Low cost porous alumina with tailored gas permeability and mechanical properties prepared using rice husk and sucrose for filter applications

•Tailoring of pore microstructure by varying RH content and its size.•Effect of pore microstructure on mechanical strength.•Effect of pore microstructure on permeability constants (Darcian and non-Darcian).•Comparison of experimental results with the theoretical predictions.•Influence of pore microstructure on pressure drop of nitrogen gas flow rate.

The present study demonstrates a cost effective way to produce porous alumina with 39–70 vol% porosity and 64–516 μm avg. pore size (length), using 20–40 wt% rice husk (RH) of <75 μm, 75–180 μm, 180–355 μm, 355–420 μm, and 420–600 μm sizes as pore former and sucrose as binder as well as a pore former. Microstructure of samples revealed interconnected pore microstructure consisting of mixture of coarse elongated pores and fine pores (avg. size 4 μm), created during burnout of RH and sucrose, respectively. Mechanical properties such as three point bending strength (98–14 MPa) and compressive strength (82–6 MPa) of the developed samples were strongly dependent on their porosity and pore size. Also, the Darcian permeability (k1) and non-Darcian permeability (k2) of porous alumina were a strong function of pore microstructure. The Darcian permeability ranges from 0.38 × 10−10 to 9.15 × 10−10 m2 which is in the order of magnitude of gas filters. The non Darcian permeability ranges from 0.33 × 10−5 to 3.92 × 10−5 m. Experimental results agree closely with predictions made based on Forchhemier equation. The developed porous alumina is considered potentially useful in filtration and gas purging applications.

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