On-site chemosensing and quantification of Cr(VI) in industrial wastewater using one-step synthesized fluorescent carbon quantum dots

Abstract

Wastewater from the vanadium extraction industry contains Cr(VI) and severely threatens the environment in China. The on-site monitoring and quantitative determination of Cr(VI) in this wastewater is urgently needed to protect the environment and human health. To address this issue, amino-functionalized carbon quantum dots (CQDs) were easily synthesized as fluorescence probes. CQD fluorescence was selectively and sensitively quenched by Cr(VI) due to the formation of ionic bonds between Cr(VI) anions and the amino groups on the CQD surface. On-site semiquantitative Cr(VI) chemosensing was realized with a portable UV lamp easily, rapidly, and cost-efficiently, providing on-stream visual proof for the dischargeability of the waste stream. The CQDs-based quantitative Cr(VI) determination method for the industrial wastewater was established with a linear range spanning 4 orders of magnitude and a limit of detection as low as 140 nmol/L, far exceeding the Cr(VI) concentration limit for the discharge of Cr(VI)-containing industrial wastewater in China. This quantitative chemosensing method is highly selective and sensitive in complex solutions, including the wastewater from the vanadium extraction industry. Therefore, this CQDs-based chemosensing method can be used not only for on-site chemosensing and quantitative Cr(VI) concentration determination in wastewater, but has considerable potential for monitoring hazardous materials in other industrial effluents.