Research

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13 pages, 4450 KiB

Open AccessArticle

Chemical Delamination Applicable to a Low-Energy Recycling Process of Photovoltaic Modules

by Jiří Vaněk, Kristyna Jandova, Petr Vanýsek and Petr Maule

Processes 2023, 11(11), 3078; https://doi.org/10.3390/pr11113078 - 26 Oct 2023

Viewed by 883

This work follows the current trend and need to ensure the best recyclability of retired materials. This paper focuses on experiments with chemical delamination of polymer layers on crystalline silicon photovoltaic cells. The aim of the study is to separate individual components of [...] Read more.

This work follows the current trend and need to ensure the best recyclability of retired materials. This paper focuses on experiments with chemical delamination of polymer layers on crystalline silicon photovoltaic cells. The aim of the study is to separate individual components of a PV module so that the components can be subsequently recycled with low energy demand. The ultimate goal is to separate whole silicon cells for reuse rather than for recycling. Several solvents (e.g., toluene, cyclohexane, tetrahydrofuran, and the commercial solvent U 6002 (a mixture of xylene and 2-ethoxyethylacetate)) were used to disrupt the polymer layers. The results showed toluene to be the most effective solvent, which acted the fastest and was able to disrupt the EVA (ethylene-vinyl acetate) film structure the most. The main problem of the investigated chemical delamination was the concurrent solvent absorption by the EVA film. This phenomenon was observed for all solvents. The absorption prevented the dissolution of the EVA film and changed its dimension, causing the adhering silicon cells to crack. While, as the final experiment shows, chemical delamination is, as done, a more energy-intensive process in terms of total energy consumption than the current chemical mechanical processes, we propose in the next development the recapture of toluene from the swollen EVA. Full article

(This article belongs to the Special Issue State of the Art of Waste Utilization and Resource Recovery)

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12 pages, 2917 KiB

Open AccessArticle

Electrocatalytic Ni-Co Metal Organic Framework for Efficient Urea Oxidation Reaction

by Hua Yu, Wei Xu, Hongchao Chang, Guangyao Xu, Lecong Li, Jiarong Zang, Rong Huang, Luxia Zhu and Binbin Yu

Processes 2023, 11(10), 3035; https://doi.org/10.3390/pr11103035 - 22 Oct 2023

Cited by 1 | Viewed by 1080

Abstract

Energy shortage and environmental pollution have become the most serious problems faced by human beings in the 21st century. Looking for advanced clean energy technology to achieve sustainable development of the ecological environment has become a hot spot for researchers. Nitrogen-based substances represented [...] Read more.

Energy shortage and environmental pollution have become the most serious problems faced by human beings in the 21st century. Looking for advanced clean energy technology to achieve sustainable development of the ecological environment has become a hot spot for researchers. Nitrogen-based substances represented by urea are environmental pollutants but ideal energy substances. The efficiency of urea-based energy conversion technology mainly depends on the choice of catalyst. The development of new catalysts for urea oxidation reaction (UOR) has important application value in the field of waste energy conversion and pollution remediation based on UOR. In this work, four metal–organic framework materials (MOFs) were synthesized using ultrasound (NiCo-UMOFs) and hydrothermal (NiCo-MOFs, Ni-MOFs and Co-MOFs) methods to testify the activity toward UOR. Materials prepared using the hydrothermal method mostly form large and unevenly stacked block structures, while material prepared using ultrasound forms a layer-by-layer two-dimensional and thinner structure. Electrochemical characterization shows NiCo-UMOFs has the best electrocatalytic performance with an onset potential of 0.32 V (vs. Ag/AgCl), a Tafel slope of 51 mV dec⁻¹, and a current density of 13 mA cm⁻² at 0.5 V in a 1 M KOH electrolyte with 0.7 M urea. A prolonged urea electrolysis test demonstrates that 45.4% of urea is removed after 24 h. Full article

(This article belongs to the Special Issue State of the Art of Waste Utilization and Resource Recovery)

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13 pages, 1214 KiB

Open AccessFeature PaperArticle

Activated Carbon Aerogel as an Electrode with High Specific Capacitance for Capacitive Deionization

by Wei Wang, Kerui Li, Ge Song, Minghua Zhou and Peng Tan

Processes 2022, 10(11), 2330; https://doi.org/10.3390/pr10112330 - 09 Nov 2022

Cited by 8 | Viewed by 1525

Abstract

In this study, carbon aerogels (CAs) were synthesized by the sol-gel method, using environmentally friendly glucose as a precursor, and then they were further activated with potassium hydroxide (KOH) to obtain activated carbon aerogels (ACAs). After the activation, the electrochemical performance of the [...] Read more.

In this study, carbon aerogels (CAs) were synthesized by the sol-gel method, using environmentally friendly glucose as a precursor, and then they were further activated with potassium hydroxide (KOH) to obtain activated carbon aerogels (ACAs). After the activation, the electrochemical performance of the ACAs was significantly improved, and the specific capacitance increased from 19.70 F·g⁻¹ to 111.89 F·g⁻¹. Moreover, the ACAs showed a stronger hydrophilicity with the contact angle of 118.54° compared with CAs (69.31°). When used as an electrode for capacitive deionization (CDI), the ACAs had not only a better diffuse electric double layer behavior, but also a lower charge transfer resistance and intrinsic resistance. Thus, the ACA electrode had a faster CDI desalination rate and a higher desalination capacity. The unit adsorption capacity is three times larger than that of the CA electrode. In the desalination experiment of 100 mg·L⁻¹ sodium chloride (NaCl) solution using a CDI device based on the ACA electrode, the optimal electrode spacing was 2 mm, the voltage was 1.4 V, and the flow rate was 30 mL·min⁻¹. When the NaCl concentration was 500 mg·L⁻¹, the unit adsorption capacity of the ACA electrode reached 26.12 mg·g⁻¹, much higher than that which has been reported in many literatures. The desalination process followed the Langmuir model, and the electro-sorption of the NaCl was a single layer adsorption process. In addition, the ACA electrode exhibited a good regeneration performance and cycle stability. Full article

(This article belongs to the Special Issue State of the Art of Waste Utilization and Resource Recovery)

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Review

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26 pages, 1045 KiB

Open AccessReview

Fenton: A Systematic Review of Its Application in Wastewater Treatment

by Matheus Pimentel Prates, Suzana Maria de Oliveira Loures Marcionílio, Karine Borges Machado, Danyelle Medeiros de Araújo, Carlos A. Martínez-Huitle, Arizeu Luiz Leão Arantes and José Eduardo Ferreira da Silva Gadêlha

Processes 2023, 11(8), 2466; https://doi.org/10.3390/pr11082466 - 16 Aug 2023

Cited by 2 | Viewed by 2250

Abstract

The use of new technologies for the removal of pollutants from wastewater has become globally necessary due to the complexity and facilities defined by conventional treatments. Advanced oxidative processes, specifically the Fenton process, have become widely applied given their low cost and ease [...] Read more.

The use of new technologies for the removal of pollutants from wastewater has become globally necessary due to the complexity and facilities defined by conventional treatments. Advanced oxidative processes, specifically the Fenton process, have become widely applied given their low cost and ease of use. Therefore, this study aimed to evaluate the progression of the scientific publications on the implementation of Fenton process, investigating their space–time evolution. Additionally, useful solutions, trends, and gaps in the applications for the removal of pollutants with this methodology were identified, and also different remediation strategies and the design of new treatments for wastewaters were identified within this scientometric analysis. Bibliometric research was conducted in two scientific databases, Web of Science and Scopus, from 2011 to 2022, and we identified 932 and 1263 studies with the word “Fenton,” respectively. When these publications are associated with the treatment of alternative effluents, an increase in publications from 2011 (r = 0.95, p < 0.001) and 2013 (r = 0.93, p < 0.001) was observed when analyzing both databases, indicating the relevance of the theme. Among these studies, several of them were conducted on the bench scale (89.8% and 98.3%, Web of Science and Scopus, respectively) and in aqueous matrix (97.8% and 98.4%, Web of Science and Scopus, respectively), with being China the main country with publications associated with these words (28.33% and 41.9%), while Brazil is related to 3.65% and 2.29% of the total studies in Web of Science and Scopus, respectively. In addition, this review provides a guideline for new applications for different species in the matrices and describes the evolution of technological solutions to meet Sustainable Development Goal 6: clean water and sanitation. Full article

(This article belongs to the Special Issue State of the Art of Waste Utilization and Resource Recovery)

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31 pages, 4765 KiB

Open AccessFeature PaperReview

Progress in Electroreduction of CO₂ to Form Various Fuels Based on Zn Catalysts

by Laxia Wu, Lin Wu, Chang Guo, Yebin Guan, Huan Wang and Jiaxing Lu

Processes 2023, 11(4), 1039; https://doi.org/10.3390/pr11041039 - 29 Mar 2023

Cited by 5 | Viewed by 2480

Abstract

Carbon dioxide (CO₂) is one of the main greenhouse gases and the major factor driving global climate change. From the viewpoint of abundance, economics, non-toxicity, and renewability, CO₂ is an ideal and significant C1 resource, and its capture and recycling [...] Read more.

Carbon dioxide (CO₂) is one of the main greenhouse gases and the major factor driving global climate change. From the viewpoint of abundance, economics, non-toxicity, and renewability, CO₂ is an ideal and significant C1 resource, and its capture and recycling into fuels and chemical feedstocks using renewable energy is of great significance for the sustainable development of society. Electrochemical CO₂ reduction reactions (CO₂RRs) are an important pathway to utilize CO₂ resources. Zinc has been demonstrated as an effective catalyst for CO₂RRs. Numerous studies have focused on improving the efficiency of zinc-based catalysts by tuning their morphology and components, as well as controlling their oxidation states or doping. However, only a handful of reviews have evaluated the performance of Zn-based CO₂RR electrocatalysts. The present review endeavors to fill this research gap and introduces the recent progress in using CO₂RRs to create various fuels (carbon-containing substances or hydrocarbons) using zinc-based catalysts, including Zn monomers, Zn-containing bimetals, oxide-derived Zn catalysts, and single/dual Zn atom catalysts. The mechanism of the electroreduction reaction of CO₂ is discussed. Based on the previous achievements, the current stage and the outlook for future developments in the field are summarized. This review will provide a reference for future research on CO₂RRs to generate fuels using Zn-based catalysts and their commercialization. Full article

(This article belongs to the Special Issue State of the Art of Waste Utilization and Resource Recovery)

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20 pages, 3479 KiB

Open AccessFeature PaperReview

Recent Developments of Light-Harvesting Excitation, Macroscope Transfer and Multi-Stage Utilization of Photogenerated Electrons in Rotating Disk Photocatalytic Reactor

by Zhe Jiang, Kan Li and Jinping Jia

Processes 2023, 11(3), 838; https://doi.org/10.3390/pr11030838 - 10 Mar 2023

Viewed by 1564

Abstract

The rotating disk photocatalytic reactor is a kind of photocatalytic wastewater treatment technique with a high application potential, but the light energy utilization rate and photo quantum efficiency still need to be improved. Taking photogenerated electrons as the starting point, the following contents [...] Read more.

The rotating disk photocatalytic reactor is a kind of photocatalytic wastewater treatment technique with a high application potential, but the light energy utilization rate and photo quantum efficiency still need to be improved. Taking photogenerated electrons as the starting point, the following contents are reviewed in this work: (1) Light-harvesting excitation of photogenerated electrons. Based on the rotating disk thin solution film photocatalytic reactor, the photoanodes with light capture structures are reviewed from the macro perspective, and the research progress of light capture structure catalysts based on BiOCl is also reviewed from the micro perspective. (2) Macroscope transfer of photogenerated electrons. The research progress of photo fuel cell based on rotating disk reactors is reviewed. The system can effectively convert the chemical energy in organic pollutants into electrical energy through the macroscopic transfer of photogenerated electrons. (3) Multi-level utilization of photogenerated electrons. The photogenerated electrons transferred to the cathode can also generate H₂O₂ with oxygen or H₂ with H⁺, and the reduction products can also be further utilized to deeply mineralize organic pollutants or reduce the nitrate in water. This short review will provide theoretical guidance for the further application of photocatalytic techniques in wastewater treatment. Full article

(This article belongs to the Special Issue State of the Art of Waste Utilization and Resource Recovery)

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16 pages, 636 KiB

Open AccessFeature PaperReview

Ligand-Enhanced Zero-Valent Iron for Organic Contaminants Degradation: A Mini Review

by Qi Chen, Minghua Zhou, Yuwei Pan and Ying Zhang

Processes 2023, 11(2), 620; https://doi.org/10.3390/pr11020620 - 17 Feb 2023

Cited by 5 | Viewed by 1801

Abstract

For nearly three decades, zero-valent iron (ZVI) has been used in wastewater treatment and groundwater and soil remediation. ZVI can degrade contaminants by reactions of adsorption, redox, and co-precipitation. It can also react with oxidants like hydrogen peroxide, persulfate, and ozone to produce [...] Read more.

For nearly three decades, zero-valent iron (ZVI) has been used in wastewater treatment and groundwater and soil remediation. ZVI can degrade contaminants by reactions of adsorption, redox, and co-precipitation. It can also react with oxidants like hydrogen peroxide, persulfate, and ozone to produce highly reactive radicals that can rapidly remove and even mineralize organic contaminants. However, the application of ZVI is also limited by factors such as the narrow pH range and surface passivation. The addition of chelating agents such as nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), or citrate to the ZVI-based processes has been identified to greatly increase the iron stability and improve the efficiency of contaminant degradation. From the perspective of commonly used organic and inorganic chelating agents in ZVI applications, the review addresses the current status of ligand-enhanced ZVI degradation of organic contaminants, illustrates the possible reaction mechanism, and provides perspectives for further research. Full article

(This article belongs to the Special Issue State of the Art of Waste Utilization and Resource Recovery)

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14 pages, 2042 KiB

Open AccessFeature PaperReview

Metal Recovery and Electricity Generation from Wastewater Treatment: The State of the Art

by Qing-Yun Chen, Ruo-Chen Lu, Yu-Cheng Zhu and Yun-Hai Wang

Processes 2023, 11(1), 88; https://doi.org/10.3390/pr11010088 - 28 Dec 2022

Viewed by 1715

Abstract

The recovery of metal resources from wastewater is very important for both resource recovery and wastewater treatment. Compared with traditional metal-polluted wastewater treatment technologies, advanced wastewater treatment technologies with the functions of both recovering metals and generating electricity have been developed rapidly in [...] Read more.

The recovery of metal resources from wastewater is very important for both resource recovery and wastewater treatment. Compared with traditional metal-polluted wastewater treatment technologies, advanced wastewater treatment technologies with the functions of both recovering metals and generating electricity have been developed rapidly in recent years. These advanced technologies include microbial fuel cells, photo fuel cells, coupled redox fuel cells, etc. In this paper, these advanced technologies are elaborated from their principles to their applications in wastewater treatment for metals recovery and electricity generation. The recent progress of these technologies was also reviewed. The effects of different metal ions, cell configurations, and various operating parameters on their performance were also discussed. Although these technologies are promising, the challenges and the efforts needed to overcome them are also highlighted. Full article

(This article belongs to the Special Issue State of the Art of Waste Utilization and Resource Recovery)

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