Study On Preparation And Application Of TiO₂/Bentonite Pillared Composite

A series of TiO₂/bentonite pillared composite were prepared by hydrothermal method with diversified modified bentonite ( calcium bentonite, sodium bentonite, acid bentonite and organic bentonite) and TiCl4 . Various factor in the preparation including bentonite suspension density and Ti/clay and digestion time of pillar agent and drop ways and hydrothermal treatment conditions were studied. Their structure were characterized by XRD, DTA-TG and FT-IR. methyl orange was particularly conducted to study the absorption and photocatalytic degradation. The photoatalytic of degradation mechanism was researched.The results showed that interlayer spacing of the compositeprepared with different modified bentonite increased as follows: Or-Ti-Mt(2.182nm) >Na-Ti-Mt (1.986nm) >Ca-Ti-Mt (1.826nm) >H-Ti-Mt(1.5237) , in which replacement of Si by Ti during hydrothermalreaction were not occured. Diversified composite consisted of TiO2pillared clays with sized about 2.1-2.3nm anatase on its surface. Variouscomposite showed good thermal stability.The synthetic condition was optimized as follows: initial suspension density of bentonite(10wt%), Ti/clay=10 mmol/g, digestion time of pillar agent>24h, positive direction order(dropping from suspension to pillaredsolution), hydrothermal treatment conditions (100°C, 5h).The isothermal absorption of TiCVbentonite pillared composite followed the Freundlich equation for equilibrium concentration between 0 with 6mg/L. Absorption kinetics were conformed with Langmuir equation. The absorptive rate constant were kOr-Ti-Mt=0.5084, k_Na-Ti-Mt=0.3403, k h-ti-mi =0.4213, k.Ca-Ti-Mt=:0.4162 respectively. It was anticipated that they could be used as adsorbent for polluting organic substance. Synergism of distribution and surface absorption in absoption process was observed , and the distribution showed the leading effect. Adsorptive capacity order as follows: Or-Ti-Mt > Or- Ti > Na-Ti-Mt > H3-Ti-Mt > H3-Mt> Ca-Ti-Mt > Na-Mt > Ca- Mt. The adsorbent could be regenerated by calcination on 450°C.The photocatalytic reaction of methyl orange with TiO2/ bentonite pillared composite was in accord with first-order rate equation mechanism, The degradation efficiency increased as follows: Or-Ti-Mt> Na-Ti-Mt > Ca-Ti-Mt > H-Ti-Mt >TiO2. The photodegradation of methyl orange, i.e., breakage of the chromophore were responsible for the characteristic color of the azo dyes, rather than its discorloration or bleaching. The —N=N—bond of the dyes in this study the most active sites for oxidative attack. It was applicable for photocatalytic degradation of low concentration of polluted organic substance because of its terrific catalytic activity with concentration < 20mg/L. Catalyst could be...