China’s carbon neutrality: an extensive and profound systemic reform

● China has pledged ambitious carbon peak and neutrality goals for mitigating global climate change. ● Major challenges to achieve carbon neutrality in China are summarized. ● The new opportunities along the pathway of China’s carbon neutrality are discussed from four aspects. ● Five policy suggestions for China are provided. China is the largest developing economy and carbon dioxide emitter in the world, the carbon neutrality goal of which will have a profound influence on the mitigation pathway of global climate change. The transition towards a carbon-neutral society is integrated into the construction of ecological civilization in China, and brings profound implications for China’s socioeconomic development. Here, we not only summarize the major challenges in achieving carbon neutrality in China, but also identify the four potential new opportunities: namely, the acceleration of technology innovations, narrowing regional disparity by reshaping the value of resources, transforming the industrial structure, and co-benefits of pollution and carbon mitigation. Finally, we provide five policy suggestions and highlight the importance of balancing economic growth and carbon mitigation, and the joint efforts among the government, the enterprises, and the residents.     

Property-performance relationship of core-shell structured black TiO2 photocatalyst for environmental remediation

● Properties and performance relationship of CSBT photocatalyst were investigated. ● Properties of CSBT were controlled by simply manipulating glycerol content. ● Performance was linked to semiconducting and physicochemical properties. ● CSBT (W:G ratio 9:1) had better performance with lower energy consumption. ● Phenols were reduced by 48.30% at a cost of $2.4127 per unit volume of effluent. Understanding the relationship between the properties and performance of black titanium dioxide with core-shell structure (CSBT) for environmental remediation is crucial for improving its prospects in practical applications. In this study, CSBT was synthesized using a glycerol-assisted sol-gel approach. The effect of different water-to-glycerol ratios (W:G = 1:0, 9:1, 2:1, and 1:1) on the semiconducting and physicochemical properties of CSBT was investigated. The effectiveness of CSBT in removing phenolic compounds (PHCs) from real agro-industrial wastewater was studied. The CSBT synthesized with a W:G ratio of 9:1 has optimized properties for enhanced removal of PHCs. It has a distinct core-shell structure and an appropriate amount of Ti³⁺ cations (11.18%), which play a crucial role in enhancing the performance of CSBT. When exposed to visible light, the CSBT performed better: 48.30% of PHCs were removed after 180 min, compared to only 21.95% for TiO₂ without core-shell structure. The CSBT consumed only 45.5235 kWh/m³ of electrical energy per order of magnitude and cost $2.4127 per unit volume of treated agro-industrial wastewater. Under the conditions tested, the CSBT demonstrated exceptional stability and reusability. The CSBT showed promising results in the treatment of phenols-containing agro-industrial wastewater.     

A pyrazine based metal-organic framework for selective removal of copper from strongly acidic solutions

● pz-UiO-66 was synthesized facilely by a solvothermal method. ● Efficient capture of copper from highly acidic solution was achieved by pz-UiO-66. ● pz-UiO-66 exhibited excellent selectivity and capacity for copper capture. ● Pyrazine-N in pz-UiO-66 was shown to be the dominant adsorption site. The selective capture of copper from strongly acidic solutions is of vital importance from the perspective of sustainable development and environmental protection. Metal organic frameworks (MOFs) have attracted the interest of many scholars for adsorption due to their fascinating physicochemical characteristics, including adjustable structure, strong stability and porosity. Herein, pz-UiO-66 containing a pyrazine structure is successfully synthesized for the efficient separation of copper from strongly acidic conditions. Selective copper removal at low pH values is accomplished by using this material that is not available in previously reported metal–organic frameworks. Furthermore, the material exhibits excellent adsorption capacity, with a theoretical maximum copper uptake of 247 mg/g. As proven by XPS and FT-IR analysis, the coordination of pyrazine nitrogen atoms with copper ions is the dominant adsorption mechanism of copper by pz-UiO-66. This work provides an opportunity for efficient and selective copper removal under strongly acidic conditions, and promises extensive application prospects for the removal of copper in the treatment for acid metallurgical wastewater.     

Passive convergence-permeable reactive barrier (PC-PRB): An effective configuration to enhance hydraulic performance

● A novel PRB configuration based on passive convergent flow effect was proposed. ● A 2D finite-difference hydrodynamic model, PRB-Flow, was developed. ● PC-PRB can significantly enhance the hydraulic capture capacity of PRB. ● The PRB geometric dimensions and materials cost are effectively reduced. ● The dominant influential factor of the PC-PRB capture width is pipe length, L_p. A novel permeable reactive barrier (PRB) configuration, the so-called passive convergence-permeable reactive barrier (PC-PRB), is proposed to overcome several shortcomings of traditional PRB configurations, such as high dependency to site hydrogeological characteristics and plume size. The PC-PRB is designed to make the plume converge towards the PRB due to the passive hydraulic decompression-convergent flow effect. The corresponding passive groundwater convergence (PC) system is deployed upstream of the PRB system, which consists of passive wells, water pipes, and a buffer layer. A two-dimensional (2D) finite-difference hydrodynamic code, entitled PRB-Flow, is developed to examine the hydraulic performance parameters (i.e., capture width (W) and residence time (t)) of PC-PRB. It is proved that the horizontal 2D capture width (W_h) and vertical 2D capture depth (W_v) of the PC-PRB remarkably increase compared to that of the continuous reactive barrier (C-PRB). The aforementioned relative growth values in order are greater than 50% and 25% in this case study. Therefore, the PRB geometric dimensions as well as the materials cost required for the same plume treatment lessens. The sensitivity analysis reveals that the dominant factors influencing the hydraulic performance of the PC-PRB are the water pipe length (L_p), PRB length (L_PRB), passive well height (H_w), and PRB height (H_PRB). The discrepancy between the W_h of PC-PRB and that of the C-PRB (i.e., ΔW_h) has a low correlation with PRB parameters and mainly depends on L_p, which could dramatically simplify the PC-PRB design procedure. Generally, the proposed PC-PRB exhibits an effective PRB configuration to enhance hydraulic performance.     

Win-Win: Anthropogenic circularity for metal criticality and carbon neutrality

● Anthropogenic circularity science is an emerging interdisciplinary field. ● Anthropogenic circularity was one effective strategy against metal criticality. ● Carbon neutrality is becoming the new industry paradigm around the world. ● Growing circularity could potentially minimize the CO₂ emission. Resource depletion and environmental degradation have fueled a burgeoning discipline of anthropogenic circularity since the 2010s. It generally consists of waste reuse, remanufacturing, recycling, and recovery. Circular economy and “zero-waste” cities are sweeping the globe in their current practices to address the world’s grand concerns linked to resources, the environment, and industry. Meanwhile, metal criticality and carbon neutrality, which have become increasingly popular in recent years, denote the material's feature and state, respectively. The goal of this article is to determine how circularity, criticality, and neutrality are related. Upscale anthropogenic circularity has the potential to expand the metal supply and, as a result, reduce metal criticality. China barely accomplished 15 % of its potential emission reduction by recycling iron, copper, and aluminum. Anthropogenic circularity has a lot of room to achieve a win-win objective, which is to reduce metal criticality while also achieving carbon neutrality in a near closed-loop cycle. Major barriers or challenges for conducting anthropogenic circularity are deriving from the inadequacy of life-cycle insight governance and the emergence of anthropogenic circularity discipline. Material flow analysis and life cycle assessment are the central methodologies to identify the hidden problems. Mineral processing and smelting, as well as end-of-life management, are indicated as critical priority areas for enhancing anthropogenic circularity.     

Characterization and variation of dissolved organic matter in composting: a critical review

● Effect of composting approaches on dissolved organic matter (DOM). ● Effect of composting conditions on the properties of DOM. ● Character indexes of DOM varied in composting. ● The size, hydrophobicity, humification, and electron transfer capacity increased. ● The hydrophilicity, protein-like materials, and aliphatic components reduced. As the most motive organic fraction in composting, dissolved organic matter (DOM) can contribute to the transfer and dispersal of pollutants and facilitate the global carbon cycle in aquatic ecosystems. However, it is still unclear how composting approaches and conditions influence the properties of compost-derived DOM. Further details on the shift of DOM character indexes are required. In this study, the change in properties of compost-derived DOM at different composting approaches and the effect of composting conditions on the DOM characteristics are summarized. Thereafter, the change in DOM character indexes’ in composting was comprehensively reviewed. Along with composting, the elements and spectral properties (chromophoric DOM (CDOM) and fluorescent DOM (FDOM)) were altered, size and hydrophobicity increased, and aromatic-C and electron transfer capacity were promoted. Finally, some prospects to improve this study were put forward. This paper should facilitate the people who have an interest in tracing the fate of DOM in composting.     

Mechanistic insights into the selective photocatalytic degradation of dyes over TiO2/ZSM-11

● TiO₂/ZSM-11 was prepared by a facile solid state dispersion method. ● Mechanism for photocatalytic degradation of dyes was investigated. ● Both experimental and MD simulations were conducted. ● Chemisorption instead of electrostatic interaction played a critical role. Photocatalytic degradation is a promising way to eliminate dye contaminants. In this work, a series of TiO₂/ZSM-11 (TZ) nanocomposites were prepared using a facile solid state dispersion method. Methyl orange (MO), methylene blue (MB), and rhodamine B (RhB) were intentionally chosen as target substrates in the photocatalytic degradation reactions. Compared to pristine TiO₂, negative effect was observed on MO degradation while promoted kinetics were collected on MB and RhB over TZ composites. Moreover, a much higher photocatalytic rate was interestingly achieved on RhB than MB, which indicated that a new factor has to be included other than the widely accepted electrostatic interaction mechanism to fully understand the selective photodegradation reactions. Systematic characterizations showed that TiO₂ and ZSM-11 physically mixed and maintained both the whole framework and local structure without chemical interaction. The different trends observed in surface area and the photo-absorption ability of TZ composites with reaction performance further excluded both as the promotion mechanism. Instead, adsorption energies predicted by molecular dynamics simulations suggested that differences in the adsorption strength played a critical role. This work provided a deep mechanistic understanding of the selective photocatalytic degradation of dyes reactions, which helps to rationally design highly efficient photocatalysts.     

Electro-conductive crosslinked polyaniline/carbon nanotube nanofiltration membrane for electro-enhanced removal of bisphenol A

● A crosslinked polyaniline/carbon nanotube NF membrane was fabricated. ● Electro-assistance enhanced the removal rate of the NF membrane for bisphenol A. ● Intermittent voltage-assistance can achieve nearly 100% removal of bisphenol A. ● Membrane adsorption–electro-oxidation process is feasible for micropollutant removal. Nanofiltration (NF) has attracted increasing attention for wastewater treatment and potable water purification. However, the high-efficiency removal of micropollutants by NF membranes is a critical challenge. Owing to the adsorption and subsequent diffusion, some weakly charged or uncharged micropollutants, such as bisphenol A (BPA), can pass through NF membranes, resulting in low removal rates. Herein, an effective strategy is proposed to enhance the BPA removal efficiency of a crosslinked polyaniline/carbon nanotube NF membrane by coupling the membrane with electro-assistance. The membrane exhibited a 31.9% removal rate for 5 mg/L BPA with a permeance of 6.8 L/(m²·h·bar), while the removal rate was significantly improved to 98.1% after applying a voltage of 2.0 V to the membrane. Furthermore, when BPA coexisted with humic acid, the membrane maintained 94% removal of total organic carbon and nearly 100% removal of BPA at 2.0 V over the entire filtration period. Compared to continuous voltage applied to the membrane, an intermittent voltage (2.0 V for 0.5 h with an interval of 3.5 h) could achieve comparable BPA removal efficiency, because of the combined effect of membrane adsorption and subsequent electrochemical oxidation. Density functional theory calculations and BPA oxidation process analyses suggested that BPA was adsorbed by two main interactions: π–π and hydrogen-bond interactions. The adsorbed BPA was further electro-degraded into small organic acids or mineralized to CO₂ and H₂O. This work demonstrates that NF membranes coupled with electro-assistance are feasible for improving the removal of weakly charged or uncharged micropollutants.     

Effect of Cu-ZSM-5 catalysts with different CuO particle size on selective catalytic oxidation of N,N-Dimethylformamide

● A series of Cu-ZSM-5 catalysts were tested for DMF selective catalytic oxidation. ● Cu-6 nm samples showed the best catalytic activity and N₂ selectivity. ● Redox properties and chemisorbed oxygen impact on DMF catalytic oxidation. ● Isolated Cu²⁺ species and weak acidity have effects on the generation of N₂. N, N-Dimethylformamide (DMF), a nitrogen-containing volatile organic compound (NVOC) with high emissions from the spray industry, has attracted increasing attention. In this study, Cu-ZSM-5 catalysts with different CuO particle sizes of 3, 6, 9 and 12 nm were synthesized and tested for DMF selective catalytic oxidation. The crystal structure and physicochemical properties of the catalyst were studied by various characterization methods. The catalytic activity increases with increasing CuO particle size, and complete conversion can be achieved at 300–350 °C. The Cu-12 nm catalyst has the highest catalytic activity and can achieve complete conversion at 300 °C. The Cu-6 nm sample has the highest N₂ selectivity at lower temperatures, reaching 95% at 300 °C. The activity of the catalysts is determined by the surface CuO cluster species, the bulk CuO species and the chemisorbed surface oxygen species. The high N₂ selectivity of the catalyst is attributed to the ratio of isolated Cu²⁺ and bulk CuO species, and weak acidity is beneficial to the formation of N₂. The results in this work will provide a new design of NVOC catalytic oxidation catalysts.     

Low-temperature caproate production,microbial diversity,and metabolic pathway in xylose anaerobic fermentation

● Converting xylose to caproate under a low temperature of 20 °C by MCF was verified. ● Final concentration of caproate from xylose in a batch reactor reached 1.6 g/L. ● Changing the substrate to ethanol did not notably increase the caproate production. ● Four genera, including Bifidobacterium , were revealed as caproate producers. ● The FAB pathway and incomplete RBO pathway were revealed via metagenomic analysis. Mixed culture fermentation (MCF) is challenged by the unqualified activity of enriched bacteria and unwanted methane dissolution under low temperatures. In this work, caproate production from xylose was investigated by MCF at a low temperature (20 °C). The results showed that a 9 d long hydraulic retention time (HRT) in a continuously stirred tank reactor was necessary for caproate production (~0.3 g/L, equal to 0.6 g COD/L) from xylose (10 g/L). The caproate concentration in the batch mode was further increased to 1.6 g/L. However, changing the substrate to ethanol did not promote caproate production, resulting in ~1.0 g/L after 45 d of operation. Four genera, Bifidobacterium, Caproiciproducens, Actinomyces, and Clostridium_sensu_stricto_12, were identified as the enriched caproate-producing bacteria. The enzymes in the fatty acid biosynthesis (FAB) pathway for caproate production were identified via metagenomic analysis. The enzymes for the conversion of (C_n+2)-2,3-Dehydroxyacyl-CoA to (C_n+2)-Acyl-CoA (i.e., EC 1.3.1.8 and EC 1.3.1.38) in the reverse β-oxidation (RBO) pathway were not identified. These results could extend the understanding of low-temperature caproate production.     

Collaborative control of fine particles and ozone required in China for health benefit

● Increased DAAO offsets 3/4 of the decrease of DAAP in 2013–2020. ● DAAO increases are mainly due to O₃ concentration increase and population aging. ● Health benefit from PM_2.5 reduction after 2017 is larger than that before 2017. ● Reducing PM_2.5 concentration by 1% results in 0.6% reduction of DAAP. ● Reducing O₃ concentration by 1% results in 2% reduction of DAAO. PM_2.5 concentration declined significantly nationwide, while O₃ concentration increased in most regions in China in 2013–2020. Recent evidences proved that peak season O₃ is related to increased death risk from non-accidental and respiratory diseases. Based on these new evidences, we estimate excess deaths associated with long-term exposure to ambient PM_2.5 and O₃ in China following the counterfactual analytic framework from Global Burden Disease. Excess deaths from non-accidental diseases associated with long-term exposure to ambient O₃ in China reaches to 579 (95% confidential interval (CI): 93, 990) thousand in 2020, which has been significantly underestimated in previous studies. In addition, the increased excess deaths associated with long-term O₃ exposure (234 (95% CI: 177, 282) thousand) in 2013–2020 offset three quarters of the avoided excess deaths (302 (95% CI: 244, 366) thousand) mainly due to PM_2.5 exposure reduction. In key regions (the North China Plain, the Yangtze River Delta and the Fen-Wei Plain), the former is even larger than the latter, particularly in 2017–2020. Health benefit of PM_2.5 concentration reduction offsets the adverse effects of population growth and aging on excess deaths attributed to PM_2.5 exposure. Increase of excess deaths associated with O₃ exposure is mainly due to the strong increase of O₃ concentration, followed by population aging. Considering the faster population aging process in the future, collaborative control, and faster reduction of PM_2.5 and O₃ are needed to reduce the associated excess deaths.     

Electrocatalytic biofilm reactor for effective and energy-efficient azo dye degradation: the synergistic effect of MnOx/Ti flow-through anode and biofilm on the cathode

● MnO _x /Ti flow-through anode was coupled with the biofilm-attached cathode in ECBR. ● ECBR was able to enhance the azo dye removal and reduce the energy consumption. ● Mn^IV=O generated on the electrified MnO _x /Ti anode catalyzed the azo dye oxidation. ● Aerobic heterotrophic bacteria on the cathode degraded azo dye intermediate products. ● Biodegradation of intermediate products was stimulated under the electric field. Dyeing wastewater treatment remains a challenge. Although effective, the in-series process using electrochemical oxidation as the pre- or post-treatment of biodegradation is long. This study proposes a compact dual-chamber electrocatalytic biofilm reactor (ECBR) to complete azo dye decolorization and mineralization in a single unit via anodic oxidation on a MnO_x/Ti flow-through anode followed by cathodic biodegradation on carbon felts. Compared with the electrocatalytic reactor with a stainless-steel cathode (ECR-SS) and the biofilm reactor (BR), the ECBR increased the chemical oxygen demand (COD) removal efficiency by 24 % and 31 % (600 mg/L Acid Orange 7 as the feed, current of 6 mA), respectively. The COD removal efficiency of the ECBR was even higher than the sum of those of ECR-SS and BR. The ECBR also reduced the energy consumption (3.07 kWh/kg COD) by approximately half compared with ECR-SS. The advantages of the ECBR in azo dye removal were attributed to the synergistic effect of the MnO_x/Ti flow-through anode and cathodic biofilms. Catalyzed by Mn^IV=O generated on the MnO_x/Ti anode under a low applied current, azo dyes were oxidized and decolored. The intermediate products with improved biodegradability were further mineralized by the cathodic aerobic heterotrophic bacteria (non-electrochemically active) under the stimulation of the applied current. Taking advantage of the mutual interactions among the electricity, anode, and bacteria, this study provides a novel and compact process for the effective and energy-efficient treatment of azo dye wastewater.     

A critical review on thermodynamic mechanisms of membrane fouling in membrane-based water treatment process

● Fundamentals of membrane fouling are comprehensively reviewed. ● Contribution of thermodynamics on revealing membrane fouling mechanism is summarized. ● Quantitative approaches toward thermodynamic fouling mechanisms are deeply analyzed. ● Inspirations of thermodynamics for membrane fouling mitigation are briefly discussed. ● Research prospects on thermodynamics and membrane fouling are forecasted. Membrane technology is widely regarded as one of the most promising technologies for wastewater treatment and reclamation in the 21st century. However, membrane fouling significantly limits its applicability and productivity. In recent decades, research on the membrane fouling has been one of the hottest spots in the field of membrane technology. In particular, recent advances in thermodynamics have substantially widened people’s perspectives on the intrinsic mechanisms of membrane fouling. Formulation of fouling mitigation strategies and fabrication of anti-fouling membranes have both benefited substantially from those studies. In the present review, a summary of the recent results on the thermodynamic mechanisms associated with the critical adhesion and filtration processes during membrane fouling is provided. Firstly, the importance of thermodynamics in membrane fouling is comprehensively assessed. Secondly, the quantitative methods and general factors involved in thermodynamic fouling mechanisms are critically reviewed. Based on the aforementioned information, a brief discussion is presented on the potential applications of thermodynamic fouling mechanisms for membrane fouling control. Finally, prospects for further research on thermodynamic mechanisms underlying membrane fouling are presented. Overall, the present review offers comprehensive and in-depth information on the thermodynamic mechanisms associated with complex fouling behaviors, which will further facilitate research and development in membrane technology.     

Catalytic urea hydrolysis by composite metal oxide catalyst towards efficient urea-based SCR process: performance evaluation and mechanism investigation

● Bimetallic oxide composite catalyst was designed for the urea-based SCR process. ● Surface chemical state and typical microstructure of catalyst was determined. ● Reaction route was improved based on intermediates and active site identification. ● TiO₂@Al₂O₃ presents an obvious promotion for urea hydrolysis. As a promising option to provide gaseous NH₃ for SCR system, catalytic urea hydrolysis has aroused great attention, and improving surface area and activity of catalysis are the crucial issues to be solved for efficient urea hydrolysis. Therefore, a composite metal oxide (TiO₂@Al₂O₃) catalyst was prepared by a simple hydrothermal method, with mesoporous alumina (γ-Al₂O₃) as substrate. The results verify the mesoporous structure and submicron cluster of TiO₂@Al₂O₃, with exposed crystal faces of (101) and (400) for TiO₂ and γ-Al₂O₃, respectively. The electronegativity difference of Ti⁴⁺ and Al³⁺ changes the charge distribution scheme around the interface, which provides abundant acid/base sites to boost the urea hydrolysis. Consequently, for an optimal proportioning with nano TiO₂ content at 10 wt.%, the hydrolysis efficiency can reach up to 35.2 % at 100 °C in 2 h, increasing by ~7.1 % than that of the blank experiment. ¹³C NMR spectrum measurements provide the impossible intermediate species during urea hydrolysis. Theoretical calculations are performed to clarify the efficient H₂O decomposition at the interface of TiO₂@Al₂O₃. The result offers a favorable technology for energy-efficiency urea hydrolysis.     

PM2.5 concentration declining saves health expenditure in China

● Monthly hospitalization expenses are sensitive to increases in PM_2.5 exposure. ● The increased PM_2.5 causes patients with CHD and LRI to stay longer in the hospital. ● The impact of PM_2.5 on total expenses for stroke is greater in southern China. ● Males may be more sensitive to air pollution than females. Air pollution has been a severe issue in China. Exposure to PM_2.5 has adverse health effects and causes economic losses. This study investigated the economic impact of exposure to PM_2.5 pollution using monthly city-level data covering 88.5 million urban employees in 2016 and 2017. This study mainly focused on three expenditure indicators to measure the economic impact considering lower respiratory infections (LRIs), coronary heart disease (CHD), and stroke. The results show that a 10 µg/m³ increase in PM_2.5 would cause total monthly expenses of LRIs, CHD, and stroke to increase by 0.226%, 0.237%, and 0.374%, respectively. We also found that LRI, CHD, and stroke hospital admissions increased significantly by 10%, 8.42%, and 5.64%, respectively. Furthermore, the total hospital stays of LRIs, CHDs, and strokes increased by 2.49%, 2. 51%, and 1.64%, respectively. Our findings also suggest heterogeneous impacts of PM_2.5 exposures by sex and across regions, but no statistical evidence shows significant differences between the older and younger adult subgroups. Our results provide several policy implications for reducing unequal public health expenditures in overpolluted countries.     

Homogeneous and heterogeneous photolysis of nitrate in the atmosphere: state of the science,current research needs,and future prospects

● Recent advances in the photolysis of nitrate/HNO₃ are reviewed. ● Mechanisms and key factors affecting the photolysis of nitrate/HNO₃ are summarized. ● Atmospheric implications and future research recommendations are provided. Nitrate is an important component of atmospheric particulate matter and affects air quality, climate, human health, and the ecosystem. Nitrate was previously considered a permanent sink for nitrogen oxides (NO_x). However, this viewpoint has been challenged in recent years because growing research evidence has shown the transformation of nitrate into NO_x (i.e., renoxification). The photolysis of nitrate/HNO₃, especially in the particulate phase or adsorbed on particles, can be a significant renoxification process in the atmosphere. The formation and photolysis of nitrate in aerosol not only change the diurnal variation of NO_x, but also provide long-distance transport of NO_x in the form of nitrate, which affects local and regional atmospheric chemistry and air quality. This review summarizes recent advances in the fundamental understanding of the photolysis of nitrate/HNO₃ under various atmospheric conditions, with a focus on mechanisms and key factors affecting the process. The atmospheric implications are discussed and future research is recommended.     

Revealing the GHG reduction potential of emerging biomass-based CO2 utilization with an iron cycle system

● Greenhouse gas mitigation by biomass-based CO₂ utilization with a Fe cycle system. ● The system including hydrothermal CO₂ reduction with Fe and Fe recovery by biomass. ● The reduction potential quantified by experiments, simulations, and an ex-ante LCA. ● The greatest GHG reduction potential is −34.03 kg CO₂-eq/kg absorbed CO₂. ● Ex-ante LCA supports process optimization to maximize GHG reduction potential. CO₂ utilization becomes a promising solution for reducing anthropogenic greenhouse gas (GHG) emissions. Biomass-based CO₂ utilization (BCU) even has the potential to generate negative emissions, but the corresponding quantitative evaluation is limited. Herein, the biomass-based CO₂ utilization with an iron cycle (BCU-Fe) system, which converts CO₂ into formate by Fe under hydrothermal conditions and recovers Fe with biomass-derived glycerin, was investigated. The GHG reduction potential under various process designs was quantified by a multidisciplinary method, including experiments, simulations, and an ex-ante life-cycle assessment. The results reveal that the BCU-Fe system could bring considerable GHG emission reduction. Significantly, the lowest value is −34.03 kg CO₂-eq/kg absorbed CO₂ (−2.44 kg CO₂-eq/kg circulated Fe) with the optimal yield of formate (66%) and Fe (80%). The proposed ex-ante evaluation approach not only reveals the benefits of mitigating climate change by applying the BCU-Fe system, but also serves as a generic tool to guide the industrialization of emerging carbon-neutral technologies.     

Water quality soft-sensor prediction in anaerobic process using deep neural network optimized by Tree-structured Parzen Estimator

● Hybrid deep-learning model is proposed for water quality prediction. ● Tree-structured Parzen Estimator is employed to optimize the neural network. ● Developed model performs well in accuracy and uncertainty. ● Usage of the proposed model can reduce carbon emission and energy consumption. Anaerobic process is regarded as a green and sustainable process due to low carbon emission and minimal energy consumption in wastewater treatment plants (WWTPs). However, some water quality metrics are not measurable in real time, thus influencing the judgment of the operators and may increase energy consumption and carbon emission. One of the solutions is using a soft-sensor prediction technique. This article introduces a water quality soft-sensor prediction method based on Bidirectional Gated Recurrent Unit (BiGRU) combined with Gaussian Progress Regression (GPR) optimized by Tree-structured Parzen Estimator (TPE). TPE automatically optimizes the hyperparameters of BiGRU, and BiGRU is trained to obtain the point prediction with GPR for the interval prediction. Then, a case study applying this prediction method for an actual anaerobic process (2500 m³/d) is carried out. Results show that TPE effectively optimizes the hyperparameters of BiGRU. For point prediction of COD_eff and biogas yield, R² values of BiGRU, which are 0.973 and 0.939, respectively, are increased by 1.03%–7.61% and 1.28%–10.33%, compared with those of other models, and the valid prediction interval can be obtained. Besides, the proposed model is assessed as a reliable model for anaerobic process through the probability prediction and reliable evaluation. It is expected to provide high accuracy and reliable water quality prediction to offer basis for operators in WWTPs to control the reactor and minimize carbon emission and energy consumption.     

Evaluating the impact of sulfamethoxazole on hydrogen production during dark anaerobic sludge fermentation

● SMX promotes hydrogen production from dark anaerobic sludge fermentation. ● SMX significantly enhances the hydrolysis and acidification processes. ● SMX suppresses the methanogenesis process in order to reduce hydrogen consumption. ● SMX enhances the relative abundance of hydrogen-VFAs producers. ● SMX brings possible environmental risks due to the enrichment of ARGs. The impact of antibiotics on the environmental protection and sludge treatment fields has been widely studied. The recovery of hydrogen from waste activated sludge (WAS) has become an issue of great interest. Nevertheless, few studies have focused on the impact of antibiotics present in WAS on hydrogen production during dark anaerobic fermentation. To explore the mechanisms, sulfamethoxazole (SMX) was chosen as a representative antibiotic to evaluate how SMX influenced hydrogen production during dark anaerobic fermentation of WAS. The results demonstrated SMX promoted hydrogen production. With increasing additions of SMX from 0 to 500 mg/kg TSS, the cumulative hydrogen production elevated from 8.07 ± 0.37 to 11.89 ± 0.19 mL/g VSS. A modified Gompertz model further verified that both the maximum potential of hydrogen production (P_m) and the maximum rate of hydrogen production (R_m) were promoted. SMX did not affected sludge solubilization, but promoted hydrolysis and acidification processes to produce more hydrogen. Moreover, the methanogenesis process was inhibited so that hydrogen consumption was reduced. Microbial community analysis further demonstrated that the introduction of SMX improved the abundance of hydrolysis bacteria and hydrogen-volatile fatty acids (VFAs) producers. SMX synergistically influenced hydrolysis, acidification and acetogenesis to facilitate the hydrogen production.     

Ozonation of aromatic monomer compounds in water: factors determining reaction outcomes

● p- CNB and IBP were selected, to explore factors determining ozonation outcomes. ● •OH contributed only 50 % to IBP removal, compared to the 90 % for p -CNB removal. ● IBP achieved fewer TOC removal and more by-product types and quantities. ● A longer ring-opening distance existed during the degradation of IBP. ● Multiple positions on both branches of IBP were attacked, consuming more oxidants. For aromatic monomer compounds (AMCs), ozonation outcomes were usually predicted by the substituents of the benzene ring based on the electron inductive effect. However, the predicted results were occasionally unreliable for complex substituents, and other factors caused concern. In this study, p-chloronitrobenzene (p-CNB) and ibuprofen (IBP) were selected for ozonation. According to the electron inductive theory, p-CNB should be less oxidizable, but the opposite was true. The higher rates of p-CNB were due to various sources of assistance. First, the hydroxyl radical (•OH) contributed 90 % to p-CNB removal at pH 7.0, while its contribution to IBP removal was 50 %. Other contributions came from molecular O₃ oxidation. Second, p-CNB achieved 40 % of the total organic carbon (TOC) removal and fewer by-product types and quantities, when compared to the results for IBP. Third, the oxidation of p-CNB started with hydroxyl substitution reactions on the benzene ring; then, the ring opened. However, IBP was initially oxidized mainly on the butane branched chain, with a chain-shortening process occurring before the ring opened. Finally, the degradation pathway of p-CNB was single and consumed fewer oxidants. However, both branches of IBP were attacked simultaneously, and three degradation pathways that relied on more oxidants were proposed. All of these factors were determinants of the rapid removal of p-CNB.