Removal of amoxicillin from contaminated water using aloe barbadensis miller bio-adsorbent

Abstract

In this study, an aloe vera biomass-based adsorbent was developed for the adsorptive removal of pharmaceutical waste from contaminated water. Adsorbent was prepared from the stem of aloe vera by chemical (H3PO4 and NaOH) activation methods. Batch adsorption experiments were carried out at varying amounts of adsorbent weight (0.2–1g), pH (3–9), contact time (10–90 min), and temperature (30–70 °C). The adsorbent was signaled by different analytical instruments, such as Fourier Transform Infrared (FT-IR), thermogravimetric analysis (TGA/DTG), and X-ray diffraction (XRD). The prepared adsorbent reveals the highest removal efficiency of 91.92 % at pH values of 5.8. This pH corresponds to the point of zero charge (Pzc) value of the prepared adsorbent. Beyond Pzc of the adsorbent, percent removal was decreased due to electrostatic repulsion between the negatively charged amoxicillin molecule and the adsorbent surface. It was noted that the removal efficiency of the adsorbent decreases with increasing temperature, suggesting that the adsorption of amoxicillin over activated aloe vera is an exothermic process. In such a case, the highest removal efficiency of 91.92 % was recorded at an operating temperature of 30 °C, a pH of 5.8, an adsorbent dose of 1g, and a contact time of 30 min. Fitting the experimental data to different kinetic and isotherm models indicated that the experimental data were well fitted by the pseudo second order kinetic (R2 = 0.999) and Freundlich isotherm (R2 = 0.998) models, respectively. The negative values of enthalpy and Gibbs free energy showed that the adsorption process is exothermic in nature.