Hibiscus leaf petiole derived activated carbon as a potential sorbent for basic green 4 and reactive yellow 15 dye exclusion from aqueous solution

In this study, hibiscus leaf petiole powder is used as a source of carbon to prepare bio-adsorbent. This bioadsorbent is carbonized by heating and activated thereafter by means of KOH and employed as an alternative adsorbent for Basic Green 4 (BG4) and Reactive Yellow 15 (RY15) dyes. Microstructural features observed from scanning electron microscope (SEM) shows the presence of openings/voids before adsorption and their disappearance after dye adsorption. Fourier transform infrared (FTIR) spectrum shows the shift in peak positions of prominent functional moieties post adsorption endorsing the contact between bio-adsorbent and the dye molecules. The dye adsorption performance of as prepared bio-adsorbent on both the dyes were evaluated by varying the solution pH value between 3 and 9, initial dye concentration, Co between 30-90 mg/L, interaction time, t between 10 and 60 min and adsorbent dose, m between 0.1 and 0.6 g/50 ml. The optimal condition investigated for dye exclusion is computed to be Co = 30 mg/L, t = 40 min, m = 0.3 g for both the dyes. However, the pH values of 9 and 3 respectively were found to be optimum for the removal of BG4 and RY15. Maximum adsorption capacity (qm) for RY15 and BG4 were found to be 41.23 and 61.38 mg/g respectively revealing hibiscus leaf derived activated carbon as an excellent bio-adsorbent. The adsorption kinetics of both dyes followed pseudosecond-order model and the adsorption isotherms is best suited to Langmuir model. These findings confirm that the as prepared bio-adsorbent can be successfully employed as an unconventional adsorbent to remove the toxic dyes from aqueous solutions.