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Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology

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

Deadline for manuscript submissions: closed (31 October 2024) | Viewed by 14094

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Special Issue Editors

Dr. Fanhui Guo

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School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
Interests: biomass; supercapacitor; hierarchical porous carbon; CO₂ adsorption
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Jianjun Wu

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School of Chemical Engineering & Technology, China University of Mining & Technology, Xuzhou 221116, China
Interests: clean coal technology; porous materials design; thermodynamics; catalyst; wastewater treatment; CO₂ capture; sustainable energy production

Dr. Jianbo Zhang

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Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100090, China
Interests: industrial solid waste disposal; extraction of elements; mineral phases activation; ceramics; refractory materials; separation technology
Special Issues, Collections and Topics in MDPI journals

Dr. Longfei Tang

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School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200231, China
Interests: municipal solid waste; pollution control; clean coal technology; biomass gasification; minerals processing; advanced characterization methods

Dr. Yonghui Bai

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State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering, School of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, China
Interests: coal structure and reactivity; gasification; waste source emission reduction; low-quality carbon materials; strategic metal element recovery

Special Issue Information

Dear Colleagues,

Human production and life must consume extensive amounts of resources and energy. Low-quality materials, including low-grade minerals, waste biomass, industrial waste, electronic waste, spent tires, municipal waste, organic wastewater, VOCs, and so on, are closely related to this consumption. Poor treatment and utilization of low-grade materials will cause great waste of resources and serious pollution to the environment. Low-grade materials are considered as misplaced resources, and it is of great significance to understand green and low-carbon cycle development. The separation of low-grade materials by physical and chemical methods is expected to obtain materials of various properties, which can be further recovered and recycled to fully utilize resources. In general, the conversion technologies (such as surface modification, thermochemical processing, etc.) of low-grade materials by physicochemical methods can significantly improve material properties, which is a promising path for the high-value utilization of low-grade materials. We are pleased to invite you to submit scientific articles, reviews, and short communications on the latest developments in low-quality materials treatment technologies (separation, adsorption, leaching, catalyst, thermochemical processing, flocculation, etc.), as well as the recycling and recovery of low-quality materials, and their conversion to high-value products.

Dr. Fanhui Guo
Prof. Dr. Jianjun Wu
Dr. Jianbo Zhang
Dr. Longfei Tang
Dr. Yonghui Bai
Guest Editors

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Keywords

waste disposal
separation technology
thermochemical processing
physicochemical modification
adsorption
leaching
catalyst
CO₂ capture and conversion
resource recovery
clean energy production

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Published Papers (9 papers)

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Research

16 pages, 20293 KiB

Open AccessArticle

Physicochemical Characteristics of Residual Carbon and Inorganic Minerals in Coal Gasification Fine Slag

by Le Li, Jing Liu, Xiangyang Li, Zeyu Peng, Chun Han, Wenhao Lian, Bin Xue, Chenmin Gao, Qian Zhang and Wei Huang

Molecules 2024, 29(16), 3956; https://doi.org/10.3390/molecules29163956 - 21 Aug 2024

Viewed by 737

Abstract

Investigating the physicochemical properties and embedding forms of residual carbon (RC) and slag particles (SPs) in coal gasification fine slag (FS) is the basis for achieving its separation and utilization. An in-depth understanding of their compositional characteristics allows for targeted treatment and utilization programs for different components. In this work, the physicochemical properties and embedding forms of RC and SPs in FS were systematically investigated. An innovative calculation method is proposed to determine the mass fraction of dispersed carbon particles, dispersed mineral-rich particles, and carbon–ash combined particles by using a high-temperature heating stage coupled with an optical microscope. The unburned RC with a rough, loose surface and a well-developed pore structure acted as a framework in which the smaller spherical SPs with a smooth surface were embedded. In addition, the sieving pretreatment process facilitated the enrichment of the RC. Moreover, the RC content showed significant dependencies according to the FS particle size. For FS with a particle size of 0.075–0.150 mm, the mass proportions of dispersed carbon, ash particles, and the carbon–ash combination were 15.19%, 38.72%, and 46.09%, respectively. These findings provide basic data and reliable technical support for the subsequent carbon and ash separation process and the comprehensive utilization of coal gasification slag. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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13 pages, 8054 KiB

Open AccessArticle

Resource Recovery of Spent Lithium-Ion Battery Cathode Materials by a Supercritical Carbon Dioxide System

by Yuanpeng Fu, Xianshu Dong and Burçak Ebin

Molecules 2024, 29(7), 1638; https://doi.org/10.3390/molecules29071638 - 5 Apr 2024

Viewed by 1464

Abstract

The increasing global market size of high-energy storage devices due to the boom in electric vehicles and portable electronics has caused the battery industry to produce a lot of waste lithium-ion batteries. The liberation and de-agglomeration of cathode material are the necessary procedures to improve the recycling derived from spent lithium-ion batteries, as well as enabling the direct recycling pathway. In this study, the supercritical (SC) CO₂ was innovatively adapted to enable the recycling of spent lithium-ion batteries (LIBs) based on facilitating the interaction with a binder and dimethyl sulfoxide (DMSO) co-solvent. The results show that the optimum experimental conditions to liberate the cathode particles are processing at a temperature of 70 °C and 80 bar pressure for a duration of 20 min. During the treatment, polyvinylidene fluoride (PVDF) was dissolved in the SC fluid system and collected in the dimethyl sulfoxide (DMSO), as detected by the Fourier Transform Infrared Spectrometer (FTIR). The liberation yield of the cathode from the current collector reaches 96.7% under optimal conditions and thus, the cathode particles are dispersed into smaller fragments. Afterwards, PVDF can be precipitated and reused. In addition, there is no hydrogen fluoride (HF) gas emission due to binder decomposition in the suggested process. The proposed SC-CO₂ and co-solvent system effectively separate the PVDF from Li-ion battery electrodes. Thus, this approach is promising as an alternative pre-treatment method due to its efficiency, relatively low energy consumption, and environmental benign features. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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15 pages, 3426 KiB

Open AccessArticle

Recovery of Cembratrien-Diols from Waste Tobacco (Nicotiana tabacum L.) Flowers by Microwave-Assisted Deep Eutectic Solvent Extraction: Optimization, Separation, and In Vitro Bioactivity

by Tao Yu, Long Yang, Xianchao Shang and Shiquan Bian

Molecules 2024, 29(7), 1563; https://doi.org/10.3390/molecules29071563 - 31 Mar 2024

Cited by 2 | Viewed by 1550

Abstract

Deep eutectic solvents (DESs) are novel solvents with physicochemical properties similar to those of ionic liquids, and they have attracted extensive attention for the extraction of bioactive compounds from different plant materials in the context of green chemistry and sustainable development. In this study, seven DESs with different polarities were explored as green extraction solvents for cembratrien-diols (CBT-diols) from waste tobacco flowers. The best solvent, DES-3 (choline chloride: lactic acid (1:3)), which outperformed conventional solvents (methanol, ethanol, and ethyl acetate), was selected and further optimized for microwave-assisted DES extraction using the response surface methodology. The maximum yield of CBT-diols (6.23 ± 0.15 mg/g) was achieved using a microwave power of 425 W, microwave time of 32 min, solid/liquid ratio of 20 mg/mL, and microwave temperature of 40 °C. Additionally, the isolated CBT-diols exhibited strong antimicrobial activity against Salmonella, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Pseudomonas aeruginosa and antitumor activity in the human liver cancer HepG2 and SMMC-7721 cell lines. This study highlights the feasibility of recovering CBT-diols from tobacco flower waste using DESs and provides opportunities for potential waste management using green technologies. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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28 pages, 4528 KiB

Open AccessArticle

Coal-Derived Humic Substances: Insight into Chemical Structure Parameters and Biomedical Properties

by Maria V. Zykova, Kristina A. Bratishko, Evgeny E. Buyko, Lyudmila A. Azarkina, Vladimir V. Ivanov, Dmitrii A. Mihalyov, Evgeniya S. Trofimova, Marina G. Danilets, Anastasia A. Ligacheva, Andrey I. Konstantinov, Alexander A. Ufandeev, Evgenia S. Rabtsevich, Larisa A. Drygunova, Anastasia P. Zima, Sergey R. Bashirov, Elena V. Udut and Mikhail V. Belousov

Molecules 2024, 29(7), 1530; https://doi.org/10.3390/molecules29071530 - 29 Mar 2024

Cited by 3 | Viewed by 1191

Abstract

An investigation was carried out on humic substances (HSs) isolated from the coal of the Kansk-Achinsk basin (Krasnoyarsk Territory, Russia). The coal HSs demonstrate the main parameters of molecular structure inherent to this class of natural compounds. An assessment was performed for the chemical, microbiological, and pharmacological safety parameters, as well as the biological efficacy. The HS sample meets the safety requirements in microbiological purity, toxic metals content (lead, cadmium, mercury, arsenic), and radionuclides. The presence of 11 essential elements was determined. The absence of general, systemic toxicity, cytotoxicity, and allergenic properties was demonstrated. The coal HS sample was classified as a Class V hazard (low danger substances). High antioxidant and antiradical activities and immunotropic and cytoprotective properties were identified. The ability of the HS to inhibit hydroxyl radicals and superoxide anion radicals was revealed. Pronounced actoprotective and nootropic activities were also demonstrated in vivo. Intragastric administration of the HS sample resulted in the improvement of physical parameters in mice as assessed by the “swim exhaustion” test. Furthermore, intragastric administration in mice with cholinergic dysfunction led to a higher ability of animals with scopolamine-induced amnesia to form conditioned reflexes. These findings suggest that the studied HS sample is a safe and effective natural substance, making it suitable for use as a dietary bioactive supplement. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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14 pages, 4946 KiB

Open AccessArticle

Correlation between Flow Temperature and Average Molar Ionic Potential of Ash during Gasification of Coal and Phosphorus-Rich Biomass

by Chaoyue Zhao, Qingyun Wang, Xiaoyong Men, Yuchen Li, Linmin Zhang, Yonghui Bai, Xudong Song, Jiaofei Wang, Min Yao and Guangsuo Yu

Molecules 2023, 28(23), 7858; https://doi.org/10.3390/molecules28237858 - 30 Nov 2023

Viewed by 1113

Abstract

The co-gasification of biomass and coal is helpful for achieving the clean and efficient utilization of phosphorus-rich biomass. A large number of alkali and alkaline earth metals (AAEMs) present in the ash system of coal (or biomass) cause varying degrees of ash, slagging, [...] Read more.

{PO}_{4}^{3^{-}}

, which has a strong affinity for AAEMs (especially for Ca²⁺) to produce minerals dominated by calcium phosphates or alkaline Ca-phosphate, effectively mitigating the aforementioned problems. To investigate the changing behavior of the slag flow temperature (FT) under different CaO/P₂O₅ ratios, 72 synthetic ashes with varying CaO/P₂O₅ ratios at different Si/Al contents and compositions were prepared, and their ash fusion temperatures were tested. The effects of different CaO/P₂O₅ ratios on the FT were analyzed using FactSage thermodynamic simulation. A model for predicting slag FT at different CaO/P₂O₅ ratios was constructed on the basis of the average molar ionic potential (I_a) method and used to predict data reported from 19 mixed ashes in the literature. The results showed that I_a and FT gradually increased with a decreasing CaO/P₂O₅ ratio, and the main mineral types shifted from anorthite → mullite → berlinite, which reasonably explained the decrease in ash fusion temperatures in the mixed ash. The established model showed good adaptability to the prediction of 19 actual coal ash FTs in the literature; the deviation of the prediction was in the range of 40 °C. The model proposed between FT and I_a based on the different CaO/P₂O₅ ratios can be used to predict the low-rank coal and phosphorus-rich biomass and their mixed ashes. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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16 pages, 2892 KiB

Open AccessArticle

Preparation of Carbon-Based Solid Acid Catalyst from High-Sulfur Petroleum Coke with Nitric Acid and Ball Milling, and a Computational Evaluation of Inherent Sulfur Conversion Pathways

by Qing Huang, Natalia M. Cabral, Xing Tong, Annelisa S. Schafranski, Pierre Kennepohl and Josephine M. Hill

Molecules 2023, 28(20), 7051; https://doi.org/10.3390/molecules28207051 - 12 Oct 2023

Viewed by 1424

Abstract

A series of petroleum coke (petcoke)-derived solid acid catalysts were prepared via nitric acid treatment with or without ball milling pretreatment. The inherent sulfur in petcoke was converted to sulfonic groups, which were active sites for the esterification of octanoic acid and methanol at 60 °C, with ester yields of 14–43%. More specifically, samples without ball milling treated at 120 °C for 3 h had a total acidity of 4.67 mmol/g, which was 1.6 times that of the samples treated at 80 °C, despite their −SO₃H acidities being similar (~0.08 mmol/g). The samples treated for 24 h had higher −SO₃H (0.10 mmol/g) and total acidity (5.25 mmol/g) but not increased catalytic activity. Ball milling increased the defects and exposed aromatic hydrogen groups on petcoke, which facilitated further acid oxidation (0.12 mmol −SO₃H/g for both materials and total acidity of 5.18 mmol/g and 5.01 mmol/g for BP-N-3/120 and BP-N-8/90, respectively) and an increased ester yield. DFT calculations were used to analyze the pathways of sulfonic acid group formation, and the reaction pathway with NO₂• was the most thermodynamically and kinetically favourable. The activities of the prepared catalysts were related to the number of −SO₃H acid sites, the total acidity, and the oxygen content, with the latter two factors having a negative impact. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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14 pages, 3856 KiB

Open AccessArticle

Catalytic Gasification of Petroleum Coke with Different Ratios of K₂CO₃ and Evolution of the Residual Coke Structure

by Man Zhang, Hongyu Ban, Zhiqing Wang, Xinning Xiang, Xiaolei Wang and Qian Zhang

Molecules 2023, 28(19), 6779; https://doi.org/10.3390/molecules28196779 - 23 Sep 2023

Cited by 2 | Viewed by 1918

Abstract

The catalytic gasification of petroleum coke with different ratios of K₂CO₃ was investigated by a thermogravimetric analyzer (TGA) using the non-isothermal method. The initial, peak, and final gasification temperatures of the petroleum coke decreased greatly as the amount of K₂CO₃ increased, and the catalytic reaction became saturated at a concentration of K⁺ higher than 5 mmol/g; with the further increase in catalyst; the gasification rate varied slightly, but no inhibition effect was observed. The vaporization of the catalyst was confirmed during the gasification at high temperatures. The structural evolution of the residual coke with different carbon conversions was examined by X-ray diffraction (XRD), Raman spectroscopy, and N₂ adsorption analyses during gasification with and without the catalyst. The results showed that the carbon crystallite structure of the residual coke varied in the presence of the catalyst. As the carbon conversion increased, the structure of the residual coke without the catalyst became more ordered, and the number of aromatic rings decreased, while the graphitization degree of the residual coke in the presence of the catalyst decreased. Meanwhile, the surface area and pore volume of petroleum coke increased in the gasification process of the residual coke, irrespective of the presence of the catalyst. However, the reactivity of the residual coke did not change much with the variation in the carbon and pore structure during the reaction. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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13 pages, 3909 KiB

Open AccessArticle

Surface Modification of a Lignin-Derived Carbon-Supported Co-Based Metal/Oxide Nanostructure for Alkaline Water Splitting

by Guoning Li, Faming Liu, Weiyang Ma, Hui Li and Shijie Li

Molecules 2023, 28(15), 5648; https://doi.org/10.3390/molecules28155648 - 26 Jul 2023

Viewed by 1346

Abstract

Exploring low-cost and eco-friendly bifunctional electrocatalysts of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolytes is still highly desired, and is crucial for water electrolysis and sustainable hydrogen generation. In this work, we report a facile pyrolysis–oxidation strategy to convert by-product lignin into bifunctional OER/HER electrocatalysts (Co/Co₃O₄-NPC-400) composed of Co/Co₃O₄ anchored on N-doped carbon with a surface of rich oxygen vacancies and oxygen-containing groups. The co-pyrolysis of lignin and NH₄Cl can achieve a N-doped carbon matrix with a hierarchical pore structure, while the air-annealing process can induce the formation of oxygen-containing groups and oxygen vacancies. Owing to its surface properties, hierarchical pore structure and multiple active components, the constructed Co/Co₃O₄-NPC-400 possesses bifunctional catalytic activity and superior stability for OER/HER, especially for unexpected OER activity with a high current density of about 320 mA∙cm⁻² at a potential of 1.8 V (vs. RHE). Water electrolysis using Co/Co₃O₄-NPC-400 as both the anode and the cathode needs a cell voltage of 1.95 and 2.5 V to attain about 10 and 400 mA∙cm⁻² in 1 M KOH. This work not only provides a general strategy for the preparation of carbon-supported electrocatalysts for water splitting, but also opens up a new avenue for the utilization of lignin. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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15 pages, 6588 KiB

Open AccessArticle

Structural Characterization and Molecular Model Construction of High-Ash Coal from Northern China

by Benkang Zhu, Xianshu Dong, Yuping Fan, Xiaomin Ma, Suling Yao, Yuanpeng Fu, Ruxia Chen and Ming Chang

Molecules 2023, 28(14), 5593; https://doi.org/10.3390/molecules28145593 - 23 Jul 2023

Cited by 4 | Viewed by 2016

Abstract

High-ash coal, also known as low-grade coal, has becomes a viable alternative in recent years to high-quality coal because available resources have become increasingly scarce due to extensive mining activity. This work aims to provide a comprehensive understanding of the structural characteristics of high-ash coal and construct a plausible molecular structure to elucidate its chemical reactivity in future applications. Its properties were investigated using Solid-state ¹³C nuclear magnetic resonance (¹³C NMR), X-ray photoelectron spectroscopy analysis (XPS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The molecular structure was constructed and validated using Material Studio, LAMMPS Software Package, and MATLAB program. The characterization results revealed that high-ash coal contains 72.15% aromatic carbon, significantly surpassing the percentage of aliphatic carbon (27.85%). The ratio of bridgehead carbon to peripheral aromatic carbon was calculated as 0.67, indicating that the pentacene is the main carbon skeleton form in the high-ash coal structure. Furthermore, oxygen-containing functional groups presented as C=O/O–C–O, C–O, and COO– within the structure along with pyridine and pyrrolic structures. Consequently, the molecular structure comprises pentacene with aliphatic carbon chains, such as methylene, that connect the benzene rings and form a three-dimensional network. The results of a simulated IR spectrum and contact angle simulation aligned with the experimental results, validating the molecular structure of high-ash coal. The chemical formula for the high-ash coal model was determined as C₂₀₃H₁₈₉N₇O₆₁S with a molecular weight of 3734.79. Full article

(This article belongs to the Special Issue Separation, Recovery and Conversion of Low-Quality Materials via Physicochemical Technology)

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