Alginate-Bentonite-Based Hydrogels Designed to Obtain Controlled-Release Formulations of Dodecyl Acetate.

Dodecyl acetate (DDA), a volatile compound present in insect sex pheromones, was incorporated into alginate-based granules to obtain controlled-release formulations (CRFs). In this research, not only was the effect of adding bentonite to the basic alginate-hydrogel formulation studied, but also that of the encapsulation efficiency on the release rate of DDA in laboratory and field experiments. DDA encapsulation efficiency increased as the alginate/bentonite ratio increased. From the preliminary volatilization experiments, a linear relationship was found between the DDA release percentage and the amount of bentonite present in the alginate CRFs. Laboratory kinetic volatilization experiments showed that the selected alginate-bentonite formulation (DDAB75A10) exhibited a prolonged DDA release profile. The value of the diffusional exponent obtained from the Ritger and Peppas model (n = 0.818) indicated that the release process follows a non-Fickian or anomalous transport mechanism. Field volatilization experiments showed a steady release of DDA over time from the alginate-based hydrogels tested. This result, together with those obtained from the laboratory release experiments, allowed the obtainment of a set of parameters to improve the preparation of alginate-based CRFs for the use of volatile biological molecules, such as DDA, in agricultural biological control programs.

Alginate-based hydrogels modified with olive pomace and lignin to removal organic pollutants from aqueous solutions.

In this study, new hybrid biopolymers based on alginate and low cost materials belong lignocellulose group such as lignin and olive pomace were used to removal organic pollutants. The organic carbon content, granule size, average mass, zero charge point, water uptake and swelling of the resulting alginate-based modified adsorbents were measured. The homogeneity, complexity and encapsulation viability of the novel biopolymers were studied by FT-IR, TGA and SEM. As model of emerging contaminants belong to glucocorticoids group prednisolone drug was selected. 3,4-dichloroaniline (3,4-DCA) was chosen as aniline derivate pollutant. The efficiency of the bioadsorbents to removal 3,4-dichloroaniline and prednisolone was performed by kinetic and equilibrium batch adsorption studies. The experimental data was found well correlated to the pseudo-second order kinetic model. The adsorption of 3,4-DCA and prednisolone was mainly affected by the organic carbon content of the bioadsorbent. A higher adsorption capacity was observed for lignin-alginate based bioadsorbents. The removal efficiency was higher than 90% for 3,4-DCA in all prepared bioadsorbents, reached up to 49% for prednisolone using the bioadsorbent with the higher lignin content. These results suggest the promising potential for the prepared eco-friendly bioadsorbents to removal organic pollutants from water, mainly for aniline derivate such as 3,4-DCA.

Degradation studies of quizalofop-p and related compounds in soils using liquid chromatography coupled to low and high resolution mass analyzers.

A comprehensive degradation study of quizalofop-p, quizalofop-p-ethyl, quizalofop-p-tefuryl and propaquizafop in soil samples have been firstly performed using ultra high performance liquid chromatography coupled to Orbitrap mass spectrometry (UHPLC-Orbitrap-MS). Thus, metabolites or degradation products, such as CHHQ (dihydroxychloroquinoxalin), CHQ (6-chloroquinoxalin-2-ol), PPA ((R)-2-(4-hydroxyphenoxy)propionic acid) and 2,3-dihydroxyquinoxaline were also monitored. An extraction procedure based on QuEChERS procedure was used. Acidified water (0.1M hydrochloric acid) and acidified acetonitrile (1% acetic acid, (v/v)) were used as extraction solvents, and magnesium sulfate and sodium chloride were used as salts. Dispersive solid phase extraction with C18 as sorbent, was needed as a clean-up step. Several commercial products (Panarex®, Master-D® and Dixon®) were used to evaluate the degradation of the target compounds into their metabolites. The concentration of the main active substances (quizalofop-p-tefuryl, quizalofop-p-ethyl and propaquizafop) decreased during the degradation studies, whereas the concentration of quizalofop-p increased. Dissipation rates of half-live of quizalofop-p were also evaluated, and it was observed that this compound is easily degraded, obtaining values lower than 1day. Taking into account that quizalofop-p is the R enantiomer of quizalofop, a chiral separation was performed by liquid chromatography coupled to tandem mass spectrometry, concluding that in samples containing quizalofop-p-tefuryl, there was a 15% contribution from the S enantiomer and a 85% contribution from the R enantiomer. Metabolites such as PPA, CHHQ and CHQ were detected in soil samples after 15days of application commercial product at concentrations between the limits of detection (LOD) and the limits of quantification (LOQ). CHQ and CHHQ were detected at concentrations higher than the LOQ in samples after 50 and 80days of application, with their concentration increasing during this time up to 500%.

Preparation and Characterization of Azadirachtin Alginate-Biosorbent Based Formulations: Water Release Kinetics and Photodegradation Study.

The botanical insecticide azadirachtin was incorporated in alginate-based granules to obtain controlled release formulations (CRFs). The basic formulation [sodium alginate (1.47%) - azadirachtin (0.28%) - water] was modified by the addition of biosorbents, obtaining homogeneous hybrid hydrogels with high azadirachtin entrapment efficiency. The effect on azadirachtin release rate caused by the incorporation of biosorbents such as lignin, humic acid, and olive pomace in alginate formulation was studied by immersion of the granules in water under static conditions. The addition of the biosorbents to the basic alginate formulation reduces the rate of release because the lignin-based formulation produces a slower release. Photodegradation experiments showed the potential of the prepared formulations in protecting azadirachtin against simulated sunlight, thus improving its stability. The results showed that formulation prepared with lignin provided extended protection. Therefore, this study provides a new procedure to encapsulate the botanical insecticide azadirachtin, improving its delivery and photostability.

Preparation and characterization of imidacloprid lignin-polyethylene glycol matrices coated with ethylcellulose.

Imidacloprid, a systemic insecticide that has a water solubility of 610 mg L(-1), has been formulated in lignin-polyethylene glycol matrices by a melting process. This formulation was coated in a Wurster type fluidized-bed equipment using ethylcellulose and dibutyl sebacate. Imidacloprid has been entrapped, with an entrapment efficiency higher than 87% in all cases. Thermogravimetric analysis, differential scanning calorimetry, and Fourier transformed infrared spectroscopy studies indicate the stability and compatibility of polymers and imidacloprid. Scanning electron microscopy images show a homogeneous film of ethylcellulose in coated formulations. From T(50) values (the time taken for 50% of the active ingredient to be released into water), the release rate of imidacloprid is controlled by changing the thickness of the coating film and modifying its surface properties by adding a plasticizer. T(50) values, ranging from 3.02 to 168.6 h, allow supplying the appropriate amount of imidacloprid in each specific agronomic practice to increase the efficiency of this bioactive material and minimize the risk of environmental pollution.

Prevention of chloridazon and metribuzin pollution using lignin-based formulations.

The herbicides chloridazon and metribuzin, identified as groundwater pollutants, were incorporated in lignin-based granules with different sizes to obtain controlled release formulations (CRFs) and reduce water pollution risk. Kinetics release tests in water and soil showed that the release rate of both from CRFs diminished in comparison to technical products. A linear correlation was obtained between the time taken for 50% of the active ingredient to be released (T(50)) into water and granule size of the CRFs. Besides, a linear correlation was reached between T(50) values in water and soil. Mobility experiments carried out in calcareous soil show that the use of lignin-based CRFs reduces the presence of both herbicides in the leachate compared to the technical grade products. The set of experiments developed in this research can be useful to design, prepare and evaluate formulations with CR properties which can reduce the pollution derived from the use of herbicides.

Use of ethylcellulose to control chlorsulfuron leaching in a calcareous soil.

Controlled release formulations (CRFs) have been researched to reduce the water-polluting risk derived from the use of conventional formulations of chlorsulfuron. Coated chlorsulfuron granules were produced in a Wuster-type fluidized-bed equipment using two different amounts of ethylcellulose. The highest one was modified by the addition of a plasticizer such as dibutyl sebacate. The encapsulation efficiency and morphological properties of coated granules having been studied, the chlorsulfuron kinetic release in water was studied. In addition, the mobility of chlorsulfuron in a calcareous soil was finally carried out. High encapsulation efficiency was obtained, being nearly 100% in all cases. SEM pictures show a homogeneous film in coated CRFs; thickness oscillates between 23.32 microm for the system prepared with a 10% of ethylcellulose and 32.61 microm for the system prepared with a 20% ethylcellulose plus plasticizer. The rate of chlorsulfuron release from coated CRFs is diminished in all cases in relation to chlorsulfuron commercial formulation, the latter being completely dissolved in <1 h, but it took at least 50 days to release 90% of chlorsulfuron from the formulation coated with a 20% ethylcellulose plus plasticizer. Using a generic equation, the time taken for 50% of the active ingredient to be released into water (t(50)) was calculated. From the analysis of the t(50) values, it can be deduced that the release rate of chlorsulfuron can be mainly controlled by changing the thickness of the coating film, by modifying the surface properties of the coating film, and by adding a plasticizer. Mobility experiments carried out in calcareous soil show that the use of coated CRFs reduces the presence of chlorsulfuron in the leachate compared to commercial formulation.

Controlled release systems to prevent the agro-environmental pollution derived from pesticide use.

Different controlled release formulations (CRFs) of isoproturon, imidacloprid and cyromazine have been studied to contribute to diminish, somehow, the problems related to the application of conventional formulations. The alginate-based CRFs were based on sodium alginate (1.90%), Technical grade (TG) isoproturon or imidacloprid (1.20%), natural bentonite (3.30%), and water (93.6%), and the lignin-based CRF was based on kraft lignin (50.0%) and TG cyromazine (50.0%). The mobility of non-formulated TG pesticides and CRFs were compared by using soil columns. The use of CRFs retard release and reduce the presence of pesticides in the leachate and, moreover, the pesticides stay in the soil longer. Sorption capacity of the soil for pesticides was measured using batch experiments. The results obtained (11.67 mg kg(- 1) for isoproturon, 3.17 mg kg(- 1) for imidacloprid and 0.63 mg kg(-1) for cyromazine) were in agreement with those obtained under dynamic conditions.

Modeling pesticide leaching and dissipation in a mediterranean littoral greenhouse.

The one-dimensional chromatographic flow model PEARL was used to simulate the movement of the insecticide imidacloprid and the fungicide procymidone through a greenhouse soil. The model was parametrized using measured and literature values of soil hydrological parameters. Soil water movement and soil temperature were reasonably well described by the model. The ability of PEARL to simulate the fate of imidacloprid and procymidone following four applications of each compound was evaluated against greenhouse data. Simulated imidacloprid residues in the 0-10 cm layer were in good agreement with measured data. Below 10 cm, the model overestimated imidacloprid remaining following the spray applications, whereas simulated residues following the chemigation applications were in reasonable agreement with measured data. Simulated residues of procymidone in the 0-10 cm layer were in general agreement with measured values. In the 10-20 cm layer, peaks in simulated concentrations occurred later than observed in the greenhouse. Predictions of procymidone residues below 20 cm were poor and underestimated compared to the measured data. For both pesticides, discrepancies between modeled and measured data in the 10-20 cm layer were attributed to the drip irrigation method used in the greenhouse. The model was unable to satisfactorily predict pesticide movement from the soil surface by irrigation water unless the scenario was modified to reflect the localized pattern of water application. Scenario analysis indicated that air boundary layer thickness is a key parameter for readily volatilized pesticides such as procymidone. This is of particular relevance to the greenhouse environment, where the boundary layer thickness may be greater than that in outdoor conditions.

Effects of dissolved organic carbon on phosphate retention on two calcareous soils.

To evaluate the effects of dissolved organic carbon (DOC) on phosphate retention (including both sorption and/or precipitation reactions) on soils, experiments were performed by using two typical calcareous soils from southeastern Spain (Calcic Regosol and Luvic Xerosol) and two different types of DOC: (1) extracts from a commercial peat (DOC-PE) and (2) high-purity tannic acid (DOC-TA). The experiments were carried out from a 0.01 M CaCl2 aqueous medium at 25 degrees C. The results obtained show that the presence of both DOC-PE and DOC-TA, over a concentration range of 15 (DOC-15) to 100 (DOC-100) mg L(-1), produces in all cases a decreasing amount of phosphate retained in the soils studied, the decrease observed being higher when DOC-PE is used as source of DOC. The values of the decrease observed when DOC-PE was added ranged between 19.9% (DOC-15) and 15.6% (DOC-100) for the Calcic Regosol and between 17.3% (DOC-70, DOC-100) and 14.6% (DOC-15) for the Luvic Xerosol. The variation observed when DOC-TA was added ranged between 8.5% (DOC-100) and 0.5% (DOC-35) for the Calcic Regosol and between 7.0% (DOC-100) and 1.0% (DOC-15) for the Luvic Xerosol.

Use of activated bentonites in controlled-release formulations of atrazine.

The herbicide atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) was incorporated in alginate-based granules to obtain controlled-release (CR) properties. The basic formulation [sodium alginate (1.40%)-atrazine (0.60%)-water] was modified by the addition of sorbents. The effect on atrazine release rate caused by the incorporation of acid-treated bentonite (0.5 and 2.5 M H2SO4) in alginate formulation was studied by immersion of the granules in water under static conditions. The water uptake, sorption capacity of the sorbent, permeability, and time taken for 50% of the active ingredient to be released into water, t50, were calculated for the comparison of the preparations. t50 values were longer for those formulations containing acid-treated bentonite (36.78 and 29.01 days for 0.5 and 2.5 M H2SO4 treatments, respectively) than for the preparation without bentonite (9.69 days). On the basis of a parameter of an empirical equation used to fit the herbicide release data, it appears that the release of atrazine from the various formulations into water is controlled by diffusion mechanism. The sorption capacity of the sorbents and the permeability of the formulations (ranging from 4.99 to 20.83 mg day(-1) mm(-1)) were the most important factors affecting herbicide release.