Regeneration Of Powder Activated Carbon By Solvent Method

Powder activated carbon(PAC) adsorption is an effective method for osmosis concentrated water(ROC) treatment. If saturated PAC are discarded directly after adsorption, not only well cause environmental pollution, but also cause the waste of resource. To regenerate the waste PAC can realize the recycled use of PAC and reduce the consumption of PAC and the expenses for treating the waste. The regeneration methods for the PAC have thermal destruction, wet air oxidation, solvent method and microwave method, etc. Among them, the required equipment of the solvent regeneration method is simple, the carbon loss caused by the method is small, and it is an effective way to regenerate waste PAC.In this topic, the efficiency of the solvent method for the regeneration of saturated PAC loaded with organic matter is researched. With methanol and ethanol as solvent, respectively using single-stage and two-stage countercurrent regeneration and multiple-stage recycling regeneration of saturated PAC, the regeneration rate(RE) of these three methods are discussed and compared with each other. The results indicate that the adsorption of organic matter on the PAC which are regenerated by methanol or ethanol accords well with the Freundlich isothermal adsorption equation. As the regeneration time increases, the RE of PAC regenerated by methanol or ethanol increases. As the solid-liquid ratio increases, the RE decreases. The optimal regeneration time of methanol and ethanol is 40 min. The results of single-stage regeneration show that when the regeneration temperature is room temperature, oscillation speed is 200 rpm, the regeneration time is 40 min, the solid-liquid ratio is less than 100 g/L, the RE of ethanol regeneration is better than that of methanol. But as the solid-liquid ratio is more than 100 g/L, the RE of methanol regeneration is better than that of ethanol. After the regeneration of PAC by methanol and ethanol, there is a relationship between the residual organic matter concentration(qe) in the PAC and the organic matter concentration(Cr) dissolved in the methanol or ethanol. The relationship can be described by using the power equation. qe becomes higher with the increase of the solid-liquid ratio. Cr becomes lower with the increase of the solid-liquid ratio. The RE of single-stage regeneration is inferior to the RE of two-stage countercurrent regeneration. The RE of "old regenerant"(which has been used once) is lower than the RE of "new regenerant"(unused), combine the two and the RE is superior to the result of either. Two-stage countercurrent regeneration can improve the efficiency of the solvent regeneration and realize the recycling of the solvent. In multiple-stage recycling regeneration of saturated PAC, if the number of regeneration is increased, the efficiency of the regeneration by methanol or ethanol is reduced, the residual organic matter concentration in the PAC is increased, and the organic matter concentration dissolved in the methanol or ethanol is reduced. What is more, under the same condition and the number of regeneration, the RE of PAC regenerated by methanol is lower than the RE of PAC regenerated by ethanol.