二水硫酸钙粒度和陈化时间对高岭土颗粒在水中沉降过程的影响规律

Effect of particle size and aging time of calcium sulphate dihydrate on the sedimentation of kaolinite in water

针对二水硫酸钙的混凝性能,利用测定悬浊液浊度和ζ电位的方法,考察了二水硫酸钙粒度和陈化时间对高岭土颗粒在水中沉降过程的影响规律。二水硫酸钙颗粒加入到含有高岭土颗粒的水中之后,其浊度发生了明显的降低。不同粒度的二水硫酸钙对高岭土悬浊液的浊度有不同的脱除效果,且粒度越小、除浊性能越好;当二水硫酸钙粒度小于75μm时可使浊度由2 810 NTU降低到70.1 NTU,优于大颗粒二水硫酸钙对悬浊液的除浊效果。在投入到高岭土悬浊液之前,将二水硫酸钙预先在水中进行陈化,发现当陈化时间为20～30 min时,可使高岭土悬浊液的浊度降至68.9 NTU,浊度降低的效果最好。此外,二水硫酸钙可使高岭土悬浊液的ζ电位绝对值减小,意味着颗粒间静电斥力减小,从而有助于沉降。

The effects of the particle size and aging time of calcium sulphate dihydrate on the sedimentation of suspended kaolinite particles in water were investigated experimentally.The turbidity and potential were measured.The turbidity decreased significantly when calcium sulfate dihydrate particles were added into the kaolinite suspension.The smaller the particle size of calcium sulphate dihydrate, the better turbidity removal is.When the calcium sulfate dihydrate particle was less than 75/lm in size, the turbidity was decreased from 2 810 NTU to 70.1 NTU,which is better than that using larger calci- um sulphate dihydrate particles.The best turbidity removal was performed when the calcium sulphate dihydrate was aging for 20～30 minutes.Then 68.9 NTU was got in lowest turbidity.Calcium sulphate dihydrate can make the absolute value of ζ potential of kaolin suspension decreased, indicating the weakening of electrostatic repulsion between particles and the strengthening of sedimentation tendency.