Sep 2023, Volume 17 Issue 9

Cover illustration

  • Front Cover Story (See: Xufang Wang, Dongli Guo, Jinna Zhang, Yuan Yao, Yanbiao Liu, 2023, 17(9): 106)
    The presence of micropollutants in water bodies pose threaten to human health and advanced strategies are urgently needed to deal with this challenging issue. The usage of permanganate (KMnO4) to decompose micropollutants is a promising option, however, the poor reaction kinetics and low KMnO4 utilization efficiency yet to be resolved. Herein, we rationally designed a [Detail] ...

    Download cover

  • Select all
    Yi Qian
    Xiping Kan, Xia Yu, Wentao Zhao, Shuguang Lyu, Shuying Sun, Gang Yu, Qian Sui

    ● A systematic framework was developed to identify i-PPCPs for landfill leachate.

    ● The wide-scope target analysis offered a basis for comprehensive i-PPCP screening.

    ● Source-specificity and representativeness analysis helped to refine i-PPCPs.

    ● Erythromycin, gemfibrozil and albendazole were identified as i-PPCPs for leachate.

    Identifying potential sources of pharmaceuticals and personal care products (PPCPs) in the environment is critical for the effective control of PPCP contamination. Landfill leachate is an important source of PPCPs in water; however, it has barely been involved in source apportionment due to the lack of indicator-PPCPs (i-PPCPs) in landfill leachates. This study provides the first systematic framework for identifying i-PPCPs for landfill leachates based on the wide-scope target monitoring of PPCPs. The number of target PPCPs increased from < 20 in previous studies to 68 in the present study. Fifty-nine PPCPs were detected, with median concentrations in leachate samples ranging from below the method quantification limit (MQL) to 41 μg/L, and 19 of them were rarely reported previously. A total of 29 target compounds were determined to be PPCPs of high concern by principal component analysis according to multiple criteria, including occurrence, exposure potential, and ecological effect. Coupled with source-specificity and representativeness analysis, erythromycin, gemfibrozil, and albendazole showed a significant difference in their occurrence in leachate compared to other potential sources (untreated and treated municipal wastewater and livestock wastewater) and correlated with total PPCP concentrations; these were recommended as i-PPCPs for leachates. Indicator screening procedure can be used to develop a sophisticated source apportionment method to identify sources of PPCPs from adjacent landfills.

    Caiyan Qu, Lushan Li, Fan Feng, Kainian Jiang, Xing Wu, Muchuan Qin, Jia Tang, Xi Tang, Ruiyang Xiao, Di Wu, Chongjian Tang

    ● N2H4 addition enhanced and recovered anammox performance under Cr(VI) stress.

    ● N2H4 accelerated electron transfer of Cr(VI) reduction for detoxification.

    ● N2H4 enhanced anammox metabolism for activity recovery from Cr(VI) inhibition.

    ● Extracellular Cr(VI) reduction to less toxic Cr(III) was the dominant mechanism.

    The hexavalent chromium (Cr(VI)) would frequently impose inhibition to anaerobic ammonium oxidation (anammox) process, hindering the efficiency of nitrogen removal in wastewater treatment. Hydrazine (N2H4), which is an intermediate product of anammox, participates in intracellular metabolism and extracellular Cr(VI) reduction. However, the roles of N2H4-induced intracellular metabolism and extracellular reduction in nitrogen removal under Cr(VI) stress remain unclear. The addition of 3.67 mg/L of N2H4 increased the anammox activity by 17%. As an intermediate, N2H4 enhanced anammox metabolism by increasing the heme c content and electron transfer system activity. As a reductant, N2H4 accelerated the reduction of c-Cyts-mediated extracellular Cr(VI) to the less toxic Cr(III). Extracellular Cr(III) accounts for 74% of the total Cr in a Cr(VI)-stressed anammox consortia. These findings highlight that N2H4-induced extracellular Cr(VI) reduction is the dominant mechanism for the survival of anammox consortia. We also found that N2H4 increased the production of extracellular polymeric substances to sequester excessive Cr(VI) and produced Cr(III). Taken together, the study findings suggest a potential strategy for enhancing nitrogen removal from ammonium-rich wastewater contaminated with Cr(VI).

    Jinbo Wang, Jiaping Wang, Wei Nie, Xuguang Chi, Dafeng Ge, Caijun Zhu, Lei Wang, Yuanyuan Li, Xin Huang, Ximeng Qi, Yuxuan Zhang, Tengyu Liu, Aijun Ding

    ● The emission reduction causes significant change in organic aerosol composition.

    ● The atmospheric oxidizing capacity improved during emission reduction.

    ● The mixed oxygenated organic aerosol contributed higher during emission reduction.

    Organic aerosol (OA) is a major component of atmospheric particulate matter (PM) with complex composition and formation processes influenced by various factors. Emission reduction can alter both precursors and oxidants which further affects secondary OA formation. Here we provide an observational analysis of secondary OA (SOA) variation properties in Yangtze River Delta (YRD) of eastern China in response to large scale of emission reduction during Chinese New Year (CNY) holidays from 2015 to 2020, and the COVID-19 pandemic period from January to March, 2020. We found a 17% increase of SOA proportion during the COVID lockdown. The relative enrichment of SOA is also found during multi-year CNY holidays with dramatic reduction of anthropogenic emissions. Two types of oxygenated OA (OOA) influenced by mixed emissions and SOA formation were found to be the dominant components during the lockdown in YRD region. Our results highlight that these emission-reduction-induced changes in organic aerosol need to be considered in the future to optimize air pollution control measures.

    Xuejun Long, Jun Luo, Zhenxing Zhong, Yanxu Zhu, Chunjie Zhang, Jun Wan, Haiyan Zhou, Beiping Zhang, Dongsheng Xia

    ● Synergistic removal of carbamazepine (CBZ) was obtained in the FeS-S2O82– process.

    ● SO4•− and •OH were identified as the main radicals in the FeS-S2O82– process.

    ● Heterogeneous oxidation would be dominant first, followed by homogeneous reaction.

    ● Degradation pathway of CBZ was well elucidated by experiments and DFT calculations.

    As persulfate (S2O82–) is being increasingly used as an alternative oxidizing agent, developing low-cost and eco-friendly catalysts for efficient S2O82– activation is potentially useful for the treatment of wastewater containing refractory organic pollutant. In this study, the degradative features and mechanisms of carbamazepine (CBZ) were systematically investigated in a novel FeS- S2O82– process under near-neutral conditions. The results exhibited that CBZ can be effectively eliminated by the FeS-S2O82– process and the optimal conditions were: 250 mg/L FeS, 0.5 mmol/L S2O82–, and pH = 6.0. The existence of Cl (1 and 50 mmol/L) has little influence on the CBZ elimination, while both HCO3 and HPO42− (1 and 50 mmol/L) significantly suppressed the CBZ removal in the FeS-S2O82– process. CBZ could be degraded via a radical mechanism in the FeS-S2O82– process, the working radical species (i.e., SO4•− and •OH) were efficiently formed via the promoted decomposition of S2O82– by the surface Fe2+ on the FeS and the dissolved ferrous ions in solution. Based on the identified oxidized products and Fukui index calculations, a possible degradation pathway of CBZ was speculated. More importantly, a two-stage oxidation mechanism of CBZ elimination was speculated in the FeS-S2O82– process, the activation of S2O82– by the surface-active Fe(II) of FeS dominated in the initial 5 min, while homogeneous oxidation reactions played more essential parts than others in the following reaction stage (5–60 min). Overall, this study demonstrated that the FeS-S2O82– process is capable of removing CBZ from water efficiently.

    Tongyao Ju, Siyu Han, Fanzhi Meng, Li Lin, Jinglin Li, Kailun Chen, Jianguo Jiang

    ● Both amorphous and crystalline silicon are completely separated from coal fly ash.

    ● Porous silica is synthesized out of coal fly ash.

    ● No residues is produced during the whole synthesis process.

    ● The one-step method to synthesize silica don’t need long-time reaction and aging.

    Ordered mesoporous silica materials exhibit enormous potential in industrial production. Since coal fly ash (CFA) is abundant in Si, it has become a green and promising way to utilize CFA by synthesizing porous silica materials. However, the stable crystalline structure of CFA limits the extraction of Si, and the residue is generated during the process of extracting Si. In this work, we proposed a no-residue method to synthesize ordered mesoporous silica out of CFA. Sodium carbonate (Na2CO3) was used to reconstruct the crystals of the CFA, and the calcined mixture then directly reacted with the precipitators. This method combined the process of Si extraction and porous material synthesis. In this method, no residue was generated and the silicon in both amorphous and crystalline phases of CFA was fully utilized. By this method, the extraction efficiency of Si was increased from 31.75% to nearly 100%. The as-synthesized mesoporous silica had a highly-ordered pore structure with a space group of la-3d, a surface area of 663.87 m2/g, a pore volume of 0.41 cm3/g, and an average pore diameter of 2.73 nm. The mechanism of crystalline transformation and material structure formation were systematically studied. This method provides a new idea to dispose of CFA and synthesize porous silica materials.

    Sajjad Haider, Rab Nawaz, Muzammil Anjum, Tahir Haneef, Vipin Kumar Oad, Salah Uddinkhan, Rawaiz Khan, Muhammad Aqif

    ● 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.

    Yin Liu, Matthias C. Rillig, Quan Liu, Jingjing Huang, Muhammad Amjad Khan, Xiaohui Li, Qin Liu, Qingqing Wang, Xuesong Su, Linyi Lin, Yang Bai, Genmao Guo, Yi Huang, Yong Sik Ok, Shan Hu, Junfeng Wang, Honggang Ni, Qing Huang

    ● Microplastic (MP) abundance in soil of China was highly heterogeneous.

    ● MP abundance was higher near large rivers and central land affected by monsoons.

    ● MP abundance was correlated with longitude, mulching film, and average temperature.

    ● Factors suitable for predicting MP pollution using models were discussed.

    Microplastics (MPs) are found worldwide in high abundance, posing a potential threat to ecosystems. Despite the ubiquity of MPs in the environment, very little is known about the regional distribution of MPs and underlying factors affecting this distribution in the field, which likely include human activity, but also features of the environment itself. Here, out of a total of 1157 datapoints investigated in 53 Chinese studies, 9.68% datapoints were removed as outliers in the heterogeneity analysis. This review revealed that the abundance of MPs was highly heterogeneous. In addition, microplastic (MP) distribution maps based on China demonstrated that the highest abundance of MPs tended to occur near large rivers and central land affected by the intersection of two monsoons. The model-fitting and previous studies showed that MP abundance in China was correlated with longitude, agricultural mulching film usage per capita, temperature, and precipitation. However, due to the heterogeneity of MPs and the low matching degree between the current environmental data and the sampling points, this pattern was not as evident as reported in any single study. Factors affecting the distribution of MPs can not be captured by linear relationships alone, and systematic selection of suitable environmental factors and further model optimization are needed to explore the cause of MP pollution in soil. Overall, this review revealed an uneven distribution of MPs and serves as a reference for model prediction to assess and control plastic pollution in natural soil environments.

    Zirui Zhang, Chenhang Zhang, Huan Liu, Feng Bin, Xiaolin Wei, Running Kang, Shaohua Wu, Wenming Yang, Hongpeng Xu

    ● Catalytic combustion in fluidized bed realizes efficient heat and mass transfer.

    ● Catalytic combustion in fluidized bed reduces the lean combustion limits.

    ● Catalytic combustion and flame combustion can be coupled.

    ● The diffusion/kinetics limited reaction model is suitable for catalytic combustion.

    A micro fluidized bed reactor was used to study the self-sustaining catalytic combustion of carbon monoxide (CO). The Cu1−xCexOy catalyst, as well as the pure CuO and CeO2, are used to investigate the contributing mechanism of different active sites including dispersed CuO and Cu–Ce solid solutions. The ignition temperature (Ti) of CO over these catalysts at a flow rate of 2000 mL/min followed the order: 74 °C (Cu0.5Ce0.5Oy) < 75 °C (Cu0.25Ce0.75Oy) < 84 °C (Cu0.75Ce0.25Oy) < 105 °C (CuO) < 500 °C (CeO2). Furthermore, the lean combustion limits (equivalence ratio ϕ) over these catalysts under the flow rates of 750–3000 mL/min (through fixed, bubbling, and fluidized bed) were also measured, which are Cu0.5Ce0.5Oy < Cu0.25Ce0.75Oy < Cu0.75Ce0.25Oy < CuO < CeO2. The fluidized bed was simulated using the Eulerian two-fluid model (TFM) coupled with a diffusion/kinetic-limited reaction model to evaluate the influence of operation conditions on the self-sustained combustion of CO. The predicted maximum temperature agreed with the experimental measurements, demonstrating the validity of the kinetic model and simulation parameters. The results of catalytic combustion with increasing CO concentrations suggest that the catalytic combustion reaction could co-exist with the flamed combustion. When a high concentration of CO is used, a blue-purple flame caused by CO combustion appears in the upper part of the fluidized bed, indicating that the range of CO-containing exhaust gas purification could be expanded to a larger range using the fluidized-bed catalytic combustion technique.

    Xi Luo, Ao Li, Xue Xia, Peng Liang, Xia Huang

    ● Appreciable H2O2 production rate was achieved in MRCs utilizing NH4HCO3 solutions.

    ● Carbon black outperformed activated carbon as the catalyst for H2O2 production.

    ● The optimum carbon black loading for H2O2 production on air-cathode was 10 mg/cm2.

    ● The optimum number of cell pairs was determined to be three.

    ● A maximum power density of 980 mW/m2 was produced by MRCs with 5 cell pairs.

    H2O2 was produced at an appreciable rate in microbial reverse-electrodialysis cells (MRCs) coupled with thermolytic solutions, which can simultaneously capture waste heat as electrical energy. To determine the optimal cathode and membrane stack configurations for H2O2 production, different catalysts, catalyst loadings and numbers of membrane cell pairs were tested. Carbon black (CB) outperformed activated carbon (AC) for H2O2 production, although AC showed higher catalytic activity for oxygen reduction. The optimum CB loading was 10 mg/cm2 in terms of both the H2O2 production rate and power production. The optimum number of cell pairs was determined to be three based on a tradeoff between H2O2 production and capital costs. A H2O2 production rate as high as 0.99 ± 0.10 mmol/(L·h) was achieved with 10 mg/cm2 CB loading and 3 cell pairs, where the H2O2 recovery efficiency was 52 ± 2% and the maximum power density was 780 ± 37 mW/m2. Increasing the number of cell pairs to five resulted in an increase in maximum power density (980 ± 21 mW/m2) but showed limited effects on H2O2 production. These results indicated that MRCs can be an efficient method for sustainable H2O2 production.

    Chen Zhou, Ermias Gebrekrstos Tesfamariam, Youneng Tang, Ang Li

    ● EPS immobilizes U(VI) via adsorption, bioreduction and desorption.

    ● This work provides a framework to quantify the three immobilization processes.

    ● The non-equilibrium adsorption of U follows pseudo-second-order kinetics.

    ● The equilibrium adsorption of U followed Langmuir and Freundlich isotherms.

    Hexavalent uranium (U(VI)) can be immobilized by various microbes. The role of extracellular polymeric substances (EPS) in U(VI) immobilization has not been quantified. This work provides a model framework to quantify the contributions of three processes involved in EPS-mediated U(VI) immobilization: adsorption, bioreduction and desorption. Loosely associated EPS was extracted from a pure bacterial strain, Klebsiella sp. J1, and then exposed to H2 and O2 (no bioreduction control) to immobilize U(VI) in batch experiments. U(VI) immobilization was faster when exposed to H2 than O2 and stabilized at 94% for H2 and 85% for O2, respectively. The non-equilibrium data from the H2 experiments were best simulated by a kinetic model consisting of pseudo-second-order adsorption (ka = 2.87 × 10−3 g EPS·(mg U)−1·min−1), first-order bioreduction (kb = 0.112 min−1) and first-order desorption (kd = 7.00 × 10−3 min−1) and fitted the experimental data with R2 of 0.999. While adsorption was dominant in the first minute of the experiments with H2, bioreduction was dominant from the second minute to the 50th min. After 50 min, adsorption was negligible, and bioreduction was balanced by desorption. This work also provides the first set of equilibrium data for U(VI) adsorption by EPS alone. The equilibrium experiments with O2 were well simulated by both the Langmuir isotherm and the Freundlich isotherm, suggesting multiple mechanisms involved in the interactions between U(VI) and EPS. The thermodynamic study indicated that the adsorption of U(VI) onto EPS was endothermic, spontaneous and favorable at higher temperatures.

    Xufang Wang, Dongli Guo, Jinna Zhang, Yuan Yao, Yanbiao Liu

    ● A CNT filter enabled effective KMnO4 activation via facilitated electron transfer.

    ● Ultra-fast degradation of micropollutants were achieved in KMnO4/CNT system.

    ● CNT mediated electron transfer process from electron-rich molecules to KMnO4.

    ● Electron transfer dominated organic degradation.

    Numerous reagents have been proposed as electron sacrificers to induce the decomposition of permanganate (KMnO4) by producing highly reactive Mn species for micropollutants degradation. However, this strategy can lead to low KMnO4 utilization efficiency due to limitations associated with poor mass transport and high energy consumption. In the present study, we rationally designed a catalytic carbon nanotube (CNT) membrane for KMnO4 activation toward enhanced degradation of micropollutants. The proposed flow-through system outperformed conventional batch reactor owing to the improved mass transfer via convection. Under optimal conditionals, a > 70% removal (equivalent to an oxidation flux of 2.43 mmol/(h·m2)) of 80 μmol/L sulfamethoxazole (SMX) solution can be achieved at single-pass mode. The experimental analysis and DFT studies verified that CNT could mediate direct electron transfer from organic molecules to KMnO4, resulting in a high utilization efficiency of KMnO4. Furthermore, the KMnO4/CNT system had outstanding reusability and CNT could maintain a long-lasting reactivity, which served as a green strategy for the remediation of micropollutants in a sustainable manner. This study provides new insights into the electron transfer mechanisms and unveils the advantages of effective KMnO4 utilization in the KMnO4/CNT system for environmental remediation.

    Hao Zheng, Jian Cheng, Hung Chak Ho, Baoli Zhu, Zhen Ding, Wencong Du, Xin Wang, Yang Yu, Juan Fei, Zhiwei Xu, Jinyi Zhou, Jie Yang

    ● A study assessing the temperature-injury relationship was conducted among students.

    ● The maximum risks of injury appeared at moderate temperatures.

    ● The temperature effect on outdoor falls was greater in older students.

    Although studies have suggested that non-optimal temperatures may increase the risk of injury, epidemiological studies focusing on the association between temperature and non-fatal injury among children and adolescents are limited. Therefore, we investigated the short-term effect of ambient temperature on non-fatal falls and road traffic injuries (RTIs) among students across Jiangsu Province, China. Meteorological data and records of non-fatal outdoor injuries due to falls and RTIs among students aged 6–17 were collected during 2018–2020. We performed a time-stratified case-crossover analysis with a distributed lag nonlinear model to examine the effect of ambient temperature on the risk of injury. Individual meteorological exposure was estimated based on the address of the selected school. We also performed stratified analyses by sex, age, and area. A total of 57322 and 5455 cases of falls and RTIs were collected, respectively. We observed inverted U-shaped curves for temperature-injury associations, with maximum risk temperatures at 18 °C (48th of daily mean temperature distribution) for falls and 22 °C (67th of daily mean temperature distribution) for RTIs. The corresponding odds ratios (95% confidence intervals) were 2.193 (2.011, 2.391) and 3.038 (1.988, 4.644) for falls and RTIs, respectively. Notably, there was a significant age-dependent trend in which the temperature effect on falls was greater in older students (P-trend < 0.05). This study suggests a significant association between ambient temperature and students’ outdoor falls and RTIs. Our findings may help advance tailored strategies to reduce the incidence of outdoor falls and RTIs in children and adolescents.