Research On Both Polyaspartic Acid- Based Scale Inhibition Dispersing Agents And Their Synergistic Scale Inhibition Effect With Magnetic Field

Polyaspartic acid (PASP) is a kind of biodegradable environmentally friendly scale inhibition dispersing agents. Its performance of scale and corrosion inhibition, however, is worse than the other scale inhibition dispersing agents. In this paper, PASP-based composite scale inhibition dispersing agents and their synergistic scale inhibition effect with magnetic field were investigated in order to develop an environmentally friendly and high-efficient water treatment technique used in industrial circulating cooling water system.For the purpose of increasing scale inhibition rate, a new kind of high-efficient scale inhibition dispersing agent, acrylic acid-acrylic ester-itaconic acid tercopolymer(AA-AE-IA), was synthesized. The effect of the polymerization conditions, such as initiator, chain transfer agent, and reaction temperature, on the scale inhibition rate of AA-AE-IA was studied, and the suitable synthetic reaction conditions were optimized. Experimental results showed that its scale inhibition dispersing performance was better than that of the other acrylic acid copolymers.PASP was synthesized by a thermal-polycondensation technique.The relationship between the scale inhibition rate and the molecular weight of PASP was determined, and its scale inhibition performance for calcium carbonate and calcium sulfate was researched under different conditions. Then the scale inhibition performance of the composites of PASP and acrylic acid copolymer or phosphonic scale inhibition dispersing agents was investigated. The result showed that the composite of PASP and AA-AE-IA tercopolymer possessed a significantt synergism, and the scale inhibition rate was increased greatly. A new PASP-based composite with excellent scale and corrosion inhibition performance was developed by compounding PASP,AA-AE-IA and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA). Under the conditions of Ca2+ 639mg.L-1, water temperature 800C, and PASP+AA-AE-IA+PBTCA 40mg.L-1, the static concentration scale inhibition rate reached 98.7%, and the corrosion inhibition rate got 96.5%. In addition, the scale inhibition performance of PASP+AA-AE-IA+PBTCA composite on both calcium carbonate and calcium sulfate was investigated under the conditions of different dosages, water temperature, water hardness and experiment time, and then the quantitative relationship between the scale inhibition rate and the factors above mentioned was determined. On the basis of experimental studies, the industrial production and application of PASP+AA-AE-IA+PBTCA composite were realized successfully.A dynamic experimental device for circulating cooling water system equipped with magnetic water treatment, was designed and assembled by the author. The crystallization kinetics of calcium carbonate in the presence of magnetic field, and the scale inhibition dispersing mechanism of the magnetic field were studied. The effect of experimental conditions including magnetic field intensity, water temperature, water velocity and hardness on calcium carbonate crystallization process and scale inhibiton rate was also investigated. The reason why the magnetic field possessed a certain scale inhibition function is that it increased the content of aragonite in calcium carbonate crystallite and made the crystallite distorting.A new water treatment technique used in circulating cooling water system employing the synergism of PASP-based scale inhibition dispersing agents and magnetic field was put forward. The synergistic scale inhibition performance of the magnetic field and PASP or PASP+AA-AE-IA+PBTCA was investigated under different operation conditions. Both the static and dynamic experiments showed that there existed a remarkable synergism between the magnetic field and the scale inhibition dispersing agents, and that synergistic scale inhibition effect of the magnetic field and PASP+AA-AE-IA+PBTCA was better than that of magnetic field and PASP, and that the synergistic scale inhibition effect kept steady within a wide range of water hardness and temperature. Under the dynamic experimental conditions, the scale inhibition rate of PASP+AA-AE-IA+PBTCA or PASP in the presence of magnetic field can increase more then 20 % and 13 %, respectively. The calcium carbonate crystal samples were characterized by SEM and XRD techniques and the results showed that the synergism between the magnetic field and PASP-based scale inhibition dispersing agents could distort calcium carbonate crystallite more remarkably, causing the calcium carbonate crystallite to get much finer and more dispersive.