Removal of Ni²⁺ from waste water by Na-X zeolite synthesized from coal fly ash

Na-X zeolite (ZFA) was successfully synthesized from coal fly ash (CFA) through NaOH fusion and hydrothermal treatments and used to remove Ni2+ in waster water. To obtain the optimum conditions of Ni²⁺ sorption on the ZFA, the influence of operation conditions like solution pH value, adsorbent dose, contact time, Ni²⁺ ion concentration and adsorption temperature was investigated. The results showed that the ZFA obtained in this work is comparable with the 13X zeolites synthesized from chemicals in the efficiency of Ni²⁺  removal from wastewater. More than 90% of Ni²⁺  could be removed by ZFA from the waste water with initial Ni²⁺ concentration of 20mg/L~150mg/L at 20℃, solution pH value of 6, sorbent dose of 10g/L, and contact time of 15min. The adsorption of Ni²⁺  on the ZFA fits the Langmuir isotherm well; its monolayer adsorption capacity reaches 11.2×10^-3 at 20℃. ZFA exhibits good regenerability and its removal efficiency for Ni²⁺ does not decrease within five recycles.