The effect of metal ions on calcium carbonate precipitation and scale formation

Abstract

Scale formation in domestic heating appliances is a widespread problem in the UK. Scale affects the life of energy intensive domestic devices such boilers with a potentially significant impact on their energy efficiency. A number of metallic cations, such as copper and zinc have been reported to affect CaCO3 precipitation and scale formation. This study aimed to investigate closely the effect of zinc and copper on calcium carbonate (CaCO3) formation and two sets of laboratory tests were performed. The effect of both metals on CaCO3 precipitation was investigated using a standard jar tester. The longest delay in precipitation was obtained by zinc. To study CaCO3 formation on a heated surface, a rapid scaling test was developed. This test was conducted at 42?C and 70?C to examine the effect of zinc dosing on CaCO3 scale formation. The results show that zinc is effective in inhibiting scale formation on a heated surface particularly at 42?C.