Study On Preparation Of Nano-TiO₂ Photocatalytical Granulated Materials And Treatment Of Paper-mill Wastewater

With the further study of nanomaterials, nanocatalysts have attracted wide-range attention for resent several decades. Nano-TiO₂, as a new functional material for environmental protection, was studied in wastewater widely. There were some disadvanteges such as aggregation effect and recycle difficulty for suspended TiO₂. Therefor, the research of TiO₂ with mineral materials is the key for its industrialization..The treatment is difficult for paper-mill wastewater which has a character of large amount,high concentration,fuscous and little reusable as well as containing lots of contaminants. And traditional treatments are easy to bring some new ions, and induce secondary pollution, so as difficult to conform wastewater discharge standard. By contrary, some researches indicate that photocatalytic degradation of paper-mill wastewater has got satisfied effect. In addition, the production of new type environmental materials using low-grade minerals is an important way to utilize mineral resources efficiently, which helps the saving of resources, the protection of environment and sustainable development.The preparation method of a novel granulated mineral supported nanometer-TiO₂ material with high adsorption and photocatalysis was studied in this dissertation, as well as the recycle rate. The results showed that the proportion of loaded matirials - rectorite and flyash - was the main factor of photocatalytic process. And adding proper bentonite can enhance the intensity of granulated materials. Furthermore, the granulated material could be regenerated by pyrogenation with quite good removal efficiency after reuse for four times. In the process of wastewater treatment, photocatalysis combined with flocculation was adopted. And reaction kinetics and photocalytic mechanism were also discussed. The results indicated that under the condition of pH 6.5～8.5, the optimal amount of Al₃(SO₄)₂ at 8g/L, and with the addition of granulated nanometer-material of 0.12g/ml, a ultraviolet reaction time of 4 hours, both the rate of removal of chroma and COD achieved more than 80%. And the quality indexes of the wastewater after treatment conformed with paper-mill wastewater discharge standard (GB3544-2001). If add another column with new granulated materials, the quality indexes of the wastewater after only half an hour's reaction conformed with the first discharge standard. In addition, adding proper oxidant was favorable for the removal of COD, and reduced reaction time as well. Furthermore, through imitating the Langmuir and Frundlich adsorption type, the process of photocatalytic degradation could be reasonably represented by first-grade reaction kinetics. In the end, the mineral supported nano-TiO₂ granulated material was characterized by XRD,SEM, and so on. According to the photos of SEM, the recycled granulated materials remained clear configuration without illegible and air-logged phenomenons. Which proved that the granulated nano-materials had high intensity, and could endure the strike of wastewater without dispersion.