Polyvinyl Alcohol/Bentonite Composite Hydrogels for Dyes Removal

LAURA M. SANCHEZ; VERA ALVAREZ; JIMENA GONZALEZ; ROMINA OLLIER

Granada

Conferencia; 16th INTERNATIONAL CLAY CONFERENCE; 2017

Dye bearing effluents have become an important environmental hazard. In various industrial productions, such as textiles and leather, the dyeing processes are among the most polluting industrial processes because they produce enormous amounts of coloured wastewaters. It has been reported that that more than around 10,000 tons of synthetic dyes are produced every year worldwide. And the estimated amount of dyes discharged in the environment are thought to be 1-2% loss during production, and 1-10% loss during uses [1]. Moreover, in addition to their colour, some of these dyes may degrade to highly toxic and dangerous subproducts.Hydrogels are three-dimensional polymeric networks capable of imbibing large quantities of water in their structures. Polymer hydrogels have gained attention in many applications due to their unique water absorption along with its retention capacity. However, the use of hydrogels is restricted in some applications because of their poor stability and mechanical properties. Polymer/clay nanocomposite hydrogels have been developed to improve these properties. It is well-known that polymeric nanocomposites reinforced with clays show valuable improvements in their mechanical properties, heat resistance and gas permeability, regarding conventional micro and macrocompounds.This is due to the large contact area between the matrix and the filler [2]. In addition, composite hydrogels that contain clays have shown being useful to do separations in a broader range of work conditions when compared to those needed by the clays themselves [3]. Besides, bentonite is an abundant and low cost smectite-type clay in Argentina.The general objective of this work is to obtain composite hydrogels suitable to be used as absorbents for the dyes removal. Thus, composite hydrogels will be prepared employing polyvinyl alcohol (PVA) and bentonite as raw materials through a previously optimized physical crosslinking method (through freezing/thawing cycles, a non-toxic and relatively simple method), avoiding the use of potentially damaging components [4-5].The performance of the resulting nanocomposite hydrogels will be tested to remove methyleneblue, which is a cationic dye. Removal efficiencies and adsorption kinetics will be compared with the respective polymeric matrixand bentonite by themselves.