Statistical optimization of glyphosate adsorption by silver nanoparticles loaded activated carbon: Kinetics, isotherms and thermodynamics

Abstract

Glyphosate (GPh-S) contaminants pose a threat to human health, life and the environment due to the misuse of agriculture and industry. As this perspective, silver nanoparticles are loaded towards GPh-S removal through the adsorption process to improve efficiency of activated carbon. The waste corn cobs were initially selected to prepare the activated carbon, then the silver nanoparticles were loaded. The synthesized precursor was characterized through Boehm titration, SEM, TEM, FT-IR, XRD, pHzpc, BETsurface, and Raman spectroscopy etc. The batch process was carried out following parameters like as pH, contact time, temperature, initial concentration and comparative doses between activated carbon (AC) and silver-nanoparticle loaded activated carbon (AC@AgNPs). The Langmuir of AC and Freundlich of AC@AgNPs isotherm model were best fitted to describe the adsorption equilibrium, associated with the pseudo-second order kinetic. The maximum adsorption capacity achieved at 42.92 mg/g of AC and 149.25 mg/g of AC@AgNPs respectively. The thermodynamic parameters indicated that the adsorption processes were endothermic, spontaneous with favorable in higher temperature. In addition, the regeneration experiments showed that both precursors have reproduction ability. For both adsorbents, the statistical optimization through the central composite design (CCD) has been applied for experimental reduction, fitting the model in quadratic term (R2 > 0.9).