Breaking Down BPA: How Dual-Frequency Ultrasound Could Revolutionize Water Purification

Redacción HC
10/09/2025

The fight against microplastic pollution has a new contender — and it doesn’t come from chemical additives or bulky filters. Instead, it’s all about sound. Researchers from the University of Glasgow have unveiled a dual-frequency ultrasound method that shows remarkable efficiency in breaking down bisphenol A (BPA), a persistent and harmful chemical widely used in plastics.

BPA is notorious for its role as an endocrine disruptor, affecting hormonal balance in humans and aquatic species. Standard wastewater treatment systems struggle to remove it entirely, leaving trace amounts in rivers, lakes, and even tap water. This study, published in Ultrasonics Sonochemistry (DOI: 10.1016/j.ultsonch.2025.107488), asks a simple but critical question: can combining two ultrasound frequencies supercharge BPA degradation without adding any chemicals?

The Science Behind Sound-Driven Water Purification

The research team set up a series of controlled lab experiments using water contaminated with BPA. They compared three scenarios: single-frequency ultrasound, dual-frequency ultrasound, and no ultrasound at all. Using precise analytical techniques like high-performance liquid chromatography (HPLC) and total organic carbon (TOC) measurements, they monitored both BPA concentration and mineralization rates over time.

The dual-frequency setup produced striking results. When tuned to optimal conditions, it achieved up to ~94% BPA removal in the lab, alongside partial mineralization — meaning that BPA wasn’t just broken into smaller pieces, but was also degraded into simpler, less harmful compounds.

Why Two Frequencies Beat One

The key lies in acoustic cavitation — the formation and collapse of microscopic bubbles in the water. These collapsing bubbles create extreme localized conditions, generating hydroxyl radicals (•OH) capable of breaking down tough chemical bonds in BPA.

In a dual-frequency system, the interplay of two sound waves creates more intense and varied bubble patterns. This, in turn, boosts radical generation and increases the likelihood of destructive reactions with BPA molecules.

The study also notes that more power isn’t always better — beyond a certain threshold, energy efficiency drops. This means reactor design and frequency tuning are just as important as raw ultrasound intensity.

Competing with Other Advanced Treatments

When compared to other advanced oxidation processes like photocatalysis or ozonation, dual-frequency sonochemistry holds its ground — especially because it operates without the need for additional chemical reagents. This simplicity makes it appealing for decentralized water treatment applications, where access to specialized chemicals and infrastructure may be limited.

However, the method still faces challenges. The experiments were conducted in small, batch-type reactors under controlled conditions. Real-world wastewater contains a complex mix of organic matter, solids, and other pollutants that could affect efficiency.

Practical Applications and Policy Potential

The authors envision this technology as a compact, decentralized solution for removing BPA and potentially other micropollutants from industrial effluents, small-scale treatment plants, and even community-level purification systems in areas with limited resources.

Before scaling up, further research should focus on:

• Testing in continuous-flow systems.
• Evaluating energy consumption per gram of pollutant removed.
• Identifying and assessing any intermediate degradation products for toxicity.

From a policy standpoint, dual-frequency ultrasound could be integrated as a polishing step in treatment systems, complementing conventional filtration and adsorption methods. For countries dealing with widespread plastic pollution, this could be a valuable tool in meeting stricter environmental quality standards.

A Sound Solution for a Silent Threat

While BPA is just one of many persistent organic pollutants, the success of dual-frequency ultrasound in breaking it down offers a promising glimpse into the future of chemical-free water purification. If the technology proves effective in real-world conditions, it could help bridge the gap between advanced lab science and accessible clean water solutions.

The message from the researchers is clear: the right sound waves, working in harmony, could become a powerful ally in the battle against waterborne pollutants.

Topics of interest

Pollution