Person: Santos López, Aurora
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First Name
Aurora
Last Name
Santos López
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Ingeniería Química y de Materiales
Area
Ingeniería Química
Identifiers
36 results
Search Results
Now showing 1 - 10 of 36
Item Abatement of chlorobenzenes in aqueous phase by persulfate activated by alkali enhanced by surfactant addition(Journal of Environmental Management, 2022) García Cervilla, Raúl; Santos López, Aurora; Romero, Arturo; Lorenzo Fernández, DavidSites polluted by dense non-aqueous phases (DNAPLs) constitute an environmental concern. In situ chemical oxidation (ISCO) application is limited since oxidation often occurs in the aqueous phase and contaminants are usually hydrophobic. In this work, ISCO enhanced by the surfactant addition (S–ISCO) was studied for a complex liquid mixture of chlorinated organic compounds (COCs) using persulfate (PS) activated by alkali (PSA) as oxidant and Emulse-3® as a commercial non-ionic surfactant. The reaction between E3 and PSA was investigated in the absence and presence of solubilized COCs in the following concentration ranges: COCs 1.2–50 mM, PS 84–336 mM, NaOH:PS molar ratio of 2, and surfactant concentration 1–10 g⋅L− 1. In the experiments carried out in the absence of COCs, the unproductive consumption of PS was studied. The higher the surfactant concentration, the lower the ratio PS consumed to the initial surfactant concentration due to more complex micelle structures hindering the oxidation of surfactant molecules. This hindering effect was also noticed in the oxidation of solubilized COCs. The reduction of chlorobenzenes by PSA was negligible at surfactant concentrations above 2.5 g⋅L− 1, independently of the COCs concentration solubilized. Instead, a surfactant concentration of about 1 and PS concentration of 168 mM yielded a significant decrease in the time required to abate a mass of DNAPL, compared with an ISCO process, with a bearable increase in the unproductive consumption of PSItem Comparison of real wastewater oxidation with Fenton/Fenton-like and persulfate activated by NaOH and Fe(II)(Journal of Environmental Management, 2020) Rodríguez Vega, Sergio; Lorenzo Fernández, David; Santos López, Aurora; Romero Salvador, ArturoTreatment of polluted wastewaters from industrial activities has become a source of major concern for the environment. In this work, real wastewater from a physico-chemical (WWFQ) treatment was tested through different oxidation technologies: Fenton and Fenton-like reagent and persulfate activated by NaOH and Fe(II). Oxidation reactions with Fenton's reagent were carried out in a 0.25 L batch reactor at 25 °C by adding either Fe(II) or Fe(III) and H2O2 to an aqueous solution of wastewater, whose pH was previously adjusted to 2 or 3. Iron concentration ranging from 25 to 100 mg/L and peroxide concentration from 2500 to 10000 mg/L were used. The total organic carbon slightly decreased when WWFQ was treated. Moreover, better results were obtained when Fe(II) was used than Fe(III). Both iron concentration and oxidant dosage had a positive influence on the chemical oxygen demand (COD) removal, until an asymptotic value of 30% was obtained. Oxidation of pollutants contained in WWFQ was studied with persulfate (18.4–294 mM) activated with NaOH and Fe(II) (36.8–588 mM). Again, a positive influence of both persulfate and NaOH was observed, although a similar asymptotic COD value was observed. This parallelism between both technologies confirms recalcitrant compounds were obtained.Item Remediation of the Alluvial Aquifer of the Sardas Landfill (Sabiñánigo, Huesca) by Surfactant Application(Sustainability, 2022) Guadaño, Joaquín; Gómez, Jorge; Fernández, Jesús; Lorenzo Fernández, David; Dominguez Torre, Carmen M.; Cotillas Soriano, Salvador; García Cervilla, Raúl; Santos López, AuroraSardas Landfill at Sabiñánigo Huesca is polluted with Dense Non-Aqueous Liquid Phases (DNAPLs) composed of a complex mixture of chlorinated organic compounds (COCs). This DNAPL was produced as liquid waste from lindane production being dumped decades ago in the unlined landfills close to the lindane factory. This DNAPL migrated by gravity through the subsurface and accumulated in the contact between the alluvial and marls layers (about 15 m b.g.l.). Seven injections of an aqueous emulsion of a biodegradable non-ionic surfactant (E-Mulse 3®) were carried out at the most polluted areas of the Sardas alluvial. Injections were carried out between April and November 2021 using different surfactant concentrations (6.7, 20, 25 and 50 g/L), injection volumes (0.2 to 7 m3) and injection flow rates (0.08–0.85 m3/h). Injected fluids were extracted in the same well or surrounding wells, and the time elapsed between surfactant injection and extraction varied between 24 and 72 h. A total of 22 m3 were injected into the alluvial, and more than double this injected volume was extracted. Injection and extraction points were in the contact between the marls and the alluvial layer. Extracted fluid accumulated in tanks, and phases separated. DNAPL recovered here was mobilized rather than solubilized and managed as toxic waste. The aqueous supernatant was treated in a wastewater treatment plant with physicochemical treatment (including adsorption in activated carbon) before being discharged into the environment. The transport of the injected fluids was monitored by conductivity profiles using bromide (260–538 mg·L−1) as a conservative tracer. High radial dispersion of the injected fluid was found. Surfactant losses by adsorption in the alluvial and absorption in DNAPL were noticed, and both surfactant and contamination did not escape from the capture zone. Monitoring since 2018 of the COCS in groundwater and the DNAPL presence in the contact between alluvial and marls layers showed a significant reduction of COCs in the treated zone with the surfactant injections.Item LED visible light assisted photochemical oxidation of HCHs in aqueous phases polluted with DNAPL(Process Safety and Environmental Protection, 2022) Conte, Leandro O.; Cotillas Soriano, Salvador; Sánchez Yepes, Andrés; Lorenzo Fernández, David; Santos López, AuroraThis work focuses on removing hexachlorocyclohexanes (HCHs) found in groundwater polluted with dense non-aqueous phase liquids (DNAPLs) by photo-oxidation with hydrogen peroxide or persulfate using LED visible light and ferrioxalate as the catalyst. Single oxidation tests were also performed to evaluate the contribution of LED-vis light on HCHs removal. Results show that it is possible to attain the degradation of HCHs up to 85% in 420 min with persulfate, whereas percentages lower than 40% are obtained when using hydrogen peroxide. Using both oxidants in the presence of ferrioxalate and LED visible light promotes the generation of hydroxyl and sulfate radicals under circumneutral pH values, which are the main responsible species for HCHs removal. Specifically, an oxidant conversion higher than 50% was achieved during the photochemical treatment with both oxidants, whereas conversions below 20% were obtained in the absence of LED visible light irradiation. On the other hand, DNAPL produced as liquid residuum of lindane production contains other chlorinated organic compounds (COCs), which are susceptible to being oxidized by hydroxyl and sulfate radicals, generating competitive oxidation reactions. The final conversion of chlorbenzenes reaches values close to 100% and HCHs are only effectively removed when persulfate is used as the oxidant. This better performance indicates that the photo-oxidation of DNAPL polluted groundwater with LED-vis light should be carried out with persulfate to ensure the removal of more dangerous COCs. This confirms the excellent ability of sulfate radicals for C-Cl bond breakdown.Item Sustainable reuse of toxic spent granular activated carbon by heterogeneous fenton reaction intensified by temperature changes(Chemosphere, 2023) Sánchez Yepes, Andrés; Santos López, Aurora; Rosas, Juana M.; Rodríguez-Mirasol, José; Cordero, Tomás; Lorenzo Fernández, DavidA common strategy for removing highly toxic organic compounds, such as chlorinated organic compounds, is their adsorption on granular activated carbon. Spent granular activated carbon results in a toxic residue to manage; therefore, the regeneration and reuse of granular activated carbon on the site would be advisable. This work studies the regeneration of a granular activated carbon saturated in 1,2,4-trichlorobenzene, chosen as the model chlorinated organic compounds, by heterogeneous Fenton, where iron was previously immobilised on the granular activated carbon surface. This methodology avoids the addition of iron to the aqueous phase at concentrations above the allowable limits and the need for acidification. Three successive cycles of adsorption-regeneration were carried out batchwise (5 gGAC·L−1) with a granular activated carbon saturated with 300 mg124-TCB·gGAC−1. The recovery of the adsorption capacity after regeneration was studied with H2O2 (166 mM, 1.5 the stoichiometric dosage), at different concentrations adsorbed with iron adsorbed concentrations (0–12 mgFe·gGAC−1) and temperatures (20–80 °C). Stable recovery of the adsorption capacity values of 65% were obtained at 180 min with 12 mgFe·gGAC−1 and 60 °C. The porosity and surface chemistry of the adsorbent remained very similar after different adsorption-regeneration cycles without iron leaching into the aqueous phase. The oxidant consumption was close to the stoichiometric value for the mineralization of 1,2,4−trichlorobenzene, with a low unproductive consumption of H2O2 with granular activated carbon. In addition, no aromatic or chlorinated by-products were detected in the aqueous solution obtained in the regeneration process. The negligible toxicity of the aqueous phase with the Microtox bioassay confirmed the absence of toxic oxidation by-products. Keywords: Heterogeneous fenton; Adsorption; Regeneration; Activated carbon; Chlorinated organic compoundsItem Application of Chelating Agents to Enhance Fenton Process in Soil Remediation: A Review(Catalysts, 2021) Checa-Fernández, Cristina Alicia; Santos López, Aurora; Romero, Arturo; Dominguez Torre, Carmen M.Persistent organic contaminants affecting soil and groundwater pose a significant threat to ecosystems and human health. Fenton oxidation is an efficient treatment for removing these pollutants in the aqueous phase at acidic pH. However, the in-situ application of this technology for soil remediation (where pHs around neutrality are required) presents important limitations, such as catalyst (iron) availability and oxidant (H2O2) stability. The addition of chelating agents (CAs), forming complexes with Fe and enabling Fenton reactions under these conditions, so-called chelate-modified Fenton process (MF), tries to overcome the challenges identified in conventional Fenton. Despite the growing interest in this technology, there is not yet a critical review compiling the information needed for its real application. The advantages and drawbacks of MF must be clarified, and the recent achievements should be shared with the scientific community. This review provides a general overview of the application of CAs to enhance the Fenton process for the remediation of soils polluted with the most common organic contaminants, especially for a deep understanding of the activation mechanisms and influential factors. The existing shortcomings and research needs have been highlighted. Finally, future research perspectives on the use of CAs in MF and recommendations have been provided.Item Enhanced remediation of a real HCH-polluted soil by the synergetic alkaline and ultrasonic activation of persulfate(Chemical Engineering Journal, 2022) Checa Fernández, Alicia; Santos López, Aurora; Conte, Leandro O.; Romero, Arturo; Dominguez Torre, Carmen M.The desorption of hydrophobic organic compounds (HOCs) and limited mass transfer in soil systems is a significant challenge for efficient soil remediation by oxidation treatments. The utilization of sonochemistry is a promising technology to enhance the decontamination of HOCs-polluted soils. In this work, ultrasound (US) was coupled to NaOH for activating persulfate (PS) to enhance the remediation of a real soil polluted with hexachlorocyclohexanes (HCHs) (ΣHCHs = 404 mg kg− 1 ). Batch experiments (mass aqueous/soil ratio, VL/WS = 2) were performed to evaluate the effect of US on HOCs desorption and oxidation. Moreover, the influence of US power (0–245 W, corresponding to 0–91 W L-1 of US power density) and the initial oxidant concentration (CPS = 10–60 g L-1) on pollutants abatement, dechlorination degree, and oxidant consumption have been studied. Scanning electron microscopy (SEM) images verified that the US facilitates the breakdown of soil aggregates, enhancing the desorption of trichlorobenzenes (TCBs) (generated from HCHs alkaline hydrolysis) from the soil. Moreover, their subsequent oxidation is favouring because of higher radical species concentrations and the temperature rise. An increase in the US power up to 165 W accelerates the production rate of radicals, improving the pollutants’ degradation. The difference between pollutant oxidation and dechlorination decreases with increasing US power, associated with a lower concentration of intermediate chlorinated compounds. In the same way, the initial oxidant concentration plays a fundamental role in the remediation treatment. At the selected operating conditions (CPS = 60 g L-1, NaOH/PS = 2, 165 W), a pollutants degradation and dechlorination of 0.94 and 0.74, respectively, were achieved in just 3 h of reaction time.Item Abatement of 1,2,4-Trichlorobencene by Wet Peroxide Oxidation Catalysed by Goethite and Enhanced by Visible LED Light at Neutral pH(Catalysts, 2021) Lorenzo Fernández, David; Santos López, Aurora; Sánchez-Yepes, Andrés; Óscar Conte, Leandro; Dominguez Torres, Carmen MaríaThere is significant environmental concern about chlorinated organic compounds (COCs) in wastewater, surface water, and groundwater due to their low biodegradability and high persistence. In this work, 1,2,4-trichlorobenzene (124-TCB) was selected as a model compound to study its abatement using wet peroxide oxidation at neutral pH with goethite as a heterogeneous catalyst, which was enhanced with visible monochromatic light-emitting diode (LED) light (470 nm). A systematic study of the main operating variables (oxidant and catalyst concentration and irradiance) was accomplished to investigate their influence in the abatement of 124-TCB in water. The reaction was carried out in a well-mixed reactor of glass irradiated by a visible LED light. The hydrogen peroxide concentration was tested from 0 to 18 mM, the goethite concentration within the range 0.1–1.0 g·L−1 and the irradiance from 0.10 to 0.24 W·cm−2 at neutral pH. It was found that this oxidation method is a very efficient technique to abate 124-TCB, reaching a pollutant conversion of 0.9 when using 0.1 g·L−1 of goethite, 18 mM of H2O2, and 0.24 of W·cm−2. Moreover, the system performance was evaluated using the photonic efficiency (ratio of the moles of 124-TCB abated and the moles of photons arriving at the reactor window). The maximum photonic efficiencies were obtained using the lowest lamp powers and moderate to high catalyst loads.Item Acute Toxicity Evaluation of Lindane-Waste Contaminated Soils Treated by Surfactant-Enhanced ISCO(Molecules, 2022) Santos López, Aurora; García Cervilla, Raúl; Checa Fernández, Alicia; Domínguez, Carmen M.; Lorenzo Fernández, DavidThe discharge of lindane wastes in unlined landfills causes groundwater and soil pollution worldwide. The liquid waste generated (a mixture of 28 chlorinated organic compounds, COCs) constitutes a dense non-aqueous phase liquid (DNAPL) that is highly persistent. Although in situ chemical oxidation (ISCO) is effective for degrading organic pollutants, the low COCs solubility requires high reaction times. Simultaneous injection of surfactants and oxidants (S-ISCO) is a promising technology to solve the limitation of ISCO treatment. The current work studies the remediation of highly polluted soil (COCs = 3682 mg/kg) obtained at the Sardas landfill (Sabiñáñigo, Spain) by ISCO and S-ISCO treatments. Special attention is paid to acute soil toxicity before and after the soil treatment. Microtox®, modified Basic Solid-Phase Test (mBSPT) and adapted Organic Solvent Sample Solubilization Test (aOSSST) were used for this scope. Persulfate (PS, 210 mM) activated by alkali (NaOH, 210 mM) was used in both ISCO and S-ISCO runs. A non-ionic and biodegradable surfactant selected in previous work, Emulse®3 (E3, 5, and 10 g/L), was applied in S-ISCO experiments. Runs were performed in soil columns filled with 50 g of polluted soil, with eight pore volumes (Pvs) of the reagents injected and 96 h between successive Pv injections. The total treatment time was 32 days. The results were compared with those corresponding without surfactant (ISCO). After remediation treatments, soils were water-washed, simulating the conditions of groundwater flux in the subsoil. The treatments applied highly reduced soil toxicity (final soil toxicity equivalent to that obtained for non-contaminated soil, mBSPT) and organic extract toxicity (reduction > 95%, aOSSST). Surfactant application did not cause an increase in the toxicity of the treated soil, highlighting its suitability for full-scale applications.Item Simultaneous addition of surfactant and oxidant to remediate a polluted soil with chlorinated organic compounds: Slurry and column experiments(Journal of Environmental Chemical Engineering, 2022) García Cervilla, Raúl; Santos López, Aurora; Romero, Arturo; Lorenzo Fernández, DavidThe inadequate management of wastes associated with chlorinated organic compounds (COCs) has become a huge environmental problem. Surfactant Enhanced In-Situ Chemical Oxidation (S-ISCO) was studied as a successful technique to remediate polluted sites. This work investigated the reaction between an aqueous solution of nonionic surfactant (Emulse-3®) and an oxidant (sodium persulfate activated with NaOH) with a real polluted soil with a complex mixture of COCs from lindane liquid wastes. Two experimental setups were used. In the first one, the reactions were carried out in batch mode under slurry conditions using different surfactant concentrations (0–10 g⋅L− 1), 210 mM of persulfate and 420 mM of NaOH with an aqueous to soil ratio VL/W = 10 L⋅kg− 1. The runs were carried using a column loaded with the soil in the second experimental setup. The solution of surfactant, oxidant and activator was put in contact with soil in four pore volumes with a ratio aqueous to soil ratio VL/W = 0.2 L⋅kg− 1. Under these experimental conditions, the surfactant addition improved the reduction of COCs compared with the application carried out without surfactant, from 40.1% to values of conversion of 64.8 – 90.4%. However, an excess of surfactant hindered the COCs oxidation and increased the unproductive consumption of the oxidant, resulting in an optimal value of surfactant in the aqueous phase (1–2 g⋅L− 1). A remarkable drop in the surfactant concentration in the aqueous phase and COCs solubilized was noticed in column runs due to the surfactant adsorption.