Sorption and post-sorption performances of Cd, Pb and Zn onto peat, compost and biochar

• Published in: Journal of environmental management 2022-11, Vol.321, p.115968-115968, Article 115968
• Main Authors: Lima, Jacqueline Zanin, Ferreira da Silva, Eduardo, Patinha, Carla, Rodrigues, Valéria Guimarães Silvestre
• Format: Article
• Language: English
• Subjects: Adsorption; Bioaccessibility; Organic fraction of municipal solid waste; Potentially toxic elements; Remediation; Waste management
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2022.115968

The development of waste-derived sorbents to immobilize potentially toxic elements (PTEs) is a promising strategy, contributing to the achievement of sustainable development goals (SDGs). Therefore, this study aimed to assess the sorption performance of cadmium (Cd), lead (Pb) and zinc (Zn), comparing sorbents derived from organic fraction of municipal solid waste (composts and biochars) with peat. The physicochemical characterization, equilibrium of sorption, post-sorption analyzes and bioaccessibility were investigated. Results showed that the sorbents have distinct characteristics; however, each material have their particularities favorable to sorption. For instance, peat and composts have the highest cation exchange capacity (800–1100 mmolc kg−1), while biochar produced at 700 °C has the highest specific surface area (91.21 m2 g−1). The sorption equilibrium data revealed the actual sorption capacity and was well explained by the Freundlich and Langmuir isotherms and, in some cases, by the Dubinin-Radushkevich model. Post-sorption analyzes indicated the occurrence of several sorption mechanisms, driven by the physicochemical properties. Electrostatic interaction stood out for peat and compost. The FTIR spectrum for peat proved the complexation with oxygenated functional groups. The composts showed variations in the released cations (e.g. Ca2+ and K+), indicating cation exchange. Differently, for biochars, the XRD patterns showed that precipitation or coprecipitation seems to be one of the main mechanisms, especially for Cd and Pb. Regarding human bioaccessibility, the results of the gastric phase simulation (pH∼1.20) revealed lower percentages of Pb (33–81%) than Cd (91–99%) or Zn (82–99%), especially for the highest concentrations. Nevertheless, in numerical terms, all bioaccessible concentrations inspire care. In conclusion, among the sorbents, composts and biochars presented the best sorption performances and, therefore, have great potential for environmental applications. Furthermore, the bioaccessibility findings indicate that these assays, still little used in experiments with sorbents, are an important tool that should be better explored in the assessment of the environmental risk associated with contamination. [Display omitted] •Usage of OFMSW as feedstock for preparing composts and biochars.•Complexation and cation exchange are the main mechanisms for peat and composts.•Precipitation is the main mechanism for biochars, especially for Cd and Pb.