Boron Removal from Aqueous Solutions by Synthetic MgAlFe Mixed Oxides

Abstract

The boron removal capacity from an aqueous solutionusing MgAlFe mixed oxides from layered double hydroxides (LDH) wasstudied. They were synthesized by the coprecipitation method at 70 °Cand were characterized as potential filter materials. The Fe3+ analyzed byX-ray photoelectron spectroscopy and UV−visible diffuse reflectanceshowed their tetrahedral and octahedral coordination. Scanning electronmicroscopy micrographs and thermogravimetric and differential scanningcalorimetry analysis evidenced the presence of clusters and particlesaggregates and decreased dehydroxylation temperature when the ironcontent increased. Mixed oxides and boron solution in a ratio of 20:1Mg/B were put in a batch reactor at different contact times. The borateremoval process was due to the memory effect of the mixed oxides and superficial adsorption by electrostatic attraction. Thisfact is directly related to the specific surface area, Fe content, and surface charge. The maximum boron removals were achievedwith the CS25 and CS50 samples with values higher than 85%.