Evaluation of single-component and multi-component adsorption of metronidazole, phosphate and nitrate on activated carbon from Prosopıs julıflora

Abstract

In this investigation, activated carbon was prepared from Prosopis juliflora (PJAC) and characterized using porosimetry, scanning electron microscope (SEM-EDX), Elemental analysis (CHNS), Fourier Transmission-Infrared Radiation (FTIR) and X-ray Diffraction (XRD) analysis. Subsequently, PJAC was used in single-component (metronidazole (MNZ), phosphate (PO43−) and nitrate (NO3−)) and multi-component (MNZ:P:N) adsorption systems. As a first step, single-component batch adsorption experiments, i.e. kinetic and equilibrium studies, were conducted at controlled conditions (30 °C) and outcomes were used to find out the rate constant and maximum adsorption capacity (qm). The pseudo-second-order kinetic model was found to well represent the removals of MNZ, PO43− and NO3− on PJAC. Among the five isotherm models used, Langmuir isotherm model has predicted qm of PJAC for MNZ (17.33 mg/g), PO43− (13.55 mg/g) and NO3− (10.99 mg/g) with good correlation. In addition, the thermodynamic parameters have shown that adsorption of MNZ, PO43− and NO3− was non-spontaneous, endothermic and increased randomness in nature. In order to quantify the competitive adsorption of the multi-component system, i.e. MNZ, PO43− and NO3−, the batch experiments were conducted in the presence of all three compounds at a ratio of 1:2.5:5 at three different MNZ:P:N concentrations levels (0.1:0.25:0.5, 1:2.5:5 and 10:25:50 mg/L). The modified Langmuir competitive adsorption isotherm model was used to predict the effect of competitive adsorption. In the multi-component system, the maximum adsorption capacities of MNZ and NO3− were decreased by ∼34 and ∼2 times, respectively than single compound system; however, it was increased by ∼1.12 times for PO43−. Overall, the results indicate that PJAC could be used as a potential adsorbent for the removal of emerging pollutants and nutrients.