Infrared irradiation aided fabrication of Mn impregnated-natural bone adsorbent: Efficacy evaluation in aqueous Cr(VI) removal

• Novel preparation of Mn-impregnated-turkey bone highly efficient adsorbent.
• The infrared aided freeze-drying protocol renders superior adsorbents compared to air-drying.
• Freeze-dried adsorbent rendered improved water purification efficacy.
• Freeze-dried adsorbent exhibited greater spontaneity in Cr(VI) removal compared to its air-dried counterpart.

Novel adsorbents were developed through impregnation of manganese oxide on turkey bone by both conventional air-drying and infrared-aided-freeze-drying protocols. The adsorbents were characterized through TGA, XRD, SEM, FTIR, and BET-BJH analyses. The efficacy of the adsorbents were assessed in the adsorption of Cr(VI) from water. Under optimal pH 3.0 and 300 rpm agitation rate, the maximum static adsorption capacities of freeze-dried and air-dried adsorbents were 96.29 ± 1 mg/g and 88.65 ± 1 mg/g, respectively for 100 mg/L Cr(VI) solution. Adsorption on both air-dried (BET area 43.04 m2/g and 0.0553 cc/g pore volume) and freeze-dried (BET area 84.8 m2/g and 0.1571 cc/g pore volume) adsorbents were best fitted with Freundlich isotherm and pseudo-second-order kinetic model. Freeze-dried adsorbent exhibited greater spontaneity in Cr(VI) removal compared to its air-dried counterpart at lower temperature, as revealed through standard free energy change.

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