Characterisation and Detoxification Mechanisms of Agrowaste-Derived Biochars Containing Nanosized Particles for...

In the present study, characterisation of (nano-)biochars(NBCs) derived from agro-wastes using BET, CHNS/O, TGA/DSC, FTIR, SEM, TEM, AAS, and ICP-MS analyses confirmed physical integrity, crystalline and homogenous nature of biochars, including their elemental composition, moisture, and ash content, nanosized particles (25-100 nm), and the presence of functional groups. Maximum adsorption capacity of NBCs derived from bagasse, maize stalk, and paddy straw was found to be 66.10 ± 1.06, 75.61 ± 1.28, 73.04 ± 1.04 mg/g for lead, and 29.05 ± 0.96, 66.07 ± 1.15, 61.76 ± 1.02 mg/g for cadmium, which indicated that maize stalk biochar is the most effective. These NBCs effectively remove chromium in the range of 24.6-53.8 mg/g at a lower pH of 2.2 due to electron-donating groups; however, they were ineffective at a higher pH value of 7 because of electrostatic repulsion with negatively charged functional groups and differences in chemical speciation, surface charge, and redox potential. Pyrolysis enhanced the properties of biosorbents by increasing their porosity, surface area, and concentration of key minerals suitable for ion exchange. None of the NBCs removed ammonia and nitrite effectively. NBCs have potential applications for heavy metals removal and mitigation of stresses for climate-resilient agriculture due to their stability, recalcitrance, and water retention capacity.