Rapid pyrolysis of Cu2+-polluted eggshell membrane into a functional Cu2+-Cu+/biochar for ultrasensitive electrochemical detection of nitrite in water

Bioremediation is one of efficient methods to solve the issues of water or soil contaminated by metal ions . However, the harvested biowaste is often troublesome to handle owing to the second pollution. Herein, the waste eggshell membrane was used to adsorb Cu 2+ in wastewater, which was then converted into biochar containing copper ions (Cu 2+ -Cu + /Biochar) via a rapid pyrolysis . By integrating the collective advantages of eggshell membrane and Cu 2+ -Cu + , such as superior electrical conductivity, enlarged electrochemically active surface area, unique three-dimensional porous network characteristics, and fast charge transport, the Cu 2+ -Cu + /Biochar system can be used as a self-supporting sensor for detection of nitrite (NO 2 − ). The sensor demonstrated superior electrochemical sensing abilities accompanied by a broad linear range (1–300 μM), ultralow detection limit (0.63 μM), and high sensitivity (30.0 μA·mM −1 ·cm −2 ). In addition, the fabricated electrochemical sensor has excellent stability, good reproducibility, and strong anti-interference performance. More importantly, the sensor has a high recovery rate when it is used to detect nitrite in tap water , mineral water , and sausage, indicating the feasibility of using this sensor in practical applications. This study provides a green and sustainable approach for simultaneous treatment of biomass waste eggshell membrane, remedy of heavy metals, and electrochemical detection of nitrite.