Study of TiO2 immobilization on glass and its application on phenol photodegradation

J.A. ROSSO; P.I. VILLABRILLE; L. ROSSI

Santa Fe de la Vera Cruz

Conferencia; VI San Luis School and Conference on Surfaces, Interfaces and Catalysis; 2018

UNL INCAPE

Advanced oxidation processes are alternativetreatments to effectively remove refractory contaminants on industrialeffluents. Many of them are based on the use of TiO2 as aphotocatalyst although it has several aspects to study1. It has beenfound that the modification of this material with metals (noble, transition orlanthanide) shown an enormous potential to overcome the pristine TiO2particles limitations of visible light absorption and high recombination ofcharge carriers2. Moreover, the inmobilization of the materials onglass allow the separation and reuse of the catalysts. The aim of this work isto study the effect of different ways of inmobilization of palladium doped TiO2on phenol degradation (model contaminant) using UV irradiation. The materials wereprepared by the sol-gel method. The procedure was described in a previous paper3.The specific reagents used in this synthesis were: titanium tetraisopropoxide(TTIP), absolute ethanol, nitric acid. Palladium acetylacetonate (Pd(acac)2)was used as metal-ion precursor, in the appropriate amount to reach a doping level of0.1 nominal atomic % (0.1 at. %). Undoped TiO2 was synthetized underthe same conditions to be used as control material. Immobilizationwas performed on glass slides using the sol preparation, by dip-coating. Theglass slides were rinsed with an alkaline solution and dried before dip-coatingprocedure. A lab-made dip coater was set with a withdrawing speed of 7 mm sec-1.After the coating cycle, the glass pieces were dried at 70 °C for 24 h andcalcined at 400 °C for an hour with a heating rate of 6 °C min-1.X-raydiffraction analysis exhibited only anatase phase, with crystallite size (estimatedby Scherrer equation) of 7.06 and 10.12 nm, for doped and undoped material, respectively.The BET surface area value (by N2 physisorption) was higher for thedoped material (103 versus 94 m2 g-1). The diffusereflectance spectra of metal-doped TiO2 showed a band broadening tothe visible region over the range of 400-800 nm. Degradationof phenol ([phenol]0= 50 μM) in 40 ml aqueous solution was studiedwith UV lamps irradiation within a Rayonet RPR-100 photoreactor4.Experiments with 1 gL-1 of each catalyst suspension were performed during 2 hours. The glassslide with the immobilized doped catalyst was suspended inside the glassreaction tube and irradiation was carried out for 5 hours. In all cases,periodic sampling was performed. The concentrations of phenol and reactionintermediates were determined by HPLC (HP 1050). Completephenol degradation was observed with the Pd-doped catalyst suspension while withthe TiO2 suspension only 64% of phenol degradation was reached. Thisresult indicates a positive effect of the doping procedure. Then, theimmobilization was essayed for the doped material. In this case, the percentageof phenol degradation was 50%. As expected, the percentage of phenoldegradation using immobilized catalyst was lower than using the correspondingsuspensions because the lower efficiency of irradiation of the material.Moreover, the amount of material supported on the slide was 1.1 ± 0.2 mg, lowerthan the used at suspensions experiments. Ithas to be highlighted that the degradation of 50% of initial phenolconcentration using around 1 mg of catalyst is a promising result, especially forthe possibility to reuse it.