Separation of trace naphthalene dissolved in wastewater using microemulsion based liquid extractant followed by its detection through UV-photometric method

Abstract

The consumption of naphthalene, a recalcitrant polyaromatic hydrocarbon (PAH), has increased substantially in India in the recent past. It exhibits high tendency to get accumulated in the food chain which attributes to bioaccumulation and biomagnification amidst the aquatic lives. Due to its adverse congenital effect on human health, it requires proper remedial measures. The primary issue lies in the presence of naphthalene in water at trace level because of its low water solubility, which eventually makes its separation from water troublesome with the conventional scheme. At trace level, the concentration gradient required for transporting naphthalene from aqueous to organic phase becomes infinitesimally small, which limits the separation efficiency. Moreover, such trace quantity of pollutants in water further decreases its resolution in any high-end analytical instrument. This might pose an issue with its detection in water. Hence, the current scope of the study mainly comprises of two aspects. Primarily, an oil-in-water (O/W) microemulsion based solvent is formulated to remove trace naphthalene dissolved in water through liquid-liquid extraction. The second one was its quantification through an indigenously developed analytical dye method using the UV-spectrophotometer. 40 ​± ​0.05% naphthalene removal was observed with the microemulsion to bring the final naphthalene concentration well below the safe permissible limit. Moreover, a linear relationship K=(1.548±0.028)−(0.642±0.103)CNPh was evaluated through regression between the concentration of naphthalene and the K value (defined as the ratio of absorbance of dimerized Eosin Y with the absorbance of its monomeric form raised to the power 2). The accuracy of the developed method is found satisfactory with a regression coefficient (R2) of 0.95 and 2.05% deviation between the theoretical and experimental naphthalene concentration. Thus, the present study manifests the promising potential of formulated microemulsion based extractant for separation of naphthalene from water phase along with its easy quantification through the developed bench-top UV photometric method.