from # All Medicine by Alexandros G. Sfakianakis via Alexandros G.Sfakianakis on Inoreader https://ift.tt/2I4TuqG
Aqueous natural organic matter (NOM) contains different types of functional groups (carboxylic, phenolic, sulfidic, etc.), and hence could change the speciation of metals in environmental systems. This work is a proof-of-concept study on the interaction of three metals (Cu, Co, and Cs) with NOM using fluorescence spectroscopy. The specific aim was to determine the conditional stability constants for these three metals with NOM optical components, obtained from the quenching of fluorescence signals. Three contrasting water types were sampled in Northern Ontario: a pristine source (Cross Rd.), an urban-impacted source (Junction Creek), and an industrially impacted creek (Copper Cliff creek). In this investigation, Cu2+ was used as a benchmark, whereas Co2+ and Cs+ analyses were novel applications of this technique. Humic-like (H-like; terrestrial and microbial), fulvic-like (F-like), and protein-like (P-like) fluorescence components were found in various proportions at the three sampling sites. For these samples, the fluorescence signals of the H-, F-, and P-like components were quenched upon additions of Cu2+. The computed conditional stability constants (as log Kc) ranged from 4.46 to 6.06. In contrast, Kc values with Co2+ were measurable only for the two H-like components of the pristine sample (log Kc 3.02–4.05). Cesium (Cs+) induced quenching only for the P-like component at the industrial-impacted site (log Kc 4.82–5.03). While this study corroborates earlier reports that Cu2+-NOM interactions can be measured by fluorescence, we are showing for the first time a direct chemical interaction of Co2+ and Cs+ with specific NOM components, as reported by fluorescence quenching.
from # All Medicine by Alexandros G. Sfakianakis via Alexandros G.Sfakianakis on Inoreader https://ift.tt/2KbfCfo
Hexavalent chromium is a highly toxic metal that can enter drinking water sources. Chitosan, which contains amino and hydroxyl functional groups, is considered an appropriate candidate to remove heavy metals through absorption. In this study, a novel adsorbent, magnetic nanoparticles of chitosan modified with polyhexamethylene biguanide (Ch-PHMB NPs) was synthesized and was used to successfully remove chromium from aqueous solution. Quadratic models with independent variables including pH, adsorbent dosage, time, and the initial concentration of chromium were proposed through RSM to describe the behavior of both magnetic chitosan (M-Ch) and Ch-PHMB NPs in Cr(VI) removal. Optimized models with adjusted R2 values of 0.8326 and 0.74 for M-Ch and Ch-PHMB NPs were developed. Cr(VI) removal from aqueous solution by both absorbents followed pseudo-second-order kinetics. The experimental data were best fitted to the Temkin and Freundlich models for M-Ch and Ch-PHMB NPs, respectively. M-Ch and Ch-PHMB NPs can effectively remove the hexavalent chromium from aqueous solution with pH above 7. Ch-PHMB NPs have higher removal efficiency than M-Ch, removing up to 70% of Cr(VI) from aqueous solution. However, toxicity evaluation on Daphnia magna revealed that Ch-PHMB NPs was more toxic than M-Ch nanoparticles.
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“Mummy, what happens after we die?” Many parents have been asked this kind of question, and it is often difficult to know how best to reply. Should you be open about your own beliefs – whether they are religious, agnostic or atheist? And is it OK to sugarcoat? Recent research in developmental psychology provides some advice.
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Researchers at The University of Texas at Arlington have found that 98 percent of veterans participating in the University’s Artopia program consider that art therapy helped them cope with service-related trauma or disability. An equal percentage reported that art therapy helped them cope with everyday life.
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A new study on second language learning has recently taken the media by storm. A range of headlines – from the BBC to the Daily Mail and The Guardian – all trumpeted the depressing message that it’s impossible to become fluent in a foreign language after around age ten. All of these reports dramatically misrepresented the findings from the study, and the message they sent is flat-out wrong.
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Is self-control something you can acquire, like a new language or a taste for opera? Or is it one of those things you either have or don’t, like fashion sense or a knack for telling a good joke?
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