The chemistry of ultrasonic degradation of organic compounds

The destruction of toxic organic molecules using advanced oxidation processes (AOPs) is a potent tool for pollution control and environmental protection. Ultrasound is a convenient and effective method of generating hydroxyl radicals which is the key oxidant in AOPs. This review describes the use of ultrasound and associated chemical reactions, with and without additives, as a powerful means of remediating water contaminated with organic pollutants. After a brief introduction to ultrasound and sonochemistry, their application for the oxidation of polycyclic aromatic hydrocarbons, phenol and substituted phenols is considered. Next is the decomposition of chlorinated phenols, and other chlorinated organics, then removal of recalcitrant smaller organic molecules. A discussion follows of recent work that has investigated the effects of initial concentration of substrates; the use of different ultrasonic frequencies; the inclusion of oxidising species, inorganic particles, or salts and their contribution to enhanced degradation. Finally, brief comments are made on the status of ultrasound as an AOP treatment

Advanced Fenton processing of aqueous phenol solutions:a continuous system study including sonication effects

Our previous report based on a batch reactor system for the Advanced Fenton Process (AFP) showed that pH, hydrogen peroxide and the organic substances treated are among the most important factors affecting the oxidation efficiency. As an extended study towards its commercialisation, this paper reports the effects of the main process parameters including those relating to a new AFP flow-through system. In order to systemise and correlate the results, the Taguchi experimental design method was used. Total organic carbon (TOC) removal was utilised as the measure of the oxidation efficiency and it was found that the removal of phenol from aqueous solution at pH 2.0 and 2.5 was very similar but hydrogen peroxide supply significantly affected the TOC removal with the change of flow rate from 14.4 mL/hr to 60 mL/hr. Also, the initial concentration of phenol was a highly significant factor, with higher concentrations resulting in a lower TOC removal rate. The temperature effects in the range of 14 °C to 42 °C were investigated and it was found that there was accelerated oxidation of phenol in the early stages but after 90 minutes there was no significant difference between the results. Sonication with a bath type sonicator resulted in relatively small enhancements of TOC removal but further studies with cup-horn and probe type sonicators showed that TOC removal increased with higher intensity of sonication on additional input of hydrogen peroxide

Industrial wastewater treatment using hydrodynamic cavitation and heterogeneous advanced Fenton processing

A combination of hydrodynamic cavitation and heterogeneous advanced Fenton process (AFP) based on the use of zero valent iron as the catalyst has been investigated for the treatment of real industrial wastewater. The effect of various operating parameters such as inlet pressure, temperature, and the presence of copper windings on the extent of mineralization as measured by total organic carbon (TOC) content have been studied with the aim of maximizing the extent of degradation. It has been observed that increased pressures, higher operating temperature and the absence of copper windings are more favourable for a rapid TOC mineralization. A new approach of latent remediation has also been investigated where hydrodynamic cavitation is only used as a pre-treatment with an aim of reducing the overall cost of pollutant degradation. It has been observed that approach of latent remediation works quite well with about 50–60% removal of TOC using only minimal initial treatment by hydrodynamic cavitation

Intensification of hydroxyl radical production in sonochemical reactors

The efficacy of sonochemical reactors in chemical processing applications has been well established in the laboratory scale of operation though at a given set of operating parameters and no efforts have been directed in terms of maximizing the free radical production. In the present work, the effect of different operating parameters viz. pH, power dissipation into the system, effect of additives such as air, haloalkanes, titanium dioxide, iron and oxygen on the extent of hydroxyl radical formation in a sonochemical reactor have been investigated using salicylic acid dosimetry. Possible mechanisms for oxidation of salicylic acid in the presence of different additives have also been established. It has been observed that acidic conditions under optimized power dissipation in the presence of iron powder and oxygen result in maximum liberation of hydroxyl radicals as quantified by the kinetic rate constant for production of 2,5- and 2,3-dihydroxybenzoic acid. The study has enabled the optimization of the conditions for maximum efficacy of sonochemical reactors where free radical attack is the controlling mechanism for the chemical processing applications

The partially alternating ternary sum in an associative dialgebra

The alternating ternary sum in an associative algebra, $abc - acb - bac + bca + cab - cba$, gives rise to the partially alternating ternary sum in an associative dialgebra with products $\dashv$ and $\vdash$ by making the argument $a$ the center of each term: $a \dashv b \dashv c - a \dashv c \dashv b - b \vdash a \dashv c + c \vdash a \dashv b + b \vdash c \vdash a - c \vdash b \vdash a$. We use computer algebra to determine the polynomial identities in degree $\le 9$ satisfied by this new trilinear operation. In degrees 3 and 5 we obtain $[a,b,c] + [a,c,b] \equiv 0$ and $[a,[b,c,d],e] + [a,[c,b,d],e] \equiv 0$; these identities define a new variety of partially alternating ternary algebras. We show that there is a 49-dimensional space of multilinear identities in degree 7, and we find equivalent nonlinear identities. We use the representation theory of the symmetric group to show that there are no new identities in degree 9.Comment: 14 page

Intensification of oxidation capacity using chloroalkanes as additives in hydrodynamic and acoustic cavitation reactors

The effect of the presence and absence of the chloroalkanes, dichloromethane (CH2Cl2), chloroform (CHCl3) and carbon tetrachloride (CCl4) on the extent of oxidation of aqueous I- to I3- has been investigated in (a) a liquid whistle reactor (LWR) generating hydrodynamic cavitation and (b) an ultrasonic probe, which produces acoustic cavitation. The aim has been to examine the intensification achieved in the extent of oxidation due to the generation of additional free radicals/oxidants in the reactor as a result of the presence of chloroalkanes. It has been observed that the extent of increase in the oxidation reaction is strongly dependent on the applied pressure in the case of the LWR. Also, higher volumes of the chloroalkanes favour the intensification and the order of effectiveness is CCl4> CHCl3 > CH2Cl2. However, the results with the ultrasonic probe suggest that an optimum concentration of CH2Cl2 or CHCl3 exists beyond which there is little increase in the extent of observed intensification. For CCl4, however, no such optimum concentration was observed and the extent of increase in the rates of oxidation reaction rose with the amount of CCl4 added. Stage wise addition of the chloroalkanes was found to give marginally better results in the case of the ultrasonic probe as compared to bulk addition at the start of the run. Although CCl4 is the most effective, its toxicity and carcinogenicity may mean that CH2Cl2 and CHCl3 offer a safer viable alternative and the present work should be useful in establishing the amount of chloroalkanes required for obtaining a suitable degree of intensification

Using linked hospitalisation data to detect nursing sensitive outcomes: A retrospective cohort study

Background: Nursing sensitive outcomes are adverse patient health outcomes that have been shown to be associated with nursing care. Researchers have developed specific algorithms to identify nursing sensitive outcomes using administrative data sources, although contention still surrounds the ability to adjust for pre-existing conditions. Existing nursing sensitive outcome detection methods could be improved by using look-back periods that incorporate relevant health information from patient’s previous hospitalisations. Design and setting: Retrospective cohort study at three tertiary metropolitan hospitals in Perth, Western Australia.Objectives: The objective of this research was to explore the effect of using linked hospitalisation data on estimated incidence rates of eleven adverse nursing sensitive outcomes by retrospectively extending the timeframe during which relevant patient disease information may be identified. The research also explored whether patient demographics and/or the characteristics of their hospitalisations were associated with nursing sensitive outcomes.Results: During the 5 year study period there were 356,948 hospitalisation episodes involving 189,240 patients for a total of 2,493,654 inpatient days at the three tertiary metropolitan hospitals. There was a reduction in estimated rates for all nursing sensitive outcomes when a look-back period was applied to identify relevant health information from earlier hospitalisations within the preceding 2 years. Survival analysis demonstrates that the majority of relevant patient disease information is identified within approximately 2 years of the baseline nursing sensitive outcomes hospitalisation. Compared to patients without, patients with nursing sensitive outcomes were significantly more likely to be older (70 versus 58 years), female, have Charleson comorbidities, be direct transfers from another hospital, have a longer inpatient stay and spend time in intensive care units (p 0.001).Conclusions: The results of this research suggest that nursing sensitive outcome rates maybe over-estimated using current detection methods. Linked hospitalisation data enables the use of look-back periods to identify clinically relevant diagnosis codes recorded prior to the hospitalisation in which a nursing sensitive outcome is detected. Using linked hospitalisation data to incorporate look-back periods offers an opportunity to increase the accuracy of nursing sensitive outcome detection when using administrative data sources

Exploring students' independent learning and its relationship to mindset and academic performance.

There is increasing interest in the role of independent learning (IL) in higher education (Thomas, 2015). Indeed, several studies demonstrate the impact of IL on students' academic achievement (Difrancesca et al. 2016). Research also suggests that motivational beliefs (such as growth mindset) can foster and support IL (Yan et al. 2013), which in turn enhances academic progression, retention and student experience (Pintrich, 2004). There is, however, no simple definition of IL (McKendry and Boyd, 2012) and many students fail to understand what is expected of them. The aim of this study was to explore students' levels, understanding and style of IL, and its relationship to mindset, academic performance and engagement. Students from Robert Gordon University (n=123) were recruited via opportunistic sampling and asked to complete a Jisc online survey to measure: understanding of IL, Motivated Strategies for Learning (Duncan and McKeachie, 2005) and Growth Mindset (Dweck, 2000). Interaction with the University's Virtual Learning Environment (VLE) and academic grades were also measured. While most students considered themselves an IL (74%), had heard of the term (85%) and understood what IL was, 82% erroneously believed it meant learning on their own. Growth mindset was positively associated with level of IL, Self-Efficacy, Rehearsal, Elaboration and Organisation. Further, results indicated a positive relationship between level of IL and average grade. A-grade students engaged in significantly more IL and used more strategies of rehearsal than B-grade students. Those attaining higher grades (A/B) interacted with the VLE significantly more frequently and regularly than those attaining lower grades (C/D). The C/D grade students' interaction was more sporadic, with peaks around assessment submission deadlines. To improve academic progress and the student experience, therefore, educators need to enhance students' understanding of IL and employ an e-learning platform that is engaging, whilst enhancing the growth mindset and independent learning strategies of its learners