Biochar filtration of active pharmaceutical ingredients from wastewater

Antimicrobial resistance (AMR) is driven in part by selective pressure applied by active pharmaceutical ingredients (APIs) in environmental reservoirs. According to the UN, 80% of all wastewater flows into the environment untreated. There is therefore an urgent need to filter wastewater from sources rich in APIs, like hospitals and pharmaceutical plants, before they reach environmental reservoirs where resistance can spread.
Waste lignocellulosic biomass (LCB), a byproduct of agricultural and forestry industries, is currently the largest stream of non-edible biomass globally. Biochars produced from waste LCB are ideal filtration materials, as they are highly adsorbent, affordable, and sustainable, with morphologies and surface chemistries that are tunable by choice of production conditions. Here, we link peak pyrolysis temperatures and alkaline pretreatment of walnut shell biochars to their filtration performance, showing these materials are suitable for in-line filtration of wastewater to combat AMR. Chars produced at the highest peak pyrolysis temperature tested (450 °C) were shown to remove ~100% of tricyclic antidepressants and ~90% of clarithromycin. These findings provide a first-in-kind insight into how production conditions affect the ability of biochars to mitigate environmental AMR.