Fenton-modified Malacantha alnifolia tree bark for effective surface separation of tetracycline

This research work gave details on the application of Malacantha alnifolia tree bark as a low-cost adsorbent for the removal of tetracycline from aqueous solution. The tree bark was modified using different ratios of ferrous sulphate and hydrogen peroxide (Fenton’s reagent). Fenton modification of the adsorbent was more effective at high concentration of ferrous sulphate solution and at low concentration of hydrogen peroxide solution. Both the modified and unmodified adsorbents were characterized by x-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Boehm titration and pH of point of zero charge (pHpzc). The effects of various parameters such as pH, Fe²⁺/H₂O₂ concentration ratio, contact time, initial tetracycline concentration and adsorbent dose were studied. The experimental data were best described by Freundlich isotherm model and the adsorption kinetics followed the pseudo-second order kinetic model. The thermodynamic analysis of the adsorption processes indicated a non-spontaneous process for the unmodified adsorbent (UMA) and a spontaneous process for the modified adsorbent (MMA); change in enthalpy showed that the adsorption process for both adsorbents was exothermic and change in entropy indicated that the adsorption process was orderly. Desorption studies showed that the modified adsorbent can be regenerated more than the unmodified. Fenton-modification improved the adsorption capacity of Malacantha alnifolia tree bark.