Synthesis Of Mesoporous Silica Microspheres And Adsorption And Degradation Of Methylene Blue

Dye wastewater has a series of disadvantages such as high COD value, dark color, more salt content, difficult to biodegradate and so on. When discharged into natural streams, it could inhibit photosynthesis of the aquatic plant and damage the ecological balance. When released into the soil, the intermediate of aromatic amines could be obtained through microorganism, which is carcinogesis and mutagenicity. So dye wastewater is an important environmental pollutant.Adsorption is the most commonly used method to remove dyes. Ordered mesoporous material has large surface area and pore volume, so it has high adsorption capacity. Besides, its pore channels are ordered and adjustable, which is thought to be an ideal vector to assemble nano-particles. Especially,mesoporous SiO₂ contains many silanol groups that spread over the matrix. The silanol group tends to react with polar compounds. TiO₂ is a semiconductor of photocatalysis and potential in use because of large surface area, nontoxic, high chemically resistant, high catalytic activity, oxidative ability and long lifespan. Mesoporous SiO₂ loaded with TiO₂ may improve dispersion and affinity to enhance dye removal.In this work, mesoporous silica microspheres (MSM) with different structures were prepared by hydrothermal synthesis. Then methylene blue adsorption test was investigated. Results indicate that MSM has good adsorption capacity. BET surface, pore volume and pore size all change, and larger mesoporous size is more beneficial to adsorption. So all these parameters affect adsorption, but large pore size can not improve adsorption absolutely.Then, mesoporous silica microsphere was prepared by microwave hydrothermal synthesis,using cetyltrimethylammonium bromide (CTAB) as template agent and tetraethylorthosilicate (TEOS) as silica source. And mesoporous silica microspheres doped with TiO₂ was prepared by sol-gel method. Then methylene blue decoloration test was investigated, with respect to concentration of MB, amount of samples, pH and light illumination. Results indicate that low concentration, large amounts of samples, alkaline and UV illumination are more favorable to adsorption, and TiO₂/MSM has higher dye removal than MSM.Finally, mesoporous silica microsphere doped with copper was synthesized by a hydrothermal method. X-ray diffraction (XRD) results show that copper has been incorporated into the framework or the walls of the silica matrix successfully. Then dye adsorption test was investigated by varying the parameters such as adsorbent dosage and initial concentration of dye. The experimental results indicate that the sample is more efficient for adsorption than pure MSM. When 10 mg of Cu-MSM was added into 15 mg/L of MB concentration, MB removal reached to 95.31%, while 90.55 % to 105 mg/L. Other parameters such as pH, amounts of the sample and initial MB concentration have the same effects to Cu-MSM with MSM. The more amounts of adsorbents, the more dye removal is. Alkaline is favorable to adsorption.