Conversion of char from pyrolysis of plastic wastes into alternative activated carbons for heavy metal removal

Ledicia Pereira; Ventura Castillo; Mónica Calero; Gabriel Blázquez; Rafael R Solís; M Ángeles Martín-Lara

doi:10.1016/j.envres.2024.118558

Conversion of char from pyrolysis of plastic wastes into alternative activated carbons for heavy metal removal

Environ Res. 2024 Feb 25:250:118558. doi: 10.1016/j.envres.2024.118558. Online ahead of print.

Authors

Ledicia Pereira¹, Ventura Castillo¹, Mónica Calero², Gabriel Blázquez³, Rafael R Solís¹, M Ángeles Martín-Lara¹

Affiliations

¹ Department of Chemical Engineering, University of Granada, Avda. Fuentenueva s/n 18071 Granada Spain.
² Department of Chemical Engineering, University of Granada, Avda. Fuentenueva s/n 18071 Granada Spain. Electronic address: mcaleroh@ugr.es.
³ Department of Chemical Engineering, University of Granada, Avda. Fuentenueva s/n 18071 Granada Spain. Electronic address: gblazque@ugr.es.

PMID: 38412913
DOI: 10.1016/j.envres.2024.118558

Abstract

The valorization of post-consumer mixed plastics in pyrolysis processes represents an abundant reservoir of carbon that can be effectively converted into useful chars. This process not only holds appeal in terms of improving plastic waste concerns but also contributes to the reduction of greenhouse gas emissions, thus aligning with the principles of a circular economy paradigm. In this study, the char produced from the pyrolysis of post-consumer mixed plastic waste has been activated with Na₂CO₃, KOH, NaOH, and K₂CO₃ to improve the textural, structural, and composition characteristics, leading to improved adsorption capability. These characteristics were studied by N₂ adsorption-desorption isotherms, scanning electron microscopy, elemental and immediate analysis, and X-ray photoelectron spectroscopy. The developed surface area (S_BET) was 573, 939, 704 and 592 m² g^-1 for Na₂CO₃, KOH, NaOH and K₂CO₃ activated carbons, respectively. These activated chars (ACs) were tested for the adsorption of heavy metals in both synthetic waters containing Pb, Cd, and Cu and industrial wastewater collected at an agrochemical production plant. Na₂CO₃-AC was the best performing material. The metal uptake in synthetic waters using a batch set-up was 40, 13 and 12 mg g^-1 for Pb, Cd and Cu. Experiments in a column set-up using Na₂CO₃-AC resulted in a saturation time of 290, 16, and 80 min for Pb, Cd, and Cu synthetic waters, respectively, and metal uptakes of 26.8, 4.1, and 7.9 mg g^-1, respectively. The agrochemical effluents, containing mainly Cr, Cu, Mn, and Zn were tested in a plug-flow column. The metal uptake notably decreased compared to synthetic water due to a competition effect for active sites.

Keywords: Activated carbon; Adsorption; Agrochemicals; Char; Heavy metals; Plastic waste.