Removal of Cr (VI) from aqueous solution using magnetic biochar synthesized by a single step method

ABSTRACT

Magnetic biochar, as an adsorbent, was synthesized by a single step method, where iron salt was directly mixed with pinewood sawdust by chemical co-precipitation and subsequently pyrolyzed at 700°C for Cr (VI) removal from aqueous solution. The effects of some important parameters including adsorbent dosage (0.4–2.8 g/L), pH (1–10) of the solution, contact time (0–1440 minutes), initial concentration (30–120 mg/L), and temperature (20–40°C) were investigated in batch experiments. Both pre- and post-adsorbents were characterized by SEM-EDX and XPS to investigate the adsorption mechanism. The maximum adsorption capacity of the tested magnetic biochar under the certain experimental conditions determined as optimal was 42.7 mg/g for Cr (VI). The adsorption data were proved to be suitable for the pseudo-second order model for kinetics and the Langmuir model for isotherms with correlation R² = 0.9996 andR² > 0.9980, respectively, after fitting with four kinetic models (pseudo-first order, pseudo-second order, W-M model, and Elovich) and three isotherm models (Langmuir, Freundlich, and Temkin). The characteristic analyses further verified that the efficient particle was a mixture of iron oxides in essence, and it had a strong effect on the spontaneous and endothermic adsorption process.

GRAPHICAL ABSTRACT

KEYWORDS:

• Adsorption
• Cr (VI)
• magnetic biochar

Acknowledgments

The authors are grateful to the Analytical and Test Center of Huazhong University of Science and Technology for carrying out the analysis of the characterization of the samples.