Lamellar phases containing vanadium oxide: Synthesis, characterization and application of the adsorption of phenol from aqueous solutions

Lamellar phases of the general formula [C _nH _2n+1N(CH ₃) ₃]VO ₃ (n = 14, 16, 18) have been prepared by an ion-exchange/precipitation reaction of alkyltrimethylammonium surfactants and NaVO ₃ in an aqueous medium at room temperature. The phases were characterized by powder X-ray diffraction, transmission electron microscopy, infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry The data support a proposed crystal structure model in which single arrays of the one-dimensional chains of oligomers {(VO ₃) _n} ^n- that may be generated from the starting material NaVO ₃ fragmented by the hydration during the dissolution into water and the surfactants layers alternate. The alkyl chains of the surfactants in these materials are arranged as monolayers or deeply penetrate into the interlayer region with a tilt angle of 37°. The phenol adsorption in aqueous solution on a representative lamellar phase was investigated. The data being fitted to Langmuir Isotherms and a maximum adsorption capacity calculated from the Langmuir equation to be 178.6 mg of phenol/g for [C ₁₆H ₃₃N(CH ₃) ₃]VO ₃ have been obtained. The effect of pH on the adsorption and desorption of phenol has also been studied. Acetone solution of 20% is the best eluent for desorption of phenol from the loaded adsorbent with a desorption efficiency of 90.8%.