The effect of EDTA on the groundwater transport of thorium through sand

The effect of the anthropogenic complexing agent EDTA on thorium transport in groundwater has been studied using sand-packed columns and flow rates in the range of 20-100 m y⁻¹. The concentrations injected into the columns were in the range of 0.4-4 mM for Th and 4-40 mM for EDTA, and with EDTA:Th ratios in the range 1:1 to 10:1. The results show that EDTA can significantly increase Th transport, but two very different behaviours are observed at Th concentrations of 0.4 and 4 mM. At the lower concentration, Th breakthrough is retarded with respect to a conservative tracer, with a peak width that is consistent with a single K_d value, followed by a longer tail, and the behaviour is very sensitive to the flow rate. However at 4 mM Th, the breakthrough peak appears near to that of the tracer, and the width of the peak is consistent with a distribution of K_d values and/or a larger dispersivity than the tracer. Speciation and transport modelling have been used to interpret the data, and a model was developed that could explain the 0.4 mM behaviour. This suggests that ternary surface complexes are important in these systems, with at least two different species involved, although the complexity of Th speciation in these systems leads to significant uncertainty in the values of the equilibrium and kinetic parameters. For the 4 mM systems, the rapid transport observed could not be explained by a simple chemical model; instead it is likely that EDTA plays an important role in stabilising and transporting thorium colloids and clusters.     

Aggregation and deposition kinetics of carboxymethyl cellulose-modified zero-valent iron nanoparticles in porous media

Transport and deposition of carboxymethyl cellulose (CMC)-modified nanoparticles of zero-valent iron (NZVI) were investigated in laboratory-scale sand packed columns. Aggregation resulted in a change in the particle size distribution (PSD) with time, and the changes in average particle size were determined by nanoparticle tracking analysis (NTA). The change in PSD over time was influenced by the CMC-NZVI concentration in suspension. A particle-particle attachment efficiency was evaluated by fitting an aggregation model with NTA data and subsequently used to predict changes in PSD over time. Changes in particle sizes over time led to corresponding changes in single-collector contact efficiencies, resulting in altered particle deposition rates over time. A coupled aggregation-colloid transport model was used to demonstrate how changes in PSD can reduce the transport of CMC-NZVI in column experiments. The effects of particle concentrations in the range of 0.07 g L⁻¹ to 0.725 g L⁻¹ on the transport in porous media were evaluated by comparing the elution profiles of CMC-NZVI from packed sand columns. Changes in PSD over time could reasonably account for a gradual increase in effluent concentration between 1 and 5 pore volumes (PVs). Processes such as detachment of deposited particles also likely contributed to the gradual increase in effluent concentrations. The particle-collector attachment efficiency increased with CMC-NZVI particle concentration due to a rise in dissolved Na⁺ concentration with increased addition of Na-CMC. This inadvertent change in ionic strength led to decreased effluent concentrations at higher CMC-NZVI concentrations.     

Pore size distribution from challenge coreflood testing by colloidal flow

The transport of colloidal and suspension particles and the resultant particle retention occur in a wide range of porous media. The micro scale pore throat size distribution is an important characteristic of porous media, allowing for evaluation of important transport properties. An effective method based on micro scale modelling for the determination of overall pore throat size distribution (PSD) by injection of colloidal particle suspensions into engineered porous media with monitored inlet and breakthrough particle concentrations is developed. The treatment of inlet and outlet colloidal particle concentrations obtained in coreflooding results in a good agreement between the modelling and experimental data. Yet, some deviation was observed between the obtained PSD and that calculated by the Monte Carlo simulation based on the Descartes’ theorem.     

Interactions of low-power photons with natural opals—PBG materials,photonic control,natural metamaterials,spontaneous laser emissions,and band-gap boundary responses

One overall goal of this research was to examine types of naturally-occurring opals that exhibit photonic control to learn about previously-unknown properties of naturally occurring photonic control that may be developed for broader applications. Three different photon sources were applied consecutively to three different types of natural, flawless, gem-quality precious opals. Two photon sources were lasers (green and red) and one was simulated daylight tungsten white. As each type of precious opal was exposed to each of the photon sources, the respective refractions, reflections, and transmissions were studied. This research is the first to show that applying various pleochroic and laser photon sources to these types of opals revealed significant information regarding naturally occurring photonic control, metamaterials, spontaneous laser emissions, and microspheroid cluster (inter-PBG zone) boundary effects. Plus, minimizing ambient light and the use of low power photon sources were critical to observing the properties regarding this photonic materials research. This research yielded information applicable to the development of materials to advance applications and devices of photonics, phononics, optoelectronics, nanomaterials, and metamaterials.     

Self-assembly of water insoluble polymers into Colloidal Unimolecular Polymer (CUP) particles of 3–9 nm

Colloidal Unimolecular Polymer, CUP, particles were synthesized and characterized as a potential new and useful spheroidal polymer conformation for a variety of applications. Also known as single chain nanoparticles, these nanomaterials are gaining in popularity. The route to CUP particle formation is an innovative approach utilizing a small number of hydrophilic groups along a hydrophobic polymer backbone which transitions from a random coil conformation in organic solvent to a hard sphere in water through a slow gradient with subsequent solvent removal. The CUP particles have diameters which are proportional to their molecular weights and range typically from 3 nm to over 9 nm. These CUP particles were stable in water and free of solvent or surfactants. The sodium or potassium salts of CUP particles are spheroidal and are able to be dried then re-dissolved in water with no aggregation, unlike the original polymer. The diameters of the CUP particles correlate with the absolute number average molecular weight (M_n) and distributions from the GPC. Molecular weights from 28K to 122K are reported here and are based on an acrylic copolymer having a molar ratio of 9:1 MMA:MAA.     

On the role of metabolic activity on the transport und deposition of Pseudomonas fluorescens in saturated porous media

A study was conducted to understand the role of cell concentration and metabolic state in the transport and deposition behaviour of Pseudomonas fluorescens with and without substrate addition. Column experiments using the short-pulse technique (pulse was equivalent to 0.028 pore volume) were performed in quartz sand operating under saturated conditions. For comparison, experiments with microspheres and inactive (killed) bacteria were also conducted. The effluent concentrations, the retained particle concentrations and the cell shape were determined by fluorescent microscopy. For the transport of metabolically-active P. fluorescens without substrate addition a bimodal breakthrough curve was observed, which could be explained by the different breakthrough behaviour of the rod-shaped and coccoidal cells of P. fluorescens. The 70:30 rod/coccoid ratio in the influent drastically changed during the transport and it was about 20:80 in the effluent and in the quartz sand packing. It was assumed that the active rod-shaped cells were subjected to shrinkage into coccoidal cells. The change from active rod-shaped cells to coccoidal cells could be explained by oxygen deficiency which occurs in column experiments under saturated conditions. Also the substrate addition led to two consecutive breakthrough peaks and to more bacteria being retained in the column. In general, the presence of substrate made the assumed stress effects more pronounced. In comparison to microspheres and inactive (killed) bacteria, the transport of metabolically-active bacteria with and without substrate addition is affected by differences in physiological state between rod-shaped and the formed stress-resistant coccoidal cells of P. fluorescens.     

胶体化学的新进展与油田化学

本文基于１９９６年６月在美国Ｐｏｔｓｄａｍ举行的第７０届美国胶体与界面科学学术大会（７０ｔｈＣｏｌｏｉｄａｎｄＳｕｒｆａｃｅＳｙｍｐｏｓｉｕｍ，简写ＡＣＳＳＳ）的报告材料，结合油田化学学科的实际情况，介绍了１０年来胶体化学领域的新进展，包括：纳米粒子与分子簇研究；又趋活跃的乳状液、小乳状液、微乳状液、泡沫、凝胶研究；表面活性剂与分子有序组合体；胶体化学的发展与生命、材料、能源及环境科学；讨论了油田化学与胶体化学之间的关系。     

Transition state annealing for defect control during colloidal self-assembly

Colloidal self-assembly is an efficient method to obtain ordered 3D nanostructures. However, it suffers from the drawback that defects are difficult to eliminate in the self-assembled nanostructures. In this report, a method to reduce the defect density is proposed. It has been observed earlier that during self-assembly, the colloidal system goes through a transition state with a higher mobility than the final rigid nanostructure. This offers an opportunity to anneal out defects like vacancies and dislocations. Using in-situ reflectance spectra measurements of a self-assembling system, we demonstrate the feasibility of this transition state annealing method.     

储存期长,耐冷冻的高浓度MMLH胶体

在室内研究了常规浓度（7％—10％）的MMLH胶体经长时间（最长达10个月）存放和冷冻解决后，在泥浆中提粘、提切性能的变化。筛选出了可提高液态胶体储存稳定性和耐冷冻性的两种聚合物（SW－1和SW－2）并确定了经济合理的用量。用这两种聚合物为胶体稳定剂，研制出了保持低浓度胶体性能、储存稳定性良好（SW－1和SW－2）、耐冷冻（SW－1）的高浓度（18％）MMLH胶体。     

Direct evidence on reduced adhesion of Salbutamol sulphate particles due to L-leucine coating

Attractive van der Waals forces are responsible for unwanted agglomeration of fine dry powder particles which can cause problems e.g. with inhalable drugs in the treatment of asthma. In this article we report on experimental evidence of reduced adhesion of salbutamol sulphate particles when they are coated with L-leucine. Particle production and coating was performed using an aerosol flow reactor. The L-leucine-containing particles were fully covered with L-leucine as evidenced by X-Ray Photoelectron Spectroscopy and Scanning Electron Microscopy findings. With a suitable concentration of precursor solution the particles become rough and adhesion diminished to one fifth of the adhesion of uncoated particles. The main reason for this reduced adhesion was an increase in surface roughness, which reduced the contact area and the number of contact points thus increasing the effective separation between particles.