Ca2+、Al3+对聚丙烯酰胺在高岭土絮凝过程中作用的影响

在实验条件下,Ca²⁺、Al³⁺离子对高岭土的絮凝过程有不利影响,且pH越高Ca²⁺的影响越大,pH越低,Al³⁺的影响越大.运用分子轨道(MO)理论、溶液化学计算、电子探针测试等手段,研究探讨了其作用机理.认为在酸性和中性范围内,Ca²⁺、Al³⁺离子及它们的羟基络合正离子与聚丙烯酰胺之间的相互作用造成后者分子链发生卷曲,导致絮凝效果下降;而在pH>9范围内,Ca²⁺、Al³⁺的氢氧化物沉积在高岭土表面,阻碍或抑制了聚丙烯酰胺与高岭土之间的氢键作用.

Effects of Calcium and Aluminium Ions on Flocculating Process of Kaolin Usina Polvacrylamide as Floceulant

The effects of Ca²⁺ and Al³⁺ ions on flocculating process of kaolin using polyacrylamide as flocculant was studied. It is found that Ca²⁺ and Al³⁺ ions depress the flocculation of kaolin. The higher the pH value, the greater the effect of Ca²⁺ ion will be and the lower the pH value, the greater the effect of Al³⁺ ion will be. Mechanism nf the effects was investigated and discussed through molecular orbit (MO) theory, solution chemistry calculation and electronic probe examination. It is revealed that bonding interaction of Ca²⁺, Al³⁺ and their positively charged hydrolyzed ions with polyacrylamide causes the crooking of molecular chains of the later, resulting in a low efficiency of flocculation of kaolin under acidic and ned tral conditions; while the deposition of hydroxides of Ca²⁺, Al³⁺ ions on the surface of kaolin hinders or depress the hydrogen bond interaction between polyacrylamide and kaolin at pH values higher than 9.