The Study Of TiO₂ Porous Composite From Wollastonite And Activated Carbons From Furfural Residue

In recent years, resource and circumstance are two important issues of people. TiO2 as an important material has been used in many fields, and it has limited the applications of materials as there is not enough TiO2. So many products have been studied to replace TiO2 partly or entirely. In addition, titanium dioxide (TiO2), as an important photocatalyst has been employed for decomposing of organic pollutants in aqueous systems and in air. Refer to photodegradation, the surface areas and polymorphs of the photocatalyst are pivotal. So various strategies have been used to accept large TiO2 surface areas, such as TiO2 mesoporous molecular sieves, TiO2 pillared clays, and titania-silica mixed oxides. Refer to pollution, one is stopping pollution, the other solving pollution. When the waste was used to prepare something, we combined these two aspects.In the thesis we aim at these matters to study.(1) Wollastonite is a good raw material. It can be used as filling, and used to prepare SiO2 and TiO2 composites. Simple chemical deposition method was used in the preparation of TiO2/wollastonite nanocomposites. And as wallostonite was used the cost has declined. In acidic solution the surface of wollastonite has dissolved partly, so Ti and Si would deposite on dissolving wollastonite when improve the temperature. So the as-prepared composite has a core of wollastonite and an inner shell of dissolving wollastonite and an outer shell of TiO2 (SiO2). Depend on this result, we adjust the pretreatment time. The structure of wollastonite was destroyed completely after long enough pretreatment. So there are dissolving wollastonite, sol of TiO2, sol of SiO2 and CaSO4·nH2O in the system before deposition. In this work, we succeeded in preparing anatase TiO2/SiO2 nanocomposites with large special surface areas and narrow distribution of pore sizes from cheap materials by two different methods: crystallization in low temperature and calcination. And the N2 adsorption and desorption study revealed that the as-prepared composite has ample hole structure and large surface areas, up to 300 m2/g. Evidently, introducing wollastonite(SiO2) into the system decreases the sizes of the TiO2 nanoparticles, because the growing of hydrolysated titanium dioxide particles is limited. And after calcium sulphate were removed from the system by washing carefully, anatase modification which had formed during the hydrothermal aging were difficult to agglomerate into larger particles any more.There are many literatures of pillared TiO2 (and layered silicates were used), and wollastonite as a catenarian silicate has been studied in TiO2 composite, but there is no article in preparing of TiO2/SiO2 composite from wollastonite, and we also studied the mechanism. It revealed that there was a obvious small angle diffraction in the process as the diffusion of Ca is much rapid than Si.(2) Furfural residue is wastes of furfural, there are 10 t wastes per 1 t furfural. The environment would be contaminated if they were put in open air. And if they were used as fuel directly, as there are some used H2SO4 in the residue, boilers would be eroded by rudimental vitriol in wastes, at the same time, environment would be polluted by burning results for the second time. So the preparation of activated carbons from furfural residue by phosphoric acid activation further decrease manufacture cost as well as solve environmental problem.In the present work, the active carbon with large special surface areas and good adsorptive capacity was prepared from furfural residue by chemical activation of phosphoric acid at lower temperature. There is no important effect of rudimental H2SO4 in the residue as we use H3PO4 in the activation period. So it is very simple when we deal with furfural residue before being used. It is good enough to exenterate larger detritus and other sundries. Phosphoric acid was mixed with carbon processor, furfural residue carefully to accept that all carbon particles were completely wetted. Then the mixtures of furfural residue and phosphoric acid (in crucible) were carbonated at 200 oC to remove water in the mixture. After that the carbonated product (in crucible being covered) were activated at 500 oC in the muffle furnace for 1h. After cool to room temperature in air, the activated product was washed with deionized water until pH=6 and PO43- free water (AgNO3 test) and dried at 120 ?C. The washed water will be concentrated and recycled for another use. We can see clearly that the whole process is very simple, the equipment is facile, and the raw material is cheap. It is likely to achieve industrialization. Then the activated carbons were characterized, and the N2 adsortion and desorption revealed that the activated carbons has ample hole structure and large surface areas, up to 1200 m2/g. And the iodine sorption value of the as-prepared activated carbons is about 1760 mg/g. As a result of that the as-prepared activated carbons can be used in wastewater treatment, such as the waste water of furfural production. It revealed that the furfural and other coloured substances can be removed in water by activated carbons quickly.