Enhancement of silicate solubility by use of “green” additives: linking green chemistry and chemical water treatment

The inhibition performance of three synthetic amine/ammonium-containing cationic polymers in colloidal silica particle growth is reported. The three additives are compared to control (no additives present during silicate polymerization). The three polymers, polyethyleneimine (PEI), polyallylamine hydrochloride (PALAM) and poly(acrylamide-co-diallyl-dimethylammonium chloride) (PAMALAM), were screened in two sets of experiments: long term (24–72 h) and short term (0–8 h). Silica inhibition performance is profoundly dependent on the polymeric additive dosage. The most effective dosages were found to be 10 ppm for PEI, 20 ppm for PALAM and 80–100 ppm for PAMALAM. The inhibitory efficiency of PEI (at 10 ppm dosage) reaches 55% at 24 h (inhibitory efficiency is defined as reactive silica in ppm at the time of measurement divided by 500 ppm, times 100). PALAM reches 65% inhibitory activity at 20 ppm, after 24 h. PAMALAM at 80 ppm dosage shows 60% inhibition. Inhibitory activity drops on longer silicate polymerization times (48 and 72 h). All three inhibitors show activity higher than the control during the first 8 h, exhibiting small variations in performance.