Research On Carbon/Pottry Adsorption Composite For Removing Fluoride

The carbon/pottery composite for removing fluoride is prepared from bone charcoal, bamboo power and clay by carbonization and activation process. The characteristic of carbon/pottery composite has also been studied by BET, SEM, FTIR, etc, and this research attempted to explore the mechanisms of the removing fluoride.The optimum process conditions are determined by series of experiments as follows: a proportion of 1:2:1 for clay, bone charcoal and bamboo powder, heating rate 5℃/min, activation temperature 600℃, holding time 1h. Under optimum conditions, the defluoridation capacity is 2.214mg/g and the efficiency of defluoridation is 88.56%. Compared with clay, bone charcoal and bamboo charcoal, carbon/pottery composite have better effect for removing fluoride. Those results are attributable to the synergistic effect during defluoridation process.The optimum process conditions of defluoridation were indicated by the static and dynamic adsorption experiments: pH=6~8, 3h, 20~30℃. After treatment by adsorbent, the content of fluoride in raw water (<5mg/L) decreased to the levels of <1mg/L in finished water, which reached the national drinking water standards. Generally speaking, the filter layer is higher, flow rate is slower, raw water concentration is lower, the effective operating time is longer and multiple of through water is much more, when other conditions are kept unchanged. But the treatment efficiency can be affected by too slow flow rate.The analysis of specific surface area, pore volume and pore size distribution of carbon/pottery composite, bone charcoal, bamboo charcoal and clay show that the carbon/pottery composite enjoys the largest specific surface area ,moreover, the mesopore of the composite is dominant. The specific surface area of the composite is 326.66m2/g, and the pore volume is 0.5057cm3/g.The results of SEM show that clay and bone can perfectly combined together during the activation process. The macroporous does not block the pore of bamboo charcoal on the carbon/pottery composite. The mesoporous and microporous have good adsorption ability, the specific surface area of carbon/pottery composite increased and has a higher developed pore structure, therefore, the adsorption of fluorine ion is improved.The Infrared Spectrum analysis show that the surface functional groups and structure of carbon/pottery composite affect by the activation temperature and holding time. The higher activation temperature is benefit for the formation of P-H bond in bone charcoal or the Si-H bond in clay. With the increasing of holding time, a large amount of C-O bond can be formed. All these play a positive role for improving the defluoridation effect.