Abstract
In this study, efficient commercial photocatalyst (Degussa P25) nanoparticles were effectively dispersed and stabilized in alginate, a metal binding biopolymer. Taking advantage of alginate’s superior metal chelating properties, copper nanoparticle-decorated photocatalysts were developed after a pyrolytic or calcination-sintering procedure, yielding ceramic beads with enhanced photocatalytic and mechanical properties, excellent resistance to attrition, and optimized handling compared to powdered photocatalysts. The morphological and structural characteristics were studied using LN2 porosimetry, SEM, and XRD. The abatement of an organic pollutant (Methyl Orange, MO) was explored in the dark and under UV irradiation via batch experiments. The final properties of the photocatalytic beads were defined by both the synthesis procedure and the heat treatment conditions, allowing for their further optimization. It was found that the pyrolytic carbon residuals enabled the adhesion of the TiO2 nanoparticles, acting as binder, and increased the MO adsorption capacity, leading to increased local concentration in the photocatalyst vicinity. Well dispersed Cu nanoparticles were also found to enhance photocatalytic activity. The prepared photocatalysts exhibited increased MO adsorption capacity (up to 3.0 mg/g) and also high photocatalytic efficiency of about 50% MO removal from water solutions, reaching an overall MO rejection of about 80%, at short contact times (3 h). Finally, the prepared photocatalysts kept their efficiency for at least four successive photocatalytic cycles.
Highlights
Advanced Oxidation Processes (AOPs) are considered state-of-the-art water treatment technologies [1,2]
The extensive shell roughness of B1_600 uncovers the existence of large flakes with an average size of 2–3 microns. These flakes constitute the salient structural unit of the overall bead and consist of copper oxide- and metallic copper-decorated TiO2 NPs aggregates, kept together by the carbonized alginate phase acting as a binder
Fluid instabilities are said to arise from the friction forces involved in the contraction of alginate polymer chains to the newly forming gel front causing anisotropy
Summary
Advanced Oxidation Processes (AOPs) are considered state-of-the-art water treatment technologies [1,2]. The application of photocatalysts in powder form has been related to technical and practical problems, including the time- and energy-consuming separation/recovery of the photocatalyst from the treated solution [4,14,15,16,17], the mass transfer limitations, and the insufficient irradiation of the photocatalysts in the slurry [18,19,20,21,22] emanating from shielding effects of the suspended solid leading to significantly increasing the operational and capital costs due to the use of high power UV irradiation sources and stirring equipment, as well as the design of more complex processes for the effective separation for the photocatalyst’s retrieval downstream. Alginate beads as supporting matrixes for photocatalysts are good candidates for cationic dye adsorption [14,17] and degradation [25], heavy metals and pigments removal [26,27,28], and release of effective antibacterial agents [29]
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