A study of the extraction of cobalt II ions from an aqueous growing drop into a continuous medium of di-2-ethylhexylphosphoric acid (D2EHPA) is made. The apparatus for this technique is described and a flow injection analysis method for measuring the cobalt remaining in the aqueous phase has been developed. In this study the feed concentration of cobalt has varied between 8.48 x 10-3 and 16.97 x 10-3 mole 9-1. The D2EHPA held in n-heptane, has been altered between 0.143 and 2.41 mole P. Also, pH has been adjusted between 3.10 and 4.44. The principal temperature applied to this study was 25 ±0.5*C. Acetate buffers have been used, but it is shown by calculation that about 70% of the cobaltous ion is in an uncomplexed form. The kinetics of the extraction have been modelled using a method based upon reaction in an aqueous zone near to the liquid-liquid interface with diffusion of species towards and away from the interface. This model provided a fundamental parameter 01 which incorporates the chemical rate constant kR, the D2EHPA partition coefficient PHR, the acid dissociation constnat KD for D2EHPA and the metal ion diffusivity in the interface diffusion region. The results have been compared with those of other workers who studied the transfer of cobalt into an organic drop from an aqueous continuum. The diffusion controlling film is the aqueous one. The rate constant for, the extraction reaction equation is, from this work, kR - 106.34 M3 kmol-1 sec-1 which can be compared with that found by another worker using the reverse transfer system, i. e. kR - 106.18 m3 kmol-I sec-i. . Finally, the mass transfer coefficients were found to change with varying feed concentrations and pH, this is also in agreement with other workers who have studied different liquid-liquid systems.

No description available.

No description available.

目前，膠體粒子在眾多領域扮演著越來重要的角色，例如工業中油漆流變特性的修飾以及在醫藥靶向藥物釋放等。通過改變膠體粒子間的相互作用 ，可以設計得到適合不同需要的穩定的流體、凝膠和晶體 。而開拓膠體粒子廣泛用途的 前提是對於膠體粒子穩定性的充分理解， 因此，對溶液中粒子間的相互作用的研究很有必要 。 / 本文主要討論了兩個問題 ，均圍繞如何利用小體積膠粒子改變大體積粒子間相互作用 。第一部分 ，我們研究二元粒子懸浮液中膠體粒間的相互作用。結果顯示，帶電納米粒子的加入可以改變帶電納米粒子與平面間的相互作用。當以上三者均輕微帶電，即使在很低的濃度下， 納米粒子也會發生沉積，並導致表面間靜電排斥作用的增強 。而對於高度帶電的納米粒子， 微米粒子和平面 ，納米粒子的吸附將受到阻礙，但實驗結果顯示，此時納米粒子仍能夠引導微與平引導微與平面間的額外斥力。此現象違反傳統高電系統中小體積粒子通常引導排空引力的認知。我們認為此現象可能來源於納米粒子被困於平面附近的區域時引導的排斥力 。 在相互排斥的微米粒子及納體系中 ，這個結果是對納米光暈增強的第一個研究 ，並對利用帶電納米粒子調節二元體系穩定性的傳統方法提出挑戰。 / 在本文的第二部分，我們將對二元帶電粒子相互作用的研究擴展到流體介面。 我們系統研究了二元膠體粒子分別在油水介面和空氣上的相互作用。我們利用高分辨亮場顯微鏡和粒子追蹤方法對受限膠體粒子間的相互作用進行研究。結果顯示 ，偶極 -偶極排斥作用在油水介面和空氣上的行為一致。介面膠體粒子間的相互作用主要包括兩個方面，一是對水相電解質敏感的偶極-偶極排斥作用，二是油相中殘餘電荷的靜電排斥作用 。另外，我們的結果顯示在介面上小體積粒子的加入可以導致二維排空引力，使得大體積粒子相互靠近。與溶液中不同的是，這個二維排空引力能夠在很低濃度時發生。 相信這個結果可以鼓勵更多理論方面的研究，從而對解決有關結晶，擠阻及相轉變等基礎問題提供幫助 。 / Colloidal particies are playing an increasingly important role in a wide range of applications, from rheological modifiers in the paint industry to nanoparticies for targeted drug delivery. By altering interactions between colloidal particies, one can design stable fluids, gels or crystals needed for different purposes. Prior to exploit of a widespread application for colloidal particies, a good understanding of the stability of particies suspension and thus of the interaction between particies in aqueous suspension, are required. / In this thesis two major topics are addressed, and both of them are connected with the use of smaller particies to manipulate the interaction force between larger particies. In the first part of this thesis, I have performed an experimental investigation on the interparticie interaction in a binary particie suspension. The results show that the initial addition of charged nanoparticies can alter the interaction force between charged microparticie and plate surface. When the nanoparticie, microparticie and plate were slightly charged, sufficient nanoparticie deposition on plate occurred, leading to an increased electrostatic repulsion between the surfaces even at low nanoparticie concentration. When the nanoparticies, microparticie and plate were highly charged, the adsorption of nanoparticies onto plate/particie surfaces was hindered. Surprisingly, the addition of nanoparticies also produced a repulsive force. This observed trend is substantially different from the conventional highly charged systems where the addition of nanoparticies creates an attractive depletion force between the microparticie and plate. Our results suggest that these nanoparticies might reside to the region near the plate surface, which eventually give rise to the effective repulsive force. This is the first study to demonstrate that nanoparticie halos can also arise in binary systems of mutually but highly repulsive microparticie/nanoparticie dispersions. We believe that this finding will stimulate theoretians to investigate the nature of such induced interparticie interactions. Our study thus highlights the challenges associated with using charged nanoparticles as a tool to regulate stability in the binary particle systems. / In the second part of this thesis, we extend our study of using smaller charged colloidal particles to alter the interaction force between larger colloidal particles at the fluid-fluid interfaces. We systemically study the binary mixture of colloidal particles at both oil/water and air/water interface. We focus on resolving the interaction forces between confined colloidal particles by using a combination of high tempo-spatial resolution optical microscopy and particle tracking algorithm. Our results show that dipolar-dipolar repulsive force is consistently presented at the both air/water and oil/water systems. The interaction force between charged particles trapped at the fluid interfaces may contain two parts: the dipole-dipole repulsion which is sensitive to the electrolyte content of the water phase, and the electrostatic repulsion arised from the presence of a very small amount of residual electric charge at the particle-oil interface that is insensitive to the electrolyte content of the water phase. Moreover, our results show that the addition of small particle can lead to a 2D depletion attraction, pushing the large particles closer at the interface. Unlike in bulk solution, this depletion force occurs even at very low depletant concentration because there is no need of depletants to reside above and below the larger particles when they are confined at the interfaces. We believe this kind of 2D depletion interaction will stimulate more theoretical simulations in order to provide an insight for answering fundamental questions concerning with crystallization, jamming and other phase transitions. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Xing, Xiaochen. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Abstract also in Chinese. / Chapter 1. --- Interaction of Colloidal Particles in Bulk Solution --- p.1 / Chapter 1.1. --- Interparticle Forces --- p.1 / Chapter 1.1.1. --- Steric Stabilization and Bridging Interaction --- p.1 / Chapter 1.1.2. --- Electrostatic Stabilization --- p.2 / Chapter 1.1.3. --- Depletion Interaction --- p.4 / Chapter 1.1.4. --- Haloing Stabilization --- p.7 / Chapter 1.2. --- Surface Force Measurement Techniques --- p.10 / Chapter 1.3. --- Total Internal Reflection Microscope (TIRM) --- p.12 / Chapter 1.3.1. --- The Technique and Principle --- p.12 / Chapter 1.3.2. --- Measuring the Potentials --- p.18 / Chapter 1.4. --- References and Notes --- p.22 / Chapter 2. --- Direct Measurement of Interaction Forces in Bidispersed Particle Suspension Systems --- p.25 / Chapter 2.1. --- Introduction --- p.25 / Chapter 2.2. --- Interaction Forces in the Bidispersed Systems --- p.28 / Chapter 2.2.1. --- Direct Measurement of the Interaction Forces between Colloidal Particles in a Solution of PS Nanoparticles. --- p.28 / Chapter 2.2.1.1. --- Materials and Methods Materials and Methods Materials and Methods Materials and MethodsMaterials and Methods Materials and Methods --- p.29 / Chapter 2.2.1.2. --- Results Results --- p.32 / Chapter 2.2.1.3. --- Discussion Discussion --- p.41 / Chapter 2.2.2. --- Direct Measurement of the Interaction Forces between Colloidal Particles in a Solution of PS-co-NIPAm Nanoparticles --- p.45 / Chapter 2.3. --- Conclusion --- p.52 / Chapter 2.4. --- References and Notes --- p.54 / Chapter 3. --- Colloidal Particles at Liquid/Liquid Interface --- p.56 / Chapter 3.1. --- Introduction --- p.56 / Chapter 3.2. --- Interactions Forces between Colloidal Particles at Interface --- p.59 / Chapter 3.2.1. --- Repulsive Interactions --- p.63 / Chapter 3.2.2. --- Attractive Interactions --- p.74 / Chapter 3.2.3. --- Force Measurements of Interfacial Particles --- p.79 / Chapter 3.3. --- References and Notes --- p.82 / Chapter 4. --- Direct Measurement of Interaction Force between Colloidal Particles at Fluid Interfaces --- p.88 / Chapter 4.1. --- Materials and Method --- p.90 / Chapter 4.1.1. --- Apparatus and Sample Preparation --- p.90 / Chapter 4.1.2. --- Image processing --- p.92 / Chapter 4.1.3. --- Pair Distribution Function (PDF) and Radial Distribution Function (RDF) --- p.92 / Chapter 4.1.4. --- Pair-Potential of Particle Ensembles --- p.96 / Chapter 4.2. --- Interactions of Particles at Oil (Air)/Water Interface --- p.97 / Chapter 4.2.1. --- Interactions of Monodispersed Colloidal Particles at Oil (Air)/Water Interface --- p.97 / Chapter 4.2.2. --- Effect of Adding Salt on the Interparticle Interaction at Oil(Air)/Water Interface --- p.104 / Chapter 4.2.3. --- Interaction of Binary Particles at Oil/Water Interface --- p.108 / Chapter 4.2.4. --- Effect of Adding Salt on the Binary Particles at the Oil/Water Interface --- p.114 / Chapter 4.2.5. --- Mesostructures at the Interface --- p.118 / Chapter 4.3. --- References and Notes --- p.122

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.