Photodegradation enhancement of Congo red aqueous solution using a mixture of SnO2·xH2O gel/ZnO powder

The system tin oxide gel mixed with zinc oxide powder (SnO2·xH2O/ZnO powder) was investigated for Congo red removal from aqueous solution. The Congo red photodegradation increases when a gel of tin oxide is mixed with a small amount of zinc oxide powder (2.5% in mass). This activity increases more when tin oxide gel is mixed with smaller particles size of ZnO prepared by precipitation method. When the amount of zinc oxide is higher (25% in mass), Congo red is removed by adsorption process rather than by photodegradation. This adsorption is mainly due to zinc oxide powder. The adsorption reaction is more active when zinc oxide is mixed with tin oxide gel than when zinc oxide is used alone.