Removal Of Nickel From Water Using Modified Zeolites

The natural zeolite (clinoptilolite) of Zhejiang Jinyun were used as the experimental materiel. The modified Na-Y zeolite was got by combining NaOH melting the natural zeolite with hydro-thermal synthesis method. It was found the saturation exchange capacity (37.85 mg/g) for Ni²⁺on Na-Y zeolite is improved nine multiples than that of the natural zeolite (3.87 mg/g). The adsorption behavior of Ni²⁺ on the Na-Y zeolite was studied and discussed. The Na-Y zeolite was also applied to study the adsorption behavior and regenerative experiments of water waste that contained Ni²⁺.Experimental results show that the Na-Y zeolite is more high exchange capacity than that of natural zeolite for Ni²⁺ in water solution, and has the characteristic of "quick adsorption, slow equilibrium". The fit curve between time and adsorption amount could be well according with theequation of (?).The exchange capacity of Ni²⁺) on Na-Y zeolite increase dramatically with the increase of temperature , the initial concentration and pH, but the value of pH is smaller than 4 the exchange capacity is small, while it is larger than 8, because the Ni²⁺ would be precipitated. So the value of pH should be controlled between 4 and 8 during the experiment.The elimination percent of Ni²⁺ increases with the adding amount of zeolite. When the initial concentration is 196.52mg/L and the adding amount of zeolite is 0.45g, The elimination percent is larger than 90%. The fit curve between adsorption and the concentration of Ni²⁺ is well agreement with equations of Langmuir and Freundlich.The regenerative experiments show that the best result is obtained by the mix solutions of 0.5mol/L HCl and NaCl.The modified zeolite has still high exchange capacity after using five times.It was found that the existence of four competitive cations would decrease the exchange capacity for Ni²⁺ on zeolite, and the order of the influence is : Ca²⁺>Co²⁺> Fe³⁺> K⁺.The Na-Y zeolite are applicable in eliminating Ni²⁺ under low concentration. The elimination percent can be achieve 99% when the initial concentration of Ni²⁺ is under 200 mg/L. 0.2g Na-Y zeolite was added to the water waste which containing Pb²⁺, Ni²⁺, Zn²⁺, and their concentrations are 37.2mg/l, 25.4 mg/l, 30.3 mg/l respectively. After 2 h adsorption handing under 20℃and PH=4.5, the concentration of Ni²⁺ is 0.05 mg/l which is lower than the water waste letting standard of our country.( <1mg/l)...