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Abstract In this research Au nanoparticles, supported on Fe 3 O 4 @polyaniline as a magnetic nanocatalyst, was synthesized and its performance has been evaluated to reduce Methylene Blue (MB) and Methyl Orange (MO) from aqueous solutions. Gold nanoparticles, as a nanocatalyst with excellent activity, were prepared through the reduction of Au3+ using a wild herbal extract (Allium Sp) without any toxic chemical compounds and harmful materials. The synthesized Fe 3 O 4 @PANI-Au magnetic nanocatalyst was characterized by different instruments. To investigate the effect of nanocatalyst concentration on the degradation rate of azo dyes, two different catalyst concentrations were used at ambient temperature. According to the carried out calculations, degradation reaction of azo dyes with NaBH 4 in presence of the nanocatalyst is 103 to 104 times faster than degradation without using the catalyst. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

In this research Fe 3 O 4 @polythiophen-Ag magnetic nanocatalyst was synthesized. First Fe 3 O 4 nanoparticles were prepared in the solution and the branched polythiophene was coated on the magnetic particles. This polymer provides enough surface for precipitation of the silver nanocatalyst produced by grapefruit peel extract reduction of AgNO 3 . The synthesized catalyst was characterized by XRD, FTIR, SEM, FESEM, EDX, TEM, TGA and VSM. Finally, it was used to degrade azo dyes (methyl orange (MO) and methylene blue (MB)) in order to evaluate its catalytic performance. Ratio of the rate constants of the catalytic and non-catalytic reactions was in order of 10 5 and 10 4 for reduction reaction of MB and MO respectively. Reaction rate in the presence of catalyst was very high and just 1 min was enough to degrade the MB and MO colorant reagents. The prepared catalyst is able to take part many times in the reaction. It was recovered by a magnet after each experiment and reused 8 times without considerable loss of the activity. [ABSTRACT FROM AUTHOR]