Adsorción de flúor en aguas subterráneas utilizando carbón activado de la cascarilla de arroz

Abstract

The purpose of this research was to obtain activated carbon from rice husk for the adsorption of fluoride in groundwater of the Jesús del Gran Poder community belonging to Guano city, province of Chimborazo. The synthesis of the adsorbent was performed by chemical activation using phosphoric acid at three different concentrations: 65%, 75% and 85%. The synthesized activated carbons were characterized by instrumental analyses that included Fourier transformed infrared spectroscopy, scanning electron microscopy and surface area analysis allowing to determine the physical characteristics of the adsorbent. For the evaluation of adsorption, a multilevel factorial design of 27 repetitions and two experimental variables were carried out: concentration of the activating agent and mass of the activated carbon. Doing the experimentation, filters were elaborated using 2, 6 and 10 grams of adsorbent where the water collected from the community was poured with an initial concentration of 1.99 ppm then measure the final concentration of fluoride and evaluate its efficiency by means of the Freundlich and Langmuir isotherms. The carbon synthesized at 85% presented a surface area of 780.0 m2/g and a homogeneous structure consisting of mesopores (60%) and micropores (40%) necessary for the removal of fluorine ions. Based on the regression coefficients R2 (0.9463) it was determined that the adsorption process was adjusted to the Langmuir model, developing on a homogeneous surface in a single layer, removing up to 69.35% of fluorine ions. In summary, fluoride adsorption was optimized using 83.7% phosphoric acid and 7.5 grams of activated carbon to keep the fluoride concentration below the 1.5 ppm quality parameter. It is recommended to investigate methods of chemical aftertreatment in activated carbon in order to develop specific functional groups that favor the removal of fluoride.