Silica is one of the most abundant and problematic inorganic scalants in brackish water and industrial wastewater treatment processes. Commercial antiscalants for inorganic scale mitigation comprise polymers of unknown or proprietary composition. Commercial antiscalants are generally effective for crystalline scale (e.g., sulfate-based scales such as gypsum), but are ineffective in preventing silica scale formation due to the amorphous nature of silica and the scaling mechanisms that differ from those of crystalline scales. Such challenges in silica scale mitigation primarily originate from a lack of understanding of the detailed chemistry and condensation mechanisms of dissolved silica. Polymeric antiscalants with desirable functional groups and well-defined molecular structures can be synthesized through controlled polymerization techniques to investigate the complex interactions of antiscalants with soluble silicic acid and related stabilization mechanisms. The attained knowledge can guide the development of polymeric antiscalants that are highly effective in hindering silica scaling. Herein, we synthesized a variety of polymeric antiscalants with neutral or cationic functional groups and branched architectures via controlled radical polymerization and condensation polymerization. We first employed primary-amine based linear polymers as a model system to study the impact of other structural parameters on the antiscaling properties. Then, we translated the design principles and sophisticated understanding to other functional-group systems to further optimize the antiscalants. The performance of the synthesized antiscalants was systematically evaluated using feed waters with varying silica concentrations and ionic compositions.

Stabilization of silicic acid for silica scale mitigation: Role of polymeric antiscalant functional groups and molecular structure

ACS Fall 2021

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