Characterisation of kaolinite colloidal and flow behaviour via crystallinity measurements

This study evaluates the possibility of predicting colloidal and flow behaviour of kaolinite suspensions by measuring kaolinite crystallinity. The Hinckley index of different samples was calculated from XRD spectra as an indicator of the crystallinity. Kaolinite samples with a high Hinckley index showed a defined platy morphology with smooth surfaces of low surface area, whilst progressively roughened basal planes with prevalent broken edges were observed in kaolinite samples of lower Hinckley indices. Despite similarity in the elemental composition, the kaolinite samples present different surface charge properties, likely due to variations in exposed pH dependent edge sites. Poorly crystallised kaolinite samples were characterised by higher yield stresses and viscosities. This study highlights the importance of crystallinity characterisation towards predicting colloidal behaviour and flow characteristics of kaolinite suspensions

The psychological science accelerator’s COVID-19 rapid-response dataset

In response to the COVID-19 pandemic, the Psychological Science Accelerator coordinated three large-scale psychological studies to examine the effects of loss-gain framing, cognitive reappraisals, and autonomy framing manipulations on behavioral intentions and affective measures. The data collected (April to October 2020) included specific measures for each experimental study, a general questionnaire examining health prevention behaviors and COVID-19 experience, geographical and cultural context characterization, and demographic information for each participant. Each participant started the study with the same general questions and then was randomized to complete either one longer experiment or two shorter experiments. Data were provided by 73,223 participants with varying completion rates. Participants completed the survey from 111 geopolitical regions in 44 unique languages/dialects. The anonymized dataset described here is provided in both raw and processed formats to facilitate re-use and further analyses. The dataset offers secondary analytic opportunities to explore coping, framing, and self-determination across a diverse, global sample obtained at the onset of the COVID-19 pandemic, which can be merged with other time-sampled or geographic data

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

The Psychological Science Accelerator’s COVID-19 rapid-response dataset

In response to the COVID-19 pandemic, the Psychological Science Accelerator coordinated three large-scale psychological studies to examine the effects of loss-gain framing, cognitive reappraisals, and autonomy framing manipulations on behavioral intentions and affective measures. The data collected (April to October 2020) included specific measures for each experimental study, a general questionnaire examining health prevention behaviors and COVID-19 experience, geographical and cultural context characterization, and demographic information for each participant. Each participant started the study with the same general questions and then was randomized to complete either one longer experiment or two shorter experiments. Data were provided by 73,223 participants with varying completion rates. Participants completed the survey from 111 geopolitical regions in 44 unique languages/dialects. The anonymized dataset described here is provided in both raw and processed formats to facilitate re-use and further analyses. The dataset offers secondary analytic opportunities to explore coping, framing, and self-determination across a diverse, global sample obtained at the onset of the COVID-19 pandemic, which can be merged with other time-sampled or geographic data

A multi-country test of brief reappraisal interventions on emotions during the COVID-19 pandemic.

The COVID-19 pandemic has increased negative emotions and decreased positive emotions globally. Left unchecked, these emotional changes might have a wide array of adverse impacts. To reduce negative emotions and increase positive emotions, we tested the effectiveness of reappraisal, an emotion-regulation strategy that modifies how one thinks about a situation. Participants from 87 countries and regions (n = 21,644) were randomly assigned to one of two brief reappraisal interventions (reconstrual or repurposing) or one of two control conditions (active or passive). Results revealed that both reappraisal interventions (vesus both control conditions) consistently reduced negative emotions and increased positive emotions across different measures. Reconstrual and repurposing interventions had similar effects. Importantly, planned exploratory analyses indicated that reappraisal interventions did not reduce intentions to practice preventive health behaviours. The findings demonstrate the viability of creating scalable, low-cost interventions for use around the world

Frother Characterization Using a Novel Bubble Size Measurement Technique

Bubble size measurement is a vital part of flotation system analysis and diagnostics. This work evaluates a commercial camera probe as a novel method for in situ bubble size measurement. This device is compared to the conventional Anglo Platinum Bubble Sizer (Stone ThreeTM). It was found that, in laboratory applications, the in situ bubble size analysis technology appears to be a more user-friendly and reliable option for determining bubble size in flotation, whereas the Anglo Platinum Bubble Sizer is more applicable for full scale industrial work. This probe was then used to conduct a rigorous comparison of the behavior of different frother chemistries at a variety of background solution ionic strength conditions. The critical coalescence concentrations and the minimum Sauter mean bubble diameters were determined. Five frothers were compared in terms of their ability to reduce bubble size and sensitivity to salinity. In order to adjust plant recipe and control strategy accordingly, it is recommended that the plant would need to use less frother during periods of the high salinity of process water to achieve the minimum Sauter mean bubble size

Frother Characterization Using a Novel Bubble Size Measurement Technique

Bubble size measurement is a vital part of flotation system analysis and diagnostics. This work evaluates a commercial camera probe as a novel method for in situ bubble size measurement. This device is compared to the conventional Anglo Platinum Bubble Sizer (Stone ThreeTM). It was found that, in laboratory applications, the in situ bubble size analysis technology appears to be a more user-friendly and reliable option for determining bubble size in flotation, whereas the Anglo Platinum Bubble Sizer is more applicable for full scale industrial work. This probe was then used to conduct a rigorous comparison of the behavior of different frother chemistries at a variety of background solution ionic strength conditions. The critical coalescence concentrations and the minimum Sauter mean bubble diameters were determined. Five frothers were compared in terms of their ability to reduce bubble size and sensitivity to salinity. In order to adjust plant recipe and control strategy accordingly, it is recommended that the plant would need to use less frother during periods of the high salinity of process water to achieve the minimum Sauter mean bubble size

Fundamentals of clays: Surface and colloid science, and rheology

Introduction Relating bulk properties of clays and clay suspensions to their particle morphology or surface chemistry is a complex process due to the multiple possible types of interaction and the large number of bodies over which these forces act. The work that has been done on simple, idealized suspensions can be extended to complex multi-component suspensions, such as clay in water, with caution. This allows the observation of trends in behaviour to be given some meaning and predictions to be made. This chapter combines the surface and colloid science with macroscopic rheological behaviour due to the strong causal relationships involved. For example, what affects clay swelling behaviour also affects the rheology, and the swelling itself leads to complex rheological behaviour. Mineral Structure Silicate Minerals Silicate minerals are by far the most commonly occurring minerals in the world. All silicate minerals are based on tetrahedral building blocks. These tetrahedral units are composed of a central Si atom bonded to four surrounding O atoms, more commonly known as the silica tetrahedron. Different families of silicate minerals are based upon the numerous ways in which these tetrahedra may be combined (Klein and Hurlbut, 1993), either as isolated tetrahedra (e.g. olivine), single or double chains of tetrahedra (e.g. orthopyroxene, hornblende), as an interlocking tetrahedral framework (e.g. feldspar, quartz), or as tetrahedral sheets (e.g. talc, kaolinite). The different combinations of tetrahedral blocks are illustrated in Fig. 2.1. This review focuses on the phyllosilicate mineral family, as all clay minerals fall within this family (Deer et al., 1992). Phyllosilicate Minerals Phyllosilicate minerals are so named because the sheets of silica tetrahedral tend to give the minerals a platy/leafy habit, as illustrated in an SEM image in Fig. 2.2. There are a large number of different types of phyllosilicates in existence with a variety of different properties. The detailed structure of phyllosilicates is composed of a combination of tetrahedral and octahedral sheets. Individual octahedra are made up of two layers of four oxygen/hydroxyl atoms, with embedded magnesium or aluminium atoms arranged in an octahedral coordination, as illustrated in Fig. 1.4 and already discussed in Chapter 1

Effect of pyrite type on the electrochemistry of chalcopyrite/pyrite interactions

Pyrite is the most common sulphide gangue mineral occurring in base metal sulphide ores around the world. Pyrite is known to galvanically interact with valuable minerals such as chalcopyrite, altering their electrochemical and flotation behaviour. Different types of pyrite are known to vary in texture, chemical composition and electrochemical activity. However, the effect that these differences have on the degree of pyrite interaction with chalcopyrite are not well studied. This work examines two distinct types of pyrite from different deposits that have a similar chemical composition, but vary greatly in texture. It investigates the way in which these pyrites interact with chalcopyrite surfaces, affecting both its electrochemical behaviour and floatability. It was found that the Renison pyrite was characterised by a much higher level of surface activity than the Huanzala pyrite. This was attributed to the elevated levels of arsenic within the mineral's crystalline matrix