Biomass Conversion and Biorefinery, 2024 (SCI-Expanded)
In this work, it was aimed to remove the highly toxic rhodamine B (RhB) dye from wastewater by using a low-cost, renewable, sustainable, and completely natural adsorbent obtained from St. John’s wort (Hypericum perforatum) (HP), which is considered an agro-waste. HP was characterized by FTIR-ATR, XRD, FESEM, and pHpzc. Adsorption experiments were conducted by optimizing pH (2–12), dose (0.01–0.30 g), time (0–120 min), and concentration (10–50 mg/L). Equilibrium data were applied to linear isotherms. The results stated that the removal process occurred in a monolayer on the homogeneous surface of HP and the qm value was determined as 196.08 mg/g at 298 K. Kinetic results showed that RhB adsorption on HP followed a quasi-second-order. The effect of salt concentration onto RhB adsorption on HP adsorbent and reusability studies were conducted. Thermodynamic tests showed that the process was exothermic (ΔHAo=-13.58kJ/mol) and spontaneous (ΔGAo=-26.61kJ/mol). The results of the study indicated that HP may be a favorable adsorbent for basic dyes in wastewater. Graphical abstract: (Figure presented.)