Photocatalytic Reduction Of Cr??? By UiO-66 And TiO₂/MIL-53?Al? And Adsorption And Control-release Of Ethyl Vanillin By UiO-66

Heavy metal pollution is one of the most serious water pollution problems.It directly or indirectly threatens the health and safety of human being.Heavy metal Cr???is highly toxic.It is very easy to invade human and animal body and induce cancer through digestive system,skin and mucous tissue,and it also has enduring harm to the environment.Therefore,it is necessary to study the efficient treatment technology of the water body containing Cr???.In many water pollution treatment methods,photocatalytic technology is a new technology which can convert solar energy into chemical energy and can be applied to the treatment of harmful and toxic substances in water pollution.It has the advantages of energy saving and environmental protection and not causing secondary pollution easily.Semiconductor material is the most common photocatalyst,but its photocatalytic efficiency is generally not high,so it is the key to develop high efficient and photocatalytic activity catalyst.On the other hand,MOFs?metal-organic frameworks?material has been favored by scientists in recent years because of its advantages of large specific surface area,porous and pore structure rules,good stability and controllable photochemical properties.It can be used as a photocatalyst or a good carrier material and used in the study of photocatalytic treatment of heavy metal pollution.Published papers and related papers are also increasing rapidly.In view of the above,the MOFs material UiO-66,which has the properties of similar semiconductor,good absorption of ultraviolet light,large specific surface area and strong chemical stability,is used to combine its application with photocatalytic technology,and a series of studies have been made for the treatment of highly toxic heavy metal ions Cr???.The other MOFs material,MIL-53?Al?,is a good carrier material because of its weak absorption capacity to ultraviolet light,which is a good carrier material.Therefore,the semiconductor TiO₂ is considered to be loaded on its surface,in order to achieve a better purpose of dispersing the semiconductor material TiO₂,and thus effectively improve the efficiency of the use of UV light.Composite materials were applied to the study of photocatalytic treatment of Cr???in water.In addition,MOFs has a wide application prospect in the field of adsorption and separation because of its high specific surface area,pore volume and ordered pore structure and easy functionalization.Therefore,the application of MOFs material UiO-66 and adsorption separation technology were combined to study a series of researches on the adsorption of slow release tobacco flavoring ethyl vanillin.The main contents of the paper are as follows:?1?Semiconductor TiO₂ is loaded on MIL-53?Al?by solvent method.The photocatalytic activity of supported TiO₂ can be increased up to 2.1 times compared with pure TiO₂.The synthesized composite TiO₂/MIL-53?Al?has a large specific surface area,and the combination of MOFs carrier and TiO₂ not only maintains the stability of the carrier,but also makes TiO₂ better dispersed which greatly enhances the use of UV light.The amount of TiO₂ loaded on the MOFs material affects the photocatalytic activity of the material.?2?The photocatalytic reduction of hexavalent chromium using composite TiO₂/MIL-53?Al??100?as the photocatalyst and adjusting the chromium solution to the optimum pH shows that:Adjusting the pH of the chromium solution can be effective under the appropriate concentration of chromium solution and the amount of catalyst added,the efficiency of photocatalytic reduction of hexavalent chromium by TiO₂/MIL-53?Al??100?was improved by 18%compared with that of undoped.The photocatalytic reduction of hexavalent chromium using TiO₂/MIL-53?Al??100?as photocatalyst and methanol as sacrificial agent showed that:With the concentration of chromium solution and the amount of TiO₂/MIL-53?Al??100?added,adding proper amount of methanol to the chromium solution can greatly increase the efficiency of TiO₂/MIL-53?Al??100?photocatalytic reduction of hexavalent chromium,which is 29%higher than that when it is not added.?3?The photocatalytic reduction of hexavalent chromium using MOFs UiO-66 as the photocatalyst and adjusting the chromium solution to the optimum pH shows that:Adjusting the pH of the chromium solution can be effective under the appropriate concentration of chromium solution and the amount of catalyst added.The efficiency of photocatalytic reduction of hexavalent chromium by UiO-66 was improved by 15%compared with that of undoped.The photocatalytic reduction of hexavalent chromium using UiO-66 as photocatalyst and methanol as sacrificial agent showed that:With the concentration of chromium solution and the amount of UiO-66 added,adding proper amount of methanol to the chromium solution can greatly increase the efficiency of UiO-66 photocatalytic reduction of hexavalent chromium,which is 38%higher than that when it is not added.?4?The adsorption slow release experiment of ethyl vanillin with UiO-66 as an adsorbent showed that:In the case of saturation of material adsorption,the UiO-66/perfumer composite exhibited good permanence properties and slow release properties when the material was heated at different temperatures.When the highest of experimental temperature reaches 90?,UiO-66/perfumer composite only releases 12%of the perfume after a week.