Exploring the removal of flame retardants and chlorobenzenes by plastic-based materials

Abstract

In recent decades, emerging contaminants like chlorobenzenes and flame retardants have raised global concern due to their environmental persistence. However, research into their removal from water remains in its infancy. In this study, pentachlorobenzene (PeCB) and 2,2′,4,4′-tetrabromodiphenyl ether (BDE 47) were selected as representative chlorobenzene and flame retardant compounds, respectively. Adsorption has proven to be a reliable technique for removing emerging contaminants from aquatic environments. For this research, raw and dopamine modified polypropylene ropes (using waste ropes collected from Scottish beaches) were utilized to adsorb PeCB and BDE 47 from water. The raw plastic exhibited a higher adsorption capacity for PeCB, with an adsorption capacity of up to 686 μg/g obtained based on the Langmuir model. However, the modified plastic demonstrated enhanced removal efficiency for BDE 47, with a maximum adsorption capacity of 627 μg/g with the Langmuir model. Both processes were endothermic and spontaneous, and well fitted to Langmuir and pseudo-second-order models. Characterisation analysis revealed PeCB adsorption relied on hydrophobic and π-π interactions, whereas BDE 47 adsorption potentially involved additional n-π interactions and hydrogen bonding. These findings advance understanding of contaminant-plastic interactions in both controlled and natural aquatic environments, offering a sustainable strategy for upcycling fishery waste (i.e., ropes and nets) into functional adsorbents.