Abstract
Malachite green adsorption from aqueous solution using silver nanoparticles (AgNPs) was investigated and is reported in this study. AgNPs prepared was characterized by Fourier transform Infra-red spectroscopy (FTIR), X-ray diffractometry (XRD), UV-visible spectrophotometer and Scanning electron microscopy (SEM). The crystalline nature of the AgNP was revealed with XRD. This was supported by the observed sharp four diffraction peaks with peaks intense appeared at 2θ = 38.09°, 44.15°, 64.67°, and 77.54°. However, the SEM micrograph of the synthesized AgNPs revealed the spherical shape of AgNPs with a non-uniform granular shape attributed to bio-mediated process. Whereas, FTIR spectra of AgNPs exhibits, 3407, 2956, 2834, 2725, 1660, 1358 and 1096 cm-1, which represent free OH molecules, stretching C-H modes, stretching alkenes C = O bonds, carbonyl group stretching C-OH band, stretching C-O alcohols and ethers, respectively. The adsorption study was carried out under different conditions such as, pH, adsorbent dosage, contact time, temperature and initial concentration of dye to determine the ideal conditions and the maximum adsorption capacities. The results indicated that increase in temperature had very minimal effect on the adsorption process. The silver nanoparticle was effective in the removal of malachite green in acidic medium. Langmuir, Freundlich and Tempkin model gave a better fit to adsorption isotherms while Dubinin Radushkevich model is not appropriate for the adsorption process. Adsorption kinetics of malachite green onto AgNPs adsorbents followed both the pseudo-first-order and pseudo-second-order rate. The results indicate that AgNPs could be utilized as effective adsorbents for the removal of dyes from aqueous solution.