| In recent years, with the rapid development of printing and dyeing industry, the number and type of dye also will continue to increase. The discharge of dye wastewater is an important source of leading the water pollution problem. The dye wastewater has many disadvantages such as its recalcitrance, persistent damage and high toxicity. It can cause a serious impact on people’s health, ecological development and the steady growth of the national economy because of these disadvantages. So treating dyeing wastewater effectively is the key to solving the water pollution problem and protecting the human living environment by using a reasonable dye wastewater treatment technology.At present, the adsorption method is becoming an effective contaminant enrichment method because of its advantages such as easy operation, simple device, less energy, high adsorption capacity, high adsorption selectivity, significant effect of purifying waste water and good reproducibility. An excellent adsorbent plays an important role to treat wastewater efficiently. Adsorbents should have the following basic conditions such as strong selective adsorption capability, rich nanoscale pores and excellent permeability.Based on the above design requirements of adsorbing material, this paper aimed that the dye contaminant molecules presenting in the wastewater is too difficult to enrich, then choosed methylene blue(MB)as an analog dye wastewater to design a relatively new adsorbent material called micro/nano hierarchical hollow tube carbon material(HTC). Here, biological materials with hollow tubular structure were choosed as oriented materials and sucrose, sodium chloride and potassium hydroxide were respectively selected as carbon source, pore forming agent and activator. Then HTC was prepared by vacuum impregnation of carbon source and activator. In order to determine the optimal preparation, activation technology parameters such as the concentration of sucrose, NaCl and KOH, the activation temperature and activation time were investigated. A kind of HTC material was prepared under the condition of 10 %, 10 %, 10 %, 800 ℃, 60 min by using kapok. It had the surface area of 625.1 m2/g, total pore volume of 0.45 cm3/g and narrow pore size distribution mainly less than 2 nm. It had good performance of adsorbing MB and the adsorption saturation was up to 98.5 mg / g in MB with initial concentration of 120 mg / L.Other organisms with hollow tubular structure were selected as biotemplates. Other HTC materials were prepared by using luffa, reed and egg shell membrane as biotemplates. These samples wered investigated for adsorbing MB and compared with kapok sample. When the initial concentration of MB is 120 mg / L, the saturation adsorption capacity appeared that kapok sample > luffa sample > reed sample > egg shell membrane sample.Other organisms with thin sheet structure were selected as biotemplates. HPC were prepared by using cinnamomum camphora and campsis grandiflora. These samples wered investigated for adsorbing MB and compared with HTC materials. The results showed that the adsorption property of HTC was better than HPC. That is to say that choosing organisms with hollow tubular structure as biotemplates and mixing in carbon source can prepare HTC with entity micron pore structure and incorporeal nanoscale pore structure. And HTC had better adsorption performance for 120 mg / L MB solution than HPC.The Pore structure and morphology of HTC were investigated by XRD, FESEM, TEM and nitrogen adsorption-desorption. The results indicated that HTC material basically retained the original biotemplate morphology and hollow tubular structure. The carbon source is helpful to achieve selective replication of the entity pore structure and retain the virtual body pore structure completely or partially. The prepared material had permeability micron and rich nanoscale pore. HTC is an effectively composite of HPC and hollow tubular material. HTC is a new adsorption material with high specific surface area, rich pore structure and better adsorption performance of MB.Nitric acid solution with low concentration was choosed to achieve the surface modification treatment of HTC in order to change surface chemical property. It was observed that the material activated by nitric acid with the concentration of 10 % had a lower specific surface area but had better adsorption performance. The saturation adsorption capacity reached up to 112.8 mg/g of 120 mg/L MB.Adsorption performances in MB solution were investigated and the results showed that HTC with or without surface modification was consistent with the pseudo two adsorption kinetics model. Besides, the adsorption process of HTC belonged to Langmuir isotherm equation(R2 > 0.99) and was consistent with monolayer chemisorption process.The joint treatment of dye wastewater of HTC adsorption and TiO2 photocatalytic properties was investigated. The results showed that HTC-TiO2 was synthesized by loading TiO2 to HTC surface with a carbon-wrapped method. It can achieve a significantly better adsorption property when treating dye wastewater. It is meaningful and valuable to study the synergistic mechanism of HTC adsorption and TiO2 photocatalytic properties. |
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