Synthesis Of Polyaspartic Acid As A Gree Scale Inhibitor Using Microwave And It's Performance Evaluation

Polyaspartic acid(PASP) is a kind of scale inhibitor and polymer of amino acids which has attracted much attention of domestic and international researchers. There is no phosphor in pasp,it is not poisonous and can be totally biologic decomposed in the environment. The polyaspartic acid(PASP) polymer can be obtained by hydrolyzing PSI. the use of the ammonia gas was avoided. The react condition was optimized.All factors of the synthesizing and hydrolyzing were studied. The best preparation condinion was:the ratio MA:AM=1.2,the microwave radiation is 900W,and the time of microwave radiation is 12min.The average conversion rate attained71.7% on this condition. The best hydrolyzing factors was: hydrolyzing temperature 60℃, hydrolyzing time is 60 min,concentration of NaOH is 10mol/L.The average conversion rate attained 51.2% on this condition,and the relative molecular weight is about 3500.The IR and TG test were carried out for the product synthesized on above condition. The characyeristic peaks indicated there were amido and carboxyl groups in the molecule. Also the chart was compared with the consulted one and it proved the product was PASP. The TG analyses indicated that it was considered as a kind of water treatment medicine that can be applied at high temperature up to 400℃in water system.The scale inhibiting performance of PASP on CaCO₃ was investigated. Its mixture dosage were 60mg/L,the scale inhibiting performance was good respectively. The scale inhibiting performance of PASP on CaSO₄,BaSO₄ was investigated. The study showed that PASP was also suitable for high calcium ion. There was little difference between scale inhibiting performance of PASP on CaSO₄,BaSO₄.By quantitatively analyzing the equilibriumc oncentrations of Ca²⁺ and CO₃^2- in a super-saturated CaCO₃ solution,determining the CaCO₃ crystal structure. For PASP inhibiting the formation of CaCO₃ scale,the reasons that better scale-inhibiting performance of PASP than those of polyacrylic acid and hydrolyzed maleic anhydride had been studied.