Calcium-pyro-hydrochar derived from the spent mushroom substrate as a functional sorbent of Pb <sup>2+</sup> and Cd <sup>2+</sup> from aqueous solutions
Marija Kojić, Marija Mihajlović, Milena Marinović‐Cincović, Jelena Petrović, Đurica Katnić, Aleksandar Krstić, Svetlana Butulija, Antonije Onjia
Abstract
A calcium-pyro-hydrochar (Ca-PHC) can be distinguished as a novel sorbent of Pb 2+ and Cd 2+ from an aqueous solution. It was obtained using hydrothermal treatment of the spent mushroom substrate (SMS), followed by a CaCl 2 ·5H 2 O activation and pyrolysis. The characterisation of chars before and after modifications was done by scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET) and Fourier transform infrared (FTIR). Batch experiments were performed to examine Ca-PHC’s sorption properties and binding mechanisms to selected metal ions. The maximum sorption capacities of Ca-PHC for Pb 2+ and Cd 2+ were 297 mg g −1 , and 131 mg g −1 , respectively. The obtained results demonstrated that the sorption of Pb 2+ and Cd 2+ by Ca-PHC follows a pseudo-second kinetic model and Freundlich isotherm. The binding of the selected metals onto Ca-PHC was enabled by the ion-exchange mechanism, surface complexation, mineral precipitation and cation–π interaction. Thermodynamic parameters indicate that metal ions binding by Ca-PHC are spontaneous and endothermic. Due to the high adsorption capacities, the obtained Ca-PHC has good potential for application in industrial wastewater treatment. In addition, the demonstrated use of SMS highlights another possibility of applying this specific biomass relevant to sustainable and economical waste management in the growing mushroom industry.