CPZ: A Sustainable Approach to the Removal of Ciprofloxacin from Water

Antibiotics in aquatic environments pose a growing threat – they promote the emergence of resistant bacterial strains and disrupt ecosystems. A team of researchers has therefore developed a new adsorbent capable of efficiently removing ciprofloxacin (a widely used broad-spectrum antibiotic) from water. The combination: Chitosan / Polyacrylamide / Zeolitic Imidazolate Framework-8 (CPZ).

What is CPZ and what makes it special?

• Chitosan provides good biocompatibility and numerous functional groups suitable for binding contaminants.
• Polyacrylamide (PAM) helps improve mechanical properties and often enhances stability in aqueous environments.
• ZIF-8 (Zeolitic Imidazolate Framework-8) is a porous metal–organic framework (MOF), known for its large surface area and fine pore structure. These features enable high adsorption capacities.
• The combination of these three materials results in a composite that is both efficient and relatively eco-friendly in terms of production and application.

Key Findings

Adsorption performance
CPZ shows a high ability to adsorb ciprofloxacin from aqueous solutions. Its adsorption capacity under various conditions clearly exceeded that of many comparable materials.

Effect of pH, initial concentration, and ionic strength
As with many adsorbents, CPZ’s effectiveness strongly depends on environmental parameters. For example, different pH values led to changes in surface charge and thus binding capacity. The initial concentration of the antibiotic and the presence of additional ions in the water also influenced how much ciprofloxacin could be adsorbed.

Kinetics and isotherm modeling
The study applied classical models (e.g., Lagergren pseudo-second-order) to describe adsorption kinetics. The adsorption behavior could be fitted to common isotherms such as Langmuir or Freundlich, providing insights into surface characteristics, pore distribution, and homogeneity of binding sites.

Regenerability and sustainability
Importantly, the material can be reused multiple times without a drastic decrease in adsorption performance. This makes CPZ not only effective but also durable and economically viable.

Relevance for environment, health, and application

Environmental protection: Effective removal of antibiotics like ciprofloxacin from wastewater and natural waters can reduce environmental burden, lowering the risk of resistant bacteria developing or spreading.

Health: Clean water protects against direct and indirect health risks, especially when antibiotic residues could contaminate drinking water sources.

Technical feasibility: CPZ demonstrates that hybrid adsorbents combining natural (chitosan), synthetic/polymeric, and MOF components can be promising candidates for scalable and reproducible water treatment solutions.

Which chitosan was used?

• The study used chitosan with 98% purity.
• It was dissolved in acetic acid (99%) as a solvent to create an acidic environment in which chitosan could be dissolved or dispersed.
• Additional components of the composite were polyacrylamide and ZIF-8 (a metal–organic framework).

This combination yields a material that not only provides many functional groups (such as amino and hydroxyl groups of chitosan) but also incorporates a porous structure from ZIF-8, complemented by the stability conferred by polyacrylamide.

Possible alternatives: Which chitosan could be used?

If CPZ is to be further developed or similar materials are designed, the following chitosan characteristics and variants may be of interest:

1. Degree of deacetylation (DD)

• A higher DD provides more free amino groups that can become positively charged and interact with the negatively charged sites of ciprofloxacin.
• A lower DD may reduce solubility and adsorption capacity but could improve mechanical or structural properties for certain applications.

2. Molecular weight

• High-Mw chitosan: often better film/gel formation, greater stability, but potentially slower diffusion and adsorption rates.
• Low-Mw chitosan or chitosan oligosaccharides: faster diffusion, potentially better adsorption kinetics, but lower mechanical stability.

3. Source and purity

• Crustaceans (e.g., crabs, shrimp) are the classic source, but fungal-derived chitosan is also under investigation.
• Purity matters: impurities could interfere with adsorption behavior or affect reusability.

4. Modifications / derivatives

• Chemically modified chitosans, e.g., quaternized chitosan, carboxylated chitosan, or functionalized chitosan designed to specifically enhance ciprofloxacin binding.
• Crosslinking with other polymers or additives to improve stability, reusability, and structural integrity.

5. Physical form

• Powder, granules, films, sheets, or hydrogel-like structures – depending on the application (e.g., water treatment systems, membranes).

Outlook
CPZ is a promising material, but several further steps are required for large-scale application:
- Testing under real-world conditions (e.g., wastewater containing complex mixtures of organic and inorganic compounds).
- Long-term studies on stability and regeneration over multiple cycles.
- Evaluation of economic and ecological aspects of large-scale production.
- Assessment of safety regarding potential side effects, such as release of components or degradation products.

References
Zhang, Q. et al. (2025). CPZ nanocomposite (Chitosan/Polyacrylamide/ZIF-8) as an efficient adsorbent for ciprofloxacin removal from water. Current Research in Green and Sustainable Chemistry, 13, 100444. Verfügbar unter: https://doi.org/10.1016/j.crgsc.2025.100444
Rinaudo, M. (2006). Chitin and chitosan: Properties and applications. Progress in Polymer Science, 31(7), 603–632. DOI: 10.1016/j.progpolymsci.2006.06.001
Kumar, M. N. V. R. (2000). A review of chitin and chitosan applications. Reactive and Functional Polymers, 46(1), 1–27. DOI: 10.1016/S1381-5148(00)00038-9
Dash, M., Chiellini, F., Ottenbrite, R. M., & Chiellini, E. (2011). Chitosan—A versatile semi-synthetic polymer in biomedical applications. Progress in Polymer Science, 36(8), 981–1014. DOI: 10.1016/j.progpolymsci.2011.02.001

First published on 2nd of October 2025

Revised on 2nd of October 2025