The Sorption of Sulfamethoxazole by Aliphatic and Aromatic Carbons from Lignocellulose Pyrolysis

Massive biomass waste with lignocellulose components can be used to produce biochar for environmental remediation. However, the impact of lignocellulose pyrolysis on biochar structure in relation to the sorption mechanism of ionizable antibiotics is still poorly understood. In this paper, diverse techniques including thermogravimetric analysis and 13C nuclear magnetic resonance were applied to investigate the properties of biochars as affected by the pyrolysis of cellulose and lignin in feedstock. Cellulose-derived biochars possessed more abundant groups than lignin-derived biochars, suggesting the greater preservation of group for cellulose during the carbonization. Higher sorption of sulfamethoxazole (SMX) was also observed by cellulose-derived biochars owing to hydrogen bond interaction. Sorption affinity gradually declined with the conversion aliphatic to aromatic carbon, whereas the enhanced specific surface area (SSA) subsequently promoted SMX sorption as evidenced by increased SSA-N2 and SSA-CO2 from 350 to 450 °C. The decreased Kd/SSA-N2 values with increasing pH values implied a distinct reduction in sorption per unit area, which could be attributed to enhanced electrostatic repulsion. This work elucidated the role of carbon phases from thermal conversion of lignocellulose on the sorption performance for sulfonamide antibiotics, which will be helpful to the structural design of carbonaceous adsorbents for the removal of ionizable antibiotics

Urban Flood Loss Estimation and Evacuation Design Based on a 500-Year Extreme Flood Event in Syracuse City

To understand the potential risk of flooding in Syracuse City, New York State, USA, this research attempted to accomplish the flood hazard assessment for a simulated 500-year flood event in the downstream floodplain of Onondaga Creek within Syracuse. Based on the commonly used category of flood damages, the flood damage of Syracuse was divided into loss of buildings and loss of population. The results showed that the city’s center would have the highest damage rate for buildings and a total of 1139 buildings would be inundated, of which 326 buildings would be severely damaged by more than 80%. Furthermore, about 7390 people would be directly affected by the flood event, among which approximately 900 people might lose their lives. Communities near Onondaga Creek were assigned designated evacuation shelters based on the accessibility and distance to the shelters. The shortest available evacuation routes were calculated. More shelters should be provided in the central downtown area, with its large population, and distributed along the western bank of Onondaga Creek. This research offered a first approximate flood loss estimation that might lead to more attention and studies concerning a potential flood hazard in the future. It also provided science-based guidelines for city authorities to refer to in practical flood hazard mitigation

Synergistic effects and mechanisms of hydroxyl radical-mediated oxidative degradation of sulfamethoxazole by Fe(II)-EDTA catalyzed calcium peroxide: Implications for remediation of antibiotic-contaminated water

In this study, a modified Fenton system using calcium peroxide (CaO2) powder, as an effective source of hydrogen peroxide (H2O2), for the degradation of sulfamethoxazole (SMX) in aqueous solution was investigated. Our results indicated that degradation of SMX in Fe(II)-EDTA catalyzed CaO2 system was readily more efficient than in Fe(II) catalyzed CaO2 system. The SMX degradation efficiency was found maximum at pH 6.0 and SMX degradation was suppressed as the initial solution pH was increased. Nevertheless overall removal efficiency in this system was favorable near to neutral pH. In addition, it was observed that the higher bicarbonates (HCO3-) contents had a considerable scavenging ability to SMX degradation while low concentration exhibited auspicious role. The presence of chlorides (Cl-), nitrates (NO3-), sulfates (SO42-), and humic acid (HA) could improve SMX removal in this Fenton-like system. Furthermore, chemical probe and radical scavenging activity confirmed the formation of hydroxyl (HO center dot) and superoxide (O-2(-)center dot) radicals, and also described that the SMX degradation was predominantly due to the HO center dot-induced oxidative destruction. Electron paramagnetic resonance (EPR) studies for different systems, different pH values and different reaction times were carried out to determine the HO center dot radical intensities. EPR results showed that HO center dot intensities were higher in Fe(II)-EDTA catalyzed CaO2 system, at pH 6.0 and at 90 s reaction time, respectively. Intermediate products of SMX were identified and possible mechanism of SMX degradation was suggested. In conclusion, this work provided comprehensive knowledge for the use of Fe(II)-EDTA catalyzed CaO2 system for remediation of SMX contaminated sites

Mechanistic insights into the reactive radicals-assisted degradation of sulfamethoxazole via calcium peroxide activation by manganese-incorporated iron oxide-graphene nanocomposite: Formation of radicals and degradation pathway

In this study, fabrication of manganese-incorporated iron oxide-graphene nanocomposite (rGO-FMBO) was reported for the efficient activation of CaO2 and generation of reactive radicals for the degradation of sulfamethoxazole (SMX). The effects of different systems, catalyst dosage, oxidant dosage, different pH and different reaction time on the degradation of SMX by rGO-APTMS-FMBO/CaO2 as well as the production of free radicals were also studied. Electron paramagnetic resonance (EPR) technique was used to detect and identify the radical species in this oxidation system and these radicals were further confirmed by scavenging studies with the addition of isopropanol (IPA) and methyl viologen (MV2+). The results indicated that the CaO2 could be activated by rGO-APTMS-FMBO efficiently for the effective degradation of SMX at neutral pH (P <= 0.01). The mechanism of the activation of CaO2 by rGO-APTMS-FMBO was that carbon dioxide radicals (CO2 center dot-) generated by rGOAPTMS-FMBO could activate the Ca0 2 to produce more hydroxyl radicals (HO center dot), which favored the SMX degradation. EPR studies showed that three types of free radicals HO center dot, CO2 center dot-, and CH3 center dot were generated and the radical intensities were much higher in rGO-APTMS-FMBO/CaO2 system. Both increased pH and reaction time led to the production of more CO2 center dot-, which activated the CaO2 to give more HO center dot to degrade SMX. Transformation products/intermediates of SMX were determined and potential mechanism and degradation pathway were proposed. The findings of this study provide new insights into the mechanism of heterogeneous catalysis based on CaO2 activated by rGO-APTMS-FMBO and the reactivity of this oxidation system toward environmental contaminants

Size-dependent cytotoxicity of silver nanoparticles to Azotobacter vinelandii: Growth inhibition, cell injury, oxidative stress and internalization.

The influence of nanomaterials on the ecological environment is becoming an increasingly hot research field, and many researchers are exploring the mechanisms of nanomaterial toxicity on microorganisms. Herein, we studied the effect of two different sizes of nanosilver (10 nm and 50 nm) on the soil nitrogen fixation by the model bacteria Azotobacter vinelandii. Smaller size AgNPs correlated with higher toxicity, which was evident from reduced cell numbers. Flow cytometry analysis further confirmed this finding, which was carried out with the same concentration of 10 mg/L for 12 h, the apoptotic rates were20.23% and 3.14% for 10 nm and 50 nm AgNPs, respectively. Structural damage to cells were obvious under scanning electron microscopy. Nitrogenase activity and gene expression assays revealed that AgNPs could inhibit the nitrogen fixation of A. vinelandii. The presence of AgNPs caused intracellular reactive oxygen species (ROS) production and electron spin resonance further demonstrated that AgNPs generated hydroxyl radicals, and that AgNPs could cause oxidative damage to bacteria. A combination of Ag content distribution assays and transmission electron microscopy indicated that AgNPs were internalized in A. vinelandii cells. Overall, this study suggested that the toxicity of AgNPs was size and concentration dependent, and the mechanism of antibacterial effects was determined to involve damage to cell membranes and production of reactive oxygen species leading to enzyme inactivation, gene down-regulation and death by apoptosis

Immobilization of Trametes Versicolor laccase on Cu-alginate beads for biocatalytic degradation of bisphenol A in water: Optimized immobilization, degradation and toxicity assessment

The present work investigated the immobilization of laccase (Trametes versicolor) on Cu-alginate beads by entrapment method and its utilization to degrade bisphenol A (BPA) in aqueous medium. The immobilized laccase demonstrated higher storage stability as compared to free enzyme. Box-Behnken experimental design was used to optimize the immobilization conditions (sodium alginate concentration, CuSO4 molarity, and hardening time). The optimal conditions were found to be 3% sodium alginate concentration (W/V), 0.141 mM CuSO4 and 90 min hardening time. Experimental data exhibited that immobilized laccase (0.5 g) could degrade 96.12% of BPA (10 mg/L) at pH 5.0, 30°C, 150 rpm and 1 h of reaction. The degradation products of BPA were identified by LC-MS analysis; hence the degradation pathways were suggested. The toxicity of BPA products was judged by phytotoxicity test. Immobilized laccase could also degrade BPA in real water, hence could be considered as an efficient candidate for removing BPA in water.This work was financially supported by the National Key Research and Development Program of China (2019YFC1805203), the National Science Foundation of China (41907314, 42077123) and the University Synergy Innovation Program of Anhui Province (GXXT-2021-061).Peer reviewe

Optimized degradation of bisphenol A by immobilized laccase from Trametes versicolor using Box-Behnken design (BBD) and artificial neural network (ANN)

This study represents one of the first attempts towards bisphenol A (BPA) degradation by Trametes versicolor laccase immobilized on Ba-alginate beads. The effect of input variables including temperature (20–40 °C), BPA concentration (2–10 mg/L) and time (10–90 min) were studied using Box-Behnken design (BBD) and artificial neural network (ANN). The maximum BPA degradation of 84.34% was obtained when the temperature was 40 °C, BPA concentration 2 mg/L and time 50 min, which was accurately predicted by BBD (83.48%) and ANN (84.33%), proving the accuracy of prediction for both models. The values of R2 and MSE for BBD were found to be 0.98, 9.88, while for ANN were 0.97, 38.25, respectively. Based on higher R2 value and lower MSE, BBD was slightly better than ANN. The immobilized laccase showed higher storage stability than free laccase by retaining 68.64% and 44.62% of their activity at the same experimental conditions. Furthermore, BPA transformation was confirmed by Fourier-transform infrared spectroscopy (FTIR) analysis. GC-MS had detected the oxidative degradation products from BPA. Results showed that Ba-alginate immobilized laccase could be a promising biocatalyst in treating organic pollutants.This work was financially supported by the National Key Research and Development Program of China (2019YFC1805203), the National Natural Science Foundation of China (41907314, 42077123) and the University Synergy Innovation Program of Anhui Province (GXXT-2021-061)

The importance of evaluating metal exposure and predicting human health risks in urban-periurban environments influenced by emerging industry

The human population boom, urbanization and rapid industrialization have either directly or indirectly resulted in the serious environmental toxification of the soil-food web by metal exposure from anthropogenic sources in most of the developing industrialized world. The present study was conducted to analyze concentrations of Cd, Cr, Cu, Mn, Ni, Pb, and Zn in soil and vegetables in the urban-periurban areas influenced by emerging industry. Vegetables and their corresponding soil samples were collected and analyzed for heavy metals contents from six random sites. According to the results, the potential health risks from metals to the local communities were assessed by following the methodology described by the US-EPA. In general, the total non-carcinogenic risks were shown to be less than the limits set by the US-EPA. However, the potential risk of developing carcinogenicity in humans over a lifetime of exposure could be increased through the dietary intake of Cd, Cr and Ni. In some cases, Pb was also marginally higher than the safe level. It was concluded that some effective remedial approaches should be adopted to mitigate the risks of Cd, Cr, Ni and Pb in the study area because these metal levels have exceeded the safe limits for human health. However, new studies on gastrointestinal bioaccessibility in human are required to heighten our understanding about metals exposure and health risk assessment. (C) 2016 Elsevier Ltd. All rights reserved