Adsorption of Phenol from Wastewater Using Microwave-Assisted Ag–Au Nanoparticle-Modified Mango Seed Shell-Activated Carbon

Removal of phenol from simulated wastewater was investigated with silver–gold-nanoparticle-modified mango seed shell-activated carbon under batch experiment. The surface properties of the activated carbons were characterized using Fourier transform infrared spectroscopy (FTIR). Adsorption experiment was carried out at ambient temperature to study the effect of contact time, adsorbent dosage, and temperature on phenol adsorption. The equilibrium data were fitted to isotherm model, kinetic model, and intra-particle diffusion models. The maximum removal efficiencies increased from 55.5 to 94.55 and 71.4 to 98.1% for the unmodified and nano-modified activated carbon with increase concentration (50–250 mg/l). The correlation coefficient (R2) Langmuir, Freundlich, and Temkin were 0.3554–0.4563 and 0.2813–0.3191, 0.9150–0.9596 for nanoparticle-modified activated carbon (NCAMSS), as well as 0.5853–0.6598, 0.8159–0.8642, and 0.8159–0.8642, for unmodified activated carbon (UCAMSS). The R2 of the pseudo-first and pseudo-second orders as well as Elovich kinetic models were in the ranges 0.8661–0.9925, 0.8260–0.9942, and 0.6032–0.7505 for NCAMSS as well as 0.4846–0.6032, 0.9567–0.9929, and 0.8842–0.9786, for UCAMSS and modified activated carbon, respectively, The order of fitness/suitability of the models is pseudo-first order > Elovich > pseudo-second order. The intra-particle diffusion model showed that the rate-controlling step is influenced by pore diffusion and that boundary layer diffusion and the adsorption process is heterogeneous, exothermic, and spontaneous. It can be deduced that mango seed shell is a good precursor in the production of activated due to its high yield and good adsorption capacity and the modification of the activated carbon with nanoparticles increased the precursor adsorption properties.