Estimation of pore charge on alumina membrane prepared in typical pore forming electrolytes using zeta potential measurement

Alumina membranes were formed by anodizing aluminium in phosphoric acid medium or oxalic acid medium and then selectivity dissolving the parent aluminium. The static charge on these pores and pore size distribution of membrane determine the applicability in filtering colloidal solutions. The scanning electron micrographs showed 240 nm as pore diameter for the membrane formed in phosphoric acid medium and 2600 nm for the membrane formed in oxalic acid medium. The particle charge density was estimated from the zeta potentials and the particle size. The pore charge density estimated from the particle charge density, pore density, pore diameter and the thickness of the membrane was found to decrease with increasing pH.