Removal of antiviral ribavirin from aqueous solutions by activated carbon prepared from tobacco stems

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AbstractThe preservation of water resources is seriously threatened by the rise of pharmaceutical contamination. Ribavirin, a widely used antiviral drug, is among the pharmaceutical residues in wastewater. In this study, the adsorption capacity of activated carbon produced from tobacco stems, a by-product of the cigarette industry, was investigated. The produced activated carbon was characterised by BET, SEM-EDX and FTIR analyses. In the next step, removal of ribavirin from aqueous solutions using activated carbon was investigated. In the next step, the removal of ribavirin from aqueous solutions was tested with this activated carbon. Various factors such as initial ribavirin concentration (10–50 μg mL−1), solution pH (4–10), adsorbent amount (5–30 mg per 50 mL solution), contact time (0–150 min) and temperature (300–328 K) were investigated to determine the optimum adsorption conditions. Adsorption kinetics were investigated with first and second order pseudo models, and the equilibrium state was analyzed with Langmuir and Freundlich isotherm models. Thermodynamic parameters were calculated at different temperatures (300, 308, 318 and 328 K). The results show that a maximum removal efficiency of 91.83% was achieved at an initial concentration of 30 μg mL−1, adsorbent dose of 20 mg, contact time of 90 min and pH 7.00. The adsorption process was best described by the pseudo-second order kinetic model (R2: 0.9987) and Langmuir isotherm model (R2: 0.9971). Thermodynamic analysis shows that the process is spontaneous (ΔG < 0), exothermic (ΔH < 0) and causes a decrease in disorder in the system (ΔS < 0). This study reveals that tobacco stems can offer an environmentally friendly and economic treatment alternative.