FeOOH modified waste concrete powders to remove tetracycline in aquatic system: Performance and mechanism

The removal of tetracycline (TC) from wastewater was a necessity due to the overuse of antibiotics and its deleterious effects on the environment. In this study, an adsorbent for the removal of tetracycline was prepared by modifying waste concrete powder using a straightforward iron (iii) chloride (FeCl 3 ) precipitation method. The structure of the prepared material was characterized using a scanning electron microscope(SEM), a specific surface area and pore size analyzer (BET), a Fourier transform infrared spectroscopy(FTIR), an X-ray diffractometer (XRD), and an X-ray photoelectron spectroscopy (XPS). The characterization results demonstrated that amorphous iron (iii) hydroxyl oxides were successfully loaded onto concrete powder. The modified concrete powder exhibited a porous structure, with a notable increase in specific surface area from 12.8 m²/g to 111.5 m²/g and a substantial rise in pore volume from 0.052 cm³ /g to 0.107 cm³ /g. The results of the batch adsorption experiments demonstrated that the adsorbent exhibited a high removal rate of tetracycline, reaching 83.3 % at pH of 4, a dosage of 2 g/L, a temperature of 25°C, and a TC concentration of 10 mg /L. Furthermore, the effects of the initial pH of the solution, the dosage of the adsorbent, and the presence of co-existing ions on the adsorption of tetracycline from modified concrete powder were investigated. The adsorption kinetics revealed that the pseudo-second-order model was more consistent with the adsorption behavior, while the adsorption isotherms indicated that the Freundlich model was more suitable than the Langmuir model. Moreover, an examination of the thermodynamic outcomes substantiated that the adsorption was spontaneous, and endothermic. The primary mechanisms of TC removal by modified concrete powder are electrostatic attraction, hydrogen bonding interactions, pore-filling effects, and surface complexation. This study presented a convenient, effective, and potentially profitable method for the construction of adsorbents with low-cost to remove TC from wastewater.