Effects of starch addition on characteristics of tubular porous ceramic membrane substrates

In this work the Atterberg limits tests were used first for understanding the effects of starch addition to the plasticity of paste. The green substrates of tubular porous ceramic membranes consisting of starch were prepared using the extrusion method, followed by curing, drying, and sintering processes. The substrates thus obtained were further characterized by scanning electron microscopy, uniaxial compressive strength measurements, and permporometry to evaluate the effects of starch addition on the relevant characteristics. Experimental results have demonstrated that an addition of starch granules to the raw materials would increase the porosity, pore size, and permeability of the sintered matrices but accompanied by a decrease of the compressive strength. It revealed that the membrane substrates with desired pore sizes and permeability could be obtained by adding a proper amount of starch.

The microstructure morphology of the cross sections of the sintered substrates prepared with In this investigation, corn starch was employed as a pore former for preparing tubular porous ceramic substrates for membranes by the extrusion method. The research findings obtained are given as follows: (1) The Atterberg limits were found to be useful for evaluation the mechanical properties of paste for extrusion method in this work. (2) By using the bentonite as binder and plasticizer, starch has been proven to be an effective pore former (without the aids of any other organic additives) in this work for preparing tubular porous ceramic substrates for membranes by the extrusion method. Further studies are needed if a similar methodology is to be used for the preparation of other types of membrane. The addition of starch granules to the raw materials would yield tubular ceramic substrates of greater porosity, pore size and permeability, but a lower uniaxial compressive strength. (3) By adjusting the amount of starch added a tubular ceramic substrate of a desired pore size and permeability could be obtained accordingly. (4) The mean pore sizes for the prepared tubular porous ceramic substrates were ranging from 1 mm to 2 mm. They can be used for crossflow microfiltration. Further preparation of an intermediate layer and/or membrane layer is needed if ultrafiltration is planned.