Tetracycline absorbed onto nitrilotriacetic acid-functionalized magnetic graphene oxide: Influencing factors and uptake mechanism

A novel magnetic nanomaterial was synthesized by grafting nitrilotriacetic acid to magnetic graphene oxide (NDMGO), which was applied as an adsorbent for removing tetracycline (TC) from aqueous solutions. The nanomaterial was characterized using TG-DTA, SEM, TEM, XRD, VSM, XPS, Raman, BET surface area and zeta potential measurements. Several experimental conditions (solution pH, adsorption time, temperature, ionic strength and foreign ions) affecting the adsorption process were investigated. The results showed that the TC adsorption capacity could be affected by solution pH. The adsorption capacity of TC increased rapidly in the initial 20 min and finally reached equilibrium was about 600 min. The pseudo-second-order kinetics provided the better correlation for the experiment data. Various thermodynamic parameters indicated that the adsorption was a spontaneous and endothermic process. The presence of NaCl and background electrolytes in the solution had a slight influence on TC adsorption. Hydrogen bonds, amidation reaction pi-pi and cation-pi interaction between NDMGO and TC could be used to explain the adsorption mechanism. The regeneration experiment demonstrated that this nanomaterial possessed an excellent regeneration performance. Based on the experimental results and comparative analysis with other adsorbents, the NDMGO was a high-efficiency and reusable adsorbent for TC pollution control. (C) 2016 Elsevier Inc. All rights reserved.