Abstract
Metal nanoparticles have been reported as effective catalysts for the removal of refractory compounds from industrial wastewaters in advanced oxidation processes. Additionally, hundreds of thousands of tons of eggshells are discarded worldwide each year. In this work, this waste has been evaluated as support for the synthesis of nanomaterials by wet impregnation method. Four supported catalysts, with a load of iron or copper of 5% and 15%, were prepared and thoroughly characterized by means of different techniques (elemental analysis, XRF, XRD, FTIR, N2 adsorption-desorption, SEM, TEM and TGA). The catalysts performance was evaluated in wet oxidation tests to degrade humic acids, analyzing the evolution with time of COD, biodegradability index (BOD5/COD), color number and pH. The best results were achieved with 15% Cu and 5% Fe catalysts (COD reduction being 82.3% and 75.1%, respectively), whereas a COD reduction of 58% was obtained employing non-impregnated eggshell. This can be mainly attributed to the metal loading and the good metal distribution on the surface of the support. The BOD5 value of humic acids was initially null and, in all assays, the oxidation treatment enhanced the biodegradability. Therefore, eggshell has proved to be an interesting material to be employed as support in nanoparticles preparation.
Highlights
Nowadays, one of the main concerns for human society is the absence of clean water [1].Certainly, two-thirds of the world population might face water stress conditions by 2025, lacking freshwater sources due to water pollution [2]
The elemental analysis of the iron and copper nanomaterials supported on eggshell, named as
This can be due to a slight carbonation of the support, since this phenomenon can be found in calcium compounds, such as eggshell
Summary
Two-thirds of the world population might face water stress conditions by 2025, lacking freshwater sources due to water pollution [2]. Industrial processes are responsible for the generation of increasing amounts of wastewaters, contaminated with toxic and hazardous organic compounds, which can cause severe problems into the environment [3]. These wastewaters can be treated by various conventional treatment methods. Some of them seem to be ineffective for the complete removal of pollutants, especially refractory organic compounds, such as fulvic and humic substances [4,5]. As a major form of humic substances, humic acids (HA) present a very complex chemical structure
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