Formulation study for softening of hard water using surfactant modified bentonite adsorbent coating

As an adsorbent coating of surfactants, sodium dodecylbenzene sulfonate (SDBS) modified bentonite (SMB) has been developed for the removal of Ca2+ and Mg2+ ions from hard water. The adsorbent was characterized using SEM-EDX, Zeta-meter and FTIR analyses. It has the potential to replace expensive conventional softening treatment techniques as well as reduce the usage of excess chemicals (chemical precipitation). Hard water can be easily treated using SMB by applying the adsorbent coating to the treatment area. Testing of adsorbent was carried out in terms of effect of surfactant ratio, effect of different types of binder as well as binder ratio. The best formulation of SMB was achieved by using polyvinyl acetate (PVAc) and bentonite in the ratio of 0.75:1.0 (w/w). Langmuir, Freundlich and Temkin isotherm models were tested to describe the optimum adsorption of Ca2+ and Mg2+ ions on SMB adsorbent coating. Thermodynamic and kinetic parameters were also examined for the adsorption of metal ions at different temperatures. SMB demonstrated the highest metal (Ca2+ and Mg2+) removal efficiency (29.27 mg g(-1)) in 90 min from 120 mg L-1 hardness. On the basis of good removal capacity for Ca2+ and Mg2+ ions, SMB can be effectively used for treatment of metal ions in industrial wastewater, as well as softening of hard water. (C) 2016 Elsevier B.V. All rights reserved.