浅论铝盐的水解和吸附电中和过程中被凝聚物浓度的影响

CHARACTERISTICS OF ALUMINUM COAGULATION: THE INFLUENCE OF SUSPENSION CONCENTRATION ON HYDROLYSIS REACTION AND ADSORPTION-CHARGE NEUTRALIZATION

通过对凝聚机理和铝盐在水中水解过程的分析,提出了铝盐水解物吸附引起胶体电中和的数学模式.论述了被凝聚物浓度对铝盐水解过程的影响.在实际的凝聚过程中,铝盐的水解和向胶体表面的吸附是同时进行的,部分铝盐在完成水解之前就以中间产物的形态吸附于胶体表面.胶体溶液的浓度愈高,这种倾向就愈强.由于较低水解度的物种具有较高的单位电荷浓度,它们能显示较强的电中和能力;因此,随着胶体溶液浓度的增高,达到最佳凝聚ζ电位所需的比投药量会降低.

In this paper,the author has proposed a mathematical model to describe the process of adsorption and charge neutralization by hydrolyzed aluminum species on the basis of coagulation mechanism. The influence of suspension concentration on aluminum hydrolysis was discussed. As an aluminum salt is dosed to a suspension,the adsorption of aluminum species on the surface of the suspended particles may compete with aluminum hydrolysis arid some of the less hydrolyzed species may have already been adsorbed before the completion of hydrolysis reaction. Such a tendency may become stronger when the suspension concentration is higher.Because the less hydrolyzed aluminum species have higher specific positive charge,they are more effective in neutralizing the negative charge of the suspended particles. Therefore, as the suspension concentration becomes higher,the specific aluminum dosage required for neutralizing the particles to an optimum zeta potential for coagulation is decreased substantially. This gives a reasonable explanation of the non-stoichiometric relation between aluminum dosage and suspension concentration.