Graphitic carbon nitride/biochar composite synthesized by a facile ball-milling method for the adsorption and photocatalytic degradation of enrofloxacin

In order to enhance the removal performance of graphitic carbon nitride (g-C₃N₄) on organic pollutant, a simultaneous process of adsorption and photocatalysis was achieved via the compounding of biochar and g-C₃N₄. In this study, g-C₃N₄ was obtained by a condensation reaction of melamine at 550°C. Then the g-C₃N₄/biochar composites were synthesized by ball milling biochar and g-C₃N₄ together, which was considered as a simple, economical, and green strategy. The characterization of resulting g-C₃N₄/biochar suggested that biochar and g-C₃N₄ achieved effective linkage. The adsorption and photocatalytic performance of the composites were evaluated with enrofloxacin (EFA) as a model pollutant. The result showed that all the g-C₃N₄/biochar composites displayed higher adsorption and photocatalytic performance to EFA than that of pure g-C₃N₄. The 50% g-C₃N₄/biochar performed best and removed 45.2% and 81.1% of EFA (10 mg/L) under darkness and light with a dosage of 1 mg/mL, while g-C₃N₄ were 19.0% and 27.3%, respectively. Besides, 50% g-C₃N₄/biochar showed the highest total organic carbon (TOC) removal efficiency (65.9%). Radical trapping experiments suggested that superoxide radical (?O₂^?) and hole (h⁺) were the main active species in the photocatalytic process. After 4 cycles, the composite still exhibited activity for catalytic removal of EFA.     

Combined pollution of arsenic and Polymyxin B enhanced arsenic toxicity and enriched ARG abundance in soil and earthworm gut microbiotas

Polymyxin B (PMB) is considered as the last line of antibiotic defense available to humans. The environmental effects of the combined pollution with PMB and heavy metals and their interaction mechanisms are unclear. We explored the effects of the combined pollution with PMB and arsenic (As) on the microbial composition of the soil and in the earthworm gut, as well as the spread and transmission of antibiotic resistance genes (ARGs). The results showed that, compared with As alone, the combined addition of PMB and As could significantly increase the bioaccumulation factor and toxicity of As in earthworm tissues by 12.1% and 16.0%, respectively. PMB treatment could significantly increase the abundance of Actinobacteria in the earthworm gut (from 35.6% to 45.2%), and As stress could significantly increase the abundance of Proteobacteria (from 19.8% to 56.9%). PMB and As stress both could significantly increase the abundance of ARGs and mobile genetic elements (MGEs), which were positively correlated, indicating that ARGs might be horizontally transferred. The inactivation of antibiotics was the main resistance mechanism that microbes use to resist PMB and As stress. Network analysis showed that PMB and As might have antagonistic effects through competition with multi-drug resistant ARGs. The combined pollution by PMB and As significantly promoted the relative abundance of microbes carrying multi-drug resistant ARGs and MGEs, thereby increasing the risk of transmission of ARGs. This research advances the understanding of the interaction mechanism between antibiotics and heavy metals and provides new theoretical guidance for the environmental risk assessment and combined pollution management.     

Spatial variations in CO2 fluxes in a subtropical coastal reservoir of Southeast China were related to urbanization and land-use types

Carbon dioxide (CO2) emissions from aquatic ecosystems are important components of the global carbon cycle, yet the CO2 emissions from coastal reservoirs, especially in developing countries where urbanization and rapid land use change occur, are still poorly understood. In this study, the spatiotemporal variations in CO2 concentrations and fluxes were investigated in Wenwusha Reservoir located in the southeast coast of China. Overall, the mean CO2 concentration and flux across the whole reservoir were 41.85 ± 2.03 µmol/L and 2.87 ± 0.29 mmol/m2/h, respectively, and the reservoir was a consistent net CO2 source over the entire year. The land use types and urbanization levels in the reservoir catchment significantly affected the input of exogenous carbon to water. The mean CO2 flux was much higher from waters adjacent to the urban land (5.05 ± 0.87 mmol/m2/hr) than other land use types. Sites with larger input of exogenous substance via sewage discharge and upstream runoff were often the hotspots of CO2 emission in the reservoir. Our results suggested that urbanization process, agricultural activities, and large input of exogenous carbon could result in large spatial heterogeneity of CO2 emissions and alter the CO2 biogeochemical cycling in coastal reservoirs. Further studies should characterize the diurnal variations, microbial mechanisms, and impact of meteorological conditions on reservoir CO2 emissions to expand our understanding of the carbon cycle in aquatic ecosystems.     

Enhanced catalytic oxidation of 2,4-dichlorophenol via singlet oxygen dominated peroxymonosulfate activation on CoOOH@Bi2O3 composite

• Bi₂O₃ cannot directly activate PMS. • Bi₂O₃ loading increased the specific surface area and conductivity of CoOOH. • Larger specific surface area provided more active sites for PMS activation. • Faster electron transfer rate promoted the generation of reactive oxygen species. • ¹O₂ was identified as dominant ROS in the CoOOH@Bi₂O₃/PMS system. Cobalt oxyhydroxide (CoOOH) has been turned out to be a high-efficiency catalyst for peroxymonosulfate (PMS) activation. In this study, CoOOH was loaded on bismuth oxide (Bi₂O₃) using a facile chemical precipitation process to improve its catalytic activity and stability. The result showed that the catalytic performance on the 2,4-dichlorophenol (2,4-DCP) degradation was significantly enhanced with only 11 wt% Bi₂O₃ loading. The degradation rate in the CoOOH@Bi₂O₃/PMS system (0.2011 min⁻¹) was nearly 6.0 times higher than that in the CoOOH/PMS system (0.0337 min⁻¹). Furthermore, CoOOH@Bi₂O₃ displayed better stability with less Co ions leaching (16.4% lower than CoOOH) in the PMS system. These phenomena were attributed to the Bi₂O₃ loading which significantly increased the conductivity and specific surface area of the CoOOH@Bi₂O₃ composite. Faster electron transfer facilitated the redox reaction of Co (III) / Co (II) and thus was more favorable for reactive oxygen species (ROS) generation. Meanwhile, larger specific surface area furnished more active sites for PMS activation. More importantly, there were both non-radical (¹O₂) and radicals (SO₄⁻•, O₂⁻•, and OH•) in the CoOOH@Bi₂O₃/PMS system and ¹O₂ was the dominant one. In general, this study provided a simple and practical strategy to enhance the catalytic activity and stability of cobalt oxyhydroxide in the PMS system.     

Dual-reaction-center catalytic process continues Fenton’s story

• Dual-reaction-center (DRC) system breaks through bottleneck of Fenton reaction. • Utilization of intrinsic electrons of pollutants is realized in DRC system. • DRC catalytic process well continues Fenton’s story. Triggered by global water quality safety issues, the research on wastewater treatment and water purification technology has been greatly developed in recent years. The Fenton technology is particularly powerful due to the rapid attack on pollutants by the generated hydroxyl radicals (•OH). However, both heterogeneous and homogeneous Fenton/Fenton-like technologies follow the classical reaction mechanism, which depends on the oxidation and reduction of the transition metal ions at single sites. So even after a century of development, this reaction still suffers from its inherent bottlenecks in practical application. In recent years, our group has been focusing on studying a novel heterogeneous Fenton catalytic process, and we developed the dual-reaction-center (DRC) system for the first time. In the DRC system, H₂O₂ and O₂ can be efficiently reduced to reactive oxygen species (ROS) in electron-rich centers, while pollutants are captured and oxidized by the electron-deficient centers. The obtained electrons from pollutants are diverted to the electron-rich centers through bonding bridges. This process breaks through the classic Fenton mechanism, and improves the performance and efficiency of pollutant removal in a wide pH range. Here, we provide a brief overview of Fenton’s story and focus on combing the discovery and development of the DRC technology and mechanism in recent years. The construction of the DRC and its performance in the pollutant degradation and interfacial reaction process are described in detail. We look forward to bringing a new perspective to continue Fenton’s story through research and development of DRC technology.     

核桃果皮炭粉对3种重金属离子吸附的影响

采用均匀设计的实验方法,研究了2种核桃果皮炭粉(提取水溶性混合物和未提取水溶性混合物的核桃皮炭粉)对Cr、Cu和Cd等重金属离子的吸附最优条件以及对3种离子吸附的影响因素。结果表明,核桃皮炭粉对Cr(Ⅵ)、Cd2+和Cu2+的吸附最优条件为:pH=4,温度为60℃,浓度为150μg/mL,吸附剂用量为2.4 g,时间为120 min;pH=4.5,温度为30℃,浓度为180μg/mL,吸附剂用量为5.4 g,时间为60 min;pH=5,温度为80℃,浓度为210μg/mL,吸附剂用量为0.4 g,时间为100 min;pH和Cr(Ⅵ)浓度增大,不利于2种吸附剂对Cr(Ⅵ)的吸附;pH和温度增大,不利于2种吸附剂对Cu2+的吸附;温度和吸附剂用量增加,有利于2种吸附剂对Cd2+的吸附。未提取水溶性混合物比提取水溶性混合物的核桃果皮炭粉对3种金属的吸附显著。2种吸附剂的吸附率均表现为Cr>Cd>Cu。     

Shewanellasp．XB缺氧反硝化降解苯酚

苯酚的生物降解一直受到关注。以苯酚为惟一电子供体,研究了Shewanellasp．XB对苯酚的缺氧降解特性。研究结果表明,在反硝化条件下,当C／N为13．3时,苯酚可以完全降解,NO2--N积累量很少。另外,当加入氧化还原介体,如核黄素3μmol／L、AQDS0．01mmol／L、AQS0．05mmol／L和LQ0．01mmol／L时,苯酚降解速率分别为不加介体时的1．45、1．77、1．67和1．63倍。当以氯化铵代替硝酸盐时,苯酚也能进行厌氧发酵降解。另外,菌株XB反硝化降解苯酚可能是厌氧和好氧降解的混合过程。     

Shewanella sp.XB缺氧反硝化降解苯酚

苯酚的生物降解一直受到关注。以苯酚为惟一电子供体,研究了Shewanella sp.XB对苯酚的缺氧降解特性。研究结果表明,在反硝化条件下,当C/N为13.3时,苯酚可以完全降解,NO-2-N积累量很少。另外,当加入氧化还原介体,如核黄素3μmol/L、AQDS 0.01 mmol/L、AQS 0.05 mmol/L和LQ 0.01 mmol/L时,苯酚降解速率分别为不加介体时的1.45、1.77、1.67和1.63倍。当以氯化铵代替硝酸盐时,苯酚也能进行厌氧发酵降解。另外,菌株XB反硝化降解苯酚可能是厌氧和好氧降解的混合过程。     

Anthropogenic pollution and variability of manganese in alluvial sediments of the Yellow River,Ningxia, northwest China

Heavy metal pollution of sediments is a global concern and can be a serious problem in heavily industrialized parts of the world. Pollution by manganese is particularly common due to its ubiquitous natural occurrence, ease of mobilization, and extensive association with industry. In Ningxia, China, manganese pollution of Yellow River alluvial sediments was assessed by comparing manganese concentrations in 35 sediment samples with background values derived from similar sediments obtained at sites considered remote from potential sources of contamination. Natural background values of manganese were found to range from 192 to 323 mg/kg for surface sediments, and from 220 to 325 and 283 to 394 mg/kg for subsurface sediments at depths of 45–50 and 95–100 cm, respectively. In the study area, manganese content ranged from 565 to 1,363 mg/kg, indicating anthropogenic pollution extending to a depth of at least 1 m in the study area. All 35 samples were found to exceed the threshold effect concentration (TEC) of 460 mg/kg, below which adverse effects on sediment-dwelling organisms are not expected to occur, and one sample (T12) was found to exceed the probable effect concentration (PEC) of 1,100 mg/kg. PEC defines the threshold above which adverse effects are likely to be observed. Variogram analysis of the surface sediment manganese data revealed adherence to a Gaussian model, and ordinary kriging was used to generate a manganese distribution map. Analysis of the high nugget effect ratio indicates high, small-scale variations that are consistent with potential emissions from an adjacent electrolytic manganese plant.     

Trichloroethylene degradation by PVA-coated calcium peroxide nanoparticles in Fe(II)-based catalytic systems: enhanced performance by citric acid and nanoscale iron sulfide

Environmental Science and Pollution Research - In this study, the enhanced trichloroethylene (TCE) degradation performance was investigated by polyvinyl alcohol coated calcium peroxide...