Reduction of TDS in Water by Using Magnetic Multiwalled Carbon Nanotubes and Optimizing with Response Surface Methodology

Abstract

The present study reports the effect of magnetic multiwalled carbon nanotubes (MMWCNTs) as an adsorbent for removing total dissolved solids (TDS) from water. MMWCNTs and multiwalled carbon nanotubes (MWCNTs) were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and transmission electron microscopy (TEM). The results indicate that MWCNTs/Fe3O4 nanocomposites were well synthesized. The MMWCNTs can be easily blended in water and separated by a magnetic field. For the purpose of the study, experimental design in conjunction with central composite design was used to examine the impact of adsorbent dosage per initial concentration of total dissolved solids (D/TDS) [(mg)adsorbent)/(mg/L)initial] and initial pH on percentage of TDS removal. The following optimum results for the maximum elimination TDS from an aqueous solution were obtained: D/TDS=2 mg/(mg/L) and initial pH=3.. Under optimal amount of process parameters, maximum removal (96%) was achieved. The Langmuir, Freundlich, Temkin, Sips, and Dubinin–Radushkevich (D-R) adsorption models were used to analyze the experimental data, and the Sips isotherm model was found to be better than other isotherm models for a high concentration of TDS {625–1, mg/L [parts per million (ppm)]}. The findings suggest that the MMWCNT can undoubtedly be considered an successful adsorbent and new solution to reduce TDS in watery solutions.