Coagulated Mineral Adsorbents for Dye Removal, and Their Process Intensification Using an Agitated Tubular Reactor (ATR)

The aim of this study was to understand the efficacy of widely available minerals as dual-function adsorbers and weighter materials, for the removal of toxic azo-type textile dyes when combined with coprecipitation processes. Specifically, the adsorption of an anionic direct dye was measured on various mineral types with and without the secondary coagulation of iron hydroxide (‘FeOOH’) in both a bench-scale stirred tank, as well as an innovative agitated tubular reactor (ATR). Talc, calcite and modified bentonite were all able to remove 90–95% of the dye at 100 and 200 ppm concentrations, where the kinetics were fitted to a pseudo second-order rate model and adsorption was rapid (<30 min). Physical characterisation of the composite mineral-FeOOH sludges was also completed through particle size and sedimentation measurements, as well as elemental scanning electron microscopy to determine the homogeneity of the minerals in the coagulated structure. Removal of >99% of the dye was achieved for all the coagulated systems, where additionally, they produced significantly enhanced settling rates and bed compression. The greatest settling rate (9 mm min−1) and solids content increase (450% w/w) were observed for the calcium carbonate system, which also displayed the most homogenous distribution. This system was selected for scale-up and benchmarking in the ATR. Dye removal and sediment dispersion in the ATR were enhanced with respect to the bench scale tests, although lower settling rates were observed due to the relatively high shear rate of the agitator. Overall, results highlight the applicability of these cost-effective minerals as both dye adsorbers and sludge separation modifiers to accelerate settling and compression in textile water treatment. Additionally, the work indicates the suitability of the ATR as a flexible, modular alternative to traditional stirred tank reactors.

Rheological properties of calcite oozes: Implications for the fossilisation in the plattenkalks of the Solnhofen-Eichstätt lagoons in the Franconian Alb, Germany

We report on an experimental study to investigate the sedimentation behaviour and rheological properties of extremely fine-grained calcite oozes. The experiments are aimed at clarifying if thixotropic behaviour may have played a role in the preservation of marine biota in plattenkalks of the Solnhofen lagoons of the Franconian Alb. Calcite particles with grain sizes from 2.2 to 4.4 μm were sedimented from water, seawater proxies, and hypersaline brines with up to 14 wt.% NaCl, for 170 days. High salinities as envisioned for the bottom waters of some Solnhofen lagoons slow down settling rates of calcite and may produce plattenkalks more porous and more friable than plattenkalks elsewhere in the Solnhofen archipelago. Rheological properties of calcite suspensions were measured with an oscillation rheometer. Calcite oozes with 40 vol.% calcite in suspension behave thixotropically regardless of the salinity of the pore solutions. Thixotropic behaviour may have the potential to promote the fossilisation of marine biota. Even if the sediment cover is thin, i.e. a few millimeters, a carcass covered by a thixotropic sediment would be largely isolated from the overlying water column because pore solutions in thixotropic media hardly communicate with the overlying water column. A fish carcass covered by a thixotropic sediment could impose local-scale physicochemical conditions on its direct sedimentary envelope favourable for preservation and the replacement of organic material by inorganic materials.

SEDIMENTATION VELOCITY OF POLLEN PARTICLES OF ANEMOPHILIC PLANTS GROWING ON TERRITORY OF THE CSBG SB RAS

The settling of pollen particles of four species of anemophilic plants ( Populus alba L., Salix hybrida , Miscanthus sinensis Andersson, Chosenia arbutifolia (Pall.) A. K. Skvortsov) growing in the exposition of the CSBS SB RAS was investigated. These species are widely used in landscaping cities of the Novosibirsk region and are producers of impressive amounts of allergenic pollen, which can be carried by the wind over significant distances. The presence of a significant proportion of clusters, which include two or more pollen grains, is shown. Settling rates were determined as individual pollen grains of these plant species and their clusters, which included from two to six pollen grains. Dependence of cluster sedimentation rate on number of pollen grains included in it is established.

Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas

The objective of this work was to study the effect of muscovite and biotite on the flotation of chalcopyrite and molybdenite in seawater, and the use of sodium hexametaphosphate and sodium silicate to improve copper and molybdenum recoveries. The impact of the inorganic dispersants on the settling properties of the resulting flotation tailings was also studied. It was found that muscovite and biotite depress the flotation of chalcopyrite and molybdenite in seawater, with this depressing effect being stronger at pH 11 than at pH 9. Sodium hexametaphosphate and sodium silicate increased the recoveries of copper and molybdenum in seawater. These dispersants render the mineral particles more negatively charged and remove the hydroxy-complexes of magnesium and calcium from the mineral particles causing dispersion of the slimes. The settling rates of the flotation tailings slightly decrease when sodium hexametaphosphate and sodium silicate were added in the flotation stage. The presence of ultrafine particles dispersed by the action of the inorganic dispersants negatively impacted the flocculation and sedimentation processes leading to high flocculant consumption, low settling rates and high turbidity of the supernatant.

Point process temporal structure characterizes electrodermal activity

Electrodermal activity (EDA) is a direct readout of the body’s sympathetic nervous system measured as sweat-induced changes in the skin’s electrical conductance. There is growing interest in using EDA to track physiological conditions such as stress levels, sleep quality, and emotional states. Standardized EDA data analysis methods are readily available. However, none considers an established physiological feature of EDA. The sympathetically mediated pulsatile changes in skin sweat measured as EDA resemble an integrate-and-fire process. An integrate-and-fire process modeled as a Gaussian random walk with drift diffusion yields an inverse Gaussian model as the interpulse interval distribution. Therefore, we chose an inverse Gaussian model as our principal probability model to characterize EDA interpulse interval distributions. To analyze deviations from the inverse Gaussian model, we considered a broader model set: the generalized inverse Gaussian distribution, which includes the inverse Gaussian and other diffusion and nondiffusion models; the lognormal distribution which has heavier tails (lower settling rates) than the inverse Gaussian; and the gamma and exponential probability distributions which have lighter tails (higher settling rates) than the inverse Gaussian. To assess the validity of these probability models we recorded and analyzed EDA measurements in 11 healthy volunteers during 1 h of quiet wakefulness. Each of the 11 time series was accurately described by an inverse Gaussian model measured by Kolmogorov–Smirnov measures. Our broader model set offered a useful framework to enhance further statistical descriptions of EDA. Our findings establish that a physiologically based inverse Gaussian probability model provides a parsimonious and accurate description of EDA.

A New 3D Descriptor for Irregularly Shaped Suspended Sediment Aggregates

&lt;p&gt;Within coastal and estuarine environments suspended cohesive sediments that are often closely associated with carbon, nutrients, pathogens and pollutants form aggregates commonly known as &amp;#8216;flocs&amp;#8217;. Understanding the settling dynamics and eventual fate of flocculated sediment is therefore a major issue for the management of aquatic environments. Several factors have been reported to influence the hydrodynamic behaviour of flocs, including size, shape, density and porosity. Recent evidence suggests that of these shape exerts the greatest influence on settling rates. Yet means of characterising shape have been limited to easy to measure quantities such as fractal dimension and circularity measured in 2-dimensions (2D) that fail to capture the highly complex, irregular geometries of sediment flocs. However, recent improvements in sampling methods, 3D imaging capabilities and data processing software enable for the first time the characterisation of flocs based on their 3D morphology.&lt;/p&gt;&lt;p&gt;This study compares the morphologies of natural and artificial flocs generated under different environmental conditions. By employing a novel apparatus for the capture, immobilisation and handling of delicate floc samples, 3D X-ray micro-computed tomography (X-ray &amp;#181;CT) scans are successfully obtained and used to derive accurate volumetric reconstructions of tens of thousands of individual flocs. Using these datasets we compare different methods for describing shape, and test these for their ability to predict floc settling behaviours.&lt;/p&gt;

Seasonal and spatial variation in growth and abundance of zebra mussel (Dreissena polymorpha) in a recently invaded lake: implications for management

The control of the highly invasive zebra mussel (Dreissena polymorpha) has been flagged as a priority but success has been variable. A better understanding of the growth and drivers of settlement of zebra mussel is necessary for a more efficient management of this invasive species, but seasonal data are still relatively scant. We monitored the seasonal changes in settlement rates, density, and growth of zebra mussel in artificial substrates over one year in Cardiff Bay (UK), an artificial amenity lake invaded by zebra mussels in 2003 and where the species is rapidly expanding. Mean settling rates varied from 4,200 to 6,200 mussel m−2 over June to September mirroring changes in water temperature, and peaked at 17,960 mussels m−2, the highest density reported in Britain. Density was highest at the deepest panels (3 m). Growth varied significantly among sampling stations, with growth taking place during the summer and ceasing during winter and spring. Mixture analysis reveals the existence of multiple cohorts displaying different growth and settling rates and that follow different density dependent mechanisms, being positive density-dependent at low densities, and negative density-dependent at high densities. We suggest this creates the conditions necessary for source and sink metapopulations to develop which may need to be taken into account in management. Targeting mussels for removal in deep waters during the summer and early autumn might prove beneficial, but the existence of contrasting density-dependent mechanisms suggests that removal may be beneficial or counterproductive depending on local conditions.

Drilling fluid waste treatment using polysaccharide-grafted copolymers

A large amount of drilling fluid waste is produced as effluents during exploration and production of oil and gas. Such effluents need to be treated before their final disposal. Efficient coagulation/flocculation can reduce the total amount of disposed effluent, and both coagulation by inorganic salts and flocculation by synthetic flocculants are found to be very effective. The graft-copolymers-based flocculants were prepared using a potassium persulfate initiator solution made by grafting copolymerisation of polyacrylamide onto polysaccharide backbones (starch, guar gum and amylose) in our laboratory. The synthesised graft copolymers have been characterised using various instrumental methods of analysis. The effects of various synthetic flocculants and their concentrations have been studied in combination with the coagulants on coagulation/flocculation of bentonite-based drilling fluid waste have been studied. The effects of coagulant/flocculant dosage, electrolyte concentration and pH on the degree of flocculation of bentonite-based drilling fluid waste was investigated. It was observed that the increase in coagulant/flocculant dosage reduces the residual turbidity and improves the settling rate of the drilling fluid waste. At higher pH conditions, drilling fluid waste dispersions are highly flocculated and have high settling rates and low supernatant turbidity. The combined effect of salt concentration and coagulant/flocculant dosage improves the overall flocculation efficiency of the system.