Response surface modeling and optimization of nitrate removal from aqueous solutions using magnetic multi-walled carbon nanotubes

Abstract In this paper, the application of magnetic multi-walled carbon nanotubes (MMWCNTs) was studied for the removal of nitrate from aqueous solutions. MMWCNTs and Multi-walled carbon nanotubes (MWCNTs) are characterized by XRD, TEM, FT-IR, and VSM. The XRD results confirm that MWCNTs/Fe 3 O 4 nanocomposites were successfully synthesized by a facile hydrothermal method. The MMWCNTs can be easily manipulated in a magnetic field for the desired separation, leading to the removal of nitrate from aqueous solution. In this study, the application of response surface methodology (RSM) is presented for optimizing the removal of nitrate from aqueous solutions using MMWCNTs. The effects of D/C (adsorbent dosage per initial concentration of pollutant ((mg) adsorbent /(mg/l) initial )) and initial pH on nitrate removal (%) were evaluated by RSM. Using RSM methodology, a quadratic polynomial equation was obtained for removal of nitrate by multiple regression analysis. The optimum conditions for maximum removal of nitrate from aqueous solution were as follows: D/C (40 (mg)/(mg/l)) and initial pH = 4. Under optimal value of process parameters, maximum removal (97.15%) was obtained. The empirical Freundlich isotherm was found to describe well the equilibrium adsorption data. The adsorption capacity amount of nitrate could reach up to 183.11 mg/g at the high range concentration (50–100 mg/l). It was found out that the MMWCNTs can be considered as a promising adsorbent for removal of nitrate from aqueous solution.