Development of acrylonitrile copolymers for scale control in cooling water systems

The formation of calcium sulphate and carbonate scale has been prevented by using acrylonitrile-acrylic acid (AN-AA) and acrylonitrile-methacrylic acid (AN-MAA) copolymers over a temperature range of 50-80degreesC at different pHs from 7.0 to 8.5. The efficiency of the antiscalants was assessed by various techniques such as a chemical screening test, constant potential electrolysis and impedance measurements. The change in crystal habits by the addition of antiscalant was seen using XRD spectrum and SEM photographs. The effectiveness of polymers on microorganisms and forming gelation with calcium ion and iron-dispersing ability were also studied. The amount of scale deposition increased with increase in temperature and pH. The polymers acted as good antiscalants at low temperature and pH ranges. They also acted as good flocculants under some special conditions. For example, at a higher pH of 8.5 and temperature 80degreesC with 20 ppm dosage level of the AN-AA polymer, 100% was achieved. Further, they had good iron dispersibility and can gelate with Ca2+ ions.