Green Chemical Technology Open Access

Chemical Recycling and Upcycling of Waste Plastics: A Review

The indiscriminate disposal of plastic waste represents a significant environmental hazard. Conventional remediation techniques, such as landfilling and incineration, also encounter limitations and are unable to adequately address the pollution issue. Chemical recycling and upcycling represent an effective method for the degradation of plastics into oligomers and subsequent transformation into other product substances. This review provides an overview of the various chemical treatment methods currently in use, from the earliest thermal degradation techniques to the emerging strategies. The conventional techniques for thermal degradation of discarded plastics frequently encounter difficulties due to the necessity for elevated temperatures, substantial energy consumption, and the generation of a heterogeneous product mixture. Significant advances have been made in the fields of catalytic solvolysis, hydrotreating, and oxidative cleavage for the recycling and upcycling of plastics under mild conditions. This review provides a comprehensive overview of the chemical treatment methods currently employed for plastics, with a particular focus on the principles and current developments, as well as the reaction mechanisms involved. Additionally, it offers a detailed introduction to various advanced catalytic technologies and the catalysts utilized. Finally, it presents prospective outlooks for different methods, based on their current development status and the gap between actual needs.

Green Chemical Technology: A New Journal for Green Engineering and Green Technology

Comparative Study: Biodegradable Chelating Agents vs. Aqua Regia for Extraction of Indispensable Elements from Pyrite Ore of Bagrot, Gilgit Baltistan

This study investigates the optimization of metal extraction from Bagrot pyrite ore, with a focus on gold recovery. Initial characterization using X-ray fluorescence (XRF) provided a comprehensive elemental profile of the ore. Fire assaying was employed to establish a baseline gold concentration. Systematic leaching experiments were conducted, varying parameters such as reaction time, temperature, and stirring speed, and the results were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Among the chelating agents tested Ethylenediamine N-N′ disuccinic acid (EDDS), Ethylenediaminetetraacetic acid (EDTA), and Diethylenetriaminepentaacetic acid (DTPA) only limited efficacy in gold extraction was observed. In contrast, ammonium thiosulfate demonstrated substantial potential for effective gold recovery. Mercaptobenzothiazole (MBT) and N,N-Dimethylglycine (DMG) were determined to be ineffective for metal leaching under the tested conditions. This research highlights the critical role of reagent selection and parameter optimization in enhancing the efficiency and sustainability of gold extraction processes, positioning ammonium thiosulfate as a promising alternative to traditional cyanide-based methods.

The Discovering of Rapid Formation La(OH)₃ from LaH₃

It was found that the single crystal of LaH₃ specimen with $${Fm\overline{3}m}$$ (No.225) will decompose into powders within 24 h, which is later characterized to be La(OH)₃ by single crystal X-ray diffraction (SXRD) measurements. The discovery motivates the examination of three possible transition paths by comparing formation enthalpy with first-principles calculations and employing a custom- designed hydrogen detection setup. Furthermore, the most suitable adsorption position of O₂ molecules on the (111) surfaces has been investigated by comparing the adsorption enthalpy from different candidate positions by utilizing first-principles calculations, implying the pivotal role of O₂ molecules played in the rapid formation of La(OH)₃ along the optimal transition path.

Waste Resin Derived Carbon Materials for Sodium-Ion Batteries

As the environmental issues caused by waste resin become increasingly severe, there is an urgent need to develop ways to handle it in a high-value and harmless manner. Turning waste resin into functional carbon materials is a realizable and promising scheme, which could be a trigger to carry forward emerging sustainable battery technologies and applications. However, there are few review articles about the basics and research progress of the waste resin derived carbon materials for sodium-ion batteries. This review article provides a brief overview mainly about resin recycling and the potential usage of the resultant carbon materials for sodium-ion batteries. Specifically, we show the potential improvements in existing research, focusing on utilization of the waste as well as the significance of new routes for resin recycling. This work offers insights for the design of sustainable carbon materials for battery systems.

Recent Progress of High Safety Separator for Lithium-Ion Battery

With the rapid increase in quantity and expanded application range of lithium-ion batteries, their safety problems are becoming much more prominent, and it is urgent to take corresponding safety measures to improve battery safety. Generally, the improved safety of lithium-ion battery materials will reduce the risk of thermal runaway explosion. The separator is a key component of lithium-ion batteries. It plays a crucial role in battery safety, serving as one of the most effective measures against internal short circuits.Separator failure is a direct cause of the thermal runaway and can be specifically divided into three categories: puncture, melting, and thermal shrinkage. The requirements for an ideal lithium-ion battery separator have a synergistic effect on the electrochemical performance, safety, and scalability of lithium-ion batteries. Focus on the separator, this review summaries the mechanism of separator in thermal runaway process, and reports the recent progress of high safety separator from the perspective of material preparation.

Adsorption of Bisphenol A and 2,6-Dichlorophenol in Water Using Magnetic Phosphogypsum Composite Materials

Phenolic pollutants in water bodies pose a huge threat to human health and environmental safety. In this paper, a hydrophobicity-enhanced magnetic C-SiO₂/MPG composite was prepared by a two-step method to remove bisphenol A (BPA)and 2,6-dichlorophenol (2,6-DCP), typical phenolic trace pollutants in livestock wastewater and natural water bodies. The results of pH gradient experiments showed that C-SiO₂/MPG showed a stable removal effect on BPA in the pH range of 2–11. The adsorption of 2,6-DCP by C-SiO₂/MPG peaked at pH = 2, while the adsorption of 2,6-DCP by C-SiO₂/MPG was severely inhibited under alkaline conditions. The PSO kinetic model and the Langmuir isotherm model can better describe the adsorption process of BPA and 2,6-DCP on C-SiO₂/MPG, indicating that the monolayer chemical adsorption has a rate-controlling step. With the Langmuir equation fitting, the maximum adsorption capacity of C-SiO₂/MPG for BPA and 2,6-DCP at 298 K was calculated to be 561.79 mg/g and 531.91 mg/g, respectively. The results of adsorption thermodynamics indicated that the adsorption of BPA and 2,6-DCP on C-SiO₂/MPG was spontaneous, accompanied by a process of entropy decrease. C-SiO₂/MPG showed good environmental resistance and repeated use stability for BPA and 2,6-DCP in electrolyte ion interference, actual water samples and cycle experiments. Mechanism analysis showed that the adsorption of BPA and 2,6-DCP on C-SiO₂/MPG was mainly controlled by hydrogen bonding and hydrophobic interactions. This study designed an efficient adsorbent for phenolic pollutants that can be used in actual wastewater and broadened the resource utilization of industrial waste phosphogypsm.

Upcycling of Waste Poly(ethylene terephthalate) into 2,4-Pyridine Dicarboxylic Acid by a Tandem Chemo-Microbial Process

This study presents a chemo-microbial cascade process for the upcycling of waste poly(ethylene terephthalate) (PET) into valuable compound 2,4-pyridine dicarboxylic acid (2,4-PDCA). Initially, waste PET undergoes efficient hydrolysis to terephthalic acid (TPA) with a high yield of 92.36%, catalyzed by p-toluenesulfonic acid (PTSA). The acid catalyst exhibits excellent reusability, maintaining activity over five cycles. Subsequently, a one-pot, two-step whole-cell conversion system utilizing genetically modified Escherichia coli strains (E. coli PCA and E. coli 2,4-PDCA) converts the generated TPA into 2,4-PDCA. By integrating the PET hydrolysis module with the 2,4-PDCA biosynthesis module, the study achieves an impressive overall efficiency of 94.01% in converting challenging PET waste into valuable 2,4-PDCA. Our research presents a rational design strategy for PET upcycling and 2,4-PDCA synthesis methods. This research provides a systematic approach to PET upcycling, demonstrating its feasibility and potential for industrial application.

Chemical Recycling and Upcycling of Waste Plastics: A Review

The indiscriminate disposal of plastic waste represents a significant environmental hazard. Conventional remediation techniques, such as landfilling and incineration, also encounter limitations and are unable to adequately address the pollution issue. Chemical recycling and upcycling represent an effective method for the degradation of plastics into oligomers and subsequent transformation into other product substances. This review provides an overview of the various chemical treatment methods currently in use, from the earliest thermal degradation techniques to the emerging strategies. The conventional techniques for thermal degradation of discarded plastics frequently encounter difficulties due to the necessity for elevated temperatures, substantial energy consumption, and the generation of a heterogeneous product mixture. Significant advances have been made in the fields of catalytic solvolysis, hydrotreating, and oxidative cleavage for the recycling and upcycling of plastics under mild conditions. This review provides a comprehensive overview of the chemical treatment methods currently employed for plastics, with a particular focus on the principles and current developments, as well as the reaction mechanisms involved. Additionally, it offers a detailed introduction to various advanced catalytic technologies and the catalysts utilized. Finally, it presents prospective outlooks for different methods, based on their current development status and the gap between actual needs.utf-8

Green Chemical Technology: A New Journal for Green Engineering and Green Technology

The Discovering of Rapid Formation La(OH)₃ from LaH₃

It was found that the single crystal of LaH₃ specimen with $${Fm\overline{3}m}$$ (No.225) will decompose into powders within 24 h, which is later characterized to be La(OH)₃ by single crystal X-ray diffraction (SXRD) measurements. The discovery motivates the examination of three possible transition paths by comparing formation enthalpy with first-principles calculations and employing a custom- designed hydrogen detection setup. Furthermore, the most suitable adsorption position of O₂ molecules on the (111) surfaces has been investigated by comparing the adsorption enthalpy from different candidate positions by utilizing first-principles calculations, implying the pivotal role of O₂ molecules played in the rapid formation of La(OH)₃ along the optimal transition path.utf-8

Comparative Study: Biodegradable Chelating Agents vs. Aqua Regia for Extraction of Indispensable Elements from Pyrite Ore of Bagrot, Gilgit Baltistan

This study investigates the optimization of metal extraction from Bagrot pyrite ore, with a focus on gold recovery. Initial characterization using X-ray fluorescence (XRF) provided a comprehensive elemental profile of the ore. Fire assaying was employed to establish a baseline gold concentration. Systematic leaching experiments were conducted, varying parameters such as reaction time, temperature, and stirring speed, and the results were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Among the chelating agents tested Ethylenediamine N-N′ disuccinic acid (EDDS), Ethylenediaminetetraacetic acid (EDTA), and Diethylenetriaminepentaacetic acid (DTPA) only limited efficacy in gold extraction was observed. In contrast, ammonium thiosulfate demonstrated substantial potential for effective gold recovery. Mercaptobenzothiazole (MBT) and N,N-Dimethylglycine (DMG) were determined to be ineffective for metal leaching under the tested conditions. This research highlights the critical role of reagent selection and parameter optimization in enhancing the efficiency and sustainability of gold extraction processes, positioning ammonium thiosulfate as a promising alternative to traditional cyanide-based methods.utf-8

Waste Resin Derived Carbon Materials for Sodium-Ion Batteries

As the environmental issues caused by waste resin become increasingly severe, there is an urgent need to develop ways to handle it in a high-value and harmless manner. Turning waste resin into functional carbon materials is a realizable and promising scheme, which could be a trigger to carry forward emerging sustainable battery technologies and applications. However, there are few review articles about the basics and research progress of the waste resin derived carbon materials for sodium-ion batteries. This review article provides a brief overview mainly about resin recycling and the potential usage of the resultant carbon materials for sodium-ion batteries. Specifically, we show the potential improvements in existing research, focusing on utilization of the waste as well as the significance of new routes for resin recycling. This work offers insights for the design of sustainable carbon materials for battery systems.utf-8

Adsorption of Bisphenol A and 2,6-Dichlorophenol in Water Using Magnetic Phosphogypsum Composite Materials

Phenolic pollutants in water bodies pose a huge threat to human health and environmental safety. In this paper, a hydrophobicity-enhanced magnetic C-SiO₂/MPG composite was prepared by a two-step method to remove bisphenol A (BPA)and 2,6-dichlorophenol (2,6-DCP), typical phenolic trace pollutants in livestock wastewater and natural water bodies. The results of pH gradient experiments showed that C-SiO₂/MPG showed a stable removal effect on BPA in the pH range of 2–11. The adsorption of 2,6-DCP by C-SiO₂/MPG peaked at pH = 2, while the adsorption of 2,6-DCP by C-SiO₂/MPG was severely inhibited under alkaline conditions. The PSO kinetic model and the Langmuir isotherm model can better describe the adsorption process of BPA and 2,6-DCP on C-SiO₂/MPG, indicating that the monolayer chemical adsorption has a rate-controlling step. With the Langmuir equation fitting, the maximum adsorption capacity of C-SiO₂/MPG for BPA and 2,6-DCP at 298 K was calculated to be 561.79 mg/g and 531.91 mg/g, respectively. The results of adsorption thermodynamics indicated that the adsorption of BPA and 2,6-DCP on C-SiO₂/MPG was spontaneous, accompanied by a process of entropy decrease. C-SiO₂/MPG showed good environmental resistance and repeated use stability for BPA and 2,6-DCP in electrolyte ion interference, actual water samples and cycle experiments. Mechanism analysis showed that the adsorption of BPA and 2,6-DCP on C-SiO₂/MPG was mainly controlled by hydrogen bonding and hydrophobic interactions. This study designed an efficient adsorbent for phenolic pollutants that can be used in actual wastewater and broadened the resource utilization of industrial waste phosphogypsm.utf-8

Recent Progress of High Safety Separator for Lithium-Ion Battery

With the rapid increase in quantity and expanded application range of lithium-ion batteries, their safety problems are becoming much more prominent, and it is urgent to take corresponding safety measures to improve battery safety. Generally, the improved safety of lithium-ion battery materials will reduce the risk of thermal runaway explosion. The separator is a key component of lithium-ion batteries. It plays a crucial role in battery safety, serving as one of the most effective measures against internal short circuits.Separator failure is a direct cause of the thermal runaway and can be specifically divided into three categories: puncture, melting, and thermal shrinkage. The requirements for an ideal lithium-ion battery separator have a synergistic effect on the electrochemical performance, safety, and scalability of lithium-ion batteries. Focus on the separator, this review summaries the mechanism of separator in thermal runaway process, and reports the recent progress of high safety separator from the perspective of material preparation.utf-8

Upcycling of Waste Poly(ethylene terephthalate) into 2,4-Pyridine Dicarboxylic Acid by a Tandem Chemo-Microbial Process

This study presents a chemo-microbial cascade process for the upcycling of waste poly(ethylene terephthalate) (PET) into valuable compound 2,4-pyridine dicarboxylic acid (2,4-PDCA). Initially, waste PET undergoes efficient hydrolysis to terephthalic acid (TPA) with a high yield of 92.36%, catalyzed by p-toluenesulfonic acid (PTSA). The acid catalyst exhibits excellent reusability, maintaining activity over five cycles. Subsequently, a one-pot, two-step whole-cell conversion system utilizing genetically modified Escherichia coli strains (E. coli PCA and E. coli 2,4-PDCA) converts the generated TPA into 2,4-PDCA. By integrating the PET hydrolysis module with the 2,4-PDCA biosynthesis module, the study achieves an impressive overall efficiency of 94.01% in converting challenging PET waste into valuable 2,4-PDCA. Our research presents a rational design strategy for PET upcycling and 2,4-PDCA synthesis methods. This research provides a systematic approach to PET upcycling, demonstrating its feasibility and potential for industrial application.utf-8