Microplastics Bound Transport of Antibiotics in Aquatic Environment

Microplastics (MP) are considered as potential transport vectors for organic contaminants and heavy metals in the aquatic environment. The emerging contaminants such as pharmaceuticals may sorb onto MP and may influence by different environmental factors and physicochemical properties of MP. The study investigates the sorption behavior of Ciprofloxacin (CPX) antibiotic on polyethylene microplastics (PEMP) through batch sorption experiments. The effects of ionic strength and dissolved organic matter (DOM) were examined by introducing NaNO₃ and Humic acid (HA) in to the medium. Pure PEMP was characterized by FTIR to analyze the physicochemical properties of the adsorbent. Batch sorption experiment results showed that the sorption of CPX with pH had a gradual increase reaching a maximum sorption at pH 6-7 and then decreased which is likely due to the speciation of CPX at different pH. In the presence of 0.001 M and 0.1 M NaNO₃ ionic strength, the overall CPX sorption capacity of PEMP decreased as the ionic strength increased. Sorption capacity of CPX by PEMP decreased significantly in the range of 0.5 to 2.5 mg L^-1 of HA highlighting the influence of DOM in the aquatic environment towards the CPX sorption and mobilization by PEMP. Results of the FTIR spectrum attributing to -CH₂ and -CH₃ functional groups exhibit non-polar hydrophorbic properties of PEMP indicating that hydrophobic interactions between CPX and PEMP have been prominent around neutral pH. Hence, PEMP could be potential vectors to transport CPX in natural aquatic environment where the sorption mechanism is being influenced primarily by the characteristics of the water system and the properties of the adsorbate.