| Zeolite is a kind of non-metal mineral resource which is widely used in the national economy. At present, many kinds of deeply processing products made of zeolite have been extensively applied in the petrochemical engineering, construction industry, medicine and hygiene, agriculture, environmental protection and cosmetics industry etc. In this paper, fine processing products of zeolite were developed by using the natural zeolite mineral of Chifeng in Inner Mongolia Autonomous Region. After the structure feature and basic characteristic of zeolite were described and combined with the requirement of zeolite as adsorbent used in wastewater treatment, the methods, effect and mechanisms of the zeolite modification were discussed.In this paper, the characteristics of raw ore were analysed. The results provided the basis for the next stage processing treatment. It was found that the raw ore was Ca-heulandite and the metal cations which counterpoise electric charge are K+, Ca2+, Mg2+ and Na+. It has good heat and acid resistance, also has a certain alkali resistance. The crystal structure is destroyed when the temperature is higher than 450℃. The CEC result expresses that the cation (NH4+) exchange capacity is 48.7mmol/100g. The specific surface area is 18.601m2/g and the pore radius is 0.6～1.26nm when the zeolite granularity is 0.050～0.075mm. The capacity of Cu2+ and Pb2+ adsorption is low. It is necessary to take up modification to overcome the disadvantages that the zeolite used as adsorbent in wastewater treatment to promote its exploitation and utilization.Roasting has the function of purification and modification. It takes up a complex physical-chemical reaction in the zeolite roasting processing. The specific surface area is reduceing with the increasing of roasting temperature and the crystal structure is destroyed when the temperature is higher than 450℃. The zeolite of 0.050～0.075mm which has been roasted in 150℃for 1 hour has the highest capacity of Cu2+ and Pb2+ adsorption among the roasted zeolite.HCl, NaOH, NaCl, KCl, NH4Cl and CaCl2 were selected to modify the zeolite. The result showed that NaOH was the suitable modifier. And the experiment showed that the suitable operating conditions are:the zeolite granularity is 0.500～1.000mm, the concentration of NaOH solution was 2mol/L, the reaction time was 3h and the reaction temperature was 80℃When the initial concentration is 100mg/L in the solution, one gram modified zeolite can adsorb 99 percents Pb2+ and Cu2+, and the solutiaon met the emission standard. It takes a short time to reach the adsorption equilibrium. The adsorption equilibrium time of Pb2+ is 30min and it is 45min of Cu2+. The influence of temperature on adsorption of Cu2+ is obviously but is less on the Pb2+. A high pH is beneficial to the removing of Cu2+ and Pb2+The zeolite can remove Cu2+ and Pb2+ is the result of both ion exchange and adsorption. These two processings are not independent but are associated. The Langmuir model could describe the isothermal adsorption experimental data of zeolite adsorb Pb2+ and could deduce the maximum saturated adsorption capacity of Pb2+ was 49.261mg/g. The Freundlich model could describe the isothermal adsorption experimental data of Cu2+ rather than Langmuir model.These results are of significance on facilitating the exploitation of zeolite and its practicality in wastewater treatment. |
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