Sustainable application of surfactants in soil remediation: Selective pollutants adsorption and hydrogen peroxide-driven adsorbent regeneration.

The uncontrolled disposal of the liquid lindane wastes have led to the formation of dense non-aqueous phase liquids (DNAPL), consisting of 28 chlorinated organic compounds (COCs), contaminating soil and groundwater. Surfactant-enhanced aquifer remediation is proposed as technology to treat these sites. However, the polluted emulsion generated must be manged on-site. In this work a two-step process is applied to treat emulsion composed of E-Mulse® 3 (4 g·L-1) as surfactant and a DNAPL (2 gCOCs·L-1). In the first, the COCs were selectively adsorbed in a granular activated carbon (GAC) column with Fe (II) previously adsorbed (10-20mg·g-1) onto the carbon surface, recovering an aqueous phase with surfactant for their reuse. In the second step, the spent GAC was regenerated with a 40 g·L-1 solution of hydrogen peroxide fed to the column at 2 mL·min-1 to promote the oxidation of the COCs adsorbed in the GAC. The kinetic and adsorption model in a multisolute (surfactant and DNAPL) system has been proposed. Five successive cycles of regeneration/adsorption have been successfully applied in the column process. About 50 % of the COCs were retained from the emulsion, and more than 70 % of the surfactant was recovered. The consumption of unproductive oxidants decreased with the number of regeneration cycles. The water effluent obtained after regeneration of GAC did not present chlorinated compounds desorbed and nontoxic by-products generated, such as short-chain acids.

Association of adverse childhood experiences with irritable bowel syndrome in Mexican adults: A cross-sectional study.

BACKGROUND: Adverse childhood experiences (ACEs) are linked to the development of gastrointestinal disorders during adulthood, but there is limited research on the prevalence of ACEs in Latin American populations. This study aimed to assess the prevalence and impact of ACEs on Mexican adults with irritable bowel syndrome (IBS). METHODS: In this cross-sectional study, we recruited 290 Mexican adults (aged 18-65), including 90 individuals with IBS and 200 healthy controls. All participants completed four self-reported questionnaires: The Adverse Childhood Experiences Questionnaire (ACEs), Visceral Sensitivity Index, Irritable Bowel Syndrome Symptom Severity Scale, and Hospital Anxiety and Depression Scale. Statistical analyses included mean differences using either the Student's t-test or the Wilcoxon test, correlations assessed with Spearman's correlation coefficient, and logistic regression models. Statistical significance was defined as a p-value less than 0.05. KEY RESULTS: Among IBS subjects, the prevalence of ACEs was 80%, significantly higher than the 59% prevalence observed in controls (p < 0.0001). Individuals with ACEs exhibited elevated levels of anxiety and depression. Seventy-five percent of IBS subjects with severe symptoms reported four or more ACEs. The presence of four or more ACEs was found to be associated with an increased risk of IBS. CONCLUSIONS AND INFERENCES: ACEs are notably prevalent among Mexican individuals with IBS and are positively correlated with the severity of gastrointestinal pain. These findings underscore the critical significance of evaluating and addressing ACEs in the comprehensive management of IBS within Latin American populations.

Incidence of Small Intestinal Bacterial Overgrowth and Symptoms After 7 Days of Proton Pump Inhibitor Use: A Study on Healthy Volunteers.

INTRODUCTION: Proton pump inhibitors (PPIs) are commonly prescribed drugs. Chronic PPI use has recently been associated with the risk for developing small intestinal bacterial overgrowth (SIBO). It is not known whether the short-term prescription of a PPI can trigger SIBO. Therefore, the aim of the present study was to evaluate the incidence of SIBO and gastrointestinal symptoms after 7 days of PPI use. MATERIALS AND METHODS: A prospective, pilot, open-label study was conducted on asymptomatic healthy volunteers. The incidence of SIBO was evaluated at the baseline and after administration of 40 mg of pantoprazole once a day for 7 days, through a glucose breath test. In addition, the presence of gastrointestinal symptoms, the number of bowel movements, and the consistency of stools, according to the Bristol scale, were assessed. RESULTS: Thirty-eight healthy subjects (71.1% women, mean age 25.18 ± 6.5 years) were analyzed. The incidence of SIBO after 7 days of PPI administration was 7.8% (95% CI 1.6-21.3%). The patients that developed SIBO had a greater prevalence of bloating (p = 0.0002) and flatulence (p = 0.004) after 7 days of treatment. CONCLUSIONS: Our study showed that a short-term 7-day PPI course produced SIBO in 7.8% of healthy subjects. Although, inappropriate use of PPIs should be discouraged, but since more than 90% of subjects who received PPIs for one week did not develop SIBO, the advantages of PPI administration seem to outweigh the disadvantages.

Fecal Microbial Composition and Predicted Functional Profile in Irritable Bowel Syndrome Differ between Subtypes and Geographical Locations.

Increasing evidence suggests a microbial pathogenesis in irritable bowel syndrome (IBS) but the relationship remains elusive. Fecal DNA samples from 120 patients with IBS, 82 Mexican (IBS-C: n = 33, IBS-D: n = 24, IBS-M: n = 25) and 38 British (IBS-C: n = 6, IBS-D: n = 27, IBS-M: n = 5), were available for analysis using 16S rRNA gene sequencing. Firmicutes (mean: 82.1%), Actinobacteria (10.2%), and Bacteroidetes (4.4%) were the most abundant taxa. The analysis of all samples (n = 120), and females (n = 94) only, showed no significant differences in bacterial microbiota, but the analysis of Mexican patients (n = 82) showed several differences in key taxa (e.g., Faecalibacterium) among the different IBS subtypes. In IBS-D there were significantly higher Bacteroidetes in British patients (n = 27) than in Mexican patients (n = 24), suggesting unique fecal microbiota signatures within the same IBS subtype. These differences in IBS-D were also observed at lower phylogenetic levels (e.g., higher Enterobacteriaceae and Streptococcus in Mexican patients) and were accompanied by differences in several alpha diversity metrics. Beta diversity was not different among IBS subtypes when using all samples, but the analysis of IBS-D patients revealed consistent differences between Mexican and British patients. This study suggests that fecal microbiota is different between IBS subtypes and also within each subtype depending on geographical location.

Treatment of a Complex Emulsion of a Surfactant with Chlorinated Organic Compounds from Lindane Wastes under Alkaline Conditions by Air Stripping.

Surfactant-enhanced aquifer remediation is commonly applied in polluted sites with dense non-aqueous phase liquids (DNAPLs). This technique transfers the contamination from subsoil to an extracted emulsion, which requires further treatment. This work investigated the treatment of a complex emulsion composed of a nonionic surfactant and real DNAPL formed of chlorinated organic compounds (COCs) and generated as a lindane production waste by air stripping under alkaline conditions. The influence of the surfactant (1.5-15 g·L-1), COC concentrations (2.3-46.9 mmol·L-1), and temperature (30-60 °C) on the COC volatilization was studied and modeled in terms of an apparent constant of Henry at pH > 12. In addition, the surfactant stability was studied as a function of temperature (20-60 °C) and surfactant (2-10 g·L-1), COC (0-70.3 mmol·L-1), and NaOH (0-4 g·L-1) concentrations. A kinetic model was successfully proposed to explain the loss of surfactant capacity (SCL). The results showed that alkali and temperature caused the SCL by hydrolysis of the surfactant molecule. The increasing surfactant concentration decreased the COC volatility, whereas the temperature improved the COC volatilization. Finally, the volatilization of COCs in alkaline emulsions by air stripping (3 L·h-1) was performed to evaluate the treatment of an emulsion composed of the COCs (17.6 mmol·kg-1) and surfactant (3.5 and 7 g·L-1). The air stripping was successfully applied to remove COCs (>90%), reaching an SCL of 80% at 60 °C after 8 h. Volatilization can remove COCs from emulsions and break them, enhancing their further disposal.

Obesity Contributes to Inflammation in Patients with IBS via Complement Component 3 and C-Reactive Protein.

Irritable Bowel Syndrome (IBS) is usually a lifelong state that disturbs the digestive system. IBS has been linked to low-grade inflammation and the release of inflammatory mediators into the bloodstream. This could be associated with the degree of obesity presented by patients with IBS. Reports imply that IBS is more frequent in obese patients than in the overall population, with a prevalence of up to 31%. Here, we evaluated the serum levels of immunological and inflammation molecules and their correlation with Body Mass Index in IBS patients and the healthy control (HC). Seventy-nine serum samples of the IBS patients and thirty-five of the HC group were analyzed to determine the levels of each molecule and compare them with their BMI. Serum levels of C3 and C4 were significantly increased in IBS patients. C3 and C4 levels were higher in IBS-M and IBS-D subtypes compared with the HC group. When patients were grouped by BMI, a positive correlation between serum C3 (r = 0.49, p < 0.0001) and CRP (r = 0.40, p < 0.001) levels was found. Our results show, for the first time, a correlation between immunological molecules and BMI in IBS patients, suggesting that the inflammatory nature of obesity could contribute to the development of the symptoms in IBS through the stimulation and release of proteins as complement components and CRP.

Higher cardiovascular risk scores and liver fibrosis risk estimated by biomarkers in patients with metabolic-dysfunction-associated fatty liver disease.

BACKGROUND: The definition of metabolic-dysfunction-associated fatty liver disease (MAFLD) allows identification of metabolically complicated patients. Fibrosis risk scores are related to cardiovascular risk (CVR) scores and could be useful for the identification of patients at risk of systemic complications. AIM: To evaluate the relationship between MAFLD and CVR using the Framingham risk score in a group of Mexican patients. METHODS: Cross-sectional, observational and descriptive study carried out in a cohort of 585 volunteers in the state of Veracruz with MAFLD criteria. The risk of liver fibrosis was calculated with aspartate aminotransferase-to-platelet ratio index, nonalcoholic fatty liver disease score and fibrosis-4, as well as with transient hepatic elastography with Fibroscan®. The CVR was determined by the Framingham system. RESULTS: One hundred and twenty-five participants (21.4%) with MAFLD criteria were evaluated, average age 54.4 years, 63.2% were women, body mass index 32.3 kg/m2. The Framingham CVR was high in 43 patients (33.9%). Transient elastography was performed in 55.2% of volunteers; 39.1% with high CVR and predominance in advanced fibrosis (F3-F4). The logistic regression analysis showed that liver fibrosis, diabetes and hypertension independently increased CVR. CONCLUSION: One of every three patients with MAFLD had a high CVR, and in those with high fibrosis risk, the CVR risk was even greater.

Análisis de la composición corporal y ángulo de fase por bioimpedancia en pacientes con MAFLD / Body composition and phase angle by bioimpedance in patients with MAFLD

Objetivo: Describir las características de la composición corporal y del ángulo de fase (AF) en pacientes con MAFLD de acuerdo con fibrosis y esteatosis hepática. Pacientes y métodos: Estudio transversal, observacional y descriptivo en una cohorte de 585 voluntarios de nuestro centro con criterios de MAFLD. El riesgo de fibrosis hepática se determinó por APRI, NAFLD score y FIB-4; en riesgo indeterminado y elevado de fibrosis se realizó elastografía hepática de transición (ET) con Fibroscan®. Se realizó análisis de la composición corporal por bioimpedancia (SECA®). Se incluyeron pacientes con registro de ET y SECA®. Resultados: Se evaluaron 125 participantes (21,4%), edad 53,9±13,9 años, 62,1% mujeres, IMC 33,2±5,8kg/m2. El análisis SECA® mostró media de masa grasa de 42%±7,32 y masa muscular de 21,18kg±6,6. El AF fue 5,1±0,69; en mujeres 4,92±0,62 y en hombres 5,41±0,70. El AF en pacientes sin fibrosis fue de 5,091 vs con fibrosis 5,121 (p=0,813). En fibrosis avanzada se reportó valor bajo en comparación con el resto de los grupos (p=0,031). El AF en S3 fue mayor en comparación con S1 y S2 (5,3 vs 4,82, 4,81) (p=0,027). Conclusiones: En MAFLD el AF fue menor vs población sana mexicana. En pacientes sin fibrosis y esteatosis severa el AF se eleva proporcional al incremento de masa grasa e del IMC, y en fibrosis hepática avanzada el AF disminuye.(AU)

Objective: To describe the characteristics of the body components and phase angle (PhA) of patients with MAFLD according to those different to fibrosis and hepatic steatosis. Material and methods: Observational and descriptive study in a cohort of 585 volunteers from our center with MAFLD criteria. The risk of liver fibrosis was determined by APRI, NAFLD score and FIB-4; at an indeterminate and high risk of fibrosis, a transient elastography (Fibroscan®) were realized. Bioimpedance body composition analysis (SECA®) was performed. Patients with ET and SECA® registry were included. Bioimpedance body composition analysis (SECA®) was performed. Patients with ET and SECA® registry were included. Results: 125 participants (21.4%) were evaluated, age 53.9±13.9 years, 62.1% women, BMI 33.2±5.8kg/m2. The SECA® analysis showed mean fat mass of 42%±7.32 and muscle mass 21.18kg±6.6. The PhA was 5.1±0.69, in women 4.92±0.62 and men 5.41±0.70. PhA in patients without fibrosis was 5.091 vs with fibrosis 5.121 (P=.813). In advanced fibrosis, it reported a low value compared to the rest of the groups (P=.031). The PhA in S3 was higher compared to S1 and S2 (5.3 vs 4.82, 4.81) (P=.027). Conclusions: In MAFLD, the PhA was lower than the healthy Mexican population. In patients without fibrosis and severe steatosis, PhA rises proportionally to the increase in fat mass and BMI and in advanced liver fibrosis, PhA decreases.(AU)

Suitability of the global forest cover change map to assess climatic megadisturbance impacts on remote tropical forests.

The occurrence and combination of extreme meteorological events may lead to severe (megadisturbance) impacts on conserved forests and protected areas all over the world. Recent research has shown that megadisturbance impacts (after the events of hurricanes and prolonged drought) may be detected in subtropical forest cover using changes in spectral indices derived from satellite imagery. The objective of this study is to assess the impact of megadisturbance on forest types of the Alejandro de Humboldt National Park, Republic of Cuba in the 2001-2017 time-period. The Global Forest Cover Change (GFCC, available on the Global Forest Watch website) product was validated and indicated the prominence of megadisturbance for year 2016 (85% of the total disturbed area), largely associated with the Hurricane Matthew event. A robust estimator of the disturbed forest area, based on GFCC-stratified sampled verification sites, suggests that 11,110 ± 1,771 hectares of forest (~ 16% of the Park's total area) was affected by megadisturbance between 2001 and 2017. In 2017, about 1276 hectares of forests were impacted, presumably related to a long-lasting effect of megadisturbance due to Hurricane Matthew and prolonged droughts in previous years. Four types of tropical rainforests (especially lowland rainforest and submountainous sclerophyllous rainforest on serpentinite), that cover 43% of the National Park, accounted for about 85% of the impacts by megadisturbance. The Easternmost portion of these forests should be prioritized for conservation monitoring and possibly for forest restoration strategies. This study contributes to establishing methodological guidelines for rapid environmental assessment of remote, tropical protected areas facing the impacts of extreme meteorological events and climate change.

Non-Ionic Surfactant Recovery in Surfactant Enhancement Aquifer Remediation Effluent with Chlorobenzenes by Semivolatile Chlorinated Organic Compounds Volatilization.

Surfactant enhanced aquifer remediation is a common treatment to remediate polluted sites with the inconvenience that the effluent generated must be treated. In this work, a complex mixture of chlorobenzene and dichlorobenzenes in a non-ionic surfactant emulsion has been carried out by volatilization. Since this techhnique is strongly affected by the presence of the surfactant, modifying the vapour pressure, Pv0, and activity coefficient, γ, a correlation between Pvj0γj and surfactant concentration and temperature was proposed for each compound, employing the Surface Response Methodology (RSM). Volatilization experiments were carried out at different temperatures and gas flow rates. A good agreement between experimental and predicted remaining SVCOCs during the air stripping process was obtained, validating the thermodynamic parameters obtained with RSM. Regarding the results of volatilization, at 60 °C 80% of SVCOCs were removed after 6 h, and the surfactant capacity was almost completely recovered so the solution can be recycled in soil flushing.

Abatement of chlorobenzenes in aqueous phase by persulfate activated by alkali enhanced by surfactant addition.

Sites 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 PS.

Body composition and phase angle by bioimpedance in patients with MAFLD. / Análisis de la composición corporal y ángulo de fase por bioimpedancia en pacientes con MAFLD.

OBJECTIVE: To describe the characteristics of the body components and phase angle (PhA) of patients with MAFLD according to those different to fibrosis and hepatic steatosis. MATERIAL AND METHODS: Observational and descriptive study in a cohort of 585 volunteers from our center with MAFLD criteria. The risk of liver fibrosis was determined by APRI, NAFLD score and FIB-4; at an indeterminate and high risk of fibrosis, a transient elastography (Fibroscan®) were realized. Bioimpedance body composition analysis (SECA®) was performed. Patients with ET and SECA® registry were included. Bioimpedance body composition analysis (SECA®) was performed. Patients with ET and SECA® registry were included. RESULTS: 125 participants (21.4%) were evaluated, age 53.9±13.9 years, 62.1% women, BMI 33.2±5.8kg/m2. The SECA® analysis showed mean fat mass of 42%±7.32 and muscle mass 21.18kg±6.6. The PhA was 5.1±0.69, in women 4.92±0.62 and men 5.41±0.70. PhA in patients without fibrosis was 5.091 vs with fibrosis 5.121 (P=.813). In advanced fibrosis, it reported a low value compared to the rest of the groups (P=.031). The PhA in S3 was higher compared to S1 and S2 (5.3 vs 4.82, 4.81) (P=.027). CONCLUSIONS: In MAFLD, the PhA was lower than the healthy Mexican population. In patients without fibrosis and severe steatosis, PhA rises proportionally to the increase in fat mass and BMI and in advanced liver fibrosis, PhA decreases.

Incidence of 'new-onset' constipation and associated factors during lockdown due to the COVID-19 pandemic.

OBJECTIVE: A minimum of physical activity and low liquid intake are factors that have been associated with constipation. The health emergency brought on by the COVID-19 pandemic has resulted in adopting behaviour, such as sheltering-in-place (less mobility) and dietary changes, creating a scenario we believe to be an adequate model for examining the appearance of symptoms of constipation and its associated factors. DESIGN: A cross-sectional and descriptive study was conducted on an open population, applying an electronic survey (4 weeks after lockdown due to COVID-19 in Mexico) to evaluate demographic characteristics, physical activity, water and fibre intake, appearance of constipation symptoms (including stool consistency), and quality of life. RESULTS: Out of 678 subjects evaluated, 170 (25%, 95% CI: 21.7 to 28.4) developed symptoms of 'new-onset' constipation, with a significant decrease in the number of daily bowel movements (p<0.05) and stool consistency (p<0.05) during lockdown. Furthermore, in the 'new-onset' constipation population there was a higher proportion of subjects (79 (47%) of 170) who stopped exercising during the pandemic compared with the subjects who did not develop constipation symptoms (187 (37%) of 508, p=0.03, OR: 1.49, 95% CI: 1.0 to 2.1). The multivariate analysis (logistic regression) showed that female sex (p=0.001), water intake (p=0.039), and physical activity (p=0.012) were associated with 'new-onset' constipation. CONCLUSIONS: In our study on an open population in Mexico, we found that one-fourth of the population developed 'new-onset' constipation symptoms during the lockdown imposed due to the COVID-19 pandemic. A reduction of physical activity and less water consumption were associated factors.

Compatibility of nonionic and anionic surfactants with persulfate activated by alkali in the abatement of chlorinated organic compounds in aqueous phase.

Surfactant Enhanced In-Situ Chemical Oxidation (S-ISCO) is an emerging technology in the remediation of sites with residual Dense Non-Aqueous Phase Liquids (DNAPLs), a ubiquitous problem in the environment and a challenge to solve. In this work, three nonionic surfactants: E-Mulse3® (E3), Tween80 (T80), and a mixture of Tween80-Span80 (TS80), and an anionic surfactant: sodium dodecyl sulfate (SDS), combined with persulfate activated by alkali (PSA) as oxidant have been investigated to remove the DNAPL generated as liquid waste in lindane production, which is composed of 28 chlorinated organic compounds (COCs). Because the compatibility between surfactants and oxidants is a key aspect in the S-ISCO effectiveness the unproductive consumption of PS by surfactants was investigated in batch (up to 864 h) varying the initial concentration of PS (84-42 mmol·L-1) and surfactants (0-12 g·L-1) and the NaOH:PS molar ratio (1 and 2). The solubilization capacity of a partially oxidized surfactant was analyzed by estimating its Equivalent Surfactant Capacity, ESC, (as mmolCOCs dissolvedgsurf-1) and comparing it to the expected value for an unoxidized surfactant, ESCo. Finally, the abatement of DNAPL with simultaneous addition of surfactant and PSA was studied. At the conditions used, a negligible unproductive consumption of PS was found by SDS; meanwhile, PS consumption at 360 h ranged between 70 and 80% using the nonionic surfactants. The highest ratios of ESC/ESCo were found with SDS and E3 and these surfactants were chosen for the S-ISCO treatment. When oxidant and surfactant were simultaneously applied for DNAPL abatement the COC conversion was more than three times higher with E3 (0.6 at 360 h) than SDS. Moreover, it was obtained that the time needed for the removal of a mass of DNAPL by PSA in the absence of surfactants was notably higher than the time required when a suitable surfactant was added.

Remediation of HCHs-contaminated sediments by chemical oxidation treatments.

The intensive use of organochlorine pesticides, such as lindane (γ-HCH), and the inadequate management of their wastes, is a huge environmental problem. The lindane production during the last century has generated huge volumes of solid wastes of other HCH isomers, causing hot points of soil and groundwater contamination. The soil treated in this work was obtained from a landfill located in the nearby of an old lindane factory, containing α-HCH and ß-HCH as main contaminants. This study addresses for the first time the application of different chemical oxidation treatments, viz. Fenton process (H2O2 + Fe), persulfate (PS) activated by temperature (20 and 40 °C), by alkali (NaOH) and by the combination of alkali and temperature (NaOH, 40 °C) for the remediation of HCH-polluted soils (CHCHs = 155 mg kg-1). The intrinsic characteristics of the soil (high carbonate content) led to high consumption of H2O2 (XH2O2 ≈ 100% at 24 h) and complete iron precipitation, making unappropriated the application of the Fenton process. The efficiency of thermal PS was limited by the low solubility of HCH isomers in the aqueous phase, the high refractoriness of these compounds towards oxidation, and the presence of the contaminants in the form of particulate matter. After 25 days of treatment, a conversion of chlorinated organic compounds (COCs) of 50% was achieved (VL/Wsoil = 2, CPS = 40 g L-1, 40 °C), whereas the application of PS activated by alkali and temperature (40 °C) led to promising results. At pH above 12, HCHs were dehydrochlorinated to trichlorobenzenes, which were further oxidized by hydroxyl radicals. The hydrolysis rate of ß-HCH was the limiting step of the process, and it was favored by increasing the reaction temperature. At 40 °C, a conversion of COCs above 95% was achieved (VL/Wsoil = 2, CPS = 40 g L-1, CNaOH = 13.5 g L-1, 14 days) with low oxidant consumption (XPS = 30%).

Surfactant-Enhanced Solubilization of Chlorinated Organic Compounds Contained in DNAPL from Lindane Waste: Effect of Surfactant Type and pH.

Application of surfactants in the remediation of polluted sites with dense nonaqueous phase liquid (DNAPL) still requires knowledge of partitioning between surfactants and pollutants in the organic and aqueous phases and the time necessary to reach this balance. Two real DNAPLs, generated as wastes in the lindane production and taken from the polluted sites from Sabiñanigo (Spain), were used for investigating the solubilization of 28 chlorinated organic compounds (COCs) applying aqueous surfactant solutions of three nonionic surfactants (E-Mulse® 3 (E3), Tween®80 (T80), and a mixture of Tween®80-Span®80 (TS80)) and an anionic surfactant (sodium dodecyl sulfate (SDS)). The initial concentrations of surfactants were tested within the range of 3-17 g·L-1. The pH was also modified from 7 to >12. The uptake of nonionic surfactants into the organic phase was higher than the anionic surfactants. Solubilization of COCs with the nonionic surfactants showed similar molar solubilization ratios (MSR = 4.33 mmolCOCs·g-1surf), higher than SDS (MSR = 0.70 mmolCOCs·g-1SDS). Furthermore, under strong alkaline conditions, the MSR value of the nonionic surfactants was unchanged, and the MSR of SDS value increased (MSR = 1.32 mmolCOCs·g-1SDS). The nonionic surfactants did not produce preferential solubilization of COCs; meanwhile, SDS preferentially dissolved the more polar compounds in DNAPL. The time required to reach phase equilibrium was between 24 and 48 h, and this contact time should be assured to optimize the effect of the surfactant injected on COC solubilization.

Thermally activated persulfate for the chemical oxidation of chlorinated organic compounds in groundwater.

Chlorinated pesticides were extensively produced in the XX century, generating high amounts of toxic wastes often dumped in the surroundings of the production sites, resulting in hot points of soil and groundwater pollution worldwide. This is the case of Bailín landfill, located in Sabiñánigo (Spain), where groundwater is highly polluted with chlorobenzenes (mono, di, tri and tetra) and hexachlorocyclohexanes. This study addresses the abatement of chlorinated organic compounds (COCs) present in the groundwater coming from the Bailín landfill by thermally activated persulfate, PS (TAP). The influence of temperature (30-50 °C) and oxidant concentration (2-40 g L-1) on the efficiency of COCs (initial concentration of COCs = 57.53 mg L-1, determined by the solubility of the pollutants in water) degradation has been investigated. Raising the reaction temperature and PS concentration the degradation of COCs significantly accelerates, as a result of higher production of sulfate radicals. The thermal activation of PS implies side reactions, involving the unproductive decomposition of this oxidant. The activation energy calculated for this reaction (128.48 kJ mol-1) reveals that is slightly more favored by temperature than the oxidation of COCs by sulfate radicals (102.4-115.72 kJ mol-1). At the selected operating conditions (PS = 10 g L-1, 40 °C), the almost complete conversion of COCs and a dechlorination and mineralization degree above 80% were obtained at 168 h reaction time. A kinetic model, able to adequately predict the experimental concentration of COCs when operating at different temperatures and initial concentration of PS has been proposed.

Comparison of real wastewater oxidation with Fenton/Fenton-like and persulfate activated by NaOH and Fe(II).

Treatment 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.

Partitioning of chlorinated organic compounds from dense non-aqueous phase liquids and contaminated soils from lindane production wastes to the aqueous phase.

Hexachlorocyclohexane (HCH) and mainly the γ-HCH isomer, namely lindane, were extensively produced and used as pesticides. Huge amounts of wastes, solids and liquids, were disposed of in the surroundings of the production sites. The liquid residuum was a complex mixture of chlorinated organic compounds, COCs, from chlorobenzene to heptachlorocyclohexane. This Dense Non-Aqueous Phase Liquid, DNAPL, migrated by density through the subsurface to greater depths, being trapped or adsorbed into the soil in this movement posing a significant risk to the groundwater. Knowledge of the partitioning in water of COCs in DNAPL is a key issue to determine its fate in the environment. However, there are no data in literature for the partitioning and/or solubility of many of the COCs in this DNAPL, such as pentachlorocyclohexene, hexachlorocyclohexene and heptachlorocyclohexane despite them constitute about 13-30% of the mole fraction of the DNAPLs. In this work, the partitioning to water of COCs in free and those adsorbed onto soil has been studied. In addition, measured and predicted aqueous concentrations of each COC in the DNAPL mixture have been compared. To do this, the solubility of a compound that is a solid crystal when pure at P = 298 K and P = 1 atm has been evaluated considering the approach of sub-cooled liquid state of solid organochlorines. Samples were obtained at Sabiñanigo landfills and soils used had several grain sizes. Transformation in alkaline media of COCs had a positive environmental impact.

Methanol-enhanced degradation of carbon tetrachloride by alkaline activation of persulfate: Kinetic model.

Carbon tetrachloride (CT), a chlorinated organic compound widely used in the chemical industry during the 20th century, is nowadays a ubiquitous contaminant in groundwater and in situ technologies for its destruction are required. In this work, the degradation of CT by the alkaline activation of persulfate (PS) has been studied. Among the pool of radical species generated (hydroxyl radicals, sulfate radicals and superoxide radicals), O2∙- resulted to be the only species responsible for CT abatement. It has been found that the presence of other solvents less polar than water (hydrogen peroxide, acetone, propanol and methanol) improves CT degradation. Among them, methanol was selected as the most adequate co-solvent, leading to the complete elimination of CT (100 mg L-1, 24 h) with a moderate unproductive consumption of the oxidant. The degradation of CT increased proportionally with the concentration of this solvent (from 0.1 to 10 g L-1). The ratio NaOH:PS (from 1 to 8) did not affect the degradation of CT when working with a constant concentration of PS and highly alkaline conditions were maintained. The removal rate of CT increased as the concentration of PS increased (from 20 to 60 g L-1), while the conversion of this pollutant did not depend on its initial concentration (from 10 to 100 mg L-1). A kinetic model that considers the concentration of PS, MeOH and CT and can predict the concentration of CT with reaction time at different operating conditions, has been developed from the experimental data.