Developing efficient photocatalysts for solar hydrogen production and marine plastic degradation tackles clean energy and pollution challenges. Here, we report a CdS/CeO2/Ru photocatalyst synthesized via high-temperature reduction and impregnation-grinding. A Z-scheme heterojunction between CdS and CeO2 enables rapid charge separation, while Ru nanoparticles act as electron sinks and active sites for H2 evolution. Under visible light with 50 g/L polylactic acid (PLA), the catalyst achieves a H2 evolution rate of 56.70 mmol·g−1·h−1, which is 3780 times higher than that of CeO2 and 5.2 times higher than that of CdS, outperforming most reported PLA photoreforming systems. It retains 89.93 % of its H2 evolution rate after 50 h, demonstrating excellent stability even in natural seawater. Selective PLA conversion yields only lactic acid and pyruvate, as confirmed by GC–MS, HPLC, and in situ FTIR, with no toxic byproducts. This work introduces a seawater-compatible photocatalytic platform for simultaneous green hydrogen production and safe, value-added plastic upcycling.

The rapid accumulation of plastic waste poses a critical environmental challenge and demands effective upcycling strategies to advance a circular economy. Microwave-assisted catalysis offers a low-energy, highly efficient alternative to conventional thermal processes; however, the principles guiding catalyst design and the underlying reaction mechanisms in this context remain insufficiently understood. Here, we report a microwave-assisted catalytic approach for converting polyolefin waste into high-value hydrogen (H2) and multi-walled carbon nanotubes (MWCNTs) using a Pt-promoted Fe/Ni bimetallic catalyst. The catalyst design leverages incorporation of a very small amount of Pt (e.g., 0.3 %) to substantially lower the oxygen vacancy formation energy, as revealed by experimental characterization and density functional theory (DFT) calculations, resulting in a 3.3-fold increase in strong acid site density. These modifications reduce the activation barriers for C-H and C-C bond cleavage, enabling efficient polyolefin conversion. Butane was employed as a model compound in DFT calculation to elucidate the polyethylene decomposition reaction mechanism, which proceeds via terminal C-H bond activation, formation of conjugated olefins, and subsequent deep dehydrogenation. Under microwave treatment, the Fe/Ni-0.3 %Pt catalyst achieved an H2 yield of 53.9 mmol/g and a selectivity of 90 % from low-density polyethylene (LDPE). The carbonaceous co-products were mainly high-quality MWCNTs exhibiting excellent electromagnetic interference (EMI) shielding performance. This integrated catalytic-microwave approach demonstrates a scalable route for transforming various polyolefin wastes into clean H2 and advanced carbon materials, offering a viable pathway for sustainable energy and material production within a circular economy framework.

Spent coffee grounds (SCG), a substantial waste byproduct of the global coffee industry, are increasingly recognized as a sustainable precursor for the production of activated carbon (SCG-AC). This review systematically examines the pivotal influence of activation parameters, specifically focusing on activating agents (KOH, ZnCl2, H3PO4) and activation atmospheres, on the resultant structural evolution and performance characteristics of SCG-AC. Through a critical analysis of existing literature, we elucidate the intricate relationships between the pore structure characteristics of SCG-AC and its efficacy in pertinent environmental applications, encompassing water treatment, energy storage, and catalysis. Economic evaluations consistently highlight the notable cost-effectiveness of SCG-AC production in comparison to commercially available activated carbons, thereby underscoring its potential for scalable industrial implementation. This review concludes in evidence-based recommendations for the rational optimization of activation strategies, providing a framework for the tailored design of high-performance SCG-AC materials and advancing the field of sustainable carbon material development.

Converting CO2 into valuable chemicals with low cost is significantly attractive for building a carbon-neutral society. Compared to the high energy-consuming CO2 chemical reduction methods, this study proposed a plasma-assisted waste conversion process at room temperature and atmospheric pressure. A coaxial dielectric barrier discharge (DBD) reactor was utilized for plasma-assisted CO2 reduction. Ethylene (C2H4), simulating waste plastic pyrolysis gas, was introduced into the reactor under ambient conditions. The effects of key parameters - CO2/C2H4 molar ratio (4:1-1:4), plasma voltage (20-50 V), and feed flow rate (50-500 mL/min) - were systematically investigated to optimize the production of oxygen-containing liquid hydrocarbons. Product composition was analyzed through GC-MS, revealing dominant alcohols (e.g. 1-butanol, 26.81%) and acids (e.g. acetic acid, 23.92%). Results show CO2 can be successfully reduced to liquid hydrocarbon products, and the main effect on product distributions is the CO2/C2H4 molar ratio. The selectivity of typical products (1-butanol l and acetic acid) were theoretically discussed through DFT analysis, enhancing the understanding of the reaction process involved in the hydrogenation reduction of aldehydes to alcohols and the oxidation of aldehydes to acids. This study represents a novel approach for CO2 reduction by utilizing waste plastic pyrolysis.

The large annual yield, wide application, and massive discard of plastics and tires have brought severe environmental issues. It is urgent to find an efficient way to recycle waste plastics and tires as high-value chemicals and energy fuels. Pyrolysis has long been considered a clean and productive technology. However, waste polymers are complex mixtures. The co-pyrolysis of the mixture is difficult but essential for energy and material recovery. This study investigated the co-pyrolysis of polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC) and tire waste (TW) using Thermogravimetric (TG) analysis, Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS), and lab-scale experiments. TG analysis showed that synergistic effect between PVC and TW was the most significant among all the experiments. In the lab-scale experiments, the interaction of PE/PVC and PE/TW improved olefin yield due to the synergistic effect while aromatics formation was promoted by PS/TW. The quality of the pyrolysis gas of PVC/TW was extremely high in the aspect of H2 concentration. However, the component distribution of co-pyrolysis oil of PVC/TW revealed no evident synergistic effect in the micro-scale experiment. Finally, the possible reaction pathways were proposed to get a better understanding of co-pyrolysis. Our study provided theoretical guidance for mixed polymer co-pyrolysis and product regulation.

The management of massive plastic waste is an issue of global concern. Microwave-initiated catalytic gasification has garnered significant attention in plastic upcycling, yet achieving high syngas yield with low-cost catalysts remains a challenge. This study developed a near-zero-cost microwave-absorbable catalyst derived from waste bauxite residue reduced by tire-derived carbon black (FBRC). Experimental results demonstrate the exceptional electromagnetic absorption properties and catalytic activity of FBRC. The highest syngas yield reached 4.23 Nm3 per kg waste plastic with a purity of 97 %. Furthermore, the H2/CO ratio was tunable between 0.63 and 3.81 by adjusting the catalyst dosage and composition. The remarkable performance of FBRC was attributed to the synergistic effects of microwave selective internal heating, thermal catalysis, oxidation reactions. This work proposed a waste-derived low-cost catalyst for microwave-assisted plastic gasification process, aimed to develop a rapid method for converting organic waste into valuable products.

The advancement of low-cost biochar derived from organic solid wastes is highly desirable, as it serves as an efficient and environmentally friendly absorbent for CO2 abatement. Textile dyeing sludge (TDS) and corncob are two common types of carbonaceous solid wastes that are abundant and easily accessible. In this study, TDS and corncob were co-pyrolyzed to produce a series of CO2 adsorption biochars (SCs). Results show that the synergetic and self-catalytic effects of the reaction between alkali/alkaline earth metals and the organic matters in TDS and corncob can increase biochar yield and enhance the ultra-micropore structure accounting for effective CO2 adsorption. Moreover, the specific surface area of SC activated at 700 degrees C (SC700) was higher than corncob-based biochar. SC700 exhibited the highest CO2 adsorption capacity (128.1 mg/g) among the SCs, which was more than double that of TDS biochar. This is primarily because SC700 had the highest specific surface area of ultramicropores (544.38 m2/g) and ultra-micropore volume (0.16 cm3/g) among the SCs. After ten cycles tests, SC700 still showed good CO2 adsorption-desorption performance, with a decrease of less than 1.5 %. The analysis of in situ DFIRT spectroscopy revealed that the CO2 adsorption of SC700 involved both physical and chemical adsorption processes, with physical adsorption being dominant. This study provides an environmentally friendly and cost-effective method for the utilization of TDS and corncob to produce valuable biochar for CO2 adsorption.

The use of photoreforming to treat plastics and degrade plastics to small molecular organic matter is an emerging approach to solve white pollution in the ocean and produce new energy. Structurally defective g-C3N4 (COCN) is compounded by adding ascorbic acid during the synthesis of graphitic carbon nitride (g-C3N4). L-cysteine is added to compose L-CdS. By constructing a heterojunction, we synthesize the ternary composite COCN/L-CdS/ Ni2P. The hydrogen production rate of COCN/L-CdS/Ni2P reaches 29.11 mmol/g/h at 5 h, which is 7.52 times and 727.7 times of L-CdS and COCN, respectively. During the production of hydrogen, polylactic acid (PLA) is degraded to pyruvate. This study demonstrates that COCN/L-CdS/Ni2P can not only photoreformate plastics in seawater into small molecular organics, but also efficiently produce H2 using seawater as a hydrogen source. This has a significant role to treat plastic pollution in seawater and product clean energy.

Domestic landfills function as both significant sinks and sources of microplastics (MPs). Inadequate management and re-excavation of landfill mineralized refuse can lead to the release of these emerging contaminants into the surrounding environment, resulting in secondary pollution. Therefore, systematic risk assessments of MPs in landfills are crucial for understanding their environmental impact and informing mitigation strategies. This research investigated three landfills in economically diverse regions of Southeast China, including two sanitary landfills and one informal dump site. A uniform sampling and analytical approach, including solvent extraction and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS), was applied to quantify mixed MPs of polyethylene (PE), polypropylene (PP), and polystyrene (PS) across 68 mineralized refuse samples. The average MPs concentrations in the three landfills ranged from 0.44 to 1.56 g/ (kg mineralized refuse by mass), and 0.105 to 0.397 g/ (m3 mineralized refuse by volume). Sanitary landfills contained higher MPs levels due to prolonged degradation under harsh landfill conditions. However, despite its older landfill age, the dump site exhibited lower MPs concentrations but a higher diffusion threat due to the lack of effective preventive measures. This research demonstrated that MPs contamination risk was also driven by landfill age and regional economic status. These findings provide a quantitative basis for assessing MPs pollution in landfills and emphasize the need for targeted strategies to mitigate MPs release into the environment.

An efficient oxygen carrier (OC) is in great demand in the biomass chemical looping gasification (BCLG) process. In the present study, an innovative rare earth oxide doped ferric oxide OC (Fe2O3-REaOb) derived from the Nd-Fe-B sintered magnet waste scraps was employed for the BCLG process for hydrogen-rich syngas production. The critical variables, including the temperature of gasification, the mass ratio of OC/biomass, the mass ratio of steam/biomass, and the cycle performance of the novel OC, were investigated regarding syngas yield and carbon conversion efficiency. Results found that the optimum conditions were achieved at 900 degrees C, with a mass ratio of OC to biomass of 3:1 and a mass ratio of steam to biomass of 0.4, and a syngas yield of 1.19 Nm(3)/kg with an H-2/CO mole ratio of 2.45, and a carbon conversion efficiency of 76.80% was reached. Additionally, a comparison between Fe2O3-REaOb OC, Fe2O3-Al2O3 OC, and Fe2O3-CeO2 OC was also conducted, with Fe2O3-REaOb OC demonstrating a superior performance. The synergistic effects between REaOb and Fe2O3, particularly the generation of perovskite oxide NdFeO3, contributed to the excellent performance of the Fe2O3-REaOb OC during the BCLG process. The outward diffusion of Fe and sintering of the OC reduced the syngas yield and carbon conversion efficiency by about 16.00% and 25.00% over the 20 redox cycles of the BCLG process. In summary, Fe2O3-REaOb can be an efficient and promising OC for hydrogen-rich syngas production in the BCLG process.

OBJECTIVES:This study aimed to provide a universal and reliable reference system quantifying temporomandibular joint (TMJ) morphological and positional changes.METHODS:Large field-of-view (FOV) cone-beam computed tomography (CBCT) images (20 TMJs) from 10 preorthognathic surgery patients and limited FOV CBCT images (40 TMJs) from 20 splint therapy-treated patients with temporomandibular disorders were collected. TMJ-specific reference system including a TMJ horizontal reference plane (TMJHP) and a local coordinate system (TMJCS) was constructed with landmarks on cranial base. Its application for TMJ measurements and its spatial relationship to common Frankfort horizontal plane (FHP) and maxillofacial coordinate system (MFCS) were evaluated.RESULTS:Five relevant landmarks were selected to optimally construct TMJ-specific reference system. General parallelism between TMJHP and FHP was demonstrated by minimal angular and constant distance deviation (1.714 ± 0.811º; 2.925 ± 0.817 mm). Additionally, tiny axial orientational deviations (0.181 ± 6.805º) suggested TMJCS rivaled MFCS. Moreover, small deviations in orientations and distances (1.232 ± 0.609º; 0.310 ± 0.202 mm) indicated considerable reliability for TMJCS construction, with intraclass correlation coefficients (ICCs) ranging from 0.999 to 1.000. Lastly, slight discrepancies in translations and rotations revealed high reliability for condylar positional and morphological measurements (ICC, 0.918-0.999).LIMITATIONS:TMJ-specific reference system was merely tested in two representative FOVs.CONCLUSIONS:This study provides a universal and reliable reference system for TMJ assessment that is applicable to both limited and large FOV CBCT. It would improve comparability among diverse studies and enable comprehensive evaluations of TMJ positional and morphological changes during TMJ-related treatment follow-up such as splint therapy and disease progression.

In this study, the atmospheric dielectric barrier discharge (DBD) plasma was proposed for the degradation of polystyrene microplastics (PS-MPs) for the first time, due to its ability to generate reactive oxygen species (ROS). The local temperature in plasma was found to play a crucial role, as it enhanced the degradation reaction induced by ROS when it exceeded the melting temperature of PS-MPs. Factors including applied voltage, air flow rate, and PS-MPs concentration were investigated, and the degradation products were analyzed. High plasma energy and adequate supply of ROS were pivotal in promoting degradation. At 20.1 kV, the degradation efficiency of PS-MPs reached 98.7% after 60 min treatment, with gases (mainly COx, accounting for 96.4%) as the main degradation products. At a concentration of 1 wt%, the PS-MPs exhibited a remarkable conversion rate of 90.6% to COx, showcasing the degradation performance and oxidation degree of this technology. Finally, the degradation mechanism of PS-MPs combined with the detection results of ROS was suggested. This work demonstrates that DBD plasma is a promising strategy for PS-MPs degradation, with high energy efficiency (8.80 mg/kJ) and degradation performance (98.7% within 1 h), providing direct evidence for the rapid and comprehensive treatment of MP pollutants.

Huge amounts of plastic products are produced, utilized, and discarded each year, contributing to the increasingly serious ecological problem. Photoreforming, a solar-driven technology, provides an uncomplicated route to simultaneously recycle plastics and facilitate hydrogen (H2) production. Herein, we proposed innovative CdS/NiS composites which used visible light to drive H2 evolution from plastic wastes. Results confirmed that the loading of NiS on CdS could facilitate the transmission of photoexcited electrons, which greatly improved the photocatalytic performance. The H2 production capability of CdS/NiS was more than 6 times higher than that of pure CdS, and the highest H2 yield reached 62.9 mmol g-1 h-1 under optimized conditions when polylactic acid (PLA) was treated. Typical polyester plastics, including polyethylene terephthalate (PET), poly-butylene adipate (PBA), polybutylene terephthalate (PBT), and poly (butyleneadipate-co-terephthalate) (PBAT), as well as raw PLA drink straws, were also successfully employed as the hole scavenger to enhance H2 generation. This system utilized abundant resources (solar energy and waste plastics) and worked under mild conditions, proffering a sustainable approach for H2 synthesis together with waste plastic pollutant reduction for a carbon-neutral future.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Landfill mining (LFM), which refers to the excavation, processing, treatment and recycling of formerly buried waste, is widely regarded as an effective strategy for the management of landfills. It may offer environmental, economic, and energy potential benefits through the mitigation of greenhouse gas emissions and the recovery of dormant materials, land resources, and energy carriers. Thus, carrying out an environment-economic-energy (3E) assessment of LFM is essential. However, LFM projects assessed from 3E perspectives are hardly documented. This work focuses on the 3E analysis model for assessing the feasibility of LFM which compared two scenarios of mining and non-mining. It innovatively combines the principles of 3E assessment and Monte Carlo Simulation in an effort to understand how different waste compositions affect potential outcomes of 3E aspects and their interrelationships. And this conbined method was first applied on case study of a typical MSW LFM project in China (Baotian landfill). It was found that the average equivalent CO2 emissions and leachate yield from LFM were 162.78 kgCO2·t-1 and 0.04 m3·t-1, respectively, which were considerably lower than the 513.50 kgCO2·t-1 and 1.13 m3·t-1 if the landfill was to be maintained for 30 years after closure. Moreover, the average profit of LFM project was 8.34 USD·t-1 compared to -2.80 USD·t-1 without excavation. Lastly, the average energy recovery through LFM was 143.62 kWh·t-1, while no energy was recovered in the non-mining scenario. The results suggest that LFM is more sustainable for waste management than non-mining. The sensitivity analyses indicate a tight interconnection among 3E aspects.

Dechlorination is essential for the chemical recycling of waste polyvinyl chloride (PVC) plastics. This study investigated the use of non-thermal plasma (NTP) for chlorine removal, with a focus on the effects of treatment time and discharge power on dechlorination efficiency. The results showed that longer treatment times and higher discharge powers led to better dechlorination performance. The maximum efficiency (98.25%) and HCl recovery yield (55.72%) were achieved at 180 W power after 40 min of treatment where 96.44% of Cl existed in the form of HCl gas, 1.44% in the liquid product, and 2.12% in the solid residue product. NTP at a discharge power of 150 W showed better dechlorination performance compared to traditional thermal pyrolysis treatment in temperatures ranging from 200 to 400 °C. The activation energy analysis of the chlorine removal showed that compared to pyrolysis-based dechlorination (137.09 kJ/mol), NTP-based dechlorination (23.62 kJ/mol) was more easily achievable. This work presents a practical method for the dechlorination of waste PVC plastic using a novel technology without requiring additional thermal and pressure input.

The huge amount of plastic waste accumulated in landfills has caused serious microplastic (MP) pollution to the soil environment, which has become an urgent issue in recent years. It is challenging to deal with the non -biodegradable MP pollutants in actual soil from landfills. In this study, a coaxial dielectric barrier discharge (DBD) system was proposed to remediate actual MP-contaminated landfill soil due to its strong oxidation ca-pacity. The influence of carrier gas type, applied voltage, and air flow rate was investigated, and the possible degradation pathways of MP pollutants were suggested. Results showed the landfill soil samples contained four common MP pollutants, including polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) with sizes ranging from 50 to 1500 mu m. The MP pollutants in the soil were rapidly removed under the action of reactive oxygen species (ROS) generated by DBD plasma. Under the air flow rate of 1500 mL min -1, the maximum remediation efficiency represented by mass loss reached 96.5% after 30 min treatment. Compared with nitrogen, when air was used as the carrier gas, the remediation efficiency increased from 41.4% to 81.6%. The increased applied voltage from 17.5 to 24.1 kV could also promote the removal of MP contaminants. Suf-ficient air supply was conducive to thorough removal. However, when the air flow rate reached 1500 mL min- 1 and continued to rise, the final remediation efficiency would be reduced due to the shortened residence time of ROS. The DBD plasma treatment proposed in this study showed high energy efficiency (19.03 mg kJ-1) and remediation performance (96.5%). The results are instructive for solving MP pollution in the soil environment.

Landfilling is the most traditional disposal method of domestic waste. Plastic waste in landfill sites could degrade to microplastics (MPs) and diffuse to the surrounding environment with leachate. However, MPs pollution in landfill mineralized refuse has not been well recognized. In the present research, a detection method for mixed MPs of polyethylene (PE), polypropylene (PP), and polystyrene (PS) based on Py-GC/MS was established and verified. The method is suitable for the rapid quantitative detection of large-batch of complex solid matrix samples, with an average deviation of less than 10%. Based on the method, samples from a landfill site in South China were studied, where PE was found to be the main component. The total concentration of MPs in mineralized refuse was 7.62 kg/t in the old area and 5.49 kg/t in the young area. Further analysis showed that the content of MPs was correlated with that of plastic waste and the landfill age, indicating that a considerable proportion was secondary MPs. The reserves of MPs in landfill sites may have reached an alarming number. In the absence of adequate safeguards, quantities of MPs may spread from the landfill sites, resulting in serious pollution of the surrounding soil and groundwater.