Microwave green synthesis of PVP-stabilised gold nanoparticles and their adsorption behaviour for methyl orange

In this work, gold nanoparticles (AuNPs) were prepared by the microwave irradiation method and comparative studies on the removal of dye by adsorption on activated carbon (AC) and polyvinylpyrrolidone (PVP)-supported AuNPs-coated AC were made. The uniform and stable AuNPs were prepared by the reduction of gold chloride (HAuCl4) using glucose as reducing agent and PVP as a stabilising and capping agent. The resulting AuNPs were characterised by transmission electron microscopy (TEM) and UV-Vis spectroscopy. The TEM technique showed the presence of AuNPs with an average size of 20 nm. The effect of various process parameters has been investigated by following the column adsorption technique at room temperature. Percentage removal of dye increased with the decrease in initial concentration and increased with the increase in contact time. Adsorption data were modelled with the Freundlich isotherms. The Freundlich isotherm model has been applied to the equilibrium adsorption data. Desorption studies were made to elucidate recovery of the adsorbate and adsorbent for the economic competitiveness of the removal system. The adsorption capacity of the water-desorbed adsorbate reduced from 97% to 60% for n = 6 cycles.