Ammonium Removal From Water By Modified Zeolite And The Regeneration Study

The phenomenon of excessive ammonium in waters has becoming more and more serious in recent years. Excessive nitrogen in lakes and rivers can cause eutrophication that will lead to the decrease of dissolved oxygen, which make the death of fishes, shrimps and other aquatic organisms from suffocation. Excessive nitrogen in drinking water can cause many diseases for people. Therefore, it is important to remove the ammonium from waters.Five kinds of salt solutions (NaCl、KCl、CaCl2. MgCl2and BaCl2) were used to modify N-Z in this article and the one owing the maximum adsorption capacity was calcined. It was founded the M-Z-1adsorption obtained by using10%(wt%) NaCl solution to immerse N-Z for24h was the optimal modified zeolite. The adsorption capacity of M-Z-1was5.94mg/g, which was1.9times larger of N-Z. The results of Characterization showed the immersion of NaCl solution just increased the content of Na+in N-Z and the surface and the pores structures nearly didn’t be changed. Hence, the increase of adsorption capacity of M-Z-1mainly depended on the increase of Na+The batch adsorption experiment of adsorption rate indicated the adsorption rate of M-Z-1was faster than that of N-Z when the particle size, the rotation speed and the initial ammonium concentration were all the same. The ks value of M-Z-1was larger than that of N-Z, implying the adsorption rate of M-Z-2was faster, which was coincident with the experimental result; The intra-particle diffusion was the rate limit step for M-Z-1. The study of adsorption isotherms indicated the calculated monolayer maximum adsorption capacity by Langmuir model of M-Z-1was11.73mg/g, which was1.4times larger of N-Z; The KL, KF and1/n values implying the adsorption capacity of M-Z-1was higher and the affinity of M-Z-1with ammonium was stronger and the adsorption of M-Z-1was more favorable. The results of thermodynamic indicated ammonium removal by M-Z-1was spontaneous, exothermic and the degree of freedom decreases during adsorption; The adsorption spontaneity of M-Z-1was better than that of N-Z and higher temperature led to lower adsorption capacity of M-Z-1. The experiment of mechanism’s verification indicated the adsorption of ammonium was virtually the ion exchange between NH4+and Na+.The result of batch regeneration experiment showed the regeneration effect of NaCl solution was the best. The adsorption fraction was90%when using3%(wt) NaCl solution to regenerate M-Z-1for3h at normal temperature and the regeneration activity ration was nearly80%. The mechanism of regeneration was the ion exchange between NH4+and Na+.The result of continuous experiments showed the breakthrough volume was about250at the space velocity of2.0h-1depending on inlet ammonium concentration of5.0mg/L and pH of8.0. The breakthrough volume after the sixth adsorption was steady to130that was52%of the first one. The results indicated that ammonium removal from water by M-Z-1was technically feasible and the application prospect was good.