Valorisation of invasive plant (Rhododendron ponticum) biomass into activated biochar as a sustainable adsorbent for emerging pharmaceutical contaminant removal from water

Abstract

The common issue of water contamination by pharmaceuticals are increasingly recognised as emerging contaminants in water as they pose significant environmental and health risks, necessitating innovative and sustainable approaches to water treatment. Activated biochar represents an effective solution for the removal of pharmaceuticals from water. Here, the focus was on the valorisation of Rhododendron ponticum, an invasive plant species in Ireland, into high-surface-area activated biochar through thermo-chemical treatments. In this work, phosphoric acid (H₃PO₄) was used for activation at two different temperatures (550 and 650 °C), which resulted in activated biochars that exhibited excellent adsorption properties with surface area of 876.3 and 869.2 m² g⁻¹ when treated at 550 and 650 °C, respectively. Structural and composition properties of the produced biochars were investigated by elemental CHNS (carbon, hydrogen, nitrogen, and sulphur) composition analysis, moisture content, fixed carbon, ash, and volatile matter. Acetylsalicylic acid (ASA), commonly referred to as aspirin, was used as a model pharmaceutical compound, and its removal from water was significantly enhanced by the activation process. The inactivated biochar showed the lowest ASA adsorption (113 mg g⁻¹), whereas the activated biochar exhibited much higher adsorption levels (267–296 mg g⁻¹). These results demonstrate that the biochar produced here is highly effective for the removal of aspirin from water. By converting problematic invasive biomass into a valuable resource, this work contributes to addressing environmental concerns associated with both invasive species and water pollution by developing eco-friendly adsorbent materials for removing emerging pharmaceutical contaminants from water.