可见光催化剂Ag_3PO_4/海泡石的制备及降解染料废水性能

Preparation of visible light-driven Ag_3PO_4/ sepiolite photocatalyst and its photocatalytic function for degrading dye sewage

以沉淀法、离子交换法和原位法制备了Ag_3PO_4/海泡石复合光催化剂,采用XRD、FTIR、UV-Vis-DRS对其结构进行了表征,以可见光驱动催化降解日落黄染料为探针反应,考察了制备方法对催化剂光催化性能的影响。结果表明:Ag_3PO_4与海泡石成功复合并产生了协同作用,催化剂中Ag_3PO_4均为立方晶型,部分Ag_3PO_4进入了海泡石层间,改变了其晶面有序性并拓宽了层间距,海泡石对Ag_3PO_4的复合提高了Ag_3PO_4的稳定性和光催化活性;其中,离子交换法制备的光催化剂中Ag_3PO_4与海泡石的复合程度最高,Ag_3PO_4稳定性最强,光催化活性最好,在可见光驱动下,该催化剂对50 mg/L的日落黄降解率可达97.16%,并且对其他3种50 mg/L的染料废水的降解率也在86%以上,此外,该催化剂再生2次后仍保持良好的活性和稳定性。

The paper intends to present our research on how to enhance the Ag_3PO_4 catalyst ＇s function and stability under the condition of the visible light. For the research purpose,we have first of all prepared the said Ag_3PO_4/ sepiolite composite photocatalysts in the following three well-known methods,i. e. the ion exchange method,the precipitation method and the in-situ method,respectively. Then,we have adopted XRD,FTIR and UV-VisDRS for identifying and characterizing the structure of the samples. Finally,we have made a detailed investigation of the photocatalytic properties of the aforementioned samples prepared in different methods under the visible light through the probe reaction of degrading the sunset yellow dye sewage. The results of our investigation show that the structure of Ag_3PO_4 in the above mentioned samples mainly takes a kind of cubic structure and increase the distance of crystal surface of sepiolite for part of Ag_3PO_4 particles tend to permeate into the interlayer of the sepiolite. Meanwhile,the stability of Ag_3PO_4 has been improved by loading sepiolite. The changing variation of the stable Ag_3PO_4 particles tends to go in a descending order as shown below： IE-Ag_3PO_4/ sepiolite〉PM-Ag_3PO_4/ sepiolite 〉IS-Ag_3PO_4/ sepiolite ≥ Ag_3PO_4.Such a phenomenon can be attributed to the easy transfer of Ag_3PO_4/ sepiolite composite photocatalysts,the photoinduced electrons on the conducing band of Ag_3PO_4 to sepiolite,thus resulting in the increase of the separation of photo-generated carriers and the reduction of Ag_3PO_4. Thus,the photo-degradation experiments show that Ag_3PO_4/ sepiolite composite photocatalysts are supposed to play much higher photo-degradation role than the Ag_3PO_4 catalysts,whereas the preparation methods may also produce a significant impact on the behaviors of Ag_3PO_4/ sepiolite catalysts. At the same time,the IE-Ag_3PO_4/ sepiolite,prepared by the ion exchange method tends to reveal the optimal photocatalytic activity. For example,when the initial concentration of sunset yellow dye is at a level of 50 mg / L under the visible light irradiation time of 2 h,it would be possible for the degradation rate of the sunset yellow to increase to 97. 16%,which is mainly due to the higher tendency of Ag_3PO_4 to combine with sepiolite,plus the advantageous stability of Ag_3PO_4 in the IE-Ag_3PO_4/ sepiolite composite photocatalyst. Furthermore,the IE-Ag_3PO_4/ sepiolite is also prone to settle down recycling. Therefore,the activity and stability of the above chosen sample has been made into very nice stimulator through the twice regeneration,which should be made to has a very bright application prospect in dye-processing sewage treatment.