Modified grape stem as a renewable adsorbent for cadmium removal

In order to aggregate value to the grape stem (wastes), this research aim was to increase the adsorption capacity of Cd by chemical modifications on grape stems. The grape stems were milled and sieved, resulting in the biosorbent, which was used for the chemical modifications resulting in E. H O , E. H SO and E. NaOH. These were characterized by such means as its pH , Fourier transform-infrared (FTIR) spectroscopy, porosimetry, thermal stability and scanning electron microscopy. The ideal adsorption dose, the pH influence on adsorption, kinetics, equilibrium and thermodynamics studies were carried out. The FTIR spectroscopy suggests the occurrence of carboxyl, amine, and phenolic acting in Cd sorption. The modification on grape biomass caused small increase in pore volume and specific surface area. The grape-based adsorbents have similar thermal stability, with irregular appearance and heterogeneity. 5.0 g kg is the best adsorption dose. The modified adsorbents exhibited increase in Cd removal of 66% for E. NaOH, 33% for E. H O and 8.3% for E. H SO . The use of grape stem as adsorbent is an attractive alternative, because its wastes have great availability, low cost and great potential for metal adsorption processes.