Continuous treatment of boron and fluoride in aqueous solutions using a column loaded with granulated Mg–Al layered double hydroxides intercalated with nitrates

Abstract

Mg–Al layered double hydroxides intercalated with NO3− (NO3·Mg–Al LDHs) were mixed with various amounts of epoxy resin to obtain granulated NO3·Mg–Al LDH samples. The granulated NO3·Mg–Al LDH samples were shown to be capable of adsorbing B from aqueous solutions and the experimental adsorption isotherm data fit well to the Langmuir model. In order to evaluate the continuous treatment of B and F− in aqueous solutions, a chromatographic column was loaded with granulated NO3·Mg–Al LDH with an LDH/epoxy resin ratio of 1:0.5 and H3BO3 and NaF solutions were passed through the columns under various conditions. The concentrations of B and F− in the elutions were found to increase with time. In addition, the concentrations of B and F− in the elutions also increased with increase in the flow rates and initial concentrations of H3BO3 and NaF, respectively, which were attributed to the flow of large amounts of B and F− into the column in a short duration. The experimental data from the column experiments were fit to the Thomas model. The relatively high R2 values under all the conditions suggest that the Thomas model adequately represents the results of the adsorption experiments. For the adsorption of both B and F−, the calculated qT from the Thomas model showed good agreement with the experimental qE values, confirming the validity of the Thomas model for the column experiments.