scholarly journals Production of Hydroxyl Radicals From Oxygenation of Simulated AMD In Presence of Extracellular Polymers Substances

2021 ◽  
Author(s):  
Xuewen Zhong ◽  
Fang Liu ◽  
Feifei Fan ◽  
Jian Zhu
Keyword(s):  
Hydroxyl Radicals ◽  
Reaction Mechanisms ◽  
Extracellular Polymeric Substances ◽  
Hydroxyl Groups ◽  
Extracellular Polymers ◽  
Maximum Production ◽  
Moderate Rate ◽  
Abiotic Oxidation

Abstract While the reaction mechanisms Fe(II) abiotic oxidation produce ·OH by CaCO3-induced in AMD are well-documented, little is known about the influence of extracellular polymeric substances (EPS) secreted by microorganisms on Fe(II) oxidation in AMD. Given the recent finding, this study experimently measured the cumulative concentrations of ·OH produced from oxygenation of simulated AMD in the presence of EPS. Results of this study show that the cumulative ·OH increased from 56.75 to 158.70 μM within 24 h at pH 3 with the increase in EPS concentration from 0 to 12 mg/L. An appropriate pH (about 6) and EPS (6 mg/L) concentration were required for the moderate rate of Fe(II) oxidation, corresponding to the maximum production of ·OH. The presence of EPS enhanced the ·OH production from Fe(II) oxidation in simulated AMD under acid conditions. In the presence of EPS, ·OH production is attributed mainly the complexation of Fe(II) with EPS, of which is rich of carboxyl and hydroxyl groups. Besides, the yield of ·OH increased remarkably with the addition of Fe3+. It is most likely that EPS can contribute to reduce Fe(Ⅲ) to Fe(II), which is beneficial to the production of ·OH. The findings reveal from this study supplement the fundamental of ·OH production from Fe(II) oxidation by microorganisms in natural AMD.

Kinetic Study on the Esterification of Hexanoic Acid with N,N-Dialkylamino Alcohols: Evidence for an Activation by Hydrogen Bonding

2006 ◽  
Vol 61 (5) ◽  
pp. 583-588 ◽  
Author(s):  
Stefan Breitenlechner ◽  
Thorsten Bach
Keyword(s):  
Hydrogen Bonding ◽  
Rate Increase ◽  
Order Rate Constant ◽  
Hexanoic Acid ◽  
Hydroxyl Groups ◽  
First Order ◽  
Moderate Rate ◽  
Pseudo First Order ◽  
Related Compounds ◽  
Membered Transition State

The pseudo-first order rate constant for the esterification of hexanoic acid (1) and five different N,N-dialkylamino alcohols (2) was determined in comparison to 1-hexanol (k = 0.67 · 10−5 s−1). The values range from 0.60 · 10−5 s−1 to 9.3 · 10−5 s−1. The data suggest a differing reactivity for structurally related compounds, which is directly correlated to the ability of the corresponding amino alcohol to activate the carboxylic acid by hydrogen bonding. A seven-membered transition state C≠ is postulated for reactions of 2-amino alcohols. The fastest reaction was observed for trans-2-(N,N-dimethylamino) cyclohexanol (2e), in which the amino and the hydroxyl groups are in an almost perfect synperiplanar 1,2-position. Attempts to further enhance the rate of the esterification by the addition of potential catalysts failed. Only Cu(OTf)2 (2.5 mol-%) allowed for a moderate rate increase from 7.5 · 10−5 s−1 (uncatalyzed) to 14.8 · 10−5 s−1 (catalyzed) in the esterification of hexanoic acid (1) with 2-(N,N-dimethylamino)ethanol (2a).

Characterisation of extracellular polymeric substances from different cyanobacterial species and their influence on biocalcification processes

2017 ◽  
Vol 14 (4) ◽  
pp. 254 ◽  
Author(s):  
Xiaomin Li ◽  
Kemeng Luo ◽  
Jinqian Ren ◽  
Xiangrui Wang ◽  
Qian Mu ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Protein Content ◽  
Functional Groups ◽  
Extracellular Polymeric Substances ◽  
Nucleation Site ◽  
Hydroxyl Groups ◽  
Solution Ph ◽  
Cyanobacterial Species ◽  
Sediment Formation ◽  
Global Carbon

Environmental contextExtracellular polymeric substances provide a nucleation site for calcium carbonate and hence are important for bio-calcification processes, with implications for sediment formation and the global carbon cycle. We investigate the calcification potential of polymeric substances produced by five species of cyanobacteria. The results indicate that the protein content and alkaline functional groups of the extracellular polymeric substances may have a significant effect on cyanobacterial calcification. AbstractCyanobacterial calcification plays a crucial role in the formation of freshwater calcium carbonate precipitates, with cyanobacterial extracellular polymeric substances (EPSs) contributing significantly, partly by providing a nucleation site for calcium carbonate. Despite this, cyanobacterial EPS and their effect on calcification processes have not been completely characterised. In the present study, five cyanobacterial species were selected. First, EPS characteristics of these cyanobacterial species were examined, showing that proteins dominated both EPSs released in to solution (REPSs) and cell-surface bound (LEPSs). The major EPS functional groups included acidic groups, such as carboxyl groups, and highly alkaline groups, such as hydroxyl and amino groups. The calcification ability of different cyanobacterial species was found to vary dramatically. Solution pH increased during the calcification process, which was beneficial to the supersaturation of CaCO3, and could affect the calcification potential. Precipitation, however, was positively correlated with EPS protein content and the concentration of basic functional groups, such as amino or hydroxyl groups. These results suggest EPS protein content and alkaline functional groups may have a significant effect on cyanobacterial calcification. The results also provide a potential application in that EPS proteins of cyanobacteria may have beneficial positive applications in the removal of multivalent cations from wastewater.

scholarly journals Study on the cleavage of alkyl-O-aryl bonds by in situ generated hydroxyl radicals on an ORR cathode

RSC Advances ◽  
2017 ◽  
Vol 7 (81) ◽  
pp. 51419-51425 ◽  
Author(s):  
Lei Wang ◽  
Yongmei Chen ◽  
Shuangyan Liu ◽  
Haomin Jiang ◽  
Linan Wang ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Active Sites ◽  
Bond Cleavage ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Phenolic Hydroxyl Groups

˙OH selectively attacks the active sites opposite to phenolic hydroxyl groups and leads to bond-cleavage of ether bonds.

Comparison of extraction methods for quantifying extracellular polymers in biofilms

1999 ◽  
Vol 39 (7) ◽  
pp. 211-218 ◽  
Author(s):  
Xiaoqi Zhang ◽  
Paul L. Bishop ◽  
Brian K. Kinkle
Keyword(s):  
Extraction Method ◽  
Extracellular Polymeric Substances ◽  
Cell Lysis ◽  
Extraction Methods ◽  
The Other ◽  
Protein Yield ◽  
Total Carbohydrate ◽  
Extracellular Polymers ◽  
Sulfate Reducing ◽  
Edta Extraction

Five commonly used extraction methods - regular centrifugation, EDTA extraction, ultracentrifugation, steaming extraction and regular centrifugation with formaldehyde (RCF) - were selected to study their effectiveness and repeatability in extracting extracellular polymeric substances (EPS) from aerobic/sulfate reducing and nitrifying/denitrifying biofilm samples. Biofilm EPS extraction yields were represented by carbohydrate and protein concentrations; the amount of cell lysis during the extractions was indicated by DNA concentration. The results showed that analyzing wash waters is essential in quantifying biofilm EPS; the contribution of this step varied from 8-50% of the total carbohydrate yield, depending on the extraction method. Among the extraction methods, the RCF extraction gave the greatest carbohydrate yield, the steaming extraction gave the greatest protein yield, and the other three extraction methods gave approximately equivalent amounts of carbohydrate and proteins for both types of biofilm. DNA in the EPS was 27 times smaller than in the pellets, indicating no significant cell lysis occurred during the extractions.

A DFT Study Toward the Reaction Mechanisms of TNT With Hydroxyl Radicals for Advanced Oxidation Processes

2016 ◽  
Vol 120 (20) ◽  
pp. 3747-3753 ◽  
Author(s):  
Xi He ◽  
Qun Zeng ◽  
Yang Zhou ◽  
Qingxuan Zeng ◽  
Xianfeng Wei ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Reaction Mechanisms ◽  
Advanced Oxidation Processes ◽  
Advanced Oxidation ◽  
Dft Study ◽  
Oxidation Processes
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