Thermally processed biochar: preparation, characterisation and their application for cadmium removal from surface and groundwater

ABSTRACT

The thermally modified Parthenium biochar was used as an efficient adsorbent for removal of Cd from water. Parthenium biochar (PBC) prepared at 500°C was thermally activated by re-heating it at 700°C. PBC and thermally modified biochar (TMPBC) was characterised by FTIR, SEM-EDS, BET-surface area and XRD. The surface area of TMPBC (3.44 m²g⁻¹) was higher than PBC (1.89 m²g⁻¹). The optimum conditions for Cd adsorption was found to be pH, 5.0; biochar dose, 2.5 (g L⁻¹); time, 30 min; temperature 25°C; initial Cd concentration, 100 mg L⁻¹. Cadmium removal parameters were assessed using kinetic (pseudo first and second order) and adsorption models (Langmuir, Freundlich, and Redlich-Peterson). Cd removal followed pseudo second order kinetic model. The Cd removal capacity of TMPBC (129.2 mg g⁻¹) was significantly higher than PBC (59.3 mg g⁻¹). Cd removal by TMPBC (97–99%) was also demonstrated for a surface and underground waters. FTIR, XRD and SEM-EDS analysis confirmed the ion exchange and otavite precipitation mechanisms of Cd removal by biochar. The thermal modification technique could be an alternative for commercially available activated carbons; however this needs to be explored with different biomasses and other elements.

KEYWORDS:

• Parthenium
• cadmium
• adsorption
• thermal processing
• biochar

Acknowledgements

The authors express their sincere thanks to the Director of the CSIR-Central Institute of Mining and Fuel Research, Dhanbad, India, for supporting this work. This work is the part of Ph.D of the author S.K. Fellowship provided to S.K by Central University of Rajasthan, India is greatly acknowledged. The instrumental analysis help provided by Dr. Pinaki Sarkar (TGA), Dr. Sujan Saha (surface area), Dr. B. Hazra, Mr. V. Singh (SEM-EDX), and Dr. Sudip Maity (XRD) is greatly acknowledged. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Disclosure statement

No potential conflict of interest was reported by the author(s).