The rising prevalence of pharmaceutical micropollutants in aquatic systems poses a grave risk to public health. Specifically, understanding ofloxacin adsorption mechanisms on nanoporous carbons is essential for developing effective remediation strategies. Ofloxacin, a common fluoroquinolone antibiotic, often persists in wastewater. This persistence significantly contributes to the global crisis of antimicrobial resistance (AMR), a major concern in Indian healthcare. A recent multi-scale modeling study has now elucidated how solution pH dictates the efficiency of these adsorption processes.

Researchers utilized density functional theory (DFT) and Monte Carlo simulations to analyze molecular interactions. They found that ofloxacin exists in different forms depending on the acidity or alkalinity of the water. For instance, in acidic environments, the positively charged HQ species interacts favorably with the carbon surface. This interaction occurs despite weak electrostatic repulsion because of strong van der Waals forces and π-π stacking.

Optimizing Ofloxacin Adsorption Mechanisms for Water Safety

Furthermore, the study highlighted significant challenges in basic solutions. Under high pH conditions, the negatively charged Q species faces intense electrostatic repulsion. This effect is amplified by the high electronegativity of the fluorine atom within the ofloxacin molecule. Consequently, adsorption performance drops sharply in alkaline industrial effluents. Conversely, neutral conditions provide an ideal balance for remediation.

At a neutral pH, a mixture of zwitterionic forms dominates the solution. These forms possess high dipole moments, which significantly enhances their affinity for the carbon surface. Therefore, maintaining a neutral pH could be a key design principle for future water treatment plants. By tailoring the surface functionalization of nanoporous carbons, engineers can specifically target these pharmaceutical pollutants. This approach not only improves water quality but also reduces the selective pressure for antibiotic-resistant bacteria in local river systems.

How does pH affect the removal of ofloxacin from water?

The solution pH determines the molecular charge of ofloxacin. In acidic or neutral conditions, the drug forms species that bond more easily to carbon surfaces through π-π stacking. However, in basic conditions, strong electrostatic repulsion between the negative drug ions and the carbon surface limits the removal efficiency.

Why is nanoporous carbon used for antibiotic remediation?

Nanoporous carbons provide an exceptionally high surface area and tunable chemical properties. These features allow for strong molecular interactions that are crucial for trapping large organic molecules like ofloxacin, which are often resistant to conventional wastewater treatment methods.

Disclaimer: This content is for informational and educational purposes only. It does not constitute professional medical or environmental regulatory advice. Refer to the latest local and national guidelines for clinical practice and environmental safety.

References

1. Camara FA et al. Mechanistic insights into pH-dependent ofloxacin adsorption on nanoporous carbons. Phys Chem Chem Phys. 2026 Mar 27. doi: 10.1039/d5cp04787k. PMID: 41891200.

2. Toxics Link. Menace of Antibiotic Pollution in Indian Rivers. 2022.

3. Larsson DGJ. Pollution from drug manufacturing: review and assessment of environmental role in antibiotic resistance. Chemosphere. 2014;109:99-106.