Keywords: 
• scale inhibition /
• terpolymer /
• scale inhibition performance /
• biodegradability /
• CaCO3 /
• circulating cooling water

Abstract: In the present investigation,three monomers,maleic anhydride (MA),acrylic acid (AA),and hydroxyethyl methacrylate (HAMA),were synthesized using aqueous radical polymerization,and investigated as novel biodegradable terpolymer scale inhibitors for circulating cooling water.The copolymer was analyzed using infrared spectroscopy and scanning electron microscopy (SEM) techniques.The structure of the polymer was examined.It was found that the copolymer scale inhibitor was contained in the carboxyl,sulfonic acid,and amide functional groups,and that the lattice distortion and complex solubilization is the main mechanism of copolymer inhibition of precipitation.Matrix removal evaluation and shaker cultures showed that the terpolymer is readily biodegradable;the terpolymer BOD5/COD value was 0.55.The biodegradation rate increased with increasing number of days;the extractive degradation rate increased to 75% in a culture period of 28 days.Using the comparative test of the scale inhibition performance of the terpolymer scale inhibitor and four common green scale inhibitors including polyepoxysuccinic acid,polyacrylic acid,2-phosphate butane 2,4-tricarboxylic acid,and poly (epoxy succinic acid),the influences of copolymer dosage,mass concentration of calcium ions,and water temperature on scale inhibition performance were discussed.The results showed that,when the copolymer dosage was 3 mg·L-1,water temperature was 80℃,and mass concentration of calcium ions was 480 mg·L-1,the scale inhibiting rate reached 91.35%.The copolymer performance of the calcium carbonate scale was superior to those of conventional inhibitors,and is especially appropriate for industrial circulating cooling water with high temperature and hardness.