Effect of Copper and Aluminium Metals on the Calcium Carbonate Scale Morphology, Polymorphism, Composition and Scale Inhibition Property of Hedp

Effect of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), on the polymorphism and morphology of calcium carbonate scale deposition on copper and aluminium metals was studied at 60 and 100 °C. The deposition was carried out using 0.1 M calcium chloride and 0.1 M sodium carbonate solutions over a period of 10 days. The experiments were carried out at two temperatures; 60 and 100 °C. 20 ml 0.1 M HEDP was used as inhibitor and was compared with samples prepared without HEDP under same experimental conditions. The experiment setup was designed in such a way to get samples of scale coated on metal when it is in direct contact with the sludge and without direct contact (in suspension above the sludge and under indirect heating). The samples of the metals and sludge were characterized using X-ray diffraction (XRD) and scanning electron microscopy. The results demonstrated that the polymorphic composition in the scale deposited on the metal surface varied not only with temperature, but also with the nature of the substrate.