Journal of Cleaner Production最新文献

A silica-based adsorbent (P507@COF-TpAzo/SiO₂) with nitrogen and phosphorus donors was prepared for industrial separation and recovery of Sn(IV) by in-situ growth of covalent organic framework (COF) on a silica substrate combined with vacuum impregnation. The materials were tested and analyzed by the scanning electron microscope (SEM), X-ray diffraction (XRD) and other characterization techniques, which demonstrated that the adsorbent has an enormous specific surface area, excellent heat resistance, and a regular morphological structure. The static experimental results showed that the adsorbent displayed remarkable selectivity for Sn(IV) in high HCl and HNO₃ concentration environments, with excellent kinetics (∼60 min) and outstanding adsorption capacities (60.02 mg/g in 3 M HCl, 92.59 mg/g in 3 M HNO₃) in different media at 3 M acidity. Cycle performance testing demonstrated that the adsorbent exhibited excellent stability (cycle times ≥8). Analysis using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) showed that the synergistic adsorption results of N and P were reflected, mainly by the synergistic complexation of P=O and N=N-C. The potential sites for the adsorption of the adsorbent towards Sn(IV) were predicted by density functional theory (DFT) calculations, and the adsorbent demonstrated a more stable binding energy with Sn(IV). Finally, dynamic separation and efficient enrichment (>210) of Sn(IV) in highly acidic wastewater were realized by designing a penetrating column separation process. P507@COF-TpAzo/SiO₂ satisfied the requirements of the dynamic adsorption experiments, bridging the research gap of dynamic separation, and provides a new strategy for the industrial removal and recovery of Sn(IV), as well as a way for environmental protection and industrial green production.

To further enhance CO₂ capture and sequestration in concrete waste, this study investigates the interaction of four environmental factors, i.e., temperature, relative humidity (RH), CO₂ concentration and pressure on the accelerated carbonation of recycled concrete aggregates. 29 groups of accelerated carbonation tests are performed based on the Box-Behnken design. The effects of four factors on the carbonation percentage of recycled concrete aggregates (RCAs) are analyzed using a response surface methodology. A response surface model is obtained to characterize the experimental results. Additionally, three single-factor scenarios and three multi-factor coupled scenarios are employed to show the mechanisms affecting RCA carbonation and carbonation environments. Single factor analysis indicate that RH and CO₂ concentration can significantly affect the carbonation of the RCA and the significance of the interactions follows the order of temperature - RH, RH - CO₂ concentration and temperature - CO₂ concentration. The microstructure of RCAs during carbonation is further studied and presented.

Low-carbon city pilot policies are crucial for addressing urban challenges, alleviating pressure on urban systems, and encouraging sustainable development and resilience. This study focused on Chinese cities to explore how low-carbon city pilot policies influence urban resilience. The impact of the policies on urban resilience was assessed using difference-in-differences, mediating effect, and moderating effect models, showcasing both the variation and mechanism of the effects. The results are as follows: First, the introduction of low-carbon city pilot policies has resulted in a 9.3% increase in urban resilience, with noticeable enhancements over time. Second, the influence of low-carbon city pilot policies on urban resilience demonstrates heterogeneity, particularly with more pronounced effects observed in the eastern and coastal regions, as well as in resource-based, priority, and large cities. Third, the implementation of low-carbon city pilot policies has bolstered urban resilience through the promotion of technological innovation, the transformation of industrial structures, and the improvement of energy composition, with green production having a beneficial moderating function. Fourth, low-carbon city pilot policies have a siphoning effect on urban resilience within 50 km, and a positive spatial spillover effect between 50 and 200 km, both of which diminish with increasing distance. Finally, the examination of the policy implications derived from the study's findings is addressed. This study has the potential to serve as a valuable reference for formulating urban sustainable development strategies.

Ethylene oxide (EO) is a pivotal intermediate in the chemical industry owing to its versatility and high demand. Currently, direct oxidation is the most important technical process to produce EO. This conventional process, in which ethylene is partially oxidized with air or oxygen, has limited selectivity for EO of 65–90%, leading to significant CO₂ emissions. This study explores an alternative method involving the electrochemical selective oxidation of ethylene powered by renewable electricity. The electrochemical oxidation technology is expected to reduce CO₂ emitted during EO production. Process models were developed based on existing literature data. A techno-economic evaluation and sensitivity analysis focusing on the electrochemical cell variables were conducted. In this assessment, the investment and production costs of the electro-oxidation process for EO production were compared with those of the conventional process. This assessment also compared processes producing of mono-ethylene glycol and ethylene carbonate from EO. These analyses reveal that the separation energy has a significant impact on the carbon footprint. While current economic and environmental benefits are not favorable, this study identifies key descriptors of the technology for further reducing the carbon footprint. Based on the evaluation results, this study demonstrates the potential to cut CO₂ emissions in half compared to conventional plants by utilizing the electro-oxidation of ethylene via a direct route.

The transformations of brackish water into freshwater employing porous materials such as metal-organic frameworks (MOFs) show a great potential for a green environment. But the adsorption-based desalination slows down due to slow water adsorption/desorption rates and inadequate water storage capacity in conventional adsorbents. Therefore, the restructuring of porous MOFs increases water storage and transfer rates. This paper presents a comprehensive investigation on the fabrication of ionic liquid encapsulated MIL-101 (Cr) MOFs (metal-organic frameworks), and its interactions with water for desalination applications. Firstly, the pristine MIL-101 (Cr) is encapsulated with various types/amounts of ionic liquids. Next, these MOFs are characterized via SEM (Scanning electron microscope), FTIR (Fourier transform infrared), XRD (X-ray diffraction), TGA (Thermal gravimetric analysis), N₂ adsorption techniques. The water adsorption on these MOFs is performed experimentally for a wide temperature (30–80 °C) and pressure (0 < P/Ps < 0.95) ranges. The effects of the size (or type) as well as the encapsulation ratio of ionic liquids on water adsorption behaviors are conducted. Based on the experimentally proven water adsorption (isotherms and kinetics) data, an AD (adsorption desalination) system is modelled and simulated. Finally, the AD performances in terms of the specific daily water production (SDWP) and performance ratio (PR) are parametrically studied with respect to various regeneration temperature (50–80 °C) and cycle times (100 s–1000 s). It is found that by ionic liquid encapsulation, the water uptakes/offtake rates are expedited up to 48% (for adsorption)/55% (for desorption), respectively. In addition, the water transfer (Δq) improves up to 45% more than the parent MIL-101(Cr) MOFs. Furthermore, the SDWP increases from 38 to 56 m³ of water per tonne of MOFs per day at the regeneration temperature of 70 °C. The simulation results also show that the ionic-liquid-encapsulated MIL-101 (Cr) MOFs generates water (>25 m³ water per tonne of IL-MOFs) at the regeneration temperature of 50 °C and is potential for the next generation desalination applications.

Autoclaved aerated concrete is a popular building material in constructing one- and two-family houses because of its low thermal conductivity and fire resistance. Since autoclaved aerated concrete production rose significantly in the 1960s and 1970s, increasing post-demolition volumes can be expected in the following decades. However, these are currently landfilled as high-quality recycling options are still to be established.

This study develops a new capacitated, multi-period, and multi-stage network model for optimising a Germany autoclaved aerated concrete recycling network. The multi-period character of the model enables the precise consideration of increasing post-demolition volumes by constantly allowing the move of recycling plants or opening new ones throughout the planning horizon. Additionally, the multi-stage formulation facilitates incorporating an optional second recycling step, which involves additional effort and higher revenues. The model aims to find a cost-minimised recycling network and identify optimal network transformations until 2050. Results show that recycling is preferred over landfilling. The optimised recycling network uses large recycling plants for economies of scale and opens new plants in the future to handle the expected increase in post-demolition autoclaved aerated concrete. Transport costs account for the largest share of total costs (50%), while fixed costs reach around 40%, and revenues offset approximately 20% of all costs. The total costs of the network reach about 2200 M€ until 2050, which is 4600 M€ (68%) less than without establishing recycling. The results offer new insights into cost-minimal network structures and their future development to encourage decision-makers to promote autoclaved aerated concrete recycling.

Urban green space (UGS) equity is crucial for sustainable urban development, social harmony, and stability. Given the escalating environmental justice crisis in megacity UGS, ensuring spatial justice and social equity in these areas is vital for sustainable development. This study analyzes the equity of UGS in megacity by assessing both spatial equity from the supply perspective and social equity from the demand perspective while exploring key factors driving this equity. This study found that: 1) The green Gini coefficient in Tianjin's central city, stands at 0.7787, indicating significant spatial inequity, with small UGS exhibiting the highest, followed by medium and large spaces. 2) There is a varying perception of UGS equity across different socioeconomic groups, most pronounced in the center urban area, then in the encircling urban area and remote urban area, indicating a gradual diffusion of green equity from the city center outward. 3) Key external factors influencing UGS equity include economic development, population density, traffic patterns, and local environmental quality, while internal factors like accessibility and size also play a role in spatial equity. Thus, enhancing UGS equity in megacities requires not only top-down supply interventions but also bottom-up demand feedback mechanisms.

For low carbon-to-nitrogen ratio municipal wastewater, full utilization of carbon sources is positive in reducing carbon emissions and carbon source addition. This study evaluated and proposed appropriate anaerobic duration control to improve nitrogen and phosphorus removal performance in Denitrifying Phosphorus Removal and Partial Denitrification coupled with Anammox (DPR-PDA) system. Excessive anaerobic duration resulted in wasted carbon source, anaerobic stage should be stopped after carbon source had been utilized. Hydraulic Retention Time-Anaerobic (HRT-An) of R1 was shortened from 5h to 0.56h, while R2 was maintained at 5h. The removal efficiency of nitrate (NO₃⁻) were 91.7% in R1 and 71.5% in R2. Peak of NO₂⁻ accumulation (Peak-NO₂^--N) during denitrification in R1 was 4.5 times than in R2. Candidatus_Brocadia as anammox bacteria was self-enriched, the abundance in R1 was 4.67 times than in R2. This provided a practical guide for optimization of wastewater treatment processes and application of anammox technology.

To recycle and utilize two types of harmful solid waste, coffee grounds (CG) and coal fly ash (CFA), a novel and low-cost superabsorbent composite (MCG-PAA/CFA) was synthesized by aqueous solution polymerization with modified coffee grounds (MCG), acrylic acid (AA) and CFA as raw materials, and it was applied to soil to improve its drought resistance. Various reaction conditions were comprehensively investigated and analyzed to assess their influence on the water absorbency of the superabsorbent composite (SAC). After optimization, the MCG-PAA/CFA exhibited water absorbency capacities of 1260(±10.6) g/g and 82(±1.4) g/g in deionized water and physiological saline, respectively. After adding 3 wt% MCG, the water absorption of SAC was improved from 415 to 746 g/g. After further introduction of 2 wt% CFA, the water absorption of SAC increased from 746 to 1260 g/g. Fourier Transform Infrared (FTIR) analysis confirmed that the grafting reaction was successful and that CFA participated in the reaction, while scanning electron microscope (SEM) and thermogravimetric analysis (TGA) results revealed that the grafting reaction and the introduction of CFA improved the surface morphology and thermal stability of the SAC. Kinetic analysis was conducted to investigate how the grafting reaction and the introduction of CFA affected the swelling and water retention kinetics of the superabsorbent composite. In the soil experiment, adding only 0.1 wt% MCG-PAA/CFA can improve the water holding capacity of sandy soil, loam soil and clay soil by 6.65%, 4.42%, and 3.76% respectively This SAC composite has great potential in soil drought resistance.