Canola meal‐derived activated biochar treated with NaOH and CO₂ as an effective tool for Cd removal

Abstract

BACKGROUND: This research assessed the capacity for Cd 2+ removal from water using canola meal-based adsorbents: canola meal chemically activated with 1 mol L -1 NaOH and pyrolyzed for 1 h at 500 °C (CAC) and the second product obtained with a similar process but with a second pyrolysis at 750 °C in CO 2 flow (CAC-CO 2 ). The materials were characterized by their chemical composition and thermal stability and using Fourier transform infrared spectroscopy, pH at point of zero charge (pH PZC ) and scanning electron microscopy. Hydroxyl and carboxyl are the most likely surface functional groups responsible for adsorption. RESULTS:The obtained pH PZC values were 10.83 for CAC and 9.84 for CAC-CO 2 . Both materials presented heterogeneous surfaces with many cavities, which increased their respective surface specific area 23 000-and 540 000-fold compared to canola meal biomass. Our best results were obtained using 4.0 g L −1 of adsorbent, at pH 7.0, with an equilibrium time of 40 and 60 min for CAC and CAC-CO 2 , respectively. The most likely mechanism predominantly involved in Cd adsorption is physical, according to Temkin nonlinear parameters, thermodynamics parameters and excellent recovery rates (67.8%).CONCLUSIONS: The use of canola meal as a feedstock for activated biochar production is an attractive and new possibility for producing a competitive adsorbent.