The Effect of Medium Acidity on the Size of Polystyrene Particles in Suspension

Author Name(s): Dinar D. Fazullin, Gennady V. Mavrin, Ilnar A. Nasyrov
Author Email: denr3@yandex.ru

Abstract

With the development of industry, there are higher requirements for the quality of process water, as well as the composition of industrial wastewater. To meet the quality requirements, water is increasingly used in membrane methods or a combination of methods with membrane purification methods. Therefore, at present, the actual issue is the development of more effective permeability and retention capacity and inexpensive membranes. Dynamic membranes have a simple method of production. For the formation of such membranes, micro-, nano-particles of a stable suspension of the membrane-forming component are required. In this work, we investigated the dependence of particle size and the stability of a suspension of polystyrene on the acidity of the medium. It is established that, with an increase in the pH of the suspension to pH = 8, an increase in the ζ-potential of the dispersed phase of polystyrene suspension is observed. The maximum values of the ζ-potential of the dispersed phase of a suspension of polystyrene are observed at pH = 7 and pH = 8. The smallest particle size of the dispersed phase of the suspension is 60.8 nm; it is formed when the pH value is 5 units. That will reduce the pore size of the membrane in the process of membrane separation of solutions due to the swelling of polymer particles.

Introduction

Currently, various types of membrane processes, baromembrane, electro-membrane and diffusion membrane processes with high cleaning efficiency and high productivity are used in water purification and water treatment processes. Of the membrane processes, the simplest and most effective are baromembrane processes, such as ultrafiltration, nanofiltration and reverse osmosis, each of which is used depending on the tasks. Membranes should have the following properties: high permeability, selectivity, unchanged characteristics during operation and storage, low cost, should be resistant to the action of shared solutions and should have sufficient mechanical strength. Dynamic membranes satisfy all these requirements – these are composite membranes, which are formed by the formation on the surface of a porous base of a semipermeable layer from suspended microparticles or dissolved substances present in the solution. For the formation of dynamic membranes, colloidal particles, neutral organic polymers, organic and inorganic polyelectrolytes are suitable [1]. The service life of dynamic membranes is almost unlimited. With mechanical damage, they can self-repair, since a new semi-permeable layer is deposited on the substrate. In [2-3], the authors used polyaniline as the surface layer of membranes. In the first work, polyaniline was applied by electrospinning followed by polymerization on the surface of nanofibers. The resulting membranes were used to remove chromium, the membrane efficiency was more than 70%. Dynamic adsorption tests were also carried out at various flow rates and volumes of chromium in water. In the second work, a polyaniline layer was obtained by polymerization of anilian hydrochloride over the surface of a substrate. The membrane was used to remove iron ions, the cleaning efficiency of iron ions was 80-90%.

Conclusion

According to the results of the study, it was found that the hydrogen index affects the particle size of polystyrene in suspension. To form a dynamic membrane layer according to the results of the study, it was found that it is necessary to use a suspension of polystyrene with an acidity of pH = 5, which will reduce the pore size of the membrane during membrane separation of solutions at pH values of more than 5 pH units due to swelling of the polymer particles. Thus, according to Fig. 1, upon separation of the solution with pH = 6, PS particles should increase by 15%, and at pH values of 7–8, the pH should be more than 3 times.

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