Background: The heavy metals are the most important pollutants their concentration of which in the environment is increasing in connection with cities and industrials development. One of these metals is chromium which, in the trivalent and Hexavalent oxidation state, is used in industries such as electroplating, glass, ceramic, tannery and leather. Hexavalent Chromium has proven several health hazards such as being carcinogenic. The aim of this study was to investigate nano-alumina modified with Schiff base ligands in removal of hexavalent chromium from aqueous solution in acidic conditions.

  Methods: This study is experimental which was performed in batch reactor at 20 ^° C temperature to investigate the effect of initial chromium concentration, adsorbent dose and reaction time on removal of chromium by nano-alumina. For adsorbent preparation, nano-alumina was purchased from Nano Kimia Pajoh company, and for increasing adsorption power, it was modified with Schiff base ligands in the presence of proper surfactant. The study was performed on the synthetic samples containing 2 and 5 mg/L concentration of chromium . The unknown concentration of Hexavalent Chromium was detected by spectrophotometer set (UV/VisibleSP-3000 Plus-Japan) at 540 nm.

  Results: According to the results, removal efficiency increases with increasing adsorbent dose and reaction time and decreases with increasing initial concentration of chromium. Results of this study indicated that Hexavalent chromium adsorption by nano-Alumina modified with Schiff base ligands reaches equilibrium at 30 minutes and maximum capacity will be obtained. The maximum removal efficiency, and adsorption capacity in optimum conditions (adsorbent dose=0.1mg/L ,pH=3), with chromium initial concentration of 5mg/L at 180 minute, were 83.4% and 4.17 mg/L respectively.

  Conclusion: Nano-alumina modified with Schiff base ligands is an effective adsorbent in removal of hexavalent chromium from aqueous solution.