Mechanism insight into the formation of H2S from thiophene pyrolysis: A theoretical study

• Possible formation pathways of H₂S were revealed in thiophene pyrolysis. • The influence of hydrogen radicals on thiophene pyrolysis was examined. • Thiophene decomposition starts with hydrogen transfer between adjacent C atoms. • The presence of hydrogen radicals significantly promotes the formation of H₂S. Pyrolysis is an efficient and economical method for the utilization of waste rubber, but the high sulfur content limits its industrial application. Currently, the migration and transformation of the element S during pyrolysis of waste rubber is far from well known. In this work, a density functional theory (DFT) method was employed to explore the possible formation pathways of H₂S and its precursors (radicals HS· and S·) during the pyrolysis of thiophene, which is an important primary pyrolytic product of rubber. In particular, the influence of reactive hydrogen radicals was carefully investigated in the thiophene pyrolysis process. The calculation results indicate that the decomposition of thiophene tends to be initiated by hydrogen transfer between adjacent carbon atoms, which needs to overcome an energy barrier of 312.4 kJ/mol. The optimal pathway to generate H₂S in thiophene pyrolysis involves initial H migration and S-C bond cleavage, with an overall energy barrier of 525.8 kJ/mol. In addition, a thiol intermediate that bears unsaturated C-C bonds is essential for thiophene pyrolysis to generate H₂S, which exists in multiple critical reaction pathways. Moreover, the presence of hydrogen radicals significantly changes the decomposition patterns and reduces the energy barriers for thiophene decomposition, thus promoting the formation of H₂S. The current work on H₂S formation from thiophene can provide some theoretical support to explore clean utilization technologies for waste rubber.     

An all-in-one FeOx-rGO sponge fabricated by solid-phase microwave thermal shock for water evaporation and purification

Developing high-efficiency photothermal seawater desalination devices is of significant importance in addressing the shortage of freshwater. Despite much effort made into photothermal materials, there is an urgent need to design a rapidly synthesized photothermal evaporator for the comprehensive purification of complex seawater. Therefore, we report on all-in-one FeOx-rGO photothermal sponges synthesized via solid-phase microwave thermal shock. The narrow band gap of the semiconductor material F...     

Spatial/temporal variations of elemental carbon, organic carbon, and trace elements in PM10 and the impact of land-use patterns on community air pollution in Paterson, NJ

An urban community PM10 (particulate matter < or = 10 microm in aerodynamic diameter) air pollution study was conducted in Paterson, NJ, a mixed land-use community that is interspersed with industrial, commercial, mobile, and residential land-use types. This paper examines (1) the spatial/temporal variation of PM10, elemental carbon (EC), organic carbon (OC), and nine elements; and (2) the impact of land-use type on those variations. Air samples were collected from three community-oriented locations in Paterson that attempted to capture industrial, commercial, and mobile source-dominated emissions. Sampling was conducted for 24 hr every 6 days from November 2005 through December 2006. Samples were concurrently collected at the New Jersey Department of Environmental Protection-designated air toxics background site in Chester, NJ. PM10 mass, EC, OC, and nine elements (Ca, Cu, Fe, Pb, Mn, Ni, S, Ti, and Zn) that had more than 50% of samples above detection and known sources or are toxic were selected for spatial/temporal analysis in this study. The concentrations of PM10, EC, OC, and eight elements (except S) were significantly higher in Paterson than in Chester (P < 0.05). The concentrations of these elements measured in Paterson were also found to be higher during winter than the other three seasons (except S), and higher on weekdays than on weekends (except Pb). The concentrations of EC, Cu, Fe, and Zn at the commercial site in Paterson were significantly higher than the industrial and mobile sites; however, the other eight species were not significantly different within the city (P > 0.05). These results indicated that anthropogenic sources of air pollution were present in Paterson. The source apportionment confirmed the impact of vehicular and industrial emissions on the PM10 ambient air pollution in Paterson. The multiple linear regression analysis showed that categorical land-use type was a significant predictor for all air pollution levels, explaining up to 42% of the variability in concentration by land-use type only.     

Characterization of atmospheric polycyclic aromatic hydrocarbons in a mixed-use urban community in Paterson, NJ: concentrations and sources

Exposure to ambient polycyclic aromatic hydrocarbons (PAHs) is a potential health concern for communities because many PAHs are known to be mutagenic and carcinogenic. However, information on ambient concentrations of PAHs in communities is very limited. During the Urban Community Air Toxics Monitoring Project, Paterson City, NJ, PAH concentrations in ambient air PM10 (particulate matter < or = 10 microm in aerodynamic diameter) were measured from November 2005 through December 2006 in Paterson, a mixed-use urban community located in Passaic County, NJ. Three locations dominated by industrial, commercial, and mobile sources were chosen as monitoring sites. The comparison background site was located in Chester, NJ, which is approximately 58 km west/southwest of Paterson. The concentrations of all of the individual PAHs at all three Paterson sites were found to be significantly higher than those at the background site (P < 0.05). The PAH profiles obtained from the three sites with different land-use patterns showed that the contributions of heavier PAHs (molecular weight > 202) to the total PAHs were significantly higher at the industrial site than those at the commercial and mobile sites. Analysis of the diagnostic ratios between PAH isomers suggested that the diesel-powered vehicles were the major PAH sources in the Paterson area throughout the year. The operation of industrial facilities and other combustion sources also partially contributed to PAH air pollution in Paterson. The correlation of individual PAH, total PAH, and the correlation of total PAHs with other air co-pollutants (copper, iron, manganese, lead, zinc, elemental carbon, and organic carbon) within and between the sampling sites supported the conclusions obtained from the diagnostic ratio analysis.     

Polybrominated diphenyl ethers in sediments of the Daliao River Estuary, China: levels, distribution and their influencing factors

The concentrations, compositional profiles, possible sources of polybrominated diphenyl ethers (PBDEs) in sediments of the Daliao River Estuary as well as the factors influencing the distribution of PBDEs were investigated. The total concentrations of PBDEs ranged from 0.13 to 1.98 ng g⁻¹ d.w. BDE209 was the dominating congener in all sediment samples, indicating the pollution of PBDEs in the Daliao River Estuary mainly came from the use of deca-BDE commercial mixtures. The intrusion of sea waters promoted the deposition of the colloid-associated PBDEs in the estuary. There were significantly negative correlations between PBDE concentration in sediment with pH value and salinity in the bottom water. The higher river flow in the flood season (summer) obviously accelerated the transport of PBDEs, and thereby increased the risk of PBDE contamination to the deep ocean. Moreover, a positive correlation between TOC and PBDE distributions was observed, suggesting that TOC regulated the distributions of PBDEs in sediments of Daliao River Estuary.     

Hemoglobin (Hb) immobilized on amino-modified magnetic nanoparticles for the catalytic removal of bisphenol A

Catalytic removal of bisphenol A from aqueous solution with hemoglobin immobilized on amino-modified magnetic nanoparticles as an enzyme catalyst was reported. The amino-modified magnetite nanoparticles were firstly prepared by the coprecipitation of Fe²⁺ and Fe³⁺ with NH₃·H₂O and then modified by 3-aminopropyltriethoxysilane. The immobilization process was optimized by examining enzyme concentration, glutaraldehyde concentration, cross-link time, and immobilization time. The optimum conditions for the removal of bisphenol A with immobilized hemoglobin were also investigated. Under the optimality conditions, the removal efficiency of bisphenol A was about 80.3%. The immobilization had a beneficial effect on the stability of hemoglobin and conversions of bisphenol A. According to the proposed breakdown pathway and the intermediates, the enzyme-catalytic removal of bisphenol A by the immobilized hemoglobin is considered to be an effective method.     

Promotion of pyrene degradation in rhizosphere of alfalfa (Medicago sativa L.)

Pot experiment was conducted to evaluate the phytoremediation of pyrene-contaminated soil using alfalfa (Medicago sativa L.). Alfalfa biomasses, microbial viable counts, dehydrogenase activity, residual pyrene concentration and pyrene removal percentage were determined after 60 days of alfalfa growth. The results indicated that pyrene had an inhibitive effect on alfalfa growth, and higher pyrene concentration seriously affected alfalfa growth. In addition, the inhibitive effect on the root was more severe than that on the shoot. When pyrene concentration reached 492 mg kg(-1) in soil, the shoot and root biomasses were only 34% and 22% of those of alfalfa growing in non-spiked soil, respectively. The rhizospheric bacterial and fungi counts were 5.0-7.5 and 1.8-2.3 times higher than those in non-rhizosphere soil, respectively. The residual concentrations of pyrene in the rhizosphere soil were lower than those in the non-rhizosphere soil. After 60 days, 69-85% and 59-80% of spiked pyrene disappeared from the rhizosphere and non-rhizosphere soils, respectively. The removal percentage decreased with increasing pyrene concentration. However, the average removal of pyrene in the rhizosphere soil was 6% higher than that in the non-rhizosphere soil. Therefore, the presence of alfalfa roots was effective in promoting the phytoremediation of freshly added pyrene into the soil.     

Accumulation of Pb, Cd, Cu and Zn in plants and hyperaccumulator choice in Lanping lead-zinc mine area, China

A field survey of higher terrestrial plants growing on Lanping lead-zinc mine, China were conducted to identify species accumulating exceptionally large concentrations of Pb, Cd, Cu and Zn of 20 samples of 17 plant species. Concentrations of Pb and Zn in soil and in plant were higher than that of Cu and Cd. Significant difference was observed among the average concentrations of four heavy metals in plants (except Cd and Cu) and in soil (except Pb and Zn) (P<0.05). For the enrichment coefficient of the four heavy metals in plant, the order of average was Pbtree>herbaceous, and herbaceous grew in soil with the highest concentrations of four heavy metals. In different areas, the concentrations of Pb, Cd, Cu and Zn in plants and soils and enrichment coefficient were different. Plants in Paomaping had more accumulating ability to Pb, Cd and Zn, and plants in Jinfeng River had more accumulating ability to Cu. Six plant species, i.e. S. cathayana, Lithocarpus dealbatus, L. plyneura, Fargesia dura, Arundinella yunnanensis and R. annae in Paomaping, had high accumulation capacity. R. annae in Paomaping had hyperaccumulating capacity to Pb, Cd and Zn, L. plyneura to Pb and Cd, and S. cathayana to Cd, respectively.     

Construction of truncated-octahedral LiMn2O4 for battery-like electrochemical lithium recovery from brine

The extraction of lithium from salt lakes or seawater has attracted worldwide attention because of the explosive growth of global demand for lithium products. The LiMn₂O₄-based electrochemical lithium recovery system is one of the strongest candidates for commercial application due to its high inserted capacity and low energy consumption. However, the surface orientation of LiMn₂O₄ that facilitates Li diffusion happens to be prone to manganese dissolut...     

Transport of bacterial cell (E. coli) from different recharge water resources in porous media during simulated artificial groundwater recharge

• The recharge pond dwelling process induced changes in cell properties. • Cell properties and solution chemistry exerted confounding effect on cell transport. • E. coli cells within different recharge water displayed different spreading risks. Commonly used recharge water resources for artificial groundwater recharge (AGR) such as secondary effluent (SE), river water and rainfall, are all oligotrophic, with low ionic strengths and different cationic compositions. The dwelling process in recharge pond imposed physiologic stress on Escherichia coli (E. coli) cells, in all three types of investigated recharge water resources and the cultivation of E. coli under varying recharge water conditions, induced changes in cell properties. During adaptation to the recharge water environment, the zeta potential of cells became more negative, the hydrodynamic diameters, extracellular polymeric substances content and surface hydrophobicity decreased, while the cellular outer membrane protein profiles became more diverse. The mobility of cells altered in accordance with changes in these cell properties. The E. coli cells in rainfall recharge water displayed the highest mobility (least retention), followed by cells in river water and finally SE cells, which had the lowest mobility. Simulated column experiments and quantitative modeling confirmed that the cellular properties, driven by the physiologic state of cells in different recharge water matrices and the solution chemistry, exerted synergistic effects on cell transport behavior. The findings of this study contribute to an improved understanding of E. coli transport in actual AGR scenarios and prediction of spreading risk in different recharge water sources.