López Valdivieso A, Reyes Bahena J L, Song S, Herrera Urbina R
Area de Ingeniería de Minerales, Instituto de Metalurgia, Universidad Autónoma de San Luis Potosí, Av. Sierra Leona 550, Lomas 2(a) Sección, San Luis Potosí, S.L.P., 78210, Mexico.
J Colloid Interface Sci. 2006 Jun 1;298(1):1-5. doi: 10.1016/j.jcis.2005.11.060. Epub 2005 Dec 27.
The effect of temperature and pH on the zeta potential of alpha-Al2O3 and adsorption of fluoride ions at the alpha-Al2O3/aqueous solution interface has been investigated through electrophoretic mobility measurements and adsorption studies, to delineate mechanisms involved in the removal of fluoride ions from water using alumina as adsorbent. When the temperature increases from 10 to 40 degrees C, the pH of the point of zero charge (pH(pzc)) shifts to smaller values, indicating proton desorption from the alumina surface. The pH(pzc) increases linearly with 1/T, which allowed estimation of the standard enthalpy change for the surface-deprotonation process. Fluoride ion adsorption follows a Langmuir-type adsorption isotherm and is affected by the electric charge at the alpha-Al2O3/aqueous solution interface and the surface density of hydroxyl groups. Such adsorption occurs through an exchange between fluoride ions and surface-hydroxyl groups and it depends on temperature, pH, and initial fluoride ion concentration. At 25 and 40 degrees C, maximum fluoride adsorption density takes place between pH 5 and 6. Increasing the temperature from 25 to 40 degrees C lowers the adsorption density of fluoride.
通过电泳迁移率测量和吸附研究，考察了温度和pH对α-Al2O3的zeta电位以及α-Al2O3/水溶液界面氟离子吸附的影响，以阐明使用氧化铝作为吸附剂从水中去除氟离子所涉及的机制。当温度从10℃升高到40℃时，零电荷点的pH（pH(pzc)）向较小值移动，表明质子从氧化铝表面解吸。pH(pzc)随1/T线性增加，这使得能够估算表面去质子化过程的标准焓变。氟离子吸附遵循朗缪尔型吸附等温线，并受α-Al2O3/水溶液界面的电荷和羟基表面密度的影响。这种吸附通过氟离子与表面羟基之间的交换发生，并且它取决于温度、pH和初始氟离子浓度。在25℃和40℃时，最大氟吸附密度出现在pH 5至6之间。将温度从25℃提高到40℃会降低氟的吸附密度。
