Laura Clarizia

Photocatalytic processes assisted by artificial solar light for soil washing effluent treatment

AbstractContaminated soil has become a growing issue in recent years. The most common technique used to remove contaminants (such as metals) from the soil is the soil washing process. However, this process produces a final effluent containing chelating agents (i.e., ethylenediaminedisuccinic acid, also known as EDDS) and extracted metals (i.e., Cu, Fe, and Zn) at concentrations higher than discharge limits allowed by the Italian and Brazilian environmental law. Therefore, it is necessary to develop further treatments before its proper disposal or reuse. In the present study, soil washing tests were carried out through two sequential paths. Moreover, different artificial sunlight-driven photocatalytic treatments were used to remove Cu, Zn, Fe, and EDDS from soil washing effluents. Metal concentrations after the additional treatment were within the Brazilian and Italian regulatory limits for discharging in public sewers. The combined TiO2-photocatalytic processes applied were enough to decontaminate the effluents, allowing their reuse in soil washing treatment. Ecotoxicological assessment using different living organisms was carried out to assess the impact of the proposed two-step photocatalytic process on the effluent ecotoxicity. Graphical Abstractᅟ

Metal-based semiconductor nanomaterials for photocatalysis

Abstract In order to support the future hydrogen economy, photocatalytic water splitting technology, based on nanosized semiconductors, has significant potential for the production of hydrogen using solar energy with a low environmental impact. Despite the numerous attempts to prepare materials able to efficiently use solar energy during the past decades, the solar-to-hydrogen energy conversion efficiency is currently far too low for the technology to be economically profitable. This chapter depicts the basics of photocatalytic water splitting and organic photoreforming and surveys metal-based semiconductor nanomaterials (i.e., metal oxides, metal (oxy)sulfides and metal (oxy)nitrides, etc.) used as photocatalysts for hydrogen production in aqueous solution under UVA or visible radiation. Special attention is paid to recent developments for enhancing the effectiveness of the most common metal-based semiconductors. The main experimental factors affecting performance and design of photocatalytic materials are critically discussed.

Removal of Copper, Iron and Zinc from Soil Washing Effluents Containing Ethylenediaminedisuccinic Acid as Chelating Agent Through Sunlight Driven Nano-TiO 2 -Based Photocatalytic Processes

The aim of the present study is the application of integrated solar nano-TiO2 based photocatalytic processes for the removal of copper, iron, zinc and (S,S)-ethylenediamine-N,N′-disuccinic acid (EDDS), used as chelating agent, from soil washing effluents produced by the remediation of samples of potentially polluted soils taken in the “Land of Fires” (Italy). Removal efficiencies of 93.5% (copper), 99.6% (iron), 99.4% (zinc), 97.2% (EDDS) and 80.7% (TOC) were reached through sunlight driven photocatalytic treatments carried out in parabolic trough collectors located in Naples (Italy). The removal degrees were achieved for an incident UVA solar energy per unit volume (Q j,n ) of 580 kJ L−1, estimated by taking into account both the effective irradiated surface area of the photoreactor (9.79 × 10−2 m2) and the local solar irradiances collected during the experiments. The combined nano-TiO2-photocatalytic processes applied were shown to sufficiently decontaminate the soil washing effluents to permit the recycling in the soil washing treatment or discharging to public sewers. The study suggests that the two-step solar photocatalytic process investigated can be really adopted as a useful solution for the decontamination of soil washing streams from some heavy metals and chelating organic agents.