Low-Cost Biosorbents Derived from Corn Husks for the Exclusion of Fe(II) and Cr(VI) Ions Undertaken Aqueous Media: Application for Wastewater Treatment

Abstract

Microcrystalline cellulose (MCC) fibres were extracted by the use of chlorine-free treatment from waste corn husk. MCC fibres were modified by periodate oxidation into 2,3-Dialdehyde cellulose (2,3-DAC) particles with 95.5% aldehyde content. Characterization was done by using FT-IR, XRD, SEM, EDX, HR-TEM and TGA analytical techniques. FT-IR analysis from corn husk to cellulose confirmed the loss of hemicellulose and lignin content due to the disappearance of the respective peaks and from cellulose to 2,3-DAC confirmed the oxidation due to the appearance of a peak at 1730 cm⁻¹ confirming the CHO group. XRD confirmed the more crystallinity of the 2,3-DAC over MCC fibres. SEM and TEM images clearly reflect the changes in the surface morphology after extraction of MCC fibres as well as after oxidation to 2,3-DAC powder. TGA analysis reported the increased thermal stability of 2,3-DAC particles over MCC fibres. Swelling capacity was estimated with respect to pH and temperature from 1 to 24 h contact time. Swelling of 2,3-DAC was almost 2 times more than MCC fibers with PSC = 842.8% in pH 9.2 solution at 25 ℃. Sorption investigations of Fe²⁺ and Cr⁶⁺ metal ions were carried out using both non-competitive as well as competitive approaches. The sorption was higher for Fe(II) by 2,3-DAC in non-competitive (80.2% R_e) as well as in competitive (71.6% R_e) approach as compared to the Cr(VI) ions. Different isotherms and kinetic models were applied to the sorption studies. The sorption follows a Pseudo-second-order kinetic model, Boyd’s kinetic model, Weber-Morris IPD model and Langmuir adsorption isotherm as best-fitting curves. Regenerated materials were employed for the repeated cycles to understand the efficiency and sustainability. Therefore, low-cost, environment-friendly biosorbents proved to be potential applicants for the removal of heavy metal ions from wastewater.