13X zeolite was synthesized for removal of tetracycline from aqueous solution. To improve the removal efficiency, FAU zeolite was exposed to ion exchange process with Cu+2. The experiments were designed by the Expert Design 7.0.0 software. The effect of experimental parameters including, initial tetracycline (TC) concentration (50, 156.5, 525, 893.5, 1000 ppm) Cu+2 dosages (0, 0.3, 1.3, 2.2, 3 gr/gr) solution pH (2, 3, 6.5, 10, 11) and contact time(20, 34.6, 85, 135.4 min) was evaluated on TC removal efficiency. For minimizing the number of experiments for a complete evaluation, response surface methodology (RSM) and central composite design (CCD) were applied by means of Expert Design 7.0.0 software. Results revealed that FAU zeolite adsorbent was effective in removal of tetracycline, where the removal efficiency was 85 %. In fact, by increasing initial TC concentration from 156.5 to 890 mg/L, the removal efficiency was increased. While, further increase in initial TC concentration over 890 mg/L, did not cause a significant enhancement in its removal efficiency. Amount of exchanged Cu to 1.75 g/g had a positive effect on the removal efficiency but in over1.75 g/g dosages, the removal efficiency showed a decreasing trend. The Expert Design 7.0.0 software was reported that the optimal operating conditions is initial tetracycline (TC) concentration 810.5 ppm, Cu+2 dosages 0.6 gr/gr, solution pH 5.3, and contact time is 113.6 min. The adsorption isotherms were fitted by Sips and Freundlich and Redlich-Peterson models. Finally, the adsorption kinetics were also studied by pseudo-second order equation.
