Synthesis of iron phosphide nanoparticles dispersed in activated carbon and their application in Fenton processes

Activated carbons containing iron compounds dispersed in their structure have shown great potential for use in advanced oxidation processes, expressively when aiming at the degradation of organic contaminants in water. In this work, we investigated the chemical and structural transformations of nanocomposites constituted by nanostructured Fe/P-containing phases dispersed in an activated carbon (obtained from the chemical activation of a lignocellulosic precursor) and the applications of the produced nanocomposites in dye degradation processes via Fenton-type reactions. X-ray diffraction and scanning electron microscopy experiments combined with energy dispersive X-ray spectrometry showed that the material synthesized at room temperature contains Fe and P compounds in different stoichiometric proportions; heat treatment at 1000 °C led to the formation of FeP (major component) and Fe2P crystalline phases, with average crystallite sizes estimated at 92 and 44 nm, respectively. Adsorption and Fenton-type degradation experiments were performed with aqueous solutions of the industrial dyes methylene blue, Eriochrome Black T, and Ponceau S. A high degree of removal (ranging from 95 to 99%) was observed for all dyes when the Fe/P-containing nanocomposites were used as adsorbents/catalysts. The occurrence of the iron phosphides was found to be especially significant in the case of the Ponceau S dye. These results illustrate the degradation efficiency of dyes and other organic compounds through the use of advanced oxidative processes via the Fenton reaction using activated carbons containing nanostructured iron phosphides. Graphical abstract