Study On Regeneration Of Magnesia-pullulan Absorbent

Adsorption is one of the most prevalent methods to treat fluoride wastewater all over the world. The adsorbents usually use once and are discarded immediately, which would cause great waste of resources. Desorption and regeneration process could improve the utilization of adsorbents and reduce the cost of wastewater treatment.In this paper, desorption and regeneration of magnesia-pullulan absorbent(Mg OP) by solvent regeneration,thermal regeneration and combination of these two methods were investigated. It has been found that strong acid had a good desorption ability of fluoride loaded Mg OPs, but the sorbents were completely dissolved, thereby they failed to proceed the regeneration. As they were not dissolved in the weak acid, deionized water, Na Cl, Na OH, Na HCO3 and Na2CO3, the desorption and regeneration rate of fluoride loaded Mg OPs were really poor. After calcination, the fluoride loaded Mg OPs could get a relatively high regeneration rate. And compared with only thermal regeneration, combination of desorption by the solvent and firing was unable to dramatically increase the regeneration rate. Later,batch trials were conducted to explore the best calcination temperature, calcination time and the regeneration stability of different fluoride loaded Mg OPs. It has been found that the best calcination temperature was 750,℃ and the best calcination time varied with the different kind of fluoride loaded Mg OP. Relatively speaking, low fluoride loaded Mg OPs had a high recycling rate. Last, the fluoride-absorption capacity of fluoride loaded Mg OPs before and after regeneration were compared. It has been found that adsorption capacity increased by 70% after firing. Before calcination, fluoride was liberated from high fluoride loaded Mg OPs in the fluorine solution, while after calcination, the liberation amount was significantly reduced. And sometimes, high fluoride loaded Mg OPs may obtain adsorption capacity again after calcination.Meanwhile, SEM, BET, XRD and FTIR techniques were applied to characterize the structure and properties of the adsorbent. Results indicated that the mechanism of adsorption were hydrogen bonding and ligand exchange. Calcination gave rise to crystallization of Mg O which was able to adsorb fluoride from solution again.On the basis of experiments, this paper proves that Mg OP can be regenerated by calcination. Besides, further researchs of the mechanism of fluoride removal and regeneration provide part of the theoretical basis for the industrial application.