Study On Coating Process And Surface Characteristics Of IOCS (Iron Oxide Coated Sand)

Deep-Bed filtration was widely used for solid/liquid separation in potable water purification process. The performance of filtration depended on the characteristics of filter media. The common media, such as silica sand and anthracite coal, was cheap and stable and widely used in granular bed filter, whereas, the nature disadvantage of common media, such as a negative potential surface, the poor specific surface, porosity and adsorption capacity, were well marked for filtration process.Now, coating with metal oxide on media surface to improving removal capacity, has become a fashionable technique for enhanced filtration, most research focused on the filtration/adsorption capacity for various contaminant and the mineralogy analysis of surface-coat. This thesis aimed to study the effect of oxide concentration, abrasion intensity and solidification temperature on coating characters, to reveal the effect of aqua pH value and coating mass on surface electric potential of media, and expected to provide theories basis to the developing and utilization of coating filter media technology.The results revealed that oxide coating treatment could change the surface shape and charged of silica sand, the surface zeta potential of iron-oxide-coated sand become lower with pH values increasing, and solidified temperature impact on the surface zeta potential was neglectable, but in the acidic and alkaline conditions the impact of solidified temperature was amplification, the surface zeta potential of iron-oxide-coated increased when oxide concentration up to 1.5mol/L, with sequent increasing of oxide concentration, the change become mild, this showed that there were limit and optimum concentration of metal oxide for filter media coating.Experiment results revealed that the surface coat with higher solidify temperature was more dense and abrasion resisting. Mixing abrasion test showed that loss mass increase under the higher G value, but with the increased of wearing cycle, the trendy of coat loss quality increase become more mild; the same conclusion drawn from the model filter backwashing process. Based on the abrasion test, the expectancy life of iron-oxide-coated sand estimated up to 324 days.