高岭石胶体的降氟作用机理

含氟溶液的高岭石吸附实验表明，其吸附能力与溶液的pH值呈现显著的负相关关系。在酸性条件下，高岭石的吸氟量较大，降氟率较高，降氟率较高；随着pH值的增大，其吸氟能力大大降低；而在碱性条件下，高岭石基本不具有吸氟能力。高岭石的吸氟量还受高岭石用量和含氟溶液浓度的影响。高岭石吸附氟主要是由于体系pH值降低，高岭石表面带正电荷而吸附F^-离子；另外，随着NaF浓度的提高，体系ζ电势减小，发生絮凝作用，高岭石携带F^-离子沉淀下来。

Defluoridation of Kaolinite Colloid

The kaolinite adsorption experiments were conducted on the fluoride solution. Results show that an excellent negative correlation exists between the adsorption ability of kaolinite and pH values of the solution. Kaolinite adsorbs more fluorine ions and the defluoridation effect is remarkable at low pH value; As pH value increases, the amount of fluorine adsorbed by kaolinite decrease rapidly; even worse, kaolinite seldom adsorbs fluorine ions in basic solution. The amount of kaolinite and the concentration of fluoride solution also influence the amount of fluorine adsorbed on kaolinite. This is believed to be the result of a positive surface charge build-up on the kaolinite at low pH that causes affinity of the negatively charged fluoride ions. In addition, as the concentration of the fluoride solution increases, the potential falls, resulting in flocculation of kaolinite together with fluoride ions.