Obtaining magnetic nanoparticles as low-cost photocatalysts for water treatments

Abstract

Heterogeneous photocatalytic processes have attracted massive attention as potentially efficient, environmentally friendly and low cost methods for water purification. However, some limitations regarding to recovery and reuse of the photocatalysts have inhibited their application in real systems. This issue can be overcome providing magnetic properties to the photocatalysts allowing an efficient separation and recovery with an external magnetic field. In this work, magnetic nanocomposites were developed to be used as photocatalysts in photochemical treatments for the degradation of pollutants from wastewater. Carbon coated iron and copper oxides nanocomposites were prepared by using the precursor method under different conditions. Soluble substances isolated from urban biowaste were used as carbon sources in the synthesis procedure. The composition, texture, structure and morphology of the nanocomposites were thoroughly characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray absorption spectroscopy (XRS), elemental analysis, nitrogen (N2) sorption analysis, thermogravimetric analysis (TGA), high resolution transmission electron microscopy (HR TEM), UV-Vis diffuse reflectance spectroscopy (DRS) and vibrating sample magnetometer (VSM). The capacity of the as-prepared nanocomposites for the generation of reactive species under UVA light was evaluated by laser flash photolysis (LFP) experiments and by the electronic paramagnetic resonance (EPR) spin-trap technique. Their photocatalytic activities were tested by using carbamazepine (CBZ) as model of an emerging pollutant (EP), under UVA light by varying different parameters including composition and concentration of the photocatalysts. The as-prepared nanocomposites showed a strong dependence of their photocatalytic activity on the synthesis conditions. Particularly, nanocomposites obtained with the lower organic matter content and pyrolyzed at 600 and 800 °C yielded the highest photocatalytic activities for the CBZ degradation. In summary, this Thesis reports the methods of preparation of magnetic photocatalysts with environmental applications, revalorizing solid urban wastes as the carbon sources necessary for the synthesis of the precursor complexes. The use of products obtained from urban wastes for making photocatalysts for the treatment of wastewaters is expected to contribute to the sustainability of these procedures.