Nonlinear regression approach for acid dye remediation using activated adsorbent: Kinetic, isotherm, thermodynamic and reusability studies

In the present article, a new adsorbent synthesized from Salvadora persica (miswak) powder with chemical activation has been applied to remove Acid Violet 17 dye from aqueous solution. Characterization of the synthesized adsorbent was carried out using the techniques of FTIR, SEM, BET, zeta potential and MS. The effect of pH, adsorbent dose, contact time, initial dye concentration and temperature were assessed in batch operation. Maximum removal was favored at pH of 2, adsorbent dose of 2 g/L and temperature as 333 K. Chemical activation has increased surface area of raw adsorbent from 58.38 to 124.99 m(2)/g. Nonlinear regression has been applied for the model fitting of the experimental data. Kinetic data was well described by pseudo-second-order model. Weber-Morris model established involvement of multiple steps in governing the adsorption mechanism. Isotherm data was well described by Freundlich model. Root mean square error analysis was also applied to check the best model fitting. Maximum adsorption capacity values were obtained as 74.28 and 141.30 mg/g for raw adsorbent and activated adsorbent, respectively. Thermodynamic calculations established endothermic and feasible nature of the adsorption. The obtained removal of 97.24 +/- 0.69% for simulated solution reduced to 91.17 +/- 0.86% in case of real effluent containing 100 mg/L of dye solution as attributed to other compounds present in the actual industrial effluent which can compete on adsorption sites along with the targeted dye. Reusability study performed using ethanol as an eluent confirmed suitability of synthesized adsorbent for dye removal from wastewater. The obtained maximum adsorption capacity along with good reusability results depicted that activated Salvadora persica could be used as an efficient adsorbent for sequestration of Acid Violet 17 from the aqueous phase.