Plant extract induced biogenic preparation of silver nanoparticles and their potential as catalyst for degradation of toxic dyes

This study focusses on the synthesis of silver nanoparticles (Ag-nPs) by citrus fruit (Citrus paradisi) peel extract as reductant while using AgNO₃ salt as source of silver ions. Successful preparation of biogenic CAg-nPs catalyst was confirmed by turning the colorless reaction mixture to light brown. The appearance of surface Plasmon resonance (SPR) band in UV-Vis spectra further assured the successful fabrication of nPs. Different techniques such as FTIR, TGA and DLS were adopted to characterize the CAg-nPs. CAg-nPs particles were found to excellent catalysts for reduction of Congo red (CR), methylene blue (MB), malachite green (MG), Rhodamine B (RhB) and 4-nitrophenol (4-NP). Reduction of CR was also performed by varying the contents of NaBH₄, CR and catalyst to optimize the catalyst activity. The pseudo first order kinetic model was used to explore the value of rate constants for reduction reactions. Results also interpret that the catalytic reduction of dyes followed the Langmuir–Hinshelwood (LH) mechanism. According to the LH mechanism, the CAg-nPs role in catalysis was explained by way of electrons transfer from donor (NaBH₄) to acceptor (dyes). Due to reusability and green synthesis of the CAg-nPs catalyst, it can be a promising candidate for the treatment of water sources contaminated with toxic dyes.