Electro-spray of high viscous liquids for producing mono-sized spherical alginate beads--颗粒学报PARTICUOLOGY

Moghadam, H., Samimi, M., Samimi, A., & Khorram, M. (2008). Electro-spray of high viscous liquids for producing mono-sized spherical alginate beads. Particuology, 6(4), 271–275. https://doi.org/10.1016/j.partic.2008.04.005

Electro-spray of high viscous liquids for producing mono-sized spherical alginate beads

Hamid Moghadam, Mohsen Samimi, Abdolreza Samimi^*, Mohamad Khorram

Chemical Engineering Department, University of Sistan and Baluchestan, Zahedan, Iran

10.1016/j.partic.2008.04.005

Volume 6, Issue 4, August 2008, Pages 271-275

Received 21 November 2007, Accepted 25 April 2008, Available online 7 July 2008.

E-mail: a.samimi@hamoon.usb.ac.ir

Highlights

Abstract

Alginate beads, often used for controlled release of enzymes and drugs, are usually produced by spraying sodium alginate liquid into a gelling agent using mechanical vibration nozzle or air jet. In this work an alternative method of electro-spray was employed to form droplets with desired size from a highly viscous sodium alginate solution using constant DC voltage. The droplets were then cured in a calcium chloride solution. The main objective was to produce mono-sized beads from such a highly viscous and non-Newtonian liquid (1000–5000 mPa s). The effects of nozzle diameter, flow rate and concentration of liquid on the size of the beads were investigated. Among the parameters studied, voltage had a pronounced effect on the size of beads as compared to flow rate, nozzle diameter and concentration of alginate liquid. The size of beads was reduced to a minimum value with increasing the voltage in the range of 0–10 kV. At the early stages of voltage increase (i.e. up to about 4 kV), the rate of size reduction was relatively low, while the dripping mode dominated. However, in the middle part of the range of applied voltage, where the rate of size reduction was high (i.e. about 4–7 kV), an unstable transition occurred between dripping and jetting. At the end part of the range (i.e. 7–10 kV) jet mode of spray was observed. Increasing the height of fall of the droplets was found to improve the sphericity of the beads, because of the increased time of flight for the droplets. This was especially identifiable at higher concentrations of the alginate liquid (i.e. 3 w/v%).

Graphical abstract

Keywords

Electro-spray; Highly viscous liquid; Constant DC electric field; Alginate beads

文章导读