Synthesis and Application of Cu-X zeolite for Removal of Antibiotic from Aqueous Solution: Process Optimization Using Response Surface Methodology

Abstract

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 $$\hbox {Cu}^{+2}$$ . The experiments were designed by the Design-Expert 7.0.0 software. The effect of experimental parameters including initial tetracycline (TC) concentration (50, 156.5, 525, 893.5, 1000 ppm) $$\hbox {Cu}^{+2}$$ dosages (0, 0.3, 1.3, 2.2, 3 g/g) 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 and central composite design were applied by means of Design-Expert 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 over 1.75 g/g dosages, the removal efficiency showed a decreasing trend. The Design-Expert 7.0.0 software reported that the optimal operating conditions are TC concentration—810.5 ppm, $$\hbox {Cu}^{+2}$$ dosages—0.6 g/g, solution pH—5.3, and contact time—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.