Laccase-like nanozymes fabricated by copper and tannic acid for removing malachite green from aqueous solution

Seeking simple, green, and inexpensive preparation methods and materials of enzyme mimics has always been highly desirable. In this paper, a nanocomposite with laccase activity was successfully fabricated by using a simple self-association method with copper and tannic acid. Characterizations through SEM, XRD, FTIR, and XPS showed that the Cu-TA hybrid composites had good spherical in shape with a diameter of about 20 nm and three different valence Cu ions (Cu2+, Cu+, and Cu-0). The catalytic activity was displayed against typical oxidation substrate of laccases, 2,4-DP. Compared to natural laccases, Cu-TA composites were able to better tolerate changes of pH, temperature, ionic strength, and storage conditions. The Cu-TA composites could remove malachite green (MG) from aqueous solutions effectively. The removal efficiency of MG was optimized using a series of batch tests with single-factor experiment design. Under the optimum conditions, the removal efficiency of MG still retained about 90% after 3 times cycles. Therefore, the Cu-TA composites, as a laccases-like nanozyme, have excellent developing potential in wastewater treatment due to the low-cost of TA and simplicity of preparation.