Green synthesis of plant supported Cu–Ag and Cu–Ni bimetallic nanoparticles in the reduction of nitrophenols and organic dyes for water treatment

In the present study, ginger rhizome powder based catalysts were synthesized for the reduction of 2‑nitrophenol (2-NP), 4‑nitrophenol (4-NP), methyl orange (MO), congo red (CR), and rhodamine B (RhB). Three different bimetallic catalysts copper-silver (Cu-Ag/GP), copper-nickel (Cu-Ni/GP) and nickel-silver (Ni-Ag/GP) loaded on ginger powder were prepared via novel and robust adsorption method. The size, morphology and structure of the synthesized catalysts were measured through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX). Cu-Ag/GP and Cu-Ni/GP exhibit outstanding catalytic activity for the reduction of all tested organic compounds. Turnover frequency of Cu-Ag/GP in the case of 2-NP and 4-NP were outstanding and reached 45.86 and 81.34 h−1, respectively, while for Cu-Ni/GP, it was 27.16 and 85.83 h−1 for 2-NP and 4-NP respectively. For Cu-Ag/GP catalyst the rate constants were 1.21 × 10−3 s−1, and 4.05 × 10−3 s−1 for 2-NP and 4-NP respectively, while for Cu-Ni/GP, it was 1.11 × 10−3 s−1, and 6.08 × 10−3 s−1 for 2-NP and 4-NP respectively. The prepared catalysts were also used for the reduction of a mixture of dyes and NPs. Besides, the synthesized catalysts showed excellent reusability and stability.