Adsorption of copper (II) by using derived-farmyard and poultry manure biochars: Efficiency and mechanism

Biochar (BC) has recently become an attractive adsorbent for the removal of toxic metals from aqueous media. In this study, the adsorption efficiency of BCs derived through farmyard and poultry manure (DBC-FYM, DBC-PM) for the removal of copper (Cu²⁺) from water was evaluated. The porosity, surface structure, internal morphology, thermal stability and functional groups of the DBCs were analyzed using different analytical techniques such as scanning electron microscopy (SEM), X-ray photon spectroscopy (XPS), thermogravimetric analyses (TGA) and fourier transmission infrared spectroscopy (FTIR). Kinetics and isothermal data were acquired by batch adsorption mode. The isothermal sorption data was well correlated (R² > 0.98) with the Freundlich model describing multilayer sorption of Cu²⁺ on heterogeneous DBCs surface. The maximum Cu²⁺ sorption was estimated as 44.50 mg/g for DBC-FYM and 43.68 mg/g for DBC-PM. The sorption data followed the pseudo-second order kinetics, indicating the chemical interaction between Cu²⁺ and the negative charged surface of DBCs. The thermodynamic parameters indicated that the reaction was exothermic and spontaneous. Post-sorption analysis of the DBCs by XPS suggested the formation of CuO and carbonate dihydroxide. The outcomes of the present study indicated that DBCs could be valuable green sorbents for removing Cu²⁺ from contaminated aqueous media.