Study On The Preparation Of Modified Stilbite And The Heavy Metals Adsorption Performance Of Modified Zeolite

Because the diseases caused by heavy metals possess the characteristics of long latent period and great damage, how to deal with the heavy metal pollution had become a problem concerned on a global basis. Cadmium, as one of the five poisons, can produce stimulation to human respiratory tract. Cadmium was not the essential element needed by human body. And cadmium had very high toxicity. With large specific surface area, stilbite was a good adsorption material which had strong adsorption capacity and ion-exchange capacity. It had been widely used in environmental remediation, environmental governance and so on. Especially in dealing with the waste water containing cadmium, it had obvious advantages.As a kind of important chemical operation method, adsorption had a very extensive application in the chemical industry and environment protection industry. The regeneration of adsorption material, was a key process to bring about reuse of the adsorbent, which can reduce the production cost. This paper studied the modified stilbite adsorption on the heavy metal cadmium by three different modification methods. The main research contents and conclusions are as follows:1.The effects of different modification ways(Acid, Alkali and Salt modified) on the adsorption efficiency of stilbite. By compering with the adsorption property of natural stilbite, the unit adsorption quality of cadmium in the solution would also gradually increase with the increase of mesh number. Moreover, the adsorption property of the modified stilbite was apparently higher than the adsorption property of natural stilbite to cadmium. At the temperature of 25 degree Celsius, when the dosages of NaOH modified stilbite, HC1 modified stilbite and NaCl modified stilbite were respectively 0.5 gram,0.7 gram and 0.7 gram, and the dosage of the natural stilbite was 0.7 gram, and the dosing pH is 6-7, and the vibration time of the modified stilbite and the natural stilbite was 4 hours and 3 hours, and the rotate speed of vibrating was 180 rounds per minute, the adsorption quality of stilbite could reach to 112.36,101.63,and 85.03 milligrams per gram which was modified by NaOH, HCl and NaCl and the adsorption quality of the nature stilbite to cadmium could 60.33 milligrams per gram.2.The adsorption of three different kinds of modified stilbite and natural stilbite was studied. The results show that the adsorption isotherms were accurately fitted by the Langmuir equation. The adsorption amounts of all modified stilbite increased with the rise of temperature and the enthalpy change of adsorptions were far greater than zero, so the adsorption of modified stilbite to heavy metal cadmium ion was an endothermic process.3. The paper studied adsorption kinetics of modified stilbite and nature stilbite on heavy metal cadmium ion. The kinetic study showed that the fitting degree of Pseudo two order kinetics equation on modified stilbite adsorbing heavy metal cadmium ion was the highest and the correlation coefficient was above 0.97 with temperature in 298k-318k.4.The effects of modified stilbite on cadmium ion’s exchange capacity were studied form the factor such as pH value, temperature, concentration and so on. It also studied the influence on coexistence between cadmium ion and other heavy metal cation and the modified stilbite on heavy metal of model wastewater’s removal effect. The result showed that the modified stilbite was destroyed in some degree after alkali treatment, but other peaks did not significantly change, making stilbite’s crystal structure transform to amorphous structure, but it didn’t completely change the crystalline structure. When pH is close to 6, the exchange capacity of modified stilbite on heavy metal cadmium ion was the biggest of all. With the rise of temperature, the ion exchange reaction rate and the adsorption rate of modified stilbite on cadmium increased. When cadmium ion coexisted with other heavy metal ions, it had an influence on modified stilbite and heavy metal cadmium ion’s exchange, it would occur to an competitive exchange.5. This paper also studied the effect of modified stilbite on the removal of heavy metals cadmium ion in the model wastewater, The result showed that the modified stilbite could effectively remove heavy metal cadmium iron in wastewater, and that the removal rate reached more than 98%.6.According to analyze the modified stilbite use by kinds of detectable characterization methods, the study showed that natural stilbite primary surface is relatively smooth and presented a flat and tight structure. Then the modified stilbite became uneven and the surface became loose and had obvious holes phenomenon, and the plane had loose distribution phenomenon, which made the surface become rough. By BET determination of specific surface area, not only the specific surface area of modified stilbite was clearly larger than the natural stilbite’s, but also the aperture increased.