Abstract
Stabilizing colloidal suspensions helps prevent scale deposition and inorganic particulate matter fouling in aqueous systems. Colloidal suspension stabilization was modeled using iron oxide (Fe2O3) suspensions in synthetic tap water containing a mixed electrolyte system that included a variety of ions interacting with suspended particles. Zeta potential measurements of suspended particles were conducted over a wide pH range (3.5 to 10) both in the absence and in the presence of deposit control polymers (DCPs). Results suggest that both polymer functional group type(s) and molecular weight (MW) impact dispersion efficiency.
Introduction
Waters used in industrial applications (boilers, cooling, etc.) often contain dissolved or particulate iron (from the feed stream and/or equipment corrosion) which contributes to scale formation and deposition.1 There are 16 known iron oxides (oxides, hydroxides or oxide hydroxides); predominantly iron is present in the +3 oxidation state. 2 Several iron oxides including hematite, magnetite and goethite may be present in industrial waters causing water coloration. The fully dispersed iron oxides do not scatter light and are therefore transparent. 3 Controlling suspended matter is a major challenge which is met through the use of corrosion inhibitors, iron ion stabilizers, chelating agents, and/or dispersants. 4 Dispersing oxide particles in water is important in the paint industry, ink formulations, and many other applications. 5-7 Dissolved oxygen oxidizes soluble iron present in subsurface waters leading to the formation of colloidal Fe2O3 suspensions which causes water coloration (red water) and clogs fluid handling equipment. Similar deposits occur in potable water systems especially following repair works in the distribution systems. 8
Iron oxide nanoparticles have been used in medical diagnostics, magnetic resonance imaging, and cancer therapies assisted by magnetic fields. 9 Ten to 100 nm mean diameter iron oxide particles have been found to be optimal for intravenous injection. Iron oxide agglomerates with mean diameter exceeding 200 nm may decrease blood circulation in certain capillaries. 10 Medical applications have used organic polymers to encapsulate particles to enhance chemical stability, dispersability, and functionality of the magnetic particle suspensions. 11 Iron particle dispersion has also been attempted through nanoparticle surface modification. Several fatty acids (e.g., phosphonic acids) have been successfully used as surface modification agents. 12 Polymers have been used for the stabilization of superparamagnetic iron oxide particles. 13