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

BACKGROUND This research assessed the capacity for Cd2+ 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 CO2 flow (CAC‐CO2). The materials were characterized by their chemical composition and thermal stability and using Fourier transform infrared spectroscopy, pH at point of zero charge (pHPZC) and scanning electron microscopy. Hydroxyl and carboxyl are the most likely surface functional groups responsible for adsorption. RESULTS The obtained pHPZC values were 10.83 for CAC and 9.84 for CAC‐CO2. 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‐CO2, 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. © 2021 Society of Chemical Industry (SCI).