Hybrid sol-gel silica adsorbent material based on grape stalk applied to cationic dye removal

The removal of azo-dyes, recalcitrant compounds found in several industrial effluents, was investigated by an environmentally friendly hybrid adsorbent material based on grape stalk encapsulated by the sol-gel method. The winemaking process produces a large amount of grape stalk. This solid waste represents an environmental problem for wineries. The hybrid adsorbent based on grape stalk was synthetized by the acid catalyzed sol-gel route and characterized by different techniques. According to the zeta potential values, the resulting hybrid material is negatively charged at a wide pH range (2.0-12.0). The adsorption of the cationic azo-dye Basic Blue 41 onto the hybrid material was evaluated in aqueous solution. The studies of pH (3.0-12.0), adsorbent concentration (0.5-5.0 g L-1), kinetic and adsorption equilibrium were investigated at 303 K. The kinetic data were best fitted to the pseudo-second order kinetic model. Equilibrium studies showed that the hybrid material achieved a maximum adsorption capacity of 205.3 mg g(-1). The large amount of solid waste generated from wine production represents a serious impasse for wineries regarding its storage and disposal, from both ecological and economical points of view. Alternatively, this agricultural solid waste may represent a source of raw material to create new products, increasing the life cycle and adding value to the previously discarded material. In this work, grape stalk was employed as adsorbent for dye removal, promoting the reduction of environmental contamination. The results showed that it is a promising material to use as efficient eco-friendly adsorbent for the treatment of wastewater.