Removal of Co-Occurring Microplastics and Metals in an Aqueous System by Pristine and Magnetised Larch Biochar

Microplastics and metals are increasingly recognised as major water contaminants with profound environmental and health consequences. The environmental co-occurrence of microplastics and metals are well documented in waterways, including urban runoff, highway balancing ponds, industrial wastewater, and mine-impacted waters, posing a multifaceted environmental threat. Urgent remedial action is required to remove co-occurring microplastics and metals from water, giving consideration to how their co-occurrence can affect remediative efforts. However, information on the sorption of microplastics and Pb and Zn simultaneously by biochar is lacking. In this current study, changes in the quantity of metal adsorbed by pristine larch biochar and magnetised larch biochar due to the presence of microplastics was assessed using spectroscopic techniques. This study demonstrated that magnetised larch biochar and pristine larch biochar both remove co-occurring microplastics, Pb, and Zn from solution. Neither magnetised larch biochar nor pristine larch biochar show any statistical difference in the sorption of Pb with the inclusion of microplastics into the aqueous matrix. However, the inclusion of microplastics result in the reduced sorption of Zn by 43% for magnetised larch biochar (p < 0.01) and 69% for pristine larch biochar (p < 0.01). Magnetised larch biochar also demonstrated greater sorption than pristine larch biochar for microplastics (p < 0.05), Zn co-occurring with microplastics (p < 0.05), and Zn with no microplastics present (p < 0.01). Despite the effects of competitive sorption between Zn and microplastics, the removal of Pb, Zn, and microplastic from a multi-contaminant system indicate that magnetic larch biochar is a viable option to remove multiple contaminants from aqueous environs where metals and microplastics are seen to co-occur.