Mechanistic Modeling and Process Design for Removal of Anionic Surfactant Using Dolochar

Abstract

The rapid rise in consumption of surfactants day by day and the consequent increase in discharge from both industrial and residential areas into bodies of water has become a cause for concern. In this study, an industrial waste material (dolochar) was used for the removal of sodium dodecyl sulfate (SDS). Adsorption experiments were executed using batch and column mode. The experimental data were analyzed by various adsorption isotherm models, including: Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R). Out of these models, the Langmuir isotherm appeared to be the best fit (R2 = 0.97) and produced a maximum adsorption capacity of 5.78 mg/g at optimized conditions. The effect of different parameters, such as adsorbent dose, contact time, pH, agitation speed, and particle size, on SDS removal efficiency was investigated. It was observed that all the variables play important roles in affecting the amount of SDS adsorbed and, therefore, the removal efficiency. Maximum adsorption capacity of 98% was attained at an adsorbent dose of 16 g/L, near neutral pH, 150 rpm as the agitation speed and particle size below 300 μm. A column study was performed with three different adsorbent doses (and hence different bed depths) of 10, 20, and 30 g. A bed depth service time (BDST) model was selected to check its validity and column performance, and to scale up the process parameters. The logit method was also applied to calculate various associated parameters. Characterization of dolochar before and after adsorption was performed using scanning electron microscopy (SEM).