Study On The Treatment Of Ammonia Using Modified Zeolite Adsorbent

As a colorless gas, ammonia has a strongly irritating smell and is lighter than ordinary air (Ammonia's specific gravity is 0.5869 of the latter). The gas can be smelt when density is above 5.3ppm. Ammonia is an alkaline material and has a corrosive and stimulating effect on the contacted skin, for the gas will absorb the moisture contained in the skin, denaturize the tissue protein, saponify the tissue fat and destroy the membrane structure.Unorganized and scattered Ammonia can be treated in mass after being recycled in a confined way. There are a number of approaches ever utilized, among which the most common ones are oxidation, absorption, adsorption, biological method and etc. The paper mainly studies the adsorption.Modified zeolites were first made by impregnating artificial zeolite respectively into acid and chlorides of copper, nickel, and zinc. Then the artificial zeolite and modified ones were used as ammonia adsorbents in dynamic conditions. Comparison was made on the ammonia removal efficiency between the artificial zeolite and modified zeolite. Compared with artificial zeolite, the ammonia-adsorption ability of modified zeolites has been much improved. Among them, the most prominent one was that of Z-CuCl2A-M ( i.e. the type of zeolite modified by the CuCl2 solution with a mass ratio of 20% and with a water content of about 250mg / g), whose adsorption ability was increased above 7 times if compared with that of the original artificial zeolite.Comparison between modified zeolite impregnated in acid and modified zeolite impregnated in metal chloride shows that, the latter has stronger ammonia absorption ability than the former one. The saturated adsorption capacity of Z-HCl-D is 6.64mg / g, but the averaged adsorption ability of the four modified zeolites, i.e. Z-ZnCl2-D,Z-NiCl2-D,Z-CuCl2A-D,Z-CuCl2B-D, is twice of that of Z-HCl-D. Comparison between the adsorption ability of Z-ZnCl2-M,Z-NiCl2-M,Z-CuCl2A-M or Z-CuCl2B-M and that of Z-HCl-M shows the same result.When studying the impact of water on the adsorption properties of modified zeolite, the ammonia-adsorptive performance of the six kinds of zeolite after wetness treatment enhanced significantly if compared with their performance in dryness. The adsorptive ability of unmodified zeolite, after wetness treatment, was enhanced almost 7 times as high as their performance in dry condition.However, when comparison was made on ammonia-adsorptive ability barely among modified zeolites ever impregnated in different metal chlorides, i.e. Z-ZnCl2-D, Z-NiCl2-D and Z-CuCl2A-D, it is found that performance of the three materials shows little difference. The experiments on other three materials, i.e. Z-ZnCl2-M,Z-NiCl2-M,Z-CuCl2A-M, are of the same result. This does not mean that different impregnating solutions made from different metal chlorides make no difference in affecting the final adsorptive ability of the modified zeolites. The little difference above-mentioned might be caused by the fact that the chemical properties of Zn2 +, Ni2 + and Cu 2+a re quite similar to each other.By comparing the adsorption ability of two modified zeolites ever impregnated separately in 20% and 10% CuCl2 solutions, it is found that the ammonia-adsorptive ability of Z-CuCl2A-M is about 1.5 times as that of Z-CuCl2B-M. Yet, when in dryness the performance of Z-CuCl2A-D and Z-CuCl2B-D is more or less the same.Based on the above study, the methods of scanning electron microscopy and X-ray diffraction analysis were introduced for a further study on the original artificial zeolite and modified zeolite samples. Scanning electron microscopy analysis shows that:the texture of Z-CuCl2A-M, which is a modified zeolite made from impregnating artificial zeolite into the CuCl2 solution with the mass faction of 20%, is most obvious and follows a rule. This also explains why modified zeolite made from impregnation into the CuCl2 solution with the mass faction of 20% shows the strongest ability in adsorbing ammonia. In the same time, the author comes to a conclusion that the reaction of ammonia adsorption by modified zeolite impregnated in metal chloride takes place on the zeolite surface. The powerful adsorption is derived from the process of complexes formation when ammonia reacts with metal chloride.