BACKGROUND 4-Nitrophenol (4-NP) is used widely in pesticides and other areas, but it can cause adverse environmental effects. Thus, it is desirable to convert it to 4-aminophenol (4-AP). Microbial synthesis of nanomaterials has the characteristics of low cost and effective control of secondary pollution. The catalytic performance of biosynthesized nanocomposites of copper (Cu) and carbon nanotubes (CNTs) in reducing 4-NP to 4-AP was evaluated. RESULTS Here, Cu nanoparticles were supported in situ on CNT nanocomposites via Shewanella oneidensis MR-1 to form Cu/CNT nanocomposites. The prepared Cu/CNTs nanocomposites were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectrometry, and energy dispersed X-ray spectroscopy. The findings showed that the Cu nanoparticles were successfully synthesized on the surface of the CNTs and that they had a typical diameter of 4 to 10 nm and high crystallinity. The catalytic performance of the nanocomposites for the reduction of 4-NP was evaluated under different initial concentrations of Cu/CNT, pH, and temperatures. The best catalytic performance, in which 99.5% 4-NP was reduced, was obtained with 3 wt% Cu/CNT at 45 degrees C and pH of 10 within 80 min. Accordingly, 4-NP degradation followed first-order kinetics, and the rate constant (k) has been calculated to be 0.0532 min(-1). The Cu/CNT nanocomposite exhibited high stability catalytic efficiency at 95.2% even after six reaction cycles. CONCLUSION The study demonstrates an environmentally friendly method for synthesizing non-noble metal nanocomposites and using them for the catalytic reduction of 4-NP. The method could be applied to prepare other efficient and reusable metallic nanocatalysts. (c) 2020 Society of Chemical Industry