Low-Temperature Synthesis of Magnetic Carbonaceous Materials Coated with Nanosilica for Rapid Adsorption of Methylene Blue

Hemant Mittal, Reshma Babu, Aasif A. Dabbawala, Saeed M. Alhassan

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


This work reports the synthesis of nanosilica-coated magnetic carbonaceous adsorbents (MCA@SiO2) using low-temperature hydrothermal carbonization technique (HCT) and the feasibility to utilize it for methylene blue (MB) adsorption. Initially, a carbon precursor (CP) was synthesized from corn starch under saline conditions at 453 K via HCT followed by the magnetization of CP again via HCT at 453 K. Subsequently, MCA was coated with silica nanoparticles. MCA and MCA@SiO2 were characterized using X-ray diffraction, Fourier transform infrared, scanning electron microscopy/energy-dispersive spectroscopy, transmission electron microscopy, and Brunauer-Emmett-Teller (BET) N2 adsorption-desorption isotherms. The BET surface area of MCA and MCA@SiO2 were found to be 118 and 276 m2 g-1, respectively. Adsorption of MB onto MCA@SiO2 was performed using batch adsorption studies and in the optimum condition, MCA@SiO2 showed 99% adsorption efficiency with 0.5 g L-1 of MCA@SiO2 at pH 7. Adsorption isotherm studies predicted that MB adsorption onto MCA@SiO2 was homogeneous monolayer adsorption, which was best described using a Langmuir model with the maximum adsorption capacity of 516.9 mg g-1 at 25 °C. During adsorption kinetics, a rapid dye removal was observed which followed pseudo-first- as well as pseudo-second-order models, which suggested that MB dye molecules were adsorbed onto MCA@SiO2 via both ion exchange as well as the chemisorption process. The endothermic and spontaneous nature of the adsorption of MB onto MCA@SiO2 was established by thermodynamics studies. Mechanism of dye diffusion was collectively governed by intraparticle diffusion and film diffusion processes. Furthermore, MB was also selectively adsorbed from its mixture with an anionic dye, that is, methyl orange. Column adsorption studies showed that approximately 500 mL of MB having 50 mg L-1 concentration can be treated with 0.5 g L-1 of MCA@SiO2. Furthermore, MCA@SiO2 was repeatedly used for 20 cycles of adsorption-desorption of MB. Therefore, MCA@SiO2 can be effectively utilized in cationic dye-contaminated wastewater remediation applications.

Original languageBritish English
Pages (from-to)6100-6112
Number of pages13
JournalACS Omega
Issue number11
StatePublished - 24 Mar 2020


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