Inhibition and Dissolution as Dual Mitigation Approaches for Colloidal Silica Fouling and Deposition in Process Water Systems:  Functional Synergies

Abstract

This paper is focused on a dual approach for silica scale control, inhibition and dissolution by use of designed chemical approaches. Inhibitors that are tested include the polyaminoamide STARBURST dendrimers (PAMAM) of generations 0.5, 1.0, 1.5, 2.0, and 2.5. Of these, only the NH 2 -terminated ones (PAMAM-1.0 and 2.0) show significant inhibitory activity, in contrast to COOH-terminated ones (PAMAM-0.5, 1.5, and 2.5), which show virtually no inhibition performance. The synergism between the above dendrimers and an anionic polyelectrolyte (poly(acrylamide-co-acrylate) copolymer) is also described. Addition of poly(acrylamide-co-acrylate) copolymer in silica supersaturated solutions containing PAMAM-1 or 2 alleviates the appearance of silica-PAMAM insoluble precipitates, resulting in stable colloids. The paper also describes silica dissolution approaches, as an alternative to inhibition, by using nonhazardous additives based on polycarboxylates with one to five -COOH groups (acetate, oxalate, citrate, diethylenetriaminepentaacetate, and others), mixed polycarboxylates/phosphonates (2-phosphonobutane-1,2,4-tricarboxylate), and amino acids (L-histidine and L-phenylalanine). Their reactivity is linked to their chemical structure in this structure/function study. The presence of additional chemical groups (e.g., -PO 3 H 2 , -NH 2 , or -OH) in the dissolver molecule augments the dissolution process.

Green silica scale inhibitors for Alkaline-Surfactant-Polymer flooding: a review

“…Increasing environmental concerns and discharge limitations have imposed additional challenges. Therefore, the discovery and successful application of low doses chemical additives that have mild environmental impact has been the focus of several researchers (Quraishi et al 1999;Demadis et al , 2004Neofotistou and Demadis 2004a, b;Mavredaki et al 2005). Recently, the use of cationic polymer as silica polymerization inhibitors has been the subject of numerous investigations.…”

“…Similar conclusions were also reported by Harrar et al (1982) in their investigation on the use of cationic polymers and surfactants in inhibiting silica polymerization under geothermal conditions (Harrar et al 1982). It is now certain that effective silica scale inhibition is dependent on the cationic charge on the polymer backbone (Demadis 2004a(Demadis , b, 2005Mavredaki et al 2005;Demadis and Stathoulopoulou 2006;Demadis and Neofotistou 2004;Neofotistou and Demadis 2004a, b).…”

“…2 Structures of PAMAM-1 and PAMAM-2 (Mavredaki et al 2007) 2007). Therefore, to combat this problem some researchers resorted to use anionic polymer additives that could work with the dendrimer inhibitors (Neofotistou and Demadis 2014;Mavredaki et al 2005Mavredaki et al , 2007. However, if the dosage of anionic polymer used is high, the activity of the dendrimers drops dramatically.…”

“…However, if the dosage of anionic polymer used is high, the activity of the dendrimers drops dramatically. It was found that the negative charge of polymer ''overwhelms'' the dendrimer and poisons its inhibitory ability (Demadis 2008;Mavredaki et al 2005). Plus, most anionic polymers used are not green and/ or have mild environmental impact.…”

Use of a Pilot Scale Heat Exchanger-Cooling Tower System for the Evaluation of Mineral Scale Inhibitors

“…These additives perform scale inhibition in "ppm" quantities and usually work synergistically with dispersant polymers [9].…”