影响酸性铬冻胶成冻因素的研究

Studies on Influencing Factors for Formation of Acidic Polyacrylamide/Chromium Gel

研究了乏酸条件下 (pH =3～ 5 )影响PAM /Cr(Ⅲ )冻胶形成的因素。冻胶形成用初冻时间 (运动粘度达到 2 0 0mm2 /s的时间 )和突破真空度BV(代表冻胶强度 )表征。根据铬 (Ⅲ )的多核羟桥络离子交联水溶液中PAM分子而成冻的机理 ,基于只有低水解度PAM才能形成酸性铬冻胶的事实 ,认为在乏酸条件下PAM的交联主要是通过酰胺基进行的。所用PAM的水解度为 8.2 8%,相对分子质量为 5 .1× 10 6。对于PAM/Na2 Cr2 O7/Na2 SO3 /水成冻体系 ,当 pH =4～ 6、温度 (4 5～ 90℃ )较高、PAM浓度 (2 .5～ 10 g/L)较大、含盐量约为 4g/L(NaCl,CaCl2 )时 ,初冻时间较短 ;对于PAM/Cr(NO3 ) 3 /水成冻体系 ,Cr(NO3 ) 3 浓度 (0 .1— 1.6 g/L)较小、pH =3～ 5时成冻时间较短。酸性铬冻胶的强度 (BV值 )与初冻时间的关系符合一般冻胶的规律 ,即成冻时间越短 ,则冻胶强度越高。

The influencing factors for formation of PAM/Cr(Ⅲ) gel under the condition of spent acid (pH=3-5) are investigated. The gel formation is characterized by pregelation time, time for kinetic viscosity to reach 200 mm 2/s, and breakthrough vaccum, value BV representing relative gel strength. According to the concept of solution crosslinking of PAM molecules by multinuclear oblation complex ion of chromium(Ⅲ) and on the basis of experimental fact that acidic chromium gel can be formed only with PAM of low hydrolysis degree, it is considered that crosslinking occurs mainly through amide groups of PAM. The PAM used is of hydrolysis degree 8.28% and molar mass 5.1×10 6. Relatively short pregelation time is observed for PAM/Na 2Cr 2O 7/Na 2SO 3/H 2O gelling systems at pH=4-6, at higher temperature (in range 45-90℃), with higher PAM concentration (in range 2.5-10 g/L) and for PAM/Cr(NO 3) 3/H 2O gelling systems at pH=3-5 or with lower chromium nitrate concentration (in range 0.1-1.6 g/L). To the acidic chromium gel a general rule for gels is applicable, too, i.e the shorter the pregelation time the higher the gel strength is.