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

Abstract

Contaminated 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 TiO-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 Abstract ᅟ.

New-Generation Washing Agents in Remediation of Metal-Polluted Soils and Methods for Washing Effluent Treatment: A Review

“…For treatment of SWSs, different physico-chemical methods can be used, including adsorption [ 81 , 82 , 83 , 84 ], precipitation [ 85 , 86 , 87 , 88 , 89 ], advanced oxidation processes [ 90 , 91 , 92 , 93 , 94 , 95 ], and membrane technology [ 96 , 97 , 98 ]. Although the latest soil remediation tests were focused on the suitability of novel WAs (DOM, HLS, and SHS from different organic wastes), data about their treatment after soil washing/soil flushing are missing.…”

“…Satyro et al [ 95 ] used TiO 2 photocatalysis for SWS treatment from EDDS soil washing, containing 7.8 mg Cu/L, 10.5 mg Fe/L, and 5.7 mg Zn/L. The combined photocatalytic process can be used for SWS treatment (Cu < 0.05 mg/L, Fe 0.09 mg/L, and Zn 0.8 mg/L).…”

Ethylenediamine-N,N′-Disuccinic Acid (EDDS)—Enhanced Flushing Optimization for Contaminated Agricultural Soil Remediation and Assessment of Prospective Cu and Zn Transport

“…Among them, the soil washing process proved to be one of the few permanent contaminated soil remediation treatments [ 6 ]. Therefore, this process can achieve good remediation performances if the operative conditions are carefully selected and optimized [ 7 , 8 , 9 ]. However, in the case of soil washing treatment, the excavation of the contaminated soil is required, and this operation is time-consuming and expensive.…”

“…Therefore the use of a biodegradable agent, such as Ethylenediamine- N , N ′-disuccinic acid (EDDS) [ 17 , 18 ], may be more advisable in order to decrease the potential risk of negative effects on the environmental quality. While the application of EDDS as a washing agent has been widely studied in several scientific research papers [ 9 , 19 , 20 ], its use as flushing agent has been tested in limited cases [ 21 , 22 ], and thus requires further investigation in more detail.…”

Soil Washing Optimization, Recycling of the Solution, and Ecotoxicity Assessment for the Remediation of Pb-Contaminated Sites Using EDDS

“…The involvement of acid solutions and/or chelating agents allows for the removal of both the most and the least mobile fractions of metals in cationic form, potentially achieving very high removal efficiency if the operative conditions of the process are correctly chosen and optimized [4]. The choice of an appropriate washing solution is a critical point, not only to guarantee the required performances, but also to avoid any problems related to its final disposal [5][6][7]. The management of spent washing solutions (SWSs), in fact, makes up a significant cost of the whole remediation process.…”