RESUMEN
Advanced oxidation processes (AOP), using semiconductor (SC) and hydroxyapatite (HA) composites, are promising due to the synergy of photocatalytic and adsorption properties. Still, dye removal efficiency of composites based on HA-SC remains low, because most of the research reported consider single SC materials. In this work, nanocrystalline xerogels of titanium oxide (TiO2) with copper oxide (CuO) and HA were synthesized by the sol-gel process. HA was obtained by the precipitation method without heat treatment and calcined in the range of 200-1000 °C. TiO2 and copper precursors were added to a sol containing HA in a 12:1 mol ratio, obtaining HA-TiO2 and HA-CuO-TiO2 nanomaterials. The xerogels were characterized by X-ray diffraction, scanning electron microscopy, emission field scanning electron microscopy and photoresponse. Their performance in the photocatalytic discoloration of an aqueous solution acid yellow dye 36 (AY36) was evaluated, using visible and UV light. The best discoloration was achieved with HA-CuO-TiO2 xerogels with HA calcined at 600 °C, showing a degradation kinetic constant of 0.24 min-1. In contrast, HA-TiO2 materials showed little or no photocatalytic activity, but strong dye adsorption/desorption. The thermal treatment of HA determines the filament-like morphology and degree of compaction of the nanomaterials, which are relevant in the crystallite size and sensitization of the SC matrix. Further studies must address the surface chemistry and rectifying properties of the best SC composite to have a more complete understanding of the mechanisms involved.
RESUMEN
A gemini surfactant imidazoline type, namely N-(3-(2-fatty-4,5-dihydro-1H-imidazol-1-yl) propyl) fatty amide, has been obtained from the fatty acids contained in the mango seed and used as a CO2 corrosion inhibitor for API X-120 pipeline steel. Employed techniques involved potentiodynamic polarization curves, linear polarization resistance, and electrochemical impedance spectroscopy. These tests were supported by detailed scanning electronic microscopy (SEM) and Raman spectroscopy studies. It was found that obtained gemini surfactant greatly decreases the steel corrosion rate by retarding both anodic and cathodic electrochemical reactions, with an efficiency that increases with an increase in its concentration. Gemini surfactant inhibits the corrosion of steel by the adsorption mechanism, and it is adsorbed on to the steel surface according to a Langmuir model in a chemical type of adsorption. SEM and Raman results shown the presence of the inhibitor on the steel surface.