羧酸聚合物对磷酸钙的阻垢作用和机理

采用静态阻垢法评定了膦酰基羧酸聚合物(POCA)、聚丙烯酸(PAA)、丙烯酸-丙烯酸羟丙酯共聚物(T-225)、水解聚马来酸酐(HPMA)等四种羧酸类聚合物阻垢剂对磷酸钙的阻垢性能, 发现在加药量为25 mg/L时几种聚合物对磷酸钙垢的阻垢率分别为100%, 94.6%, 36.2%和30.2%. 采用分子动力学(MD)方法, 模拟计算了四种聚合物与磷酸钙晶体的(110)晶面的相互作用结合能、非键作用能等参数. 结果表明: 聚羧酸与(110)晶面结合能以及非键作用能的大小排序为POCA＞T-225＞HPMA＞PAA, 结合能以及非键作用能越大, 说明聚合物与垢晶体的结合越紧密, 抑制性能越好; 因此它们对磷酸钙阻垢能力大小排序为POCA＞T-225＞HPMA＞PAA. 该理论计算与实验室静态阻垢评定结论一致. 通过对超分子对关联函数的分析, 发现POCA和T-225聚合物中羰基O原子与晶面上Ca^2＋之间形成了较弱的离子键, 但强度远比非键作用小, 非键作用主要由库仑作用和范德华作用力提供, 且库仑作用的贡献更大. 据此合成了马来酸酐-苯乙烯磺酸钠-丙烯酸羟丙酯(MA-SS-HPA)以及苯乙烯磺酸钠-丙烯酸羟丙酯-亚磷酸(MA-SS-H₃PO₃)共聚物, 加药量为18 mg/L时对磷酸钙垢的阻垢率分别为94.2%和100%, 性能优于POCA.

Scale Inhibiting Effect and Mechanism of Carboxylic Polymer on Apatite

The antiscaling performance of phosphono carboxylic acid telomer (POCA), polyacrylic acid (PAA), acrylic acid-acrylic acid hydroxypropyl acrylate copolymer (T-225) and hydrolyzed polymaleic anhydride (HPMA) on Ca₃(PO₄)₂ was studied by static scale-inhibiting method. The results show that the efficiencies of scale inhibition of four polymers are 100%, 30.2%, 94.6% and 36.2% respectively when the quality of polymer is 25 mg/L. The interactions such as binding energies and non-bind energies between four carboxylic polymer scale inhibitors and (110) crystal surface of apatite had been simulated by molecular dynamics. The orders of binding energies and non-binding energies of four polymers with (110) crystal surface are as follows: POCA＞T-225＞HPMA＞PAA, the bigger the binding energies and non-binding energies, the stronger the binding effects between polymers and crystal surface, so the scale inhibiting effect on apatite is POCA＞T-225＞HPMA＞PAA which corresponds with the experiment results. According to the analysis of pair correlation functions of polymers with crystal surface, weak ionic bonds have been formed between oxygen of carbonyl of POCA, T-225 polymer and Ca^2＋ of apatite, but they are much less than non-bonding effects mainly provided by coulomb interaction and Van der Waals interaction, in which the prior is bigger than the latter. On the basis of above theory, the copolymers of maleic anhydride-sodium p-styrene sulfonate-acrylic acid hydroxypropyl acrylate (MA-SS-HPA) and sodium p-styrene sulfonate-acrylic acid hydroxypropyl acrylate-phosphorous acid (MA-SS-H₃PO₃) were synthesized, and their efficiencies of scale inhibition on apatite are 94.2% and 100% respectively when the quantity is 18 mg/L, that is to say their performance of scale inhibition is better than POCA.