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

Author(s)

Lima, Jacqueline Zanin ; da Silva, Eduardo Ferreira ; Patinha, Carla ; Rodrigues, Valeria Guimaraes Silvestre

• Document type: Journal article
• Source: Journal of Environmental Management; v. 321, p. 17-pg., 2022-08-18.

Abstract

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 mmol(c) kg(-1)), while biochar produced at 700 degrees C has the highest specific surface area (91.21 m(2) 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 similar to 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. (AU)

• FAPESP's process: 17/16961-0 - Use of organic compost and peat in the retention of Pb, Zn and Cd and evaluation of the possible availability, toxicity and bioaccessibility of these metals after retention
• Grantee: Jacqueline Zanin Lima
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 19/00275-6 - USE OF REACTIVE MATERIALS IN THE POTENTIALLY TOXIC METALS SORPTION AND BIOACESSIBILITY AND TOXICITY ASSESSMENT AFTER RETENTION
• Grantee: Jacqueline Zanin Lima
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate