This book describes a study into two serious environmental problems, smuggled cigarette filters and dyes from the textile industry. It immobilized ferric ions in smuggled cigarette filters, with the aim of developing a new material to act as a catalyst in the degradation of the dye Reactive Black 5, through the photo-Fenton advanced oxidative process. The characterization of the material showed that the iron is homogeneously immobilized on its surface and that its structure is not modified after being used in various dye degradations. The material showed excellent performance, degrading 97.68 % of the dye in 60 minutes of reaction. The material was reused in 9 dye degradations, demonstrating excellent catalytic potential and the amount of ferric ions leached was below 3mg L1. The material was also tested in the degradation of a real effluent, reducing 70.57% of total organic carbon in 120 minutes of reaction.