gas, while the modification of [...] Read more.
Lead (Pb) pollution, especially from the incineration of municipal solid waste (MSW), poses a significant threat to the environment. Among all the effective methods, activated carbon (AC) injection serves as an effective approach for lead removal from flue gas, while the modification of ACs emerges as a crucial pathway for enhancing Pb adsorption capacities. Density functional theory (DFT) is employed in this study to investigate the mechanisms underlying the enhanced adsorption of Pb species (Pb0, PbO, and PbCl2) on nitrogen-functionalized carbonaceous surfaces. The results show that nitrogen-containing groups substantially enhance lead adsorption capacity, with adsorption energies ranging from −526.18 to −288.31 kJ/mol on nitrogen-decorated carbonaceous surfaces, much higher than those on unmodified surfaces (−310.35 to −260.96 kJ/mol). Additionally, electrostatic potential and density-of-states analyses evidence that pyridinic nitrogen atoms remarkably expand charge distribution and strengthen orbital hybridization, thereby augmenting lead capture. This research elucidates the role of nitrogen-containing functional groups in lead adsorption, offering valuable insights for the development of highly efficient biomass-derived activated carbon sorbents for lead removal. Full article
(This article belongs to the Special Issue Solid Waste and Fly Ash Chemical Treatment Methods)
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14 pages, 4983 KiB  
Article
Recycling Coal Fly Ash for Super-Thermal-Insulating Aerogel Fiber Preparation with Simultaneous Al2O3 Extraction
by Jie Gu, Lipeng Liu, Rongrong Zhu, Qiqi Song, Hanqing Yu, Pengjie Jiang, Changqing Miao, Yuxiang Du, Rui Fu, Yaxiong Wang, Yan Hao and Huazheng Sai
Molecules 2023, 28(24), 7978; https://doi.org/10.3390/molecules28247978 - 6 Dec 2023
Cited by 2 | Viewed by 1589
Abstract
A large quantity of coal fly ash is generated worldwide from thermal power plants, causing a serious environmental threat owing to disposal and storage problems. In this work, for the first time, coal fly ash is converted into advanced and novel aerogel fibers [...] Read more.
A large quantity of coal fly ash is generated worldwide from thermal power plants, causing a serious environmental threat owing to disposal and storage problems. In this work, for the first time, coal fly ash is converted into advanced and novel aerogel fibers and high-purity α-Al2O3. Silica–bacterial cellulose composite aerogel fibers (CAFs) were synthesized using an in situ sol-gel process under ambient pressure drying. Due to the unique “nanoscale interpenetrating network” (IPN) structure, the CAFs showed wonderful mechanical properties with an optimum tensile strength of 5.0 MPa at an ultimate elongation of 5.8%. Furthermore, CAFs with a high porosity (91.8%) and high specific surface area (588.75 m2/g) can inherit advanced features, including excellent thermal insulation, stability over a wide temperature range, and hydrophobicity (contact angle of approximately 144°). Additionally, Al2O3 was simultaneously extracted from the coal fly ash to ensure that the coal fly ash was fully exploited. Overall, low-cost woven CAFs fabrics are suitable for wearable applications and offer a great approach to comprehensively use coal fly ash to address environmental threats. Full article
(This article belongs to the Special Issue Solid Waste and Fly Ash Chemical Treatment Methods)
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Review

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53 pages, 8826 KiB  
Review
Recycling and Reuse of Spent LIBs: Technological Advances and Future Directions
by Long Lv, Siqi Zhou, Changqi Liu, Yuan Sun, Jubing Zhang, Changsheng Bu, Junguang Meng and Yaji Huang
Molecules 2024, 29(13), 3161; https://doi.org/10.3390/molecules29133161 - 2 Jul 2024
Viewed by 1858
Abstract
Recovering valuable metals from spent lithium-ion batteries (LIBs), a kind of solid waste with high pollution and high-value potential, is very important. In recent years, the extraction of valuable metals from the cathodes of spent LIBs and cathode regeneration technology are still rapidly [...] Read more.
Recovering valuable metals from spent lithium-ion batteries (LIBs), a kind of solid waste with high pollution and high-value potential, is very important. In recent years, the extraction of valuable metals from the cathodes of spent LIBs and cathode regeneration technology are still rapidly developing (such as flash Joule heating technology to regenerate cathodes). This review summarized the studies published in the recent ten years to catch the rapid pace of development in this field. The development, structure, and working principle of LIBs were firstly introduced. Subsequently, the recent developments in mechanisms and processes of pyrometallurgy and hydrometallurgy for extracting valuable metals and cathode regeneration were summarized. The commonly used processes, products, and efficiencies for the recycling of nickel–cobalt–manganese cathodes (NCM/LCO/LMO/NCA) and lithium iron phosphate (LFP) cathodes were analyzed and compared. Compared with pyrometallurgy and hydrometallurgy, the regeneration method was a method with a higher resource utilization rate, which has more industrial application prospects. Finally, this paper pointed out the shortcomings of the current research and put forward some suggestions for the recovery and reuse of spent lithium-ion battery cathodes in the future. Full article
(This article belongs to the Special Issue Solid Waste and Fly Ash Chemical Treatment Methods)
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