Electrokinetic remediation of a soil contaminated by the pyritic sludge spill of Aznalcollar (SW, Spain)

The electrokinetic remediation (EKR) of a soil sample contaminated with a sludge spill of pyritic mining origin is studied. The initial total metal content of the soil indicates that there is a very large concentration of Fe (about 100 g/kg), whereas other metals of environmental relevance are Zn (2390 mg/kg), Pb (1740 mg/kg), Cu (459 mg/kg) and Cd (7 mg/kg). A speciation procedure is performed for each of these metals, indicating that their mobility is quite different. Results indicate that EKR allows only the remediation of those fractions of the contaminants which are associated to the exchangeable and weak acid soluble fractions. These speciation results were used to obtain the values of the parameters that were introduced in a newly developed mathematical model which allows the prediction of the extent of the removal, the rate of recovery, and chemicals requirements. The experiments performed indicate that reversed electroosmosis (towards the anode) occurs and decreases the system performance.     

Acid Enhanced Electrokinetic Remediation of a Contaminated Soil using Constant Current Density: Strong vs. Weak Acid

The most typical enhancement for electrokinetic remediation (EKR) involves the neutralization of the alkaline front generated at the cathode by the addition of an acid to the catholyte. Although the use of strong and weak acids can be found in the literature, there is still a clear lack of reliable comparisons between them. This paper presents a comparison of the results obtained for a real lead contaminated soil treated by EKR enhanced with nitric or with acetic acid. The divergences that are usually observed in those experimental results obtained when using constant voltage drop are avoided here by the use of EKR with constant current intensity and the disposition in series of the soil lab columns. Important differences are observed in the behavior of the system when the acid was changed. The time needed to achieve the same metal recovery is more than 3 times longer for the nitric acid. A standard sequential extraction procedure was used to fractionate the lead concentration in the soil according to its mobility in a before- and after-treatment way. Regardless of these important differences observed in the remediation time, the fractionation results after the experiments were almost the same for the two acid enhanced EKRs.     

Effect of different treatments on electrokinetic remediation of Zn,Pb and Cd from a contaminated calcareous soil

Electrokinetic remediation is a promising method to decontamination of the heavy metals from soils.In this paper,the remediation of a contaminated calcareous soil with Zn,Cd and Pb sampled from around Zanjan province of Iran,was investigated using electrokinetic method.In this paper,the soil contain a high concentration of Zn (1400 mg·kg-1),Cd (15 mg·kg-1) and Pb (250 mg·kg-1).Electrokinetic decon-tamination consists of two series of experiments as follows:(1) the effect of five treatments including the use of distilled water,acetic acid and EDTA electrolyte solutions,and approaching anodes systems,and the circulation flow of electrolyte at two different voltage gradient (i.e.1.33 and 2.66 V·cm-1),and(2) the effect of moisture content (saturated,FC and 0.7FC,FC indicated soil moisture at "Field Capacity") with a voltage gradient of 1.33 V·cm-1.After applying electric current for 5 days,the results of experiments indicated that the removal efficiency of heavy metals can be increased by raising the volt-age gradient.In this matter,the highest remediation can be observed among different treatments in EDTA(Ethylene diamine tetra acetic acid) treatment (40.11％,43.10％ and 24.7％ for Zn,Cd and Pb,respectively).Moreover,the heavy metals removal at the saturated moisture was at the highest level so that 32.62％cadmium,31.33％ zinc and 18.82％ lead being removed after 120 h of electric current application.By decreasing moisture to 0.7FC,the removal percentage for the three heavy metals obtained 20.97％,18.44％ and 12.25％,respectively.Furthermore,Cd had the highest removal,and Zn and Pb were next among the three heavy metals in question.     

Electrochemically induced reactions in soils—a new approach to the in-situ remediation of contaminated soils?: Part 2: remediation experiments with a natural soil containing highly chlorinated hydrocarbons

An observed decay of immobile organic substances is not explained by the theory of electrokinetic soil remediation, when they are not transported by means of the electric field (electro-osmosis or -phoresis), as it is the case for chlorinated hydrocarbons like hexachlorobutadiene. It is assumed that the decrease of those substances is based on the presence of ‘microconductors’, particles with electronic conducting properties (e.g. metal oxides or others), inside the soil matrix. They are supposed to be able to induce electrochemical reactions in the vicinity of the contamination. Another possibility for the observed decay in their concentration are elimination reactions. Experiments and results with a natural soil containing chlorinated hydrocarbons with high boiling points coming from an industrial contamination site are presented. A decay of 80% and more for some of the substances could be observed. Degradation products (DP) with less chlorine in the molecule structure have been detected. Thus, redox- and elimination-reactions are possible. High pH-values seem to enhance the remediation.     

Electrochemically induced reactions in soils—a new approach to the in-situ remediation of contaminated soils?: Part 1: The microconductor principle

Electrochemical reactions can be induced in soils if the soil matrix contains particles or films with electronic conducting properties (‘microconductors’). In these cases, the wet soil may act as a ‘diluted’ electrochemical solid bed reactor. A discussion of this reaction principle within the soil matrix will be presented here. It will be shown, that under certain conditions, immobile organic contaminants may be converted.     

Biological treatment of a contaminated gaseous emission from a paint and varnish plant—from laboratory studies to pilot‐scale operation

A Vapour‐Phase Bioreactor (VPB), namely a biotrickling filter, was scaled‐up and operated in‐situ for the treatment of gaseous emissions from a paint and varnish industrial plant. A microbial culture able to degrade the target compounds was enriched and a laboratory‐scale VPB was established in order to evaluate the treatment's performance. The VPB presented removal efficiencies higher than 90% when exposed to Organic Loads (OL) of ca 50 g h^?1 m^?3 of reactor. The VPB was exposed to dynamic conditions often found in‐situ (eg night and weekend shutdown periods) and showed a fast capacity to recover, with and without mineral medium recirculation. After a prolonged interruption period (10 months), the VPB was not able to cope with OL of ca 25 g h^?1 m^?3 of reactor and re‐inoculation was required in order to recover the treatment performance. The VPB also showed limited treatment when exposed to higher OL (ca 500 g h^?1 m^?3 of reactor). The VPB was then scaled‐up and a 3 m³ VPB was operated in‐situ, showing removal efficiencies higher than 50% when exposed to an OL of c 5 g h^?1 m^?3 of reactor, thus complying with current legal demands. The addition of a maintenance feed was shown to be a useful tool for VPB pilot‐scale operation when shutdown periods occurred. A factorial design of experiments was carried out, which allowed reduction to one‐tenth of the initial supply of the main mineral medium constituents, namely phosphate buffer, ammonium and magnesium salts, and also elimination of the metal supplement. Overall, the VPBs were shown to be robust equipment, being able to respond actively to dynamic treatment scenarios, particularly night and weekend shutdown periods. Copyright © 2003 Society of Chemical Industry     

Cr(VI) reduction by bio and bioinorganic catalysis via use of bio‐H2: a sustainable approach for remediation of wastes

Use of biologically‐produced hydrogen (bio‐H₂) as an electron donor for Cr(VI) reduction by native and palladized cells of Desulfovibrio vulgaris NCIMB 8303 was demonstrated. The bio‐H₂ was produced fermentatively by Escherichia coli HD701 (a strain upregulated with respect to formate hydrogenlyase expression) using glucose solution or two industrial confectionery wastes as fermentable substrates. Maximum Cr(VI) reduction occurred at the expense of bio‐H₂ using palladized biomass (bio‐Pd(0)), with negligible residual Cr(VI) remaining from a 0.5 mmol dm^?3 solution after 2.5 h. Use of bio‐H₂ as the electron donor for Cr(VI) reduction by agar‐immobilized bio‐Pd(0) in a continuous‐flow system gave 90% reduction efficiency at a flow residence time of 0.7 h, which was maintained for the duration of bio‐H₂ evolution by E. coli HD701. This study shows the potential to remediate toxic metal waste at the expense of food processing waste, as a sustainable alternative to landfilling. Copyright © 2007 Society of Chemical Industry     

The use of dilute acetic acid for butyl acetate production in a reactive distillation: Simulation and control studies

The recovery of dilute acetic acid, which is widely found as a by-product in many chemical and petrochemical industries, becomes an important issue due to economic and environmental awareness. In general, separation of acetic acid in aqueous solution by conventional distillation columns is difficult, requiring a column with many stages and high energy consumption. As a result, the primary concern of the present study is the application of reactive distillation as a potential alternative method to recover dilute acetic acid. The direct use of dilute acetic acid as reactant for esterification with butanol to produce butyl acetate in the reactive distillation is investigated. Simulation studies are performed in order to investigate effect of the concentration of dilute acetic acid and key process parameters on the performance of the reactive distillation in terms of acetic acid conversion and butyl acetate production. In addition, three alternative control strategies are studied for the closed loop control of the reactive distillation. The control objective is to maintain the butyl acetate in a bottom product stream at the desired purity of 99.5 wt%.     

Computer simulation of flow‐sheets for the solvent extraction of uranium: a new route to delay the effect of chemical degradation of the organic phase during uranium recovery from acidic sulfate media

BACKGROUND: The extractants used in solvent extraction processes undergo degradation under thermal, chemical and radiolytical stresses. In the case of uranium plants, tri‐n‐octylamine, used as an extractant, slowly degrades into di‐n‐octylamine. Such degradation causes a gradual depletion of the uranium extraction isotherms and as a result, of the efficiency of uranium recovery from feed solutions. The present work highlights a new route to delay this depletion of the extraction efficiency, merely by optimizing the flow‐sheets involved in the process. Five flow‐sheets have been compared for uranium recovery from acidic sulfate media by a solution of 0.146 mol L⁻¹ tri‐n‐octylamine in kerosene modified with 5% w/w 1‐tridecanol and stripping with a 199 g L⁻¹ Na₂CO₃ solution. These five flow‐sheets include the classical counter‐current flow‐sheet with four mixers–settlers in extraction and three mixers–settlers in stripping and four unusual combined solvent extraction flow‐sheets with two independent extraction stripping loops and with one or two feed inlets. RESULTS: Computer simulation supplied evidence of the strong influence of the studied flow‐sheets on the sturdiness of the process. More precisely, the unusual combined solvent extraction flow‐sheets appeared to be significantly more efficient than the classical counter‐current one and it is shown that an advantage of this can be to delay the negative impact of gradual degradation of tri‐n‐octylamine on uranium recovery efficiency from acidic sulfate media. CONCLUSION: The replacement of classical counter‐current flow‐sheets with a unique extraction‐stripping loop in unusual combined flow‐sheets with two or more independent extraction‐stripping loops and with one or more feed inlets is a fruitful approach to delay the periodic addition of fresh tri‐n‐octylamine necessary for counter‐balancing the progressive degradation of the extraction solvent and, as a result, to delay the gradual depletion of the efficiency of uranium recovery. Copyright © 2009 Society of Chemical Industry     

Design and Engineering of “Green” Nanoemulsions for Enhanced Topical Delivery of Bakuchiol Achieved in a Sustainable Manner: A Novel Eco-Friendly Approach to Bioretinol

In the present work, we establish novel “environmentally-friendly” oil-in-water nanoemulsions to enhance the transdermal delivery of bakuchiol, the so-called “bioretinol” obtained from powdered Psoralea corylifolia seeds via a sustainable process, i.e., using a supercritical fluid extraction approach with pure carbon dioxide (SC-CO₂). According to Green Chemistry principles, five novel formulations were stabilized by “green” hybrid ionic surfactants such as coco-betaine—surfactin molecules obtained from coconut and fermented rapeseed meal. Preliminary optimization studies involving three dispersion stability tests, i.e., centrifugation, heating, and cooling cycles, indicated the most promising candidates for further physicochemical analysis. Finally, nanoemulsion colloidal characterization provided by scattering (dynamic and electrophoretic light scattering as well as backscattering), microscopic (transmission electron and confocal laser scanning microscopy), and spectroscopic (UV–Vis spectroscopy) methods revealed the most stable nanocarrier for transdermal biological investigation. In vitro, topical experiments provided on human skin cell line HaCaT keratinocytes and normal dermal NHDF fibroblasts indicated high cell viability upon treatment of the tested formulation with a final 0.02–0.2 mg/mL bakuchiol concentration. This excellent biocompatibility was confirmed by ex vivo and in vivo tests on animal and human skin tissue. The improved permeability and antiaging potential of the bakuchiol-encapsulated rich extract were observed, indicating that the obtained ecological nanoemulsions are competitive with commercial retinol formulations.     

Freezing the Bioactive Conformation to Boost Potency: The Identification of BAY 85‐8501, a Selective and Potent Inhibitor of Human Neutrophil Elastase for Pulmonary Diseases

Human neutrophil elastase (HNE) is a key protease for matrix degradation. High HNE activity is observed in inflammatory diseases. Accordingly, HNE is a potential target for the treatment of pulmonary diseases such as chronic obstructive pulmonary disease (COPD), acute lung injury (ALI), acute respiratory distress syndrome (ARDS), bronchiectasis (BE), and pulmonary hypertension (PH). HNE inhibitors should reestablish the protease–anti‐protease balance. By means of medicinal chemistry a novel dihydropyrimidinone lead‐structure class was identified. Further chemical optimization yielded orally active compounds with favorable pharmacokinetics such as the chemical probe BAY‐678. While maintaining outstanding target selectivity, picomolar potency was achieved by locking the bioactive conformation of these inhibitors with a strategically positioned methyl sulfone substituent. An induced‐fit binding mode allowed tight interactions with the S2 and S1 pockets of HNE. BAY 85‐8501 ((4S)‐4‐[4‐cyano‐2‐(methylsulfonyl)phenyl]‐3,6‐dimethyl‐2‐oxo‐1‐[3‐(trifluoromethyl)phenyl]‐1,2,3,4‐tetrahydropyrimidine‐5‐carbonitrile) was shown to be efficacious in a rodent animal model related to ALI. BAY 85‐8501 is currently being tested in clinical studies for the treatment of pulmonary diseases.