Photocatalytic solid-phase degradation of polyethylene with fluoride-doped titania under low consumption ultraviolet radiation.

Photodegradation of plastic in solid-phase requires the polymer to be composited with an efficient photocatalyst. We report herein the successful synthesis and characterization of fluoride-doped-TiO2 and its applicability, for the first time, on solid-phase photodegradation of polyethylene films. Nearly half weight loss of polyethylene, containing only 2% of the photocatalyst, is eliminated after three weeks of ultraviolet A radiation using a low consumption light emitting diode lamp, defeating previously reported data. The half-life time of the plastic was around 3 weeks, highlighting the viability of this process for real applications. Results were compared to raw PE and PE composite with well-known TiO2, resulting in, respectively, 0 and 26% of weight loss. The degradation process was monitored by optical microscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared and X-ray photoelectron spectroscopy, which revealed the formation of plastic cracks, loss of polyethylene crystallinity and thus stability, the oxidation of C-H bonds and the oxidized state of the surface compounds during photodegradation. The obtained results open a path for the future production of cleaner and self-photodegradable plastics, where the photocatalyst would be introduced in all the manufactured plastics, making possible the quicker photodegradation of the plastics that end up on the environment and the plastics reaching wastewater treatment plants.

ZnFe2O4-chitosan magnetic beads for the removal of chlordimeform by photo-Fenton process under UVC irradiation.

A simple protocol was proposed for the preparation of magnetic chitosan beads ZnFe2O4-CS via a co-precipitation method. The use of synthesized magnetic ZnFe2O4-CS beads as catalyst for the heterogeneous photo-Fenton treatment of chlordimeform insecticide (CDM) was evaluated. The photo-Fenton experiments were carried out with different synthesized catalysts by varying the molar ratio Zn/Fe in chitosan beads, the catalyst concentration and pH. Under optimal conditions using 1 g of ZnFe2O4-CS beads with a molar ratio Zn/Fe = 0.35 and at pHinitial = 3, a real wastewater doped with 20 mg L-1 of CDM was treated and complete removal of the insecticide was achieved after 7 min with a total TOC removal after 2 h of treatment. The generated carboxylic acids and ions during the photo-Fenton process were identified and quantified. The stability of the photocatalytic activity of the best catalyst in terms of pollutant removal, ZnFe2O4-CS(0.35) beads with a molar ratio Zn/Fe equal to 0.35, was satisfactory validated by four consecutive cycles. This optimal catalyst was characterized, before and after use, by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy, X-Ray Powder Diffraction and Vibrating Sample Magnetometry analysis.

Setting the Foundations of Aqueous Three-Phase Systems (A3PS) in the Quest for a Rational Design.

This work presents the first in-depth study of Aqueous Three-Phase Systems (A3PS) with the main purpose of unveiling their behaviour, hence contributing to the development of this new field. Thus, a complete definition of a quaternary system was carried through by describing all the regions in detail to represent them later on in a regular-tetrahedral diagram. The three aqueous faces of the tetrahedron demonstrated an undeviating influence in the segregation capacity. Furthermore, a method for comparing Aqueous Biphasis Systems (ABS) immiscibilities was set up in order to allow the evaluation and detection of the "limiting ABS" for the three-phase region. Finally, all this information was compiled and utilised to obtain a new strategy for an A3PS rational design, which can be applied with ABS libraries or in an experimental approach. In this sense, this strategy represents an undoubted advance towards future studies and development of A3PS, as this sequential application of the constructed knowledge is assumed to save time and resources.

Electrocoagulation: Simply a Phase Separation Technology? The Case of Bronopol Compared to Its Treatment by EAOPs.

Electrocoagulation (EC) has long been considered a phase separation process, well suited for industrial wastewater treatment since it causes a quick, drastic decay of organic matter content. This research demonstrates that EC also behaves, at least for some molecules like the industrial preservative bronopol, as an effective transformation technology able to yield several breakdown products. This finding has relevant environmental implications, pointing to EC as a greener process than described in literature. A thorough optimization of EC was performed with solutions of bronopol in a simulated water matrix, yielding the complete disappearance of the parent molecule within 20 min at 200 mA (∼20 mA/cm(2)), using Fe as the anode and cathode. A 25% of total organic carbon (TOC) abatement was attained as maximum, with bronopol being converted into bromonitromethane, bromochloromethane, formaldehyde and formic acid. N atoms were accumulated as NO3(-), whereas Br(-) was stable once released. This suggests that mediated oxidation by active chlorine, as well as by hydroxyl radicals resulting from its reaction with iron ions, is the main transformation mechanism. Aiming to enhance the mineralization, a sequential combination of EC with electro-Fenton (EF) as post-treatment process was proposed. EF with boron-doped diamond (BDD) anode ensured the gradual TOC removal under the action of (•)OH and BDD((•)OH), also transforming Br(-) into BrO3(-).

North Western Spain hot springs are a source of lipolytic enzyme-producing thermophilic microorganisms.

Several hot springs in Galicia (North Western Spain) have been investigated as potential sources of lipolytic enzyme-producing thermophilic microorganisms. After isolating 12 esterase producing strains, 9 of them were assured to be true lipase producers, and consequently grown in submerged cultures, obtaining high extracellular activities by two of them. Furthermore, a preliminary partial characterization of the crude lipase, obtained by ultrafiltration of the cell-free culture supernatant, was carried out at several pH and temperature values. It is outstanding that several enzymes turned out to be multiextremozymes, since they had their optimum temperature and pH at typical values from thermoalkalophiles. The thermal stability in aqueous solution of the crude enzymes was also assayed, and the influence of some potential enzyme stabilizing compounds was tested. Finally, the viability of the selected microorganisms has been demonstrated at bioreactor scale.

Heterogeneous electro-Fenton system using Fe-MOF as catalyst and electrocatalyst for degradation of pharmaceuticals.

In recent years, heterogeneous electro-Fenton processes have gained considerable attention as an alternative to homogeneous processes. In this context, the aim of this study is the use of a commercial iron metal-organic framework (Fe-MOF), Basolite® F-300, as a base material for the design of a heterogeneous electro-Fenton treatment system for the removal of antipyrine. Initially, the catalyst was applied as powder in aqueous solution and three key parameters of the electro-Fenton process (pH, Fe-MOF concentration and current density) were evaluated and optimized by a Central Composite Design Face Centred (CCD-FC) using antipyrine removal and energy consumption as response functions. Near complete antipyrine removal (94%) was achieved under optimal conditions: pH 3, Fe-MOF 157.78 mg/L and current density 6.67 mA/cm2, obtaining an energy consumption of 0.29 W·h per mg of antipyrine removed. Later, two electrocatalysts (Fe-MOF functionalized cathodes), prepared by different Fe-MOF immobilisation approaches (composite of carbon black/polytetrafluoroethylene or by electrospinning on Ni foam), were synthesized. Their characterisation showed notable Fe-MOF incorporation into the material and favourable properties as electrocatalysts. Both Fe-MOF functionalized cathodes were evaluated in the removal of antipyrine at different pH (acidic and natural) and current density (27.78 and 55.56 mA/cm2), achieving in the best conditions removal levels around 80% in 1 h without any operational problems. In addition, several intermediates generated during the treatment were identified and their toxicity estimated. According to the obtained results, the degradation compounds have less toxicity than the parent compounds, confirming the effectiveness of the treatment.

Nanostructured copper-organic frameworks for the generation of sulphate radicals: application in wastewater disinfection.

In recent years, the presence of pathogens in the environment has become an issue of widespread concern in society. Thus, new research lines have been developed regarding the removal of pathogens and persistent pollutants in water. In this research, the efficacy of nanostructure copper-organic framework, HKUST-1, has been evaluated for its ability to eliminate Escherichia coli and generate sulphate radicals as catalyst for the treatment of effluents with a high microbiological load via peroxymonosulphate (PMS) activation. The disinfection process has been optimized, achieving complete elimination of Escherichia coli growth after 30 min of testing using a concentration of 60.5 mg/L HKUST-1 and 0.1 mM of PMS. To overcome the operational limitations of this system and facilitate its handling and reutilization in a flow disinfection process, HKUST-1 has been efficiently encapsulated on polyacrylonitrile as a novel development that could be scaled up to achieve continuous treatment.

Scaling-up the production of thermostable lipolytic enzymes from Thermus aquaticus YT1.

The lipolytic enzymes synthesized by Thermusaquaticus YT1 present extremely interesting properties of thermostability (more than 70% of activity after 12 days at 80°C and a half-life time of 1 h at 95°C), which point out the interest of proposing efficient strategies to successfully tackle the scale-up of the production process. In this study,viable scaling-up of the production process was implemented,and relevant aspects affecting the enzyme synthesis, such as the mineral composition of the culture medium, the aeration and the agitation have been evaluated.A strategy combining the modification of the culture medium and the aeration degree was also approached by adding perfluorocarbons, compounds which improve the availability of oxygen in the culture medium. An opposite response of biomass and lipolytic activity to the aeration conditions was found between scales (about 600 U L(-1) at high aeration levels in flask vs. 150 U L(-1) at high aeration rates in reactor), which further demonstrates the important role of the hydrodynamic conditions on the suitable development of the biological process. In all cases, the cultures were kinetically characterized and the Luedeking and Piret model turned out to be a valuable tool to conclude that the produced lipolytic enzyme is a growth-associated metabolite, no matter the medium and the scale.

A process for extracellular thermostable lipase production by a novel Bacillus thermoamylovorans strain.

A lipolytic enzyme-producing thermophilic microorganism, recently isolated from a hot spring in Galicia (North Western Spain), has been investigated. First, the strain was genetically identified and tentatively named Bacillus thermoamylovorans CH6B. It produced significant levels (around 450 U/L) of extracellular lipolytic activity in shake flask cultures, and the most suitable conditions for this biological process were found at temperatures between 50 and 55 °C, and an initial pH value around 7.0. Next, a preliminary scaling up of the process was carried out in a 5-L stirred tank bioreactor, and it was concluded that operation at agitation and aeration rates of 300 rpm and 0.33 vvm, respectively, were advisable. In both type of cultures, the results were successfully fitted to logistic equations, and the relationship between lipase production and cell growth was investigated. Furthermore, some relevant properties of the crude lipolytic enzyme extracts were assessed. The crude biocatalyst preferentially hydrolysed p-nitrophenyl esters of medium and long-chain fatty acids. Thermal stability in aqueous solution of the produced enzyme was also promising, and the deactivation profiles were fitted to a series-type deactivation model.

Role of laccase and low molecular weight metabolites from Trametes versicolor in dye decolorization.

The studies regarding decolorization of dyes by laccase may not only inform about the possible application of this enzyme for environmental purposes, but also may provide important information about its reaction mechanism and the influence of several factors that could be involved. In this paper, decolorization of crystal violet and phenol red was carried out with different fractions of extracellular liquids from Trametes versicolor cultures, in order to describe the role of laccase in this reaction. Moreover, the possible role of the low molecular weight metabolites (LMWMs) also produced by the fungus was evaluated. The results confirm the existence of a nonenzymatic decolorization factor, since the nonprotein fraction of the extracellular liquids from cultures of T. versicolor has shown decolorization capability. Several experiments were performed in order to identify the main compounds related to this ability, which are probably low molecular weight peroxide compounds.

GO-TiO2 as a Highly Performant Photocatalyst Maximized by Proper Parameters Selection.

The synthesis and characterization of novel graphene oxide coupled to TiO2 (GO-TiO2) was carried out in order to better understand the performance of this photocatalyst, when compared to well-known TiO2 (P25) from Degussa. Thus, its physical-chemical characterization (FTIR, XRD, N2 isotherms and electrochemical measurements) describes high porosity, suitable charge and high electron mobility, which enhance pollutant degradation. In addition, the importance of the reactor set up was highlighted, testing the effect of both the irradiated area and distance between lamp and bulb solution. Under optimal conditions, the model drug methylthioninium chloride (MC) was degraded and several parameters were assessed, such as the water matrix and the catalyst reutilization, a possibility given the addition of H2O2. The results in terms of energy consumption compete with those attained for the treatment of this model pollutant, opening a path for further research.

An approach towards Zero-Waste wastewater technology: Fluoxetine adsorption on biochar and removal by the sulfate radical.

The appearance of pharmaceuticals in the aquatic environments has become a serious problem because of their hazardous effect on the biota. Therefore, great efforts are focussed in the removal to these pollutants from wastewaters. In this study, an innovative technology based on the principles of Zero-Waste for the management of wastewater streams is presented. Hence, adsorption of fluoxetine (FLX), selected as a model pollutant, in an eco-friendly adsorbent, biochar, was followed by an in situ removal of the pharmaceutical in the solid matrix by the action of sulfate radicals. Initially, an in-depth characterisation of the adsorbent and the adsorption process was carried out. The pseudo-second order kinetic and Freundlich isotherm described well the process, and the electrostatic attractions were revealed as the primary adsorption mechanism. Later, the removal of the FLX was studied by the sulfate radicals, in the presence of activators (Fe2+ and citric acid), in liquid and onto the biochar medium. It was concluded that in order to enhance the pollutant removal it is necessary the presence of both activators in liquid media. However, in in situ removal onto biochar, it was not necessary the Fe2+ presence and only the addition of complexing agents was required as a result of biochar's mineral content. Finally, the applicability of the proposed approach was studied in fixed-bed column assays where the adsorption and the removal of the pollutant were efficiently accomplished. This fact confirms the suitability of the developed process as a viable alternative in the treatment of wastewaters.

Electro-reversible adsorption as a versatile tool for the removal of diclofenac from wastewater.

In this study, adsorption of a non-steroidal anti-inflammatory drug such as Diclofenac (DCF) on a commercial carbonaceous aerogel honeycomb monolith (NANOLIT®-NQ40) was ascertained. Based on, the overall design of an adsorption treatment should include a feasible regeneration process for the spent adsorbent. In this work, the adsorption/desorption process was ameliorated by coupling of electrochemical technology (anodic/cathodic polarisation). It was determined that the anodic polarisation enhanced the DCF removal and it was related with the applied voltage and the disposition of the electrodes into the bulk solution. Anodic polarisation at optimal conditions (voltage 0.9 V, electrodes gap 2.5 cm and electrolyte concentration higher than 1 mM) provoked an enhancement (around 30%) in the DCF adsorption rate. The spent aerogel regeneration method for the adsorbed or electro-adsorbed DCF was investigated and cathodic polarisation proved to be a viable regeneration alternative attaining the total regeneration of aerogel. The electro-desorption mechanism seemed to be linked to the generation of repulsive intermolecular forces in the aerogel surface. Finally, the sequential electro-adsorption/electro-desorption process was performed in successive cycles. The results confirmed the feasibility of this strategy, maintaining the efficiency with no structural changes in the monolith after several cycles being the electro-reversible adsorption of pollutants on aerogel a promising technology for the removal of pharmaceuticals from wastewater.

Thermostable lipolytic enzymes production in batch and continuous cultures of Thermus thermophilus HB27.

Several studies in laboratory-scale bioreactors are undertaken in order to verify the beneficial effect of thermal spring water in the culture medium of Thermus thermophilus HB27. Two bioreactor configurations, stirred tank and airlift, are investigated to determine the most suitable one to develop a continuous process. Water mineral composition affects the lipolytic enzyme secretion and growth of T. thermophilus HB27 in both bioreactor configurations. Furthermore, the lipolytic activity is strongly enhanced when stirred tank bioreactor is used. Moreover, operation in a stirred tank at an agitation rate of 650 rpm leads to the highest total lipolytic activity (intra- and extracellular enzyme) around 280 U/L after 32 h. Continuous cultures operating in the optimised conditions determined in batch cultures are carried out. It is noticeable that the stirred tank bioreactor was able to operate in a continuous flow mode without operational problems. In addition, the lipolytic activity obtained is about 2-fold higher than that attained in batch cultures.

Current advances and trends in electro-Fenton process using heterogeneous catalysts - A review.

Over the last decades, advanced oxidation processes have often been used alone, or combined with other techniques, for remediation of ground and surface water pollutants. The application of heterogeneous catalysis to electrochemical advanced oxidation processes is especially useful due to its efficiency and environmental safety. Among those processes, electro-Fenton stands out as the one in which heterogeneous catalysis has been broadly applied. Thus, this review has introduced an up-to-date collation of the current knowledge of the heterogeneous electro-Fenton process, highlighting recent advances in the use of different catalysts such as iron minerals (pyrite, magnetite or goethite), prepared catalysts by the load of metals in inorganic and organic materials, nanoparticles, and the inclusion of catalysts on the cathode. The effects of physical-chemical parameters as well as the mechanisms involved are critically assessed. Finally, although the utilization of this process to remediation of wastewater overwhelmingly outnumber other utilities, several applications have been described in the context of regeneration of adsorbent or the remediation of soils as clear examples of the feasibility of the electro-Fenton process to solve different environmental problems.

Kaolinite adsorption-regeneration system for dyestuff treatment by Fenton based processes.

The regeneration and reuse of adsorbents is a subject of interest nowadays in order to reduce the pollution and the wastes generated in the adsorption wastewater treatment. In this work, the regeneration of the spent kaolinite by different advanced oxidation processes (Fenton, electro-Fenton and electrokinetic-Fenton) was evaluated. Initially, it was confirmed the ability of a low cost clayey material, kaolinite, for the adsorption of model dye such as Rhodamine B showing Freundlich isotherm fitting. Then, the regeneration and consequent degradation of the pollutant in the adsorbent by Fenton based processes was carried out. The role of different parameters affecting the regeneration process (H2O2:Fe2+ ratio, liquid:solid ratio) were evaluated. Working at 100:1 H2O2:Fe2+ ratio and 30min near complete dye removal (around 97%) from kaolinite was obtained by Fenton treatment. After that, a two-stage treatment for adsorption-regeneration was evaluated during five treatment cycles demonstrating its viability for regeneration of the adsorbent through dye degradation. Based on the successful application of Fenton technique, the improvement of the treatment by electro-Fenton and electrokinetic-Fenton were studied for different solid:liquid ratios achieving satisfactory regeneration values.

Scaling-up and ionic liquid-based extraction of pectinases from Aspergillus flavipes cultures.

The viability of the scaling-up of pectinases production by Aspergillus flavipes at 5L-bioreactor scale has been demonstrated by keeping constant the power input, and a drastic increase in the endo- and exopectinolytic enzyme production was recorded (7- and 40-fold, respectively). The main process variables were modelled by means of logistic and Gompertz equations. In order to overcome the limitations of the conventional downstream strategies, a novel extraction strategy was proposed on the basis of the adequate salting-out potential of two biocompatible cholinium-based ionic liquids (N1112OHCl and N1112OHH2PO4) in aqueous solutions of Tergitol, reaching more than 90% of extraction.

Immobilization of laccase of Pycnoporus sanguineus CS43.

Laccase from Pycnoporus sanguineus CS43 was successfully immobilized onto Immobead-150 and Eupergit-C by covalent binding and by entrapment in LentiKats. The highest immobilization was onto Immobead-150 (97.1±1.2%) compared to the other supports, LentiKats (89±1.1%) and Eupergit-C (83.2±1.4%). All three immobilized enzyme systems showed increased thermostability and better mechanical properties than free laccase. Moreover, after 5 cycles of reuse of these systems, 90% of initial laccase activity was retained. Immobead-150 and LentiKats systems exhibited the highest efficiencies in removal of m-cresol under the combined actions of biodegradation and adsorption, while laccase entrapped in LentiKats showed a high ability for degradation of m-cresol within 24h. In addition, the typical Michaelis-Menten enzymatic model effectively described the kinetic profile of m-cresol degradation by the enzyme entrapped in LentiKats. Based on the results obtained in the present study, it can be established that the immobilized biocatalysts developed here possess significant potential for wastewater treatment.

Elimination of radiocontrast agent diatrizoic acid by photo-Fenton process and enhanced treatment by coupling with electro-Fenton process.

The removal of radiocontrast agent diatrizoic acid (DIA) from water was performed using photo-Fenton (PF) process. First, the effect of H2O2 dosage on mineralization efficiency was determined using ultraviolet (UV) irradiation. The system reached a maximum mineralization degree of 60 % total organic carbon (TOC) removal at 4 h with 20 mM initial H2O2 concentration while further concentration values led to a decrease in TOC abatement efficiency. Then, the effect of different concentrations of Fenton's reagents was studied for homogeneous Fenton process. Obtained results revealed that 0.25 mM Fe(3+) and 20 mM H2O2 were the best conditions, achieving 80 % TOC removal efficiency at 4 h treatment. Furthermore, heterogeneous PF treatment was developed using iron-activated carbon as catalyst. It was demonstrated that this catalyst is a promising option, reaching 67 % of TOC removal within 4 h treatment without formation of iron leachate in the medium. In addition, two strategies of enhancement for process efficiency are proposed: coupling of PF with electro-Fenton (EF) process in two ways: photoelectro-Fenton (PEF) or PF followed by EF (PF-EF) treatments, achieving in both cases the complete mineralization of DIA solution within only 2 h. Finally, the Microtox tests revealed the formation of more toxic compounds than the initial DIA during PF process, while, it was possible to reach total mineralization by both proposed alternatives (PEF or PF-EF) and thus to remove the toxicity of DIA solution.

Electrokinetic-Fenton technology for the remediation of hydrocarbons historically polluted sites.

The feasibility of the electrokinetic-Fenton technology coupled with surfactants in the treatment of real historically hydrocarbons polluted soils has been studied. The characterisation of these soils from Spain and Romania was performed and identified as diesel and diesel-motor oil spillages, respectively. Moreover, the ageing of the spillages produced by the soil contamination was estimated showing the historical pollution of the sites (around 11 and 20 years for Romanian and Spanish soils, respectively). An ex-situ electrochemical treatment was performed to evaluate the adequacy of surfactants for the degradation of the hydrocarbons present in the soils. It was found an enhancement in the solubilisation and removal of TPHs with percentages increasing from 25.7 to 81.8% by the presence of Tween 80 for Spanish soil and from 15.1% to 71.6% for Triton X100 in Romanian soil. Therefore, the viability of coupling enhanced electrokinetic and Fenton remediation was evaluated through a simulated in-situ treatment at laboratory scale. The results demonstrated that the addition of the selected surfactants improved the solubilisation of the hydrocarbons and influenced the electroosmotic flow with a slight decrease. The efficiency of the treatment increased for both considered soil samples and a significant degradation level of the hydrocarbons compounds was observed. Buffering of pH coupled with the addition of a complexing agent showed to be important in the treatment process, facilitating the conditions for the degradation reactions that take place into the soil matrix. The results demonstrated the effectiveness of the selected techniques for remediation of the investigated soils.