Synthesis And Scale Inhibition Of Polyaspatic Acid Polymers

To save a large amount of industrial water, the study of effective and green water treatment agents becomes the research focus in the field of water treatment. In this study, monoisopropanolamine(PA)/ethylamine (eA) and polysuccinimide (PSI) were used to synthesize two kinds of polyaspartic acid (PASP) copolymers—PA-PASP and eA-PASP. The performances of these two kinds PASP copolymers on calcium phosphate, calcium carbonate and calcium sulphate scale inhibition were certified by a static anti-scaling method, and their performances were also compared with that of two commercial scale inhibitors 1, 1-diphosphoroethanol (HEDP) and 2-hydroxyl-phosphine acetic acid (HPAA). EA-PASP (a previously reported PASP copolymer) was also synthesized by the reaction between ethanolamine and PSI. The performance of EA-PASP on calcium phosphate inhibition was compared with that of the newly synthesized PASP copolymers. The effects of Ca+ concentration, PO43- concentration, pH and temperature on Ca3 (PO4) 2 scale inhibition by these inhibitors were also tested. Structures of these inhibitors were characterized with NMR. The biodegradability of these PASP copolymers was evaluated by the methods from national standard GB/T 21802-2008.(1) The newly synthesized PASP copolymers PA-PASP and eA-PASP have much better performances on Ca3 (PO4)2 scale inhibition than PASP, HEDP and HPAA have. At a dosage of 16 mg/L, the scale inhibition efficiency of P-1.6 on Ca3 (PO4)2 scale is 96%. At a dosage of 20 mg/L, the scale inhibition efficiency of P-1.6 on Ca3 (PO4)2 scale is 97%. The newly introduced functional group in PASP is helpful to the abilities of PASP copolymers on Ca3 (PO4)2 scale inhibition. The inhibition efficiencies of the newly synthesized PASP copolymers on CaCO3 scale were a little higher than that of PASP when the mole ratio of monoisopropanolamine (ethylamine) and polysuccinimide was 0.8. The newly introduced functional groups in PASP are also helpful to the abilities of PASP copolymers on CaCO3 scale inhibition. However, as the newly introduced functional groups increase, the inhibition efficiencies of the newly synthesized PASP copolymers on CaCO3 scale decrease. PA-PASP and eA-PASP have worse performances on CaCO3 scale inhibition than HEDP and HPAA have. The introduction of new functional groups has little influence on the performances of PA-PASP and eA-PASP on CaSO4 scale inhibition.(2) The efficiencies of Ca3(PO4)2 scale inhibition of EA-PASP,PA-PASP and eA-PASP decrease as the concentration of Ca2+ and PO43- increase, EA-PASP and PA-PASP are more tolerant than eA-PASP on the high concentration of Ca2+ and PO43-. When the concentration of Ca+ is as high as 450 mg/L, the inhibitor dosage are 16 mg/L, the scale inhibition efficiencies of E-1.6, E-2.0, P-1.6, P-2.0 and P-1.6 on Ca3(PO4)2 scales are above 80%. When the concentration of PO43- is as high as 10 mg/L, the inhibitor dosage are 16 mg/L, the scale inhibition efficiencies of EA-PASP, P-1.6, P-2.0 and P-1.6 on Ca3(PO4)2 scale are above 80%.(3) Amide groups in the PASP copolymers can still assist in inhibiting the growth of calcium phosphate scale. Both amide group and hydroxyl group are effective functional group on Ca3 (PO4)2 scale inhibition. EA (or eA) and PSI can react more completely than PA and PSI when the mole ratio of amino compound and polysuccinimide was 1.2. Smaller molecules react faster with the polysuccinimide starting material. The pH and temperature have little influence on the performances of PA-PASP and eA-PASP on Ca3 (PO4)2 scale inhibition.(4) The presence of introduced functional groups on PASP was confirmed by NMR. The result of biodegradation test indicated that the studied PASP copolymers are biodegradable.