Surface Modification And Composite Modification Of Titanium Dioxide And Its Application In Water Treatment

Apart from air pollution,soil pollution,the most intricate pollution is water pollution.Water pollution can be mainly divided into two aspects:organic and inorganic pollution.Organic pollutants include bacteria,organic dyes,etc.,while inorganic pollutants mainly refer to heavy metal ions.Titanium dioxide（TiO₂）is an excellent photocatalyst under ultraviolet light excitation,its photocatalytic activity can be trasfered to visible light region by compounding with other materials,which can broaden its photocatalytic application.As for adsorbing heavy metal ions,mesoporous TiO₂ particles can adsorb them in water.These two methods largely expand the performance of TiO₂ in dealing with water pollution.Based on the present situation of water pollution and combined with the excellent performance of TiO₂in dealing with water pollution,this paper studies compound modification and surface modification of TiO₂ from three aspects:First,mesoporous flower-like TiO₂/Graphite nanosheets（GNS）composites（TGNS）is successfully prepared by using combined methods of high-pressure homogenization（HPH）to exfoliate the graphite powder and hydrothermal method to deposit TiO₂.The mechanism is that GNS produced by HPH only aquires edge defects without any surface demage,TiO₂particles take advantage of these edge defects as starting point,then evenly distribute on the whole surface GNS.Due to the strong chemical bonds between TiO₂ and GNS,composite is uniform.As for photocatalytic performance,increasing amount of GNS largely increases the visible light use efficiency for TGNS composites.Compared with pure P25,the huge specific surface area brought by the flower-shape structure of titanium dioxide greatly improves the photocatalytic performance of TGNS.Besides,methods of preparing TGNS can also be applied to loading TiO₂ on other two-dimensional materials.Second,using hydrothermal method and high-temperature calcination with accurate temperature control can successfully prepare nano TiO₂（B）,and it is proved that TiO₂（B）has a lot of surface defects which is conducive to improve the efficiency of the visible light absorption.In addition,TiO₂（B）has equivalent effect of exfoliating the layers,which reduces the layer numbers of the two-dimensional materials,while boron nitride/TiO₂（B）（BT）,molybdenum disulfide/Ti O₂（B）（MT）and tungsten disulfide/TiO₂（B）（WT）composites can be synthesized at the same time.As for photocatalytic performance,it is concluded that the photocatalytic stability and the photocatalytic effect show reverse order.The stability order is WT<MT<BT,but the photocatalytic effect order is WT>MT>BT.Finally,low-temperature hydrothermal method by using ammonia as solvent prepares the mesoporous TiO₂（B）loaded 3D photosensitive resin materials（3-TBD）.Since light is not the essential element to adsorb heavy metal ions but the mesoporous structure,there is no need for this material to use light to adsorb heavy metal ion.The results for removing Pb²⁺,Cd²⁺,Zn²⁺,Cu²⁺in simulated waste water are good.The initial concentration,species of heavy metal ion,and the processing time are important factors for adsorption.The results of adsorbing heavy metal ion are as follows:Pb²⁺>Cd²⁺>Zn²⁺≈Cu²⁺.3-TBD possesses excellent recycling performance,which can be removed by forceps.But since the resin material is used as the base,the applicable temperature range should be no higher than 45oC.