Sol–gel assisted synthesis of porous nano-crystalline CoFe2O4 composite and its application in the removal of brilliant blue-R from aqueous phase: An ecofriendly and economical approach

• Ecofriendly and economical process to synthesize ferrite nano-composite was reported.
• 24.24 mg/g (maximum) of BB-R scavenged by PNCoFe-80 at pHi – 1.79.
• 93.5–65.41% BB-R at various concentrations and temperature removed in 1 min.
• Breakthrough and exhaustive capacities were 8.75 and 37.5 mg/g, respectively.
• PNCoFe-80 reusing potential successfully revealed by regeneration study.

Porous nano-crystalline cobalt ferrite (PNCoFe) composite was synthesized by an ecofriendly and economically appealing sol–gel route using egg albumen as a binder gel, and its applicability to remove anionic brilliant blue-R (BB-R) dye from aqueous phase was studied. The arousal of two characteristic peaks at 400 and 600 cm−1 in FT-IR spectra confirmed the formation of ferrite; in addition, TEM-EDX and XRD analysis also confirmed the formation of nano-crystalline ferrite composite. BET surface area analysis revealed the formation of porous adsorbent with surface area 335 m2/g. The adsorptive binding of BB-R on PNCoFe-80 surface was confirmed by an increase in adsorbent particle radius from 3.6 to 5.5 nm after adsorption. Acid-base titration results showed dominance of acidic sites over PNCoFe-80 surface. The pH study revealed that adsorptive forces along with electrostatic attraction between anionic dye and PNCoFe-80 surface were responsible for binding of BB-R ions over PNCoFe-80 surface. Extremely fast BB-R adsorption kinetics was observed, scavenging 65–93% of dye at various concentrations (25–100 mg/l) and temperatures (298–328 K) in 1 min. The breakthrough and exhaustive capacities were 8.75 and 37.5 mg/g, respectively. 69.75% of BB-R was recovered with EtOH @ pH 11. For five consecutive regeneration cycles, BB-R adsorption varied between 81 and 100%, while desorption efficiency was almost 100%. Preconcentration study showed 1.255 mg (66.23%) BB-R was eluted in 15 ml eluent (i.e. in three fractions of 5 ml each).

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