Background and Objective: Surfactants can be found in soaps, detergents, pharmaceutical products, personal care products, as well as in leather industries. In this study, adsorption of Sodium Dodecyl Sulfate (SDS) on magnetic multi-walled carbon nanotubes in the aqueous solutions was investigated.

Materials and methods: Surfactant concentration, adsorbent dosage, and pH values were considered as variables. Residual surfactant was measured using methylene blue method and adsorbent characteristic was determined by X-Ray diffraction and Fourier transform infrared spectroscopic analysis. Adsorption capacity, adsorption isotherm, and kinetic reaction were also investigated.

Results: Adsorption investigations demonstrated that the increase in initial SDS concentration or pH values, led to the decrease in SDS adsorption. Conversely, the same result was achieved by decreasing adsorbent dosage. After 120 min SDS adsorption became stable. By increasing in SDS concentration from 15 to 150 mg/L, adsorption capacity improved from 8 to 61 mg/g. Isotherm and kinetic data demonstrated that experimental data pursued Langmuir isotherm (R²=0.993) and pseudo-second order equation (R²=0.992).

Conclusion: Magnetic multiwall carbon nanotubes can be used as an effective and useful sorbent for SDS removal due to several advantages including: high adsorption capacity, relatively low equilibrium time, and easy separation of magnetic multiwall carbon nanotubes from aqueous solutions.