Biochar characteristics and Pb2+/Zn2+sorption capacities: the role of feedstock variation

Biochar is renowned for its potential in remediating metal-contaminated environments. This potential is mainly attributed to its metal sorption capacity which is influenced by several factors including type of the feedstock used to derive biochar. This study aims to identify the most effective biochar feedstocks for future remediation strategies against Pb2+and Zn2+contamination. Five biochars derived from different feedstocks, i.e., palm fronds, citrus wood, eucalyptus wood, eucalyptus chips, and argan nut shells—were characterized for their pH, electrical conductivity, cation exchange capacity, ash content, porosity, and specific surface area. Surface functional groups were analyzed using Fourier-transform infrared spectroscopy, and elemental composition was assessed through CHNS–O analysis. The sorption effectiveness of biochar types was evaluated at varying concentrations of Pb2+and Zn2+, employing Langmuir and Freundlich adsorption isotherms. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy assessed biochar morphology and metal associations. Pf biochar emerged as a promising candidate for future remediation, exhibiting the highest pH (8.84), electrical conductivity (10,745 µS cm−1), porosity (91%), ash content (23.9%), and specific surface area (171 m2g−1) as well as highest sorption capacity for Pb2+(175.5 mg g−1). While biochars derived from citrus wood and eucalyptus chips were notable for their high sorption capacities for Zn2+(58.4 and 28.5 mg g−1, respectively). Energy-dispersive X-ray spectroscopy analysis revealed associations of Pb2+and Zn2+notably with silica and calcium, providing insights into the sorption mechanisms.