Quantitative detection of naphthenic acids in wastewater based on superior fluorescence performance of nitrogen-rich carbon quantum dots

With the development of the petrochemical industry, a large amount of naphthenic acids in petrochemical wastewater was accumulated in the environment, causing serious environmental pollution. Most of the commonly used methods for the determination of naphthenic acids have the characteristics of high energy consumption, complicated pretreatment, long detection cycle, and the need to send samples to analytical laboratories. Therefore, it is essential to develop an efficient and low-cost field analytical method for rapidly naphthenic acids quantify. In this study, nitrogen-rich carbon quantum dots (N-CQDs) based on natural deep eutectic solvents (NADESs) was successfully synthesized by a one-step solvothermal method. The fluorescence property of carbon quantum dots was used to achieve the quantitative detection of naphthenic acids in wastewater. The prepared N-CQDs showed excellent fluorescence and stability, showed a good response to naphthenic acids and a linear relationship in the concentration range of naphthenic acids from 0.03 to 0.09 mol‧L−1. The effect of common interferents in petrochemical wastewater on the detection of naphthenic acids by N-CQDs was investigated. The results showed that N-CQDs had good specificity for the detection of naphthenic acids. N-CQDs was applied to the naphthenic acids wastewater, and the concentration of naphthenic acids in the wastewater was successfully calculated according to the fitting equation.