Iron oxide dispersants for industrial water systems: types, performance, and selection criteria

Abstract

Dispersion of solid particles separating out from fluids is very important for fouling due to deposition of unwanted materials. Dispersion and stabilization of suspended matter i.e., clay, silt, corrosion products, precipitating salts, etc., is often overcome by incorporating a dispersant in the water treatment formulation. In this paper a variety of non-polymeric, natural polyelectrolytes, synthetic, and hybrid polymers were evaluated for their efficacy as iron oxide (Fe 2 O 3 , hematite) dispersants for industrial water systems. Results reveal that performance of dispersants strongly depends on dispersant dosage, dispersing time, dispersant architecture, and the impurities present in water. Among the non-polymeric additives evaluated phosphonates perform better than polyphosphates. Surfactants (anionic, non-ionic) tested are ineffective iron oxide dispersants. Performance data on natural polyelectrolytes show that lignosulfonate exhibits better performance compared to humic, fulvic, and tannic acids. Based on the performance of synthetic polymers the order of effectiveness is: terpolymer > copolymer > homopolymer. Results on the impact of impurities (i.e., trivalent metal ions, biocides, hardness ions, etc.) suggest that these impurities show negative influence on the polymers performance. Discussion on dispersion mechanism and dispersant selection criteria is also presented.

Flocculants from wastewater

“…Aside from the use of ionic liquids to selectively recover specific EPS components, it will be worthwhile to further investigate how the different EPS-MW fractions can be recovered for various applications. For instance, anionic polyelectrolytes in the 10 3 -10 4 Da range are used as antiscalants and dispersants [75,76], those in the 10 4 -10 5 Da range are employed as coagulant aid for cationic polymers in dual polymer systems [77,78], those between 10 5 -10 6 Da are used as paper strength and drilling mud additives [79], and the highest MW (> 10 6 Da) polyelectrolytes are used as flocculants and viscosifiers [51,56]. Hence, the different EPS fractions could be recovered and explored for some of these interesting applications.…”