Preparation Of Titania-Pillared Montmorillonite And Its Application In Wastewater Treatment

Montmorillonite is one kind of natural clay minerals. It owns a typcial layer structure, whose interlayer distance can be modified. It is an excellent catalyst supporter and adsorbent with well selectivity. These enable it to be used in wastewater treatment with prospectivity. Titania (TiO2) is a one kind of semiconductors with narrow band gap. A lot of attentions were paid to its applicatins in many areas for its advantages, such as lower price, rich resource, non-toxicity and environmental friendliness.In this thesis, TiO2-pillared montmorillonite (TiO2-MMT) was prepared by a sol-hydrolysis approach, using butyl titanate as titanium resource. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The photocatalytic property of the sample was investigated through degradation of methylorange, and its property for the adsorption of heavy metal from wastewater was measured by adsorption, leaching and electrochemical recovery. XRD results show that the site of (001) plane diffraction peak of montmorillonite left-shift obviously. This indicates that its interlayer distance of (001) plane enlarges evidently. When pillared at alkaline conditions, the layer structure of montmorillonite can be destroyed, while at acidic conditions, the interlayer distance of montmorillonite can be enlarged evidently. The photocatalytic experimental results show that, compared to nanosized titania composed of mixed crystal phase (P25), the photocatalytic activity of the sample is much higher, and the optimized parameters are the dosage of the sample 8.5 g/L, the concentration of methyl orange (MO) 30 mg/L, the irradiation time 2 h. The adsorption experimental results show that, the adsorption rate of the sample for lead (Ⅱ) cationic (Pb2+) from wastewater can reach 99.9%. The leaching experimental results show that 80% of Pb2+ can be leached out from TiO2-MMT saturatedly absorbed Pb2+ in nitric acid solution at a concentration of 0.2 mol/L. Pb2+ in the leached solution can be recovered by electrochemical approach. Pb2+ can be reduced to Pb at the cathode, while it can be oxidized to PbO2 at the anode. SEM images show that the morphology of the sediment at the cathode is rod-like, which composed of many nanosilces, while that at the anode is irregular aggregation, which composed of many small ployhedral particle with different diameters and morphologies. The sample can be recycled and reused, and its absorption rate for Pb2+ can reach 95% during the process of recyclling.