Engelli Karıştırmalı Tanklarda Karıştırıcı Hızı Değişiminin Pickering Emülsiyonlarının Damlacık Boyut Dağılımı Üzerine Etkisi

Pickering emülsiyonları, katı parçacıklar ile stabilize edilmiş emülsiyonlardır. Sürfaktan bazlı emülsiyonlara potansiyel bir alternatiftirler. Pickering emülsiyonunun kararlığı, dağılmış faz damlacıklarının büyüklüğü ile ilişkilidir. Küçük damlacıklar daha kararlıdır. Pickering emülsiyonlarının kararlığı, emülsiyonları üretmek için kullanılan partiküllerin özelliklerine ve üretim işleminde sağlanan karıştırmaya bağlıdır. Bu araştırma, karıştırıcı hızının değişiminin, karıştırılmalı tankta üretilen Pickering emülsiyonlarının damlacık boyutuna etkisini incelemektedir. Silikon yağı saf su içinde dağıtılmış ve su içinde yağ türü emülsiyonlar oluşturmak için hidrofilik cam parçacıklarla stabilize edilmiştir. İki farklı boyutta farklı makaslama kapasitesine sahip iki farklı karıştırıcı kullanılmıştır: Rushton türbini ve eğimli bıçaklı türbin. Elde edilen damlacık boyut dağılımı Malvern Mastersizer 3000® ile belirlenmiştir. Yeterli akış sağlayabilen karıştırıcılar için, karıştırıcı hızının arttırılmasının emülsiyonun damlacık boyutunu azalttığı görülmüştür. Hızı azaltmanın, mevcut stabilize bir emülsiyonun damlacık boyutunu arttırdığı görülmüştür. Emülsiyon oluşumunda bir hız histerezisi gözlenmiştir. Karıştırma süresi analizi, damlacıkların tankın bazı bölgelerinde kalma süresinin, artan hızla damlacık büyüklüğünün azalmasının nedeni olduğunu doğrulamıştır.

Anahtar Kelimeler:

Pickering emülsiyonu, sıvı-sıvı karıştırma, karıştırmalı tank, damlacık birleşimi, emülsifikasyon

The Effect of the Change of Impeller Speed on the Droplet Size Distribution of Pickering Emulsions in a Baffled Stirred Tank

Pickering emulsions are emulsions stabilized by solid particles. They are a potential alternative to surfactant-based emulsions. The stability of a Pickering emulsion is related to the size of the dispersed phase droplets. Smaller droplets are more stable. The stability of Pickering emulsions depends on the properties of the particles used to produce the emulsions and the agitation provided in the production process. This paper investigates the effect of the change of impeller speed on the droplet size of Pickering emulsions produced in a baffled stirred tank. Silicon oil was dispersed into distilled water and stabilized with hydrophilic glass beads to form oil in water Pickering emulsions. Two different impellers with different shearing capacities at two different sizes were used: the Rushton turbine and the pitched blade turbine. The resulting droplet size distribution was determined with Malvern Mastersizer 3000®. For impellers with adequate flow, increasing the impeller speed decreases the droplet size of the emulsion. Decreasing the speed increases the droplet size of the emulsion. A speed hysteresis was observed in the emulsion formation. Mixing time analysis confirmed that the residence time of droplets in parts of the tank was the reason of the droplet size decrease with increasing speed.

Keywords:

Pickering emulsions, liquid-liquid mixing, stirred tank, droplet coalescence, emulsification,

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