SYNTHESIS AND CHARACTERIZATION OF ZEOLITE AND ITS APPLICATION IN ADSORPTION OF NICKEL FROM AQUEOUS SOLUTION
The synthesis and characterization of zeolite and its application in adsorption of nickel from aqueous solution was investigated. Synthesis of zeolite was performed at 90 oC for 8 h. The size of the resulting crystals increased with an increase in the water content of the reaction mixture. The synthesized zeolite was characterized by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) techniques. Crystal structure of the product was determined as zeolite X by XRD. The concentration of the nickel ion was determined using atomic absorption spectrophotometer (AA 320 – ON). Removal efficiency of nickel ion was dependent on the pH, contact time, adsorbent dosage and temperature. Batch adsorption studies conducted for the removal of nickel(II) ion at 25, 40 and 50 oC respectively showed that nickel ion adsorption increased with increase in temperature. The effect of adsorbent dosage of 0.5-4.5 g showed that there was an increase in the adsorption capacity when the adsorbent dose was increased from 2.0-4.0 g. The pH values were adjusted to 3.2, 4.3, 5.3, 6.7, 7.9 and 9.5 and it was evident from the result that at pH 5.3, uptake capacity of nickel(II) ion onto zeolite X was maximum. The effect of contact time at 10, 20, 30, 45, 60, 75 and 90 min was analysed and it was evident that adsorption of nickel was rapid in thre first 40 min followed by a gradual increase until equilibrium was attained. Adsorption data was interpreted in terms of Langmuir and Freundlich isotherms. It was observed that the experimental data fitted better to Langmuir model with a correlation factor (R2) value of 0.993 compared to Freundlich with R2 value of 0.980. The kinetics rate were modelled using pseudo-first-order and pseudo-second-order models. The pseudo-second-order model explained the adsorption kinetics most effectively. The result showed that zeolite X was effective in the removal of Ni(II) ion from aqueous solution.