The Effects Of Ion Impurities On Calcium Carbonate Scale

The literatures of impurities on calcium carbonate were reviewed. The effects of PO43-,SiO32-,Mg2+,Mn2+ and Fe3+ on Calcium carbonate were studied by static antiscale test, SEM and XRD technology when these ions exited with some scale inhibitors(AA/AMPS/HPA, Acumer5000, ATMP, PAPEMP) for inhibiting calcium carbonate scale with certain concentration ranges. The effect on the corrosion of orthophosphate, Hydroxyethyli-denediphosphonic acid (HEDP) and Zinc salt were also evaluated by weight loss, polarization curves technology.The result of static antiscale test shows that:PO43-, SiO32-, Mg2+, Mn2+ and Fe3+ almost have no scale inhibition on calcium carbonate respectively.PO43- and AA/AMPS/HPA have good synergistic effects for inhibiting calcium carbonate within certain concentration ranges.It's proved that the synergistic effect does exist between organophosphonic acids (ATMP, PAPEMP) and SiO32-, but less synergistic effect exists between copolymers and SiO32-.When Mg2+, ATMP and copolymer coexist, the CaCO3 scale inhibition rate is good and the synergistic effects are clearly.The synergistic effect does exist when low concentration of Mn2+, ATMP and copolymer are involved in the solution.Fe3+ makes the CaCO3 scale inhibition rate lower. It's also found that Fe3+ almost have no synergistic effect with antiscale.The result of SEM and XRD technology shows that:CaCO3 has a regular shape without any antiscale. Most of the scale is made of calcite; PO43- and SiO32- change the shape of calcite visibly, but Mg2+, Mn2+ make the crystal shape a little smaller.The CaCO3 crystal shape are changed obviously when ions in the experiment and the scale inhibitors coexist.The result of XRD technology shows that the scale is almost made up of calcite when the solution involves the orthophosphate. The intensity of the highest apices of XRD become lower with orthophosphate and copolymer.The result of weight loss and polarization curves shows that:Orthophosphate is anodic inhibitor in 0.05mol/L NaHCO3, acting as inhibitors at the passivation potential of carbon steel. But the active-passive behaviors of carbon steel are disappeared when the concentrate of orthophosphate was less 4mg/L.Orthophosphate, HEDP and Zn2+ have inhibited corrosion of both anode and cathode.