Enhanced synthesis of silver nanoparticles by combination of plants extract and starch for the removal of cationic dye from simulated waste water using response surface methodology

In the present study, starched silver nanoparticles (St-AgNPs) were synthesized by using polyphenolic compounds from aqueous extracts of Malus domestica-Green Delicious (MD-GD) and Lagenaria siceraria (LS) with starch. This combination not only gears up the synthesizing parameters but also the removal efficiency of dyes making it facile to be used on industrial scale. The surface morphology of pure, crystalline and non-agglomerated, spherical NPs was determined by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. The reduction of Ag+ 1 to Ag0 by polyphenolic compounds from green reducing agents and their stabilization by starch was confirmed by Fourier Transform Infrared spectroscopy (FTIR) studies. St-AgNPs were then employed for the removal of industrial dye, Malachite Green (MG) by adsorption method. Response surface methodology (RSM) was employed to optimize the operating parameters (OP) including sorbent dosage, contact time, dye concentration and temperature. % Removal Efficiency (%RE) at optimized OP was found to be 85.01% and 95.90% for St-AgNPs-MD-GD and St-AgNPs-LS, respectively. It was observed that the Langmuir isotherm was best fitted for the St-AgNPs-MD-GD system while for other systems Dubinin-Radushkevich (D-R) was established more feasible at higher temperatures. The thermodynamic study was also conducted and ΔG°, ΔS°, and ΔH° were estimated. The kinetics of dye removal depicted the pseudo second order rate constant for St-AgNPs-MD-GD system, whereas pseudo first order was observed for the St-AgNPs-LS system. Desorption of dye from adsorbent and pHpzc were also investigated. The cost evaluation of adsorbent per cubic meter was also found. It was about 126.5US$ for St-AgNPs-MD-GD and 58.10US$ for St-AgNPs-LS. The results obtained from the present study represent that this improved process can be employed on the industrial scale in economical way.