Adsorption and kinetic studies of hexavalent chromium by dehydrated Scrophularia striata stems from aqueous solutions

The unregulated discharge of heavy metals into the environment from industrial activities is an important threat to the environment. In this study, the adsorption of Cr(VI) from aqueous solution onto dehydrated Scrophularia striata stems (DSSS) was studied. The effects of pH, the adsorbent dosage, the initial Cr(V1) concentration, and the reaction time on the adsorption efficiency were investigated. The Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR), and SEM-energy dispersive X-ray (EDX) analyses were performed to assess the pores volume, chemical form, and surface morphology of the DSSS, respectively. Moreover, the kinetics and thermodynamics of Cr(VI) adsorption were theoretically interpreted using different models. The adsorption efficiency of Cr(VI) decreased as the pH and initial Cr(VI) concentration increased. Conversely, the adsorption efficiency increased as the adsorbent dose and reaction time increased. The kinetic processes of Cr(VI) adsorption were tested by applying the pseudo-first-order, pseudo-second-order, and Elovich models. The pseudo-first-order kinetic model for Cr(VI) adsorption fitted well. The Langmuir isotherm provided the best correlation for the adsorption of Cr(VI) onto DSSS. Accordingly, it is concluded that DSSS can be used as an affordable, appropriate, and environmentally friendly adsorbent for Cr(VI) adsorption from aqueous solutions.