The present work assessed the efficiency of innovative functional biochars (HCMP0-3) produced via co-pyrolysis of hydrothermally treated coal (HT-coal), chicken manure (CM), and plastic mulch (MP) for the adsorption and remediation of Cd and Pb in contaminated soils. Compared with the HCMP0, the fixed carbon contents, surface area, porosity, and metal adsorption capacity of HCMP3 increased significantly, which can facilitate multi-pathway adsorption. Incubation of HCMP2 and HCMP3 promoted the conversion of exchangeable fractions of Cd and Pb into residual fractions by increasing soil-pH, cation exchange capacity (CEC), and dissolved organic matter (DOM). Multi-spectral techniques, including EEM fluorescence, FTIR, Raman, XPS, and EDS, provided comprehensive insights into structural variations and adsorption mechanisms during the interactions of Cd and Pb with biochar. The reduction in π-electrons, carboxyl O=C-O, and C=C after the Cd/Pb adsorption highlights the synergistic integration of cation-π interactions, aromatic rings, and surface functional groups (SFGs). According to spectral and mapping results, the participation of C and O-containing SFGs indicated the binding of metal species, primarily driven by organo- and surface complexations, ion exchange, precipitation, and π-π interactions. A higher I d /I g ratio observed in Raman mapping clearly indicated an increased graphitic disorder and more amorphous carbon structures after metal adsorption. This reflects the enhanced role of tri-biomass co-pyrolytic functional biochar in metal adsorption. Similarly, HCMP3 enhanced the enzymatic activities and reduced leachate Cd/Pb by adsorbing metal ions, shifting soil-DOM, and promoting humification. Overall, these results position HCMP3 as a low-cost, high-performing, sustainable material for soil stabilization, enabling a circular economy approach to environmental protection and waste management. • Biochar properties and carbon contents improved after co-pyrolysis. • Higher I d /I g values of aged HCMP(1-3) indicated more disordered carbon structures. • HCMP(1-3) contained humic acid-like and fulvic acid-like components. • HCMP3 improved aromaticity, humification, and enzymatic activities. • FTIR mapping revealed heterogeneous redistribution of SFGs after adsorption. • HCMP3 exhibited the highest Cd and Pb surface accumulation.
Munir et al. (Sun,) studied this question.