In this work, a variety of polymers were evaluated as precipitation inhibitors for magnesium ammonium phosphate (struvite) in aqueous solution. The polymers tested include 1) homopolymers of acrylic acid and methacrylic acid of varying molecular weight (MW), maleic acid, 2-ethyloxazoline, 2) acrylic acid based co- and terpolymers containing monomers with different functional groups and 3) natural, bio- and hybrid based polymers. The results reveal that polymer performance as a struvite inhibitor is strongly affected by polymer dosage, MW, and ionic charge of the functional group. It has been observed that performance of poly(acrylic acid), PAA, is negatively impacted by increasing the struvite solution supersaturation. Moreover, inhibition of struvite by polymers increases with increasing MW with a range of ~2,000 to 60,000 investigated in this paper. Overall performance reveals the following trend by polymer type: homopolymer > copolymer > bio-, hybrid > terpolymer. SEM and XRD investigations confirm struvite crystals formation in the absence and presence of inhibitors.
Key words: magnesium ammonium phosphate, struvite, precipitation, inhibition, inhibitor