Exploration of haematite-loaded rice husk biochar as a low-cost nanosorbent to remove Cr (III) from the aqueous media

ABSTRACT In this study, the biochar of rice husk was modified to a nanosorbent upon loading with haematite for Cr (III) removal from aqueous solutions. Three adsorbents, rice husk, rice husk biochar and haematite-loaded rice husk biochar, were used for equilibrium adsorption studies. SEM and FTIR analysis revealed the presence of pores and various surface active sites on a nanomaterial, which were responsible for the adsorption of Cr (III). C–H, –O–H, C=O stretching vibrations were observed in characterised FTIR peaks. Modelling of adsorption isotherms indicated best fit for Freundlich isotherm with maximum Kf value of 12,218 and 39.5 for linear and non-linear nanomaterial experimental calculations, and positive n value in range of 1–10 for all forms of adsorbents, Dubinin–Radushkevich adsorption saturation capacity qs showed high readings of 9417 and 76.8 for haematite nanomaterial, Elovich isotherm favoured non-linear results in case of nanomaterial with increased Qm values 43.4–112.3 from raw form to nanosorbents and Temkin isotherm with. Kinetic and Thermodynamic results were also summarised. Constants k and h and Qe capacity were tabulated for Pseudo second order model with highest Qe in the range of 20.36–22.52 for haematite loaded biochar nanomaterial. Hence, haematite based rice husk biochar nanostructure was employed as an efficient adsorbent for uptake of chromium.