DOI: 10.1016/j.clay.2011.10.002
WoS: 000298513500012
15 Citations
Résumé:

Two hydrothermally synthesised allophanes (Si/Al = 0.5 and 1) were modified by heating at 400 degrees C. N-methyl-D-glucamine, a specific boron complexant, was grafted on the allophane material with Si/Al = 0.5. The surface and structural properties of the different materials were characterised by infrared spectroscopy and Si-29 CP MAS NMR spectroscopy. The porous characteristics of the different allophanes (specific surface area, pore size distribution) were determined by nitrogen adsorption at 77 K using the BET equation and the BJH model. The adsorption of boron, i.e. boric acid/borate, by the modified allophanes was studied in aqueous solutions with boron contents of 1 to 100 mg L-1. The pH-dependence of boron adsorption of all the sorbents showed a maximum at a pH value close to the pKa value of boric acid (pKa H3BO3/B (OH)(4)(-) = 9.26). The adsorption isotherms of boron by raw and modified allophanes were fitted with a double Langmuir equation, assuming the presence of two sets of adsorption sites. The grafting of N-methyl-D-glucamine did not improve the boron adsorption of the allophanes but the structural changes by heating at 400 degrees C increased the adsorption. (C) 2011 Elsevier B.V. All rights reserved.