Effect of various cyclodextrins on photodegradation of a hydrophobic herbicide in aqueous suspensions of different soil colloidal components

Hydroxypropyl-β-cyclodextrin improves the removal of polycyclic aromatic hydrocarbons by aerobic granular sludge

Polycyclic aromatic hydrocarbons (PAHs) as polar organic pollutants, their potential harm to the environment has caused widespread concern. This study describes a simple method to prepare modified aerobic granular sludge (AGS) by hydroxypropyl-β-cyclodextrin (HP-β-CD). Using HP-β-CD modified AGS as the adsorbent, the removal of specific PAHs: Fluoranthene (Fla) reached 95% comparing to 80% of the unmodified AGS. The removal of Fla was related to initial concentration, temperature and ion concentration (Na⁺, Mg²⁺). The removal efficiency of Fla reached 96.27%, 94.26% and 93.69%, when initial concentration of Fla was 10, 15 and 20 μmol/L. At temperatures of 15°C, 30°C and 45°C, the removal efficiency of Fla (15 μmol/L) gradually improved from 87.20% to 94.84% and 95.73%. The presence of Na⁺ and Mg²⁺ ions led to the deterioration of PAHs removal. With the increase of Na⁺ and Mg²⁺ concentrations, the removal efficiency of modified AGS on PAHs decreased by 3.9% and 6.5%, respectively. These findings indicate the potential application of cyclodextrins as the active sites of a complex modified polymer network for PAHs wastewater treatment.

Extraction of nonylphenol, pyrene and phenanthrene from sewage sludge and composted biosolids by cyclodextrins and rhamnolipids

Sewage sludge generated by Waste Water Treatment Plants (WWTPs) are frequently used as organic amendments in agriculture, but they contain pollutants such as Potentially Toxic Elements (PTEs) and organic contaminants which contaminate the agricultural soils. The study presented here is part of a larger study based on the application of environmentally friendly chemical and biological techniques to decrease the content of organic pollutants in sewage sludge before agricultural application. The aim of this study was to evaluate the performance of biodegradable extractants, such as some cyclodextrins (CDs), β-cyclodextrin (BCD), hydroxypropyl-β-cyclodextrin (HPBCD) and randomly methylated-β-cyclodextrin (RAMEB), and a biosurfactant (rhamnolipid, RL) on the removal and availability of pyrene (PYR), phenanthrene (PHE) and nonylphenol (NP) from several biosolids samples in order to improve their subsequent biodegradation. The influence of pollutants retention time on biosolids was studied, as well as the effect of each extractant on PTEs solubilization. Results obtained were pollutant and extractant-dependent. BCD extracted similar amounts of pollutants compared to water, whereas HPBCD and RAMEB actually increased the availability of the three pollutants in most of the samples and aging times. RL seems to be the best election for Polycyclic Aromatic Hydrocarbons (PAHs) extraction from biosolids, with percentages of extraction multiplied by more than 80 and 40 times for PHE and PYR, respectively, relative to water extraction. The extraction enhancement was the highest for NP, the most hydrophobic pollutant, reaching more than 500-fold higher with HPBCD and RAMEB. PTEs extractability was not affected by the different CDs used, but RL caused an increment in their soluble content what could endanger a subsequent biodegradation of the organic pollutants.

Advanced technologies for the remediation of pesticide-contaminated soils

The occurrence of pesticides in soil has become a highly significant environmental problem, which has been increased by the vast use of pesticides worldwide and the absence of remediation technologies that have been tested at full-scale. The aim of this review is to give an overview on technologies really studied and/or developed during the last years for remediation of soils contaminated by pesticides. Depending on the nature of the decontamination process, these techniques have been included into three categories: containment-immobilization, separation or destruction. The review includes some considerations about the status of emerging technologies as well as their advantages, limitations, and pesticides treated. In most cases, emerging technologies, such as those based on oxidation-reduction or bioremediation, may be incorporated into existing technologies to improve their performance or overcome limitations. Research and development actions are still needed for emerging technologies to bring them for full-scale implementation.

The effect of cyclodextrin complexation on the solubility and photostability of nerolidol as pure compound and as main constituent of cabreuva essential oil

Nerolidol (Ner), a major component of many plant essential oils, is known for its various biological properties. However, the low solubility of Ner in water and its susceptibility to degradation limit its application. The aim of our study was to improve the solubility and photostability of Ner through its encapsulation in different cyclodextrins (CDs). The formation constants of cis-, trans-Ner and their commercial mixture with various CDs (α-CD, β-CD, γ-CD, HP-β-CD, RAMEB, CRYSMEB and SBE-β-CD) were determined by phase solubility studies and confirmed by the spectral displacement UV-visible method. The solubility of cabreuva essential oil (EO) rich in trans-Ner was also evaluated by total organic carbon (TOC) analysis. The encapsulation efficiency (EE %) of Ner in HP-β-CD solid complexes was assessed by HPLC. The structural characterization of CD/trans-Ner inclusion complex was then conducted by NMR spectroscopy followed by molecular modelling studies. The effect of encapsulation on the Ner photostability was also carried out over time under UVB irradiation. A_L-type phase-solubility diagrams were obtained, suggesting the formation of 1:1 CD/Ner inclusion complexes. The solubility of Ner was enhanced by approximately 70-fold in the presence of 10 mM HP-β-CD. Moreover, high EE % values were obtained for 5:1 and 10:1 HP-β-CD:Ner molar ratios. NMR and molecular modelling studies revealed the most stable structure for trans-Ner inside the CD cavity with the OH group oriented towards the wider rim of the CD. Finally, CD encapsulation of Ner as pure compound or as main component of the cabreuva EO, protected it from degradation. This effect was more pronounced as the concentration of CD increased. These findings suggested that CDs are promising encapsulating carriers for Ner by enhancing its solubility and stability and thereby its application in food industry.

Bioremediation of diuron contaminated soils by a novel degrading microbial consortium

Diuron is a biologically active pollutant present in soil, water and sediments. It is persistent in soil, water and groundwater and slightly toxic to mammals and birds as well as moderately toxic to aquatic invertebrates. Its principal product of biodegradation, 3,4-dichloroaniline, exhibits a higher toxicity than diuron and is also persistent in the environment. On this basis, the objective of the study was to determine the potential capacity of a proposed novel diuron-degrading microbial consortium (DMC) for achieving not only diuron degradation, but its mineralisation both in solution as well as in soils with different properties. The consortium was tested in a soil solution where diuron was the only carbon source, and more than 98.8% of the diuron initially added was mineralised after only a few days. The consortium was composed of three diuron-degrading strains, Arthrobacter sulfonivorans, Variovorax soli and Advenella sp. JRO, the latter had been isolated in our laboratory from a highly contaminated industrial site. This work shows for the first time the potential capacity of a member of the genus Advenella to remediate pesticide-contaminated soils. However, neither of the three strains separately achieved mineralisation (ring-¹⁴C) of diuron in a mineral medium (MSM) with a trace nutrient solution (NS); combined in pairs, they mineralised 40% of diuron in solution, but the most relevant result was obtained in the presence of the three-member consortium, where complete diuron mineralisation was achieved after only a few days. In the presence of the investigated soils in suspension, the capacity of the consortium to mineralise diuron was evaluated, achieving mineralisation of a wide range of herbicides from 22.9 to 69.0%.

Natural attenuation of fluorene and pyrene in contaminated soils and assisted with hydroxypropyl-β-cyclodextrin. Effect of co-contamination

The objectives of this study were to investigate the mutual effect of the PAHs fluorene and pyrene on their respective biodegradation and dissipation processes in an agricultural soil, and to determine the effect of hydroxypropyl-β-cyclodextrin (HPBCD), used to increase the bioavailability of PAHs, on such processes. Fluorene dissipation was primarily due to abiotic processes, although a small contribution from biodegradation was also observed. Therefore, fluorene dissipation did not increase with HPBCD and its presence did not significantly alter the dehydrogenase activity. In contrast to fluorene, pyrene dissipation depended primarily on biotic factors, with endogenous soil microorganisms capable of degrading pyrene, with large increases in dehydrogenase activity. HPBCD increased biodegradation rate of pyrene. The co-contamination of soil with both PAHs did not affect fluorene evolution, but significantly inhibited pyrene biodegradation. The different abilities of soil bacterial consortia to catabolize these PAHs are discussed. Additionally, the possibility that the abiotic loss of fluorene through volatilization had a significant effect on the microbial community biodegradation of both fluorene and pyrene is examined.

γ-Cyclodextrin

γ-Cyclodextrin (γCD) is a cyclic oligosaccharide formed by bacterial digestion of starch and used as solubilizing agent and stabilizer in a variety of pharmaceutical and food products. γCD is a large (molecular weight 1297Da) hydrophilic molecule that does not readily permeate biological membranes and is rapidly digested by bacteria in the gastrointestinal tract. In humans γCD is metabolized by α-amylase that is found in, for example, saliva, bile fluid and tears. Thus, bioavailability of γCD is negligible. Also, γCD is readily excreted unchanged in the urine after parenteral administration. Like other cyclodextrins, γCD can form water-soluble inclusion complexes with many poorly-soluble compounds. In comparison with the natural αCD and βCD, γCD has the largest hydrophobic cavity, highest water solubility and the most favorable toxicological profile. The focus of this review is production, physiochemical properties, pharmacokinetics, toxicity and applications of γCD and its derivatives. Also, the aggregation behavior of γCD in aqueous media is discussed.

Effect of contact time and the use of hydroxypropyl-β-cyclodextrin in the removal of fluorene and fluoranthene from contaminated soils

Sorption-desorption experiments of fluorene (FLU) and fluoranthene (FLT) in soils were carried out and correlated to their removal from aged contaminated soils using aqueous solutions in the absence and in the presence of hydroxypropyl-β-cyclodextrin (HPBCD) as the extraction agent. FLU became more resistant to extraction in aged contaminated soils due to its initial adsorption onto the mineral and amorphous soil organic matter (SOM) domains, sites of lower binding energy from which, due to its small size, it could spread towards the condensed SOM as the contact time increased. Therefore, FLU will not be easily desorbed from aged contaminated soils due to physical entrapment mechanisms, even when using HPBCD as extractant, presenting FLU low risks to the environment. On the contrary, FLT was extracted from aged soils in the presence of HPBCD in solutions to a much greater extent than in its absence. Due to its more hydrophobic character FLT sorption in soils was relatively quicker, remaining more or less fixed on hydrophobic sites of the organic matter (OM) with different energies, and therefore the amount of FLT extracted was almost constant for different ageing times. During extraction experiments, the influence of the OM quality of the soils was also highlighted because an inverse proportionality between OM content of soil and extractability of sorbed FLT was observed. It was concluded that soils with lower OM content that had more diagenetically processed OM could block the extraction of FLT more effectively than soils with higher OM content that are less humified. This indicates the need to use not only adsorption-desorption data in contaminant fate and transport models, but also extraction studies in aged contaminated soils and other complementary analytical approaches when assessing soil contamination-related risks.

Enhanced mineralization of diuron using a cyclodextrin-based bioremediation technology

The phenylurea herbicide diuron [N-(3,4-dichlorophenyl)-N,N-dimethylurea] is widely used in a broad range of herbicide formulations and, consequently, it is frequently detected as a major soil and water contaminant in areas where there is extensive use. Diuron has the unfortunate combination of being strongly adsorbed by soil organic matter particles and, hence, slowly degraded in the environment due to its reduced bioavailability. N-Phenylurea herbicides seem to be biodegraded in soil, but it must be kept in mind that this biotic or abiotic degradation could lead to accumulation of very toxic derived compounds, such as 3,4-dichloroaniline. Research was conducted to find procedures that might result in an increase in the bioavailability of diuron in contaminated soils, through solubility enhancement. For this purpose a double system composed of hydroxypropyl-β-cyclodextrin (HPBCD), which is capable of forming inclusion complexes in solution, and a two-member bacterial consortium formed by the diuron-degrading Arthrobacter sulfonivorans (Arthrobacter sp. N2) and the linuron-degrading Variovorax soli (Variovorax sp. SRS16) was used. This consortium can achieve a complete biodegradation of diuron to CO2 with regard to that observed in the absence of the CD solution, where only a 45% biodegradation was observed. The cyclodextrin-based bioremediation technology here described shows for the first time an almost complete mineralization of diuron in a soil system, in contrast to previous incomplete mineralization based on single or consortium bacterial degradation.

Cyclodextrin inclusion complex to improve physicochemical properties of herbicide bentazon: exploring better formulations

The knowledge of the host-guest complexes using cyclodextrins (CDs) has prompted an increase in the development of new formulations. The capacity of these organic host structures of including guest within their hydrophobic cavities, improves physicochemical properties of the guest. In the case of pesticides, several inclusion complexes with cyclodextrins have been reported. However, in order to explore rationally new pesticide formulations, it is essential to know the effect of cyclodextrins on the properties of guest molecules. In this study, the inclusion complexes of bentazon (Btz) with native βCD and two derivatives, 2-hydroxypropyl-β-cyclodextrin (HPCD) and sulfobutylether-β-cyclodextrin (SBECD), were prepared by two methods: kneading and freeze-drying, and their characterization was investigated with different analytical techniques including Fourier transform infrared spectroscopy (FT-IR), differential thermal analysis (DTA), X-ray diffractometry (XRD) and differential pulse voltammetry (DPV). All these approaches indicate that Btz forms inclusion complexes with CDs in solution and in solid state, with a stoichiometry of 1:1, although some of them are obtained in mixtures with free Btz. The calculated association constant of the Btz/HPCD complex by DPV was 244±19 M(-1) being an intermediate value compared with those obtained with βCD and SBECD. The use of CDs significantly increases Btz photostability, and depending on the CDs, decreases the surface tension. The results indicated that bentazon forms inclusion complexes with CDs showing improved physicochemical properties compared to free bentazon indicating that CDs may serve as excipient in herbicide formulations.

Organo/LDH nanocomposite as an adsorbent of polycyclic aromatic hydrocarbons in water and soil-water systems

Polycyclic aromatic hydrocarbons (PAHs) are considered as priority pollutants because of their high risk to human health. In this paper, we addressed the issue of using hydrotalcite-based nanocomposites as adsorbents of six low molecular weight PAHs (acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene) to reduce their negative effects on the environment. A nanocomposite (HT-DDS) was prepared by intercalating the organic anion dodecylsulfate (DDS) in a Mg-Al hydrotalcite (HT), and then characterized using several analytical techniques. A Mediterranean soil was selected for being a high-risk scenario of groundwater contamination by leaching of pollutants. The nanocomposite displayed enhanced affinity for the PAHs in water as compared to carbonate-hydrotalcite (HTCO(3)) and its calcined product (HT500), and showed a high irreversibility of the adsorption process (hysteresis coefficient, H<0.15). The results revealed an increase of the pollutants retention in the soil by the addition of the nanocomposite that depended on the nanocomposite application rate and also on the hydrophobicity of each PAH. Accordingly, the use of HT-DDS as an amendment or barrier in contaminated soil is proposed for reducing the mobility of PAHs and, consequently, the adverse effect derived from rapid transport losses of the pollutants to the adjoining environmental compartments.

Photostabilization of the herbicide norflurazon microencapsulated with ethylcellulose in the soil-water system

Ethylcellulose-microencapsulated formulations (ECFs) of norflurazon have been shown to reduce leaching, maintaining a threshold concentration in the topsoil than the commercial formulation (CF). Since photodegradation contributes to field dissipation of norflurazon, the objective of the present work was to study if such formulations can also protect from its photodescomposition. For this purpose, aqueous solutions of CF and ECFs, containing the most important soil components (goethite, humic and fulvic acids and montmorillonite) were tested. To get a more realistic approach, studies in soil were also performed. The results were well explained by a simple first order model. DT(50) value was 3h for CF under irradiation, which was considerably lower than those corresponding to the systems where ECF was used (35 h for ECF; 260 h for ECF-goethite; 53 h for ECF-humic acids; 33 h for ECF-montmorillonite; and 28 h for ECF-fulvic acids). ECF protected against photodegradation in both aqueous solution and soil due to the gradual release of the herbicide, which reduced the herbicide available to be photodegraded. These lab-scale findings proved that ECF could reduce the herbicide dosage, minimizing its photolysis, which would be especially advantageous during the first hours after foliar and soil application.

Degradation of glyphosate in soil photocatalyzed by Fe3O4/SiO2/TiO2 under solar light

In this study, Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst was prepared via a sol-gel method, and Fe(3)O(4) particles were used as the core of the colloid. Diffraction peaks of Fe(3)O(4) crystals are not found by XRD characterization, indicating that Fe(3)O(4) particles are well encapsulated by SiO(2). FTIR characterization shows that diffraction peaks of Ti-O-Si chemical bonds become obvious when the Fe(3)O(4) loading is more than 0.5%. SEM characterization indicates that agglomeration occurs in the Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst, whereas photocatalysts modified by Fe(3)O(4)/SiO(2) present excellent visible light absorption performance and photocatalytic activity, especially when the Fe(3)O(4) loading is 0.5%. Photocatalytic degradation of glyphosate in soil by these photocatalysts under solar irradiation was investigated. Results show that 0.5% Fe(3)O(4)/SiO(2)/TiO(2) has the best photocatalytic activity. The best moisture content of soil is 30%~50%. Degradation efficiency of glyphosate reaches 89% in 2 h when the dosage of photocatalyst is 0.4 g/100 g (soil), and it increased slowly when more photocatalyst was used. Soil thickness is a very important factor for the photocatalytic rate. The thinner the soil is, the better the glyphosate degradation is. Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm(2) or above 10 mW/cm(2), but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm(2) to 10 mW/cm(2).

Direct and indirect photolysis of cyhalofop in aqueous systems

The photodegradation of the aryloxyphenoxy propionic herbicide cyhalofop-butyl (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]butylpropanoate (CyB), and of its primary metabolite (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid (CyA) was studied in water at different irradiation wavelengths. The sunlight irradiation was investigated also in the presence of humic acid (HA), Fe oxide, titanium dioxide (TiO2) and zinc oxide (ZnO) as photocatalysts. CyB and CyA were rapidly degraded by UV irradiation. CyB afforded the butyl ester of 2-[3-(4-cyano-2-fluorophenyl)-4-hydroxy-phenoxy]propanoic acid (CyI), a metabolite arising from a photo-Fries rearrangement. Instead, CyA yielded (R)-2-4-(4-carboxyl-2-fluorophenoxy)phenoxypropanoic acid (CyD), a dicarboxylic acid arising from the photo-hydrolysis of cyano group via amide. CyB was stable in simulated sunlight also in the presence of the catalysts tested. The irradiation of a CyA solution, in the presence of HA or Fe oxide, with simulated sunlight did not produce any significant degradation. In the same experimental conditions, CyA was totally mineralized in the presence of TiO2 and ZnO.

Solubility, spectroscopic properties and photostability of Rhein/cyclodextrin inclusion complex

The host-guest interaction between Rhein (Rh)--an anthraquinonic drug characterized by low water solubility and recently considered for its potential antidiabetic and antitumoral activities other than for the well-established anti-inflammatory properties--with cyclodextrins (CDs) was investigated using phase-solubility diagrams. The typical A(L) phase-solubility profiles suggest the formation of the 1:1 inclusion complexes between Rh and the two CDs investigated, namely beta-cyclodextrin and 2-hydroxypropyl-beta-cyclodextrin and the resulting constant values of complex formation, K(c), were estimated. Due to the higher K(c) value, complex of Rhein with 2-hydroxypropyl-beta-cyclodextrin was chosen for further investigation. Characterization in solution of 2-hydroxypropyl-beta-cyclodextrin/Rhein complex was achieved both by fluorescence and visible spectroscopic techniques. These results confirm the formation of inclusion complexes in solution and the 1:1 stoichiometry of the binary system. With respect to Rhein aqueous solution behavior, the inclusion complex appears to be able: (i) to enhance Rhein solubility; (ii) to control its neutral/anionic equilibrium; (iii) to affect both its electronic absorption and fluorescence spectra. Finally, the photostability of Rhein in the presence of cyclodextrins was evaluated.

Cyclodextrins – Fields of Application. Part I

This review is dedicated to different fields of use of cyclodextrins, a family of three cyclic natural oligosaccharides and their derivatives. The first part of the review gives a brief description of the main and the most recent developed applications of cyclodextrins in food, cosmetic industry, environmental protection technologies and agriculture. Different products based on inclusion complexes with cyclodextrins and technologies with different use of cyclodextrins and inclusion complexes are described.