Removal of colloidal silica in simulated seawater by a dynamic multi-short-circuited galvanic cell

Abstract

Venuto, P. 6.; tlamllton, L. A,; Landis, P. S. J. Catal. 1966a, 5, 484.Venuto, P. 6.: Hamilton, L. A.; Landis, P. S. J . Catal. I066b, 6. 253. Venuto, P. H.; Hamilton, L. A,; Landis, P. S.; Wise, T. T. J. Catal. ISSSc, 4 , Zhdanov, S. P. "Some Problems of Zeolite Crystallization"; American ChemInd. Eng. Chem. Prod. Res. Dev. 1985, 24, 468-473 ical Society: Washington, DC, 1971; Adv. Chem. Ser. 101.A dynamic multi-short-circuited galvanic cell (MSCGC) with R-AI electrodes has been used to study the removal of colloidal siHca from seawater as a pretreatment step for the desalination of seawater by use of reverse osmosis. The rate of s i b removal is observed to be affected by the flow rate of the solution through the cell and the dissolved oxygen content of the solution as well as by the nature of the aluminum electrode surface and the number of contact points (short circuits) between the aluminum and platinum. The total silica content is reduced by 95 % by use of this cell configuration. IntroductionIn order to avoid membrane fouling during the reverse osmosis desalination of seawater or brackish water, it is important to remove effectively the membrane-fouling substances. unlike heavy contaminants and those which float, colloidal materials cannot be easily removed by conventional mechanical methods, e.g., filtration, settling, etc. These membrane-fouling substances are (Liss, 1975): (a) inorganic suspended solids and colloids, such as silica, talc, quartz, floc of oxidized iron and manganese, calcium sulfate, and carbonate (scale-forming constituents when their solubility limits are exceeded) and (b) organic nutrients which promote biological growth on membrane surfaces (such as polysaccharides, phosphates, proteins, and lipids).Colloidal silica was selected as a suitable model for the inorganic colloids that are capable of fouling reverse osmosis membranes for the following reasons. Silicon in seawater is found in solution as silicate ions, in suspension as silicon dioxide, both free and in diatoms and other living organisms, and as clay minerals. Its amount is affected