Adsorption is a promising technique for removing micropollutants, particularly pharmaceuticals and personal care products (PPCPs) and heavy metals, from wastewater. While it offers high removal efficiency, adsorption is often limited by long retention times and the need for frequent process optimisation. Activated carbon, the most common adsorbent, is effective but costly and poses sustainability concerns. Therefore, the search for environmentally friendly, low-cost alternatives is crucial.
This study explores the application of ultrasound (US), a green and non-chemical technology, to enhance adsorption performance and overcome key limitations. When combined with adsorption, US not only accelerated pollutant removal but also substantially increased efficiency. For example, the removal of PPCPs such as ciprofloxacin and certain pesticides was 3 to 5 times faster using US. Remarkably, one minute of US application achieved equal or greater removal compared to 30 minutes of conventional adsorption. This trend was consistently observed in both distilled and wastewater matrices.
In addition to activated carbon, organic compost derived from municipal waste was tested as a sustainable adsorbent. It demonstrated excellent removal capacities for both organic and inorganic contaminants. With US, removal efficiencies increased further, reaching over 80% for heavy metals within the first minute of treatment using compost. These results position organic compost as a viable, eco-friendly alternative to activated carbon, with similar results identified.
The study also evaluated multiple ultrasonic reactor geometries, highlighting configurations that maximise cavitation effects and improve contact between pollutants and adsorbents.
This work demonstrates the potential of ultrasound-assisted adsorption as a rapid, effective, and sustainable solution for micropollutant removal. It advances both the technological and environmental goals of wastewater treatment, reinforcing the role of green innovations in achieving circular economy principles.