Inhibitory effects of poly(adipic acid/amine-terminated polyether D230/diethylenetriamine) on colloidal silica formation

Colloidal silica (SiO2) scale is considered to be the most undesirable inorganic deposit formed in industrial water. It is formed either in bulk or on surfaces such as membrane, heat exchangers and pipelines. Conventional mineral scale inhibitors do not inhibit its formation. Chemical cleaning is difficult and not free from hazards. Ongoing research on silica scale prevention has led to experiments using various chemical approaches, such as ion exchange, coagulation, and softening. This paper focuses on a scale inhibition approach using a novel chemical additive, adipic acid/amine-terminated polyether D230/diethylenetriamine copolymer (AA/AT/DE). The influence of various concentrations of AA/AT/DE on colloid silica formation are tested and compared to traditional mineral inhibitors, such as phosphonates and anionic polymers. Phosphonates include ATMP, HEDP, EDTMP, DTPMP, HTDMP, and PBTCA, while anionic polymers include PAA, PMA, PESA, PASP, and AA/AM. Among these, only AA/AT/DE showed significant inhibitory activity in contrast to mineral inhibitors, which showed virtually no inhibition. Based on the zeta potential of colloid silica aqueous solutions in the presence of AA/AT/DE, an attractive interaction between AA/AT/DE and silica particles may be present. AFM images of silica also confirm that AA/AT/DE can interfere with the silica polymerization reaction.