Green synthesis of copper nanoparticles using green coffee bean and their applications for efficient reduction of organic dyes

Low-cost catalysts synthesized by the green chemistry approach have increasing potential applications for removing toxic organic dyes in wastewaters due to the expense consideration and the preference for environmentally compatible materials. In this study, copper nanoparticles (Cu NPs) were successfully prepared through a facile and green method, using the solution of green coffee bean extract as a reducing and stabilizing agent and the green synthesis takes only one step. Experimental results show that the synthesized Cu NPs exhibited excellent stability. The average particle sizes of as-synthesized Cu NPs were 5–8 nm. In the process of reducing amido black 10B (AB-10B), methylene blue (MB), and xylenol orange (XO), we found Cu NPs are effectively catalysts when sodium borohydride (NaBH4) was used as the reducing agent. Then, Cu/green coffee bean powder composites (Cu/GP C) were synthesized in one step to overcome the difficulty to recover Cu NPs in aqueous solution and we used Cu/GP C as a simple simulated catalytic bed for rapidly and efficiently reducing the methylene blue for multiple times. Cu/green coffee bean powder composite (Cu/GP C) could be used as an efficient and easily recyclable catalyst for reduction of organic dyes in industrial wastewaters due to its excellent catalytic activity, low-cost, and reusability. [Display omitted] •Environmental-friendly and low-cost synthesis of Cu/green coffee bean powder nanocomposites.•The synthesized nanocomposites have superior catalytic activities for the reduction of dyes.•The simulated catalytic bed of nanocomposites can efficiently catalyze methylene blue several times in a row.