Preparation Of Titania Pillared Bentonite And Study On Photocatalytic Reduction Of Cr(â…¥) In Waste Water

Titanium pillared bentonite (Ti-PILC) with large pores, large specific surface area and high thermal stability is a kind of novel nanocomposite with layered silicates. When Ti-PILC is used in degradation of pollutants in water, high initial reaction concentration can be obtained by accumulating pollutants onto surface through bentonite substrate which has good absorption ability; photocatalysis efficiency of nano-TiO₂ in the layer can be improved by interface-coupling effect with silicate layers, thus the material exhibits excellent photocatalytic activity.In the article, Ti-PILC is synthesized by purification, modification of raw bentonite and introducing TiO₂ into the interlayers of Na-bentonite; Ti-PILC prepared is used to photocatalytical degadate Cr(VI) in the water, the mechanic of degadating is primarily investigated.Shanxi bentonite is selected as the substrate of Ti-PILC by characterizing and analyzing bentonites oringined from Liaoning, Shanxi and Brazil, then is purified by wet purification; the opimum condition of Na-modification is: NaCl use level is 6 wt%, slurry concentration is 5 wt%, modification temperature is 65℃, mofication time is 3 h.Ti-PILC is prepared by sol-gel method with using Na-bentonite and tetrabutyl titanate as raw materials, influencing of temperature and pH in pillaring are studied, the opimum condition is: acid-base ratio in pillaring agent is 1/3, pillaring temperature is 65℃, the amount of NaOH added into pillaring intermixture is 0.050 mol/L.Products before and after pillaring are characterzed via the approach of X-ray power diffaction (XRD), thermal analysis (TG-DSC), infrared absorption spectrum (IR), scanning electron microscope (SEM) and energy spectrum analysis (EDX), the results shows that: In the pillared precursor, Ti hydroxide polycations enter into the interlayers of bentonite which makes the spacing distance d₍₀₀₁₎ value grow from 1.284 nm of Na-bentonite to 1.588 nm, and causes the change of properties in the interlayers; after calcination, dehydration and dehydroxylation happen on Ti hydroxide polycations and makes the d₍₀₀₁₎ value decrease to 0.992 nm; however, the fundamental silicate frame of pillared products have not been varified and still hold a order layered structure.Under UV-light, Ti-PILC has good photocatalysis ability on degradation of Cr(VI) and calcined products presents better activity; on the condition of adding 15 g/L of Ti-PILC, 10 mg/L of initial Cr(VI) concentrate and pH=3.4, the effect of Cr(VI) degradation is best; the photo-degration process of Cr(VI) can be expressed by the reaction model of adsorption-photoinduced reduction-desorption.