碳酸钙结垢行为中临界过饱和度的变化

Change of Critical Supersaturation Ratio in CaCO_3 Scale Formation

考察了溶液温度、结垢离子接触时间、阻垢剂种类及含量对碳酸钙结晶时临界过饱和度(CSSR)的影响,并通过经典的晶体均相成核理论分析了加入阻垢剂后碳酸钙结晶时表面自由能的变化。利用扫描电子显微镜和X射线衍射技术表征了水垢试样中碳酸钙的形貌和晶型。实验结果表明,碳酸钙溶液的CSSR值随结垢离子接触时间的延长和溶液温度的升高而减小,随阻垢剂含量的增加而增大。阻垢剂的加入使碳酸钙溶液的过饱和区变宽,其中2-膦酸丁烷-1,2,4-三羧酸(PBTCA)和氨基三亚甲基膦酸(ATMP)对碳酸钙结晶时表面自由能的影响大于聚丙烯酸的影响,且PBTCA和ATMP在实验含量范围内表现出临界值效应。阻垢剂的加入使碳酸钙沉积物形貌发生变化,由以方解石为主的晶型转变为以球霰石为主的晶型。

Effects of solution temperature, contact time of fouling ions, type and concentration of scale inhibitors on critical supersaturation ratio （CSSR） of CaCO3 solution were studied. According to the light of homogeneous nucleation theory, change of surface free energy during crystallizing of CaCO3 in presence of scale inhibitors was investigated. Crystal of CaCO3 scale was characterized by means of SEM and XRD. CSSR decreases with prolonging of contact time and rise of solution temperature, but increases with raising of scale inhibitor concentration. In presence of aminotrimethylene phosphonic acid （ ATMP）, CSSR decreases more with increase of temperature than that in presence of 2 - phosphonobutane - 1,2,4 - tricarboxylic acid （ PBTCA ） or polyacrylic acid （PAA）. Effect of CaCO3 nucleation with PBTCA and ATMP on surface free energy is more obvious than that with PAA. Crystalline form of CaCO3 precipitate transforms from calcite in main into vaterite in main in presence of scale inhibitors.