Recyclable photocatalytic composites based on natural hydrogels for dye degradation in wastewaters

Two polysaccharide-based hydrogels: agarose and chitosan have been used to shape pieces containing micro-meter anatase (TiO2). The degradation of Methylene Blue and Rhodamine, two pigments frequently found in textile industry wastewaters, has been employed to test the photocatalytic capacity of such composites. These experiments were carried out indoor under an artificial light that simulates the solar spectrum. An initial test demonstrated that the agarose-containing pieces showed a degradation superior to that observed when chitosan or chitosan/agarose mixtures were used to aggregate the TiO2 powders. The following parameters: pieces geometry, surface exposition, porosity and anatase content were optimized to reach the highest degradation capability. The so obtained materials, subjected to long term and reutilization studies, showed that high degradation rates were maintained even under such conditions. Taking this into account, it can be stated that these low cost and recyclable pieces have a great potential applicability for actual wastewater depollution procedures.