Preparation Of Ti-PILC From Ca-Bent And Study On It's Adsorption And Photocatalytic Activity

In this paper, Ti-PILC was prepared directly from Ca-Bent, and studied on it's adsorption and photocatalytic activity.The optimal conditions for preparing of Ca-Ti-PILC as follow: Ca-Bent as raw materials, scattered TiCl₄ in ethanol without water, then droped into glycerine-water mixed solvents, 5 wt% for initial Ca-Bent suspension concentration, 20 mmol/g for Ti/clay, 140 °C for hydrothermal treatment temperature, 3 h for hydrothermal treatment time. Ca-Ti-PILC prepared under these conditions had the largest layer spacing distance, and showed the strongest photocatalytic activity.Ti-PILC was charactered by XRD, FT-IR, TG-DSC and BET and showed that: XRD and FT-IR showed that TiO₂ were successfully inserted in the interspace of Ca-Bent as anatase TiO₂. The interlayer of Ca-Ti-PILC was enlarged to 1.962 nm from 1.522 nm of Ca-Bent.There wasn't chemical bond between Ca-Bent layer and TiO₂. The surface of Ca-Ti-PILC was 182 m²/g and the surface of Ca-Bent was 35 m²/g.Study on it's adsorption showed that: the adsorption dynamics curve of methyl orange on Ca-Ti-PILC and Na-Ti-PILC followed the law of Bangham. Adsorption balance was reached in 30 minutes. The adsorption isotherm tallied with the isothermal adsorption equation of Freundlich. The adsorption capacity of Ca-Ti-PILC was more than that of Na-Ti-PILC, because the existence of Na⁺ reduced the adsorption capacity of methyl orange. The heat of adsorption of methyl orange on Ca-Ti-PILC and Na-Ti-PILC were -26.15 kJ/mol and -29.65 kJ/mol. The adsorption was presented by heat evolution physisorption. The pH value had influence on the adsorption. The adsorption capacity increased in acidic condition and reduced in alkaline condition.Study on it's photocatalytic activity showed that: hydroxy radicals could be produced by Ca-Ti-PILC under ultraviolet radiation. Methyl orange in water could be degraded completely due to the adsorption. The reaction was first-order reaction, and k_Ca-Ti-pILc=2.01×10^-2 min^-1. Ca-Ti-PILC could bereused as catalyst. The — N=N bond of the dyes in this study was the most active site for oxidative attack. In the photodegradation of methyl orange, breakage of the chromophore were responsible for the characteristic color of the azo dyes, rather than its discorloration or bleaching. The photocatalytic activity of Ca-Ti-PILC and Na-Ti-PILC were close. Ca-Bent could be used as raw material in the preparation of Ti-PILC instead of Na-Bent.The influence of metal cations in solution on the adsorption and photocatalytic activity of Ca-Ti-PILC was discussed for the first time in this paper. The order by adsorption capacity was K+>Ca-Ti-PILC>Fe3+>Mg2+> Al3+>Cu2+>Na+, by k was K+>Cu2+>Ca-Ti-PILONa+>Mg2+>Al3+>Fe3+. K+ could accelerate the adsorption and degradation. When the concentration of K+ was 50 mg/L the adsorbing capacity reached 12.32 mg/g. When the concentration of K+ was 100 mg/L k was 2.21 xlO"2 min'1. After analysing from the adsorption, hydroxy radicals and H2O2, we found that K+ didn't accelerate the generation of -OH, and didn't change the reaction mechanism. The reason was that K+ could accelerate the adsorption because the hydration radius of K+ was so small that it could be easily adsorbed in Ca-Ti-PILC surface.