Removal of hexavalent chromium in aquatic solutions by iron nanoparticles embedded in orange peel pith

The aim of this work was to create a biocomposite which coupled the reducing capability of iron nanoparticles with the adsorption capacity of cellulose to effectively remove hexavalent chromium from industrial wastewater. The iron nanoparticles were synthesized on the orange peel pith using a simple redox precipitation reaction to ensure the biocomposite was inexpensive and easy to produce. The nanoparticles were characterized for size, composition, oxidation state, and distribution before and after the Cr(VI) exposure. The nanoparticles were mostly 20 × 80 nm tubular shapes, but there were also some octahedral crystals around 20–40 nm. The biocomposite with the nanoparticles exhibited twice the Cr(VI) removal of the unmodified orange peel pith and also possesses over twice the adsorption capacity −5.37 mg/g vs. 1.90 mg/g.

► An iron nanoparticles in orange peel pith biocomposite is an effective Cr(VI) sorbent.
► The biocomposite removes 71% of Cr(VI) from a 10 mg/L solution vs. 34% for unmodified biomass.
► The biocomposite has a Cr(VI) capacity of 5.37 mg/g vs. 1.90 mg/g for unmodified biomass.
► The two-step adsorption involves reduction of Cr(VI) by Fe then adsorption of the Cr(III).
► The biocomposite is economical, easy to synthesize, environment friendly, and effective.