Effect Of Microplastics On Sodium Hypochlorite Disinfection And Changes In Its Toxicity On Zebrafish

Sodium hypochlorite (NaOCl) remains one of the most widely used disinfectants in water treatment, yet its performance is increasingly influenced by emerging pollutants such as microplastics. These particles alter chlorine chemistry, reduce disinfection efficiency, and modify toxicity toward aquatic organisms. Experimental evidence from controlled systems shows that NaOCl reactivity decreases in microplastic-rich waters due to adsorption and radical quenching. Zebrafish models reveal enhanced oxidative stress and behavioral changes when exposed to NaOCl–microplastic mixtures. The findings suggest that microplastics not only diminish chlorine’s disinfecting power but also shift its ecological risk profile.

Chemical Interactions Between NaOCl And NaClO In Aqueous Systems

The interplay between sodium hypochlorite species defines their reactivity in natural and engineered waters. Understanding how NaOCl and NaClO behave under variable conditions helps explain why disinfection outcomes fluctuate with environmental factors.

Structural And Reactive Characteristics Of NaOCl And NaClO

Sodium hypochlorite consists of the hypochlorite ion (ClO⁻) paired with sodium cations. In aqueous solution, it exists in equilibrium with hypochlorous acid (HOCl), depending strongly on pH. At lower pH, HOCl dominates and acts as a more potent oxidant; at higher pH, ClO⁻ prevails with reduced oxidative potential. The oxidation state of chlorine in both species is +1, enabling electron transfer reactions central to microbial inactivation.

Equilibrium Dynamics Between NaOCl And Its Dissociation Products Under Various pH Conditions

The equilibrium between HOCl and ClO⁻ can be expressed as HOCl ⇌ H⁺ + ClO⁻. This balance shifts toward molecular HOCl at acidic conditions (pH