Agro and industrial residues: Potential raw materials for photocatalyst development

Abstract Environmental contamination by organic effluents is currently one of the most serious environmental problems and, as a result, the elimination of these pollutants has been widely studied, mainly with organic phenolic pollutants. Photocatalysis have been showing an interesting process in order to optimize or replace the conventional wastewater treatments. Thus, agroindustrial waste (exhausted bark acacia) and Ziegler–Natta catalyst slurry waste were used as supports for photocatalysts. The morphology and chemical composition of the catalysts were determined by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) and the X-ray photoelectron spectroscopy (XPS). Band-gaps were determined using UV diffuse reflectance spectroscopy (DRS). Multiscale structural characterization, pore analysis and specific surface area were determined by small-angle X-ray scattering (SAXS) and N2 porosimetry 77 K. Zeta potential (ζ) measurements were carried out to verify the stability of catalyst suspensions. The photocatalysts contained Al, Mg, Si and Ti. Metallic content ranged from 0.01 to 0.83 wt%. Ti-samples showed specific surface area between from 27.3 – 562.30 m² g-1, a band gap energy (2.55 – 3.65 eV), negative surface potential and the presence of mass and surface fractals. The prepared photocatalytic systems (catalyst with support) were evaluated for phenol photodegradation, where the greatest percentage of phenol degradation was 68.4% under UV-Vis radiation, while industrial standard Degussa P25 showed 43.8% degradation. Therefore, (agro)industrial waste can be used as precursors or catalytic supports of photocatalysts supported for application in the treatment of wastewater, as phenolic compounds, meeting sustainable development.