Permanent hard water softening using carbon nanotube sheets

Permanent hard water softening using oxidized carbon nanotube (CNT) sheets was performed. CNT sheets were synthesized by chemical vapor deposition of cyclohexanol and ferrocene in nitrogen atmosphere at 750 °C, and oxidized with concentrated nitric acid at room temperature and then employed as adsorbent for permanent hard water softening. Various isotherms and kinetic models were applied to fit the experimental data. It was found out that the adsorption behavior of hard mineral ions by oxidized CNT sheets match well with the Freundlich isotherm and the pseudo-second-order kinetic model. The results demonstrated that the oxidized CNT sheets can be used as an effective adsorbent for hard water softening due to their high adsorption capacity. Also, using the oxidized CNT sheets, hard water softening without CNT leakage into water is economically feasible. ►Permanent hard water softening using oxidized carbon nanotube sheets was performed. ►Oxidized CNT sheets have high adsorption capacity for hard mineral ions (Mg 2+ and Ca 2+). ►Using the oxidized CNT sheets, hard water softening without CNT leakage is feasible.