疏水草分枝杆菌对矿物颗粒间相互作用的影响分析

通过理论计算分别得到了在无草分枝杆菌存在时赤铁矿与石英颗粒、赤铁矿颗粒之间、石英颗粒之间以及在有草分枝杆菌存在时赤铁矿颗粒之间的总作用势能V_T与颗粒距离h的关系曲线, 并对曲线进行了分析。分析表明: 在无草分枝杆菌存在时, 赤铁矿与石英颗粒之间、赤铁矿颗粒本身之间均存在着强烈地吸引作用, 且赤铁矿与石英颗粒之间的吸引作用明显大于赤铁矿颗粒本身之间的吸引作用, 而石英颗粒之间则存在着强烈地排斥作用。草分枝杆菌这种疏水性微生物的存在, 明显增大了赤铁矿颗粒本身之间的吸引作用, 使得它的吸引作用较赤铁矿和石英颗粒的吸引作用大得多。草分枝杆菌的加入, 有利于增强赤铁矿和石英颗粒之间的分离能力。     

油团聚体系中桥液作用机理的研究

试验及计算结果表明,桥液用量决定着体系中起主导作用的力——毛细作用力的大小,直接影响聚团粒度、形状和强度。毛细作用力的本质是由于液一气界面张力及由于桥液优先润湿疏水性矿粒、形成弯曲液面时所产生的附加压力的合力。计算结果还可以对油团聚体系中其它许多现象进行圆满解释,是对DLVO理论的补充、发展。     

微细粒锡石—石英疏水凝聚研究

本文研究了油酸钠在微细粒锡石、石英表面的吸附状况及在有油酸钠存在的条件下，锡石、石英以及锡石和石英粒子之间的互凝。通过理论计算用扩展的DLVO理论进行了验证，并对DLVO和扩展的DLVO理论在浮选剂存在条件下矿粒行为的预测进行了比较。     

Dispersion of ultrafine alumina in modifier solution —the role of polar interfacial interaction

Dispersion of ultrafine alumina suspension is examined by using particle size analyzer. The zeta potential and contact angle measurements were used to discuss the electrokinetic behavior and surface wettability of alumina in modifier solution, and to calculate the electrostatic interfacial intheraction forces between alumina particles. The aggregation of ultrafine alumina occurs near its PZC. Addition of modifier increases the zeta potential of alumina and its surface hydrophilicity, resulting in increase of electrostatic and hydration repulsion. It makes the suspension of ultrafine alumina completely dispersed. The average particle size of the suspension is decreased from 1.73 μm in absence of modifier to 0.8 μm in the presence of tripolyphosphate. According to polar interfacial interaction approach, the hydration forces responsible for the stability of alumina suspension in the presence of modifier have also been obtained. The extended DLVO theory is successful to describe the dispersion behavior of ultrafine alumina in modifier solution. Foundation item: The National Key Basic Research Program(973) (G1999064901-1) Biography of the first author: HU Yue-hua, professor, born in Jan. 1962, majoring in mineral processing.     

石英—硅酸钠体系与界面相互作用

本文通过沉降试验、ｚｅｔａ电位检测、接触角的测定，以及运用界面力的基本理论知识从表面热力学的角度研究并探讨了－２０μｍ的石英微粒之间的凝聚行为。从界面力的角度探讨了硅酸钠对石英微粒的分散机理或抑制机理。实验结果及理论计算证实了经典的ＤＬＶＯ理论只有被扩展才能准确地描述亲水颗粒的分散、凝聚行为。     

Influence of electrolyte and poloxamer 188 on the aggregation kinetics of solid lipid nanoparticles (SLNs)

Solid lipid nanoparticles (SLNs) have attracted increasing attention as colloidal drug carriers due to theirs advantages including low toxicity, drug targeting and modified release. However, undesired particle aggregation in aqueous dispersions would limit the applicability of SLNs for drug delivery. The purpose of the present article is to investigate the aggregation behavior of the SLNs and quantitatively evaluate how the concentration of NaCl and F68 affect the stability of the SLNs. The early stage aggregation kinetics of the SLNs was investigated over a wide range of NaCl concentrations by employing dynamic light scattering (DLS). In the presence of the NaCl, aggregation kinetics of the SLNs exhibited reaction-limited (slow) and diffusion-limited (fast) regimes. These results indicated that the aggregation behavior of these new nanoparticles can be well explained by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The critical coagulation concentration (CCC) of SLNs containing 0.0%, 0.1%, 0.5%, 2.0%, and 4.0% of Poloxamer 188 (F68) was 416, 328, 519, 607, and 602?mM, respectively, suggesting that the F68 influences the aggregation behavior of the SLNs. F68 made the SLNs more sensitive to the electrolyte when its concentration is low (0.1%), the bush of the polymer F68 has a bridging effect that accelerated the aggregation process of the SLNs. However, at the high concentration, F68 can provide the steric repulsion to the nanoparticles, which effectively stabilized the SLNs dispersions.     

磁防蜡参数优化研究与应用

应用DLVO理论论证了磁处理技术的作用机理。分析认为 ,磁场作用致使蜡晶胶粒间的范德华引力势能增大是各种磁处理效应的根本原因。通过对原油进行磁处理试验和理论研究发现 ,磁防蜡器的磁感应强度、峰值和作用次数对磁防蜡效果影响显著。对于不同油井的原油 ,磁防蜡器的参数不同 ,防蜡效果也不一样。现场应用 8口井后效果明显 ,在管理措施相同的条件下 ,因结蜡造成的平均检泵周期延长 1倍以上 ,结蜡状况明显减轻。     

Molecular dynamics simulation for aggregation phenomena of nanocolloids

Nonequilibrium molecular dynamics (MD) method was used to study the dielectrophoresis (DEP) motion of nanocolloids in non-uniform electric field. By changing the electric field strength and system temperature, aggregation phenomena of nanocolloids was analyzed. Simulation results showed that at normal temperature, though the Brownian force can affect the motion of colloids, the attractive force will increase quickly with the distance between colloids down to 12σ , which makes colloids aggregate. When the Brownian force is weak to colloid's motion, for the enhancement of electric field strength, the DEP force of colloid will increase and so did the attractive force, which finally quickens the aggregate speed. Simulation results also showed that the temperature' enhancement will increase the Brownian force of colloids, hence disturbing the colloids aggregation. Moreover, the DLVO theory was used to study the motion of a pair of interactional colloids, both the potential energy and the attractive force versus distance of colloids were presented, then the latter graph was used to compare with another graph elicited by MD method. Results showed that the two graphs were nearly the same, indicating the MD model accorded with the theory.     

A novel method for evaluating the hydrophobic interaction between coal particles and air bubbles and its role in flotation

Among surface forces, the non-Derjaguin-Landau-Verwey-Overbeek hydrophobic force between hydrophobic surfaces is critical to bubble-particle attachment and, as a result, mineralization in flotation. However, it brings challenge to study the hydrophobic interaction between coal particles and air bubbles due to lack of the hydrophobic interaction constant. In this study, a novel method was proposed to evaluate the hydrophobic interaction between coal particles and air bubbles, which comprehensively combines the extended Derjaguin-Landau-Verwey-Overbeek theory, the Stefan-Reynolds model and the experimentally measured attachment time. It was found that the attachment time between coal particles and air/oily bubbles was respectively 246 and 50 ms. The decay length for hydrophobic interactions was about 25 nm. Then, according to the obtained attachment time and decay length, the derive Stefan-Reynolds model was solved and the hydrophobic interaction energy constant between air bubbles and coal particles was determined to be ?4.19 mJ/m², about 1/7 of that between oily bubbles and coal particles. These findings clearly demonstrated the significant difference between conventional and oily-bubble flotations, and the critical role of the hydrophobic interaction in coal flotation was confirmed.     

The effect of humic acid on the stability and aggregation kinetics of WO3 nanoparticles

The physicochemical properties including size, hydrodynamic diameter, agglomeration rate, surface area, crystal structure, and surface charge were determined for WO₃ using x-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), UV-Vis spectrometer (DRS), and Zetasizer Nano ZS. The stability and aggregation behavior of WO₃ were investigated using dynamic light scattering (DLS) to monitor the hydrodynamic size and zeta potential. The effect of ionic strength was further studied using NaCl, MgCl_2. and CaCl₂ electrolytes at pH 5 as well as the effect of humic acid. WO₃ nanoparticles behaved similarly in deionized water suspensions and in the presence of NaCl electrolytes. The stability of nanoparticles was notable at low concentration (1?ppm) of humic acid particularly with NaCl electrolytes. Divalent cations enhanced agglomeration of nanoparticles even at the highest concentration of humic acid due to the formation of cation-humic acid bridges. The Derjaguin–Landau–Verwey–Overbeek theory was used to investigate the interaction energies, and it was found that van der Waals attraction forces are dominant in the presence of divalent cations.