Modification And Scale Inhibition Performance Research Of Environment-friendly Scale Inhibitor Polyaspartic Acid

The research and development of water treatment agent for processing industrialcirculating cooling water has always been the focus of attention, the greening andmulti-function of water treatment agent is the trend of the long-term development.Because of its non-toxic and biodegradability, polyaspartic acid(PASP) is consideredto be a green and environmental scale inhibitor. However comparing with other scaleinhibition dispersing agents used widely, its dispersion performance for some metalsand scale inhibition performance for some kinds of incrustation lag behind them.Therefore, in order to improve scale inhibition and dispersion performance, thissubject will study its synthesis process and its modification properties.In the first part of this paper, based on improving the dispersion, the researchstudies the synthesis process of PASP. With maleic anhydride and urea as rawmaterials，polysuccinimide(PSI) is synthesized by the solid phase condensationmethod. The optimum synthetic conditions of PSI is determined through the singlefactor test and orthogonal experiments that: the molar ratio of maleic anhydride andurea is1:1.2, and the condensation temperature is170℃, and the condensation time is40min. The author measures and calculates the degree of polymerization of PSI andthe viscosity average molecular weight of PASP and studies condensation temperatureon the influence of molecular weight and the relationship between the molecularweight and the anti-scaling rate of PASP. The findings show that the scale inhibitionperformance is better when PASP synthesized in the best synthetic conditions usingsolid phase condensation method with the viscosity average molecular weight about4000.Terpolymer of acrylic acid/acrylic amide/malefic anhydride(AA/AM/MA)issynthesized and mixed with PASP. A new PASP-based composite with excellent scaleinhibition performance is developed. The scale inhibition of combination of PASP and AA/AM/MA is discussed through the static inhibiting scale experiment. Thesynergistic effect of PASP and AA/AM/MA inhibitor dispersing agents are studied.The optimum dosage of the combination is1:0.5. It can be used in water system withhigh calcium concentration and high alkalinity, and the significant scale inhibition canstill be remained even staying in high temperature water system for long resident time.The scales of static water samples are tested in simulation recycling water, and theinhibition rate of CaCO3is found at100%.With intermediate PSI as open loop grafted compounds, different graftingpercentage of polyaspartic acid derivatives PASP-Glu are synthesized with glutamicacid(Glu). The open loop modified hydrolysis conditions in the process are studied.The influence of the molar ratio of raw materials, hydrolysis temperature andhydrolysis time on the grafting rate of synthetic product are reviewed. The best ringopening modification conditions is determined. The scale inhibitors performance,dispersion properties and biological degradation performance are evaluated throughthe calcium carbonate deposition method, measuring light transmittance method andbiological table experiment method. The results show that the derivatives ofPASP(PASP-Glu)is a environment-friendly scale inhibitor with good biodegradation.Comparing with PASP, the introduction of the carboxylic acid group improvess thescale inhibition performance of CaCO3and the dispersive performance of Fe2O3commendably.