E. González-Pradas

Lignin-based formulations to prevent pesticides pollution.

The pesticides isoproturon, imidacloprid and cyromazine, identified as groundwater pollutants, were incorporated in lignin-based formulations to obtain controlled release (CR) properties. The formulations were prepared by mixing the pesticide with a commercially available pine kraft lignin under melting conditions. A high efficiency of the preparations was therefore reached; it oscillated between 93.36% and 98.20% for the cyromazine and the isoproturon formulations. Kinetic-release experiments carried out in water showed that the release rate of isoproturon, imidacloprid and cyromazine from CR granules diminished in all cases in relation to the technical products. From the analysis of the time taken for 50% of the active ingredient to be released into water (T(50)), it can be deduced that the release rates were much higher in cyromazine CR formulations than in those prepared with isoproturon. However, imidacloprid showed an intermediate release rate. The obtained linear regression between T(50) values and granule size can be suitable to select the most appropriate formulation to avoid the isoproturon, imidacloprid and ciromazine tendency to leach.

Alginate and lignin-based formulations to control pesticides leaching in a calcareous soil

Important risk of groundwater pollution has been observed as a result of rapid leaching of highly soluble pesticides when used in agronomic practices as conventional formulations. This risk can be minimized through the application of the pesticide at a set rate using controlled release formulations (CRFs). In this research, CRFs of isoproturon, imidacloprid and cyromazine have been evaluated in a calcareous soil. The effects of two natural polymers (alginate and lignin) and two modifying sorbents (bentonite and activated carbon) on pesticide release kinetics from CRFs have been investigated, as well as mobility of pesticides using soil columns. The rate of pesticide release in soil from CRFs diminished in all cases in relation to technical products. From the analysis of the time taken for 50% of the active ingredient to be released into soil (T(50 soil)), it can be deduced that the release rate of pesticides can be controlled by using activated carbon in the alginate-based CRFs and mixing the pesticide with kraft lignin. Mobility experiments showed that the use of CRFs clearly reduces the presence of isoproturon and imidacloprid in the leachate compared to technical products, and to a lesser extent for cyromacine due to its high water solubility.

Mobility of isoproturon from an alginate-bentonite controlled release formulation in layered soil.

The mobility of isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] from an alginate-based controlled release (CR) formulation was investigated by using soil columns. A layered bed system simulating the typical arrangement under a plastic greenhouse, which is composed of sand, peat, amended soil and native soil was used. The CR formulation was based on sodium alginate (1.87%), isoproturon (1.19%), natural bentonite (3.28%), and water (93.66%), and was compared to technical grade isoproturon. The use of the alginate-bentonite CR formulation produced less vertical mobility of the active ingredient as compared to the technical product. There was no presence of herbicide in the leachate when the alginate-bentonite CR formulation was used. However, 0.90% of isoproturon appeared when the treatment was carried out with technical grade material. Isoproturon mobility was modelled using the programme CMLS, which showed the peat layer to retard pesticide leaching. Analysis of the soil columns showed the highest isoproturon concentration in the peat layer.

Adsorption of atrazine from aqueous solution on heat treated kerolites

The adsorption of 6-chloro-N(2)-ethyl-N(4)-isopropyl-1,3,5-triazine-2,4-diamine (atrazine) on heat treated kerolite samples at 110 degrees C (K-110), 200 degrees C (K-200), 400 degrees C (K-400) and 600 degrees C (K-600) from aqueous solution at 25 degrees C has been studied. The evolution of surface properties of kerolite samples such as specific surface area and porosity after heat treatment was analysed. The clays were characterised by using usual techniques: FTIR spectroscopy, XRD diffraction, TG and DTG analysis, surface analysis and Hg porosimetry. The adsorption experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K(f)) of the samples; K(f) values range from 468 mgkg(-1) for the K-110 sample up to 2291 mgkg(-1) for the K-600 sample. The values obtained for the removal efficiency (R), (percentage of pesticide removed), ranged from 48% for K-110 up to 78% for K-600. The adsorption experiments showed that the stronger heat treatment, the most effective adsorption of atrazine, so, as this type of clay is relatively plentiful, these activated samples might be used in order to remove this pesticide from water.

Mobility of imidacloprid from alginate-bentonite controlled-release formulations in greenhouse soils

The mobility of imidacloprid [1-(6-chloro-3-pyridinyl)methyl]-N-nitro-2-imidazolidinimine] from alginate-based controlled-release (CR) formulations was investigated in two different soil profiles. In one, a layered bed system simulating the typical arrangement under a plastic greenhouse, which is composed of sand, peat, amended soil and native soil, was used. In the other, the layer containing amended soil was used in order to determine the mobility of the insecticide in a soil system with a low content of organic matter and a high content of clay. Two CR formulations based on sodium alginate (1.87% wt/wt), imidacloprid (1.21%), natural or acid-treated bentonite (3.28%), and water (93.64%) were compared to technical grade imidacloprid. The use of alginate CR formulations produced less vertical mobility of the active ingredient as compared to the technical product. With the technical grade product treatment, the total amount of imidacloprid leached from columns packed with amended soil was 82.3% of that applied, whereas for the alginate-based CR formulations containing natural or acid-treated bentonite, the leached percentages were 44.7% and 37.1%, respectively. In the column experiments simulating the layered bed system, no insecticide was found in the leachate when the alginate-based CR formulations containing natural bentonite were used. However, 3% of the applied imidacloprid appeared when the treatment was carried out with technical grade material. Sorption-desorption capacities of the various soil layers for imidacloprid molecules were also calculated using batch experiments. © 1999 Society of Chemical Industry

Preliminary studies in removing atrazine, isoproturon and imidacloprid from water by natural sepiolite

Sepiolite is a hydrated magnesium silicate clay with a fibrous structure and binder properties. To calculate the potential use of sepiolite in removing atrazine [2-chloro-4-ethylamino-6-isopropilamino-1,3,5,-triazine], isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] and imidacloprid [1-(6-chloro-3-pyridinylmethyl)-N-nitroimidazolin-2-ylideneamine] from water, the adsorption of atrazine, isoproturon and imidacloprid on sepiolite desiccated at 110 °C from aqueous solution at 25 °C has been studied by using batch experiments. In addition, column experiments were carried out with the sepiolite sample using aqueous solutions of atrazine, isoproturon and imidacloprid at a concentration of 20.0 × 10−4 cmol dm−3. The experimental data points have been fitted to the Langmuir equation to calculate the adsorption capacities (Xm). Values for Xm ranged from 2.70 × 10−1 cmol kg−1 for isoproturon up to 3.97 × 10−1 cmol kg−1 for atrazine. The removal efficiency (R) ranged from 36.7% for isoproturon up to 74.3% for atrazine. The batch experiments show that the sepiolite is more effective in adsorbing atrazine than imidacloprid and isoproturon. The column experiments show that sepiolite might be reasonably used in removing atrazine, the column efficiency being 46%. The data indicate that a readily available and inexpensive Spanish sepiolite can be employed as a filter for contaminated waters with these pesticides, controlling their release to the environment. © 1999 Society of Chemical Industry

Use of bentonite and humic acid as modifying agents in alginate-based controlled-release formulations of imidacloprid

In order to prepare a formulation to be used for controlled release, imidacloprid was incorporated into alginate granules by using calcium chloride as gellant. The formulation prepared (alginate-imidacloprid-water) was modified by the addition of different sorbents. The effects on release rate of the addition of natural bentonite desiccated at 105°C, untreated, acid-treated with sulfuric acid solutions over a concentration range between 0.5 mol dm -3 and 2.5 mol dm -3 , and a commercial humic acid, were studied by immersion of the granules in water under static conditions. The time taken for 50% of the active ingredient to be released into water, (T 50 ), was calculated from the data obtained. On the other hand, the sorption-desorption processes of imidacloprid from a 0.01 M aqueous calcium chloride solution at 25°C, by natural, acid-treated bentonite samples, and humic acid, have been studied by using batch experiments in order to evaluate the potential of these materials for their application in controlled-release formulations of pesticides. The experimental data have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K f ). K f values ranged from 1.76 mg kg -1 for the untreated bentonite up to 126.9 mg kg -1 for the humic acid. A correlation study was performed with T 50 , the surface area (S) and the Freundlich parameter (K f ) of the bentonite samples in order to know the factors that affect release rate of imidacloprid from bentonite granules. A linear correlation of the T 50 values and both S and K f parameters was observed.

NITRATE REMOVAL BY CALCINED HYDROTALCITE-TYPE COMPOUNDS

The sorption of nitrate ions on calcined hydrotalcite-type compounds at 550°C (HT550), 650°C (HT650), and 850°C (HT850) from pure water solution at 25°C has been studied. The influence of the temperature was also investigated for the sample calcined at 850°C by studying the sorption process at 10 and 40°C. The experimental sorption data points were fitted to the Langmuir equation in order to calculate the sorption capacities (Xm) of the samples; Xm values range from 61.7 g kg−1 (HT550 at 25°C) to 147.0 g kg−1 (HT850 at 40°C). The values for the removal efficiency (R) obtained ranged from 70.5% for HT550 at 25°C to 99.5% for HT850 at 40°C. The sorption experiments showed that the greater the calcination temperature (850°C), the more effective the removal of nitrate. The increase in the temperature from 10 to 40°C for sample HT850 also tends to increase the sorption of nitrate from 63.3 g kg−1 to 147 g kg−1 and the corresponding removal efficiency from 71.5 to 99.5%.

Removal of linuron from water by natural and activated bentonite

The sorption of linuron on bentonite desiccated at 110°C untreated, and acid-treated with H2SO4 solutions over a concentration range between 0.25 M and 1.00 M from aqueous solution at 25°C has been studied by using batch experiments. In addition, column experiments were carried out with the bentonite sample treated with the 1.00 M H 2SO4 solution [B-A(1.00)] by using two aqueous solutions of linuron of different concentrations (C=4.97 mg dm−3 and C=7.63 mg dm−3 ). The experimental data points have been fitted to the Langmuir equation in order to calculate the sorption capacities (Xm) of the samples; Xm values range from 0.02 g kg−1 for the untreated bentonite [B-N] up to 0.20 g kg−1 for the sample acid-treated with the 1.00 M H2 SO4 solution. The removal efficiency (R ) has also been calculated; R values ranging from 15.86% for the [B-N] sample up to 41.54% for [B-A(1.00)]. The batch experiments show that the acid-treated bentonite is more effective than the natural bentonite in relation to sorption of linuron. The column experiments show that the B-A(1.00) sample might be reasonably used in removing linuron, the column efficiency increasing from 61.8% for the C=7.63 mg dm−3 aqueous solution of linuron up to 77.6% for the C=4.97 mg dm−3 one. © 1999 Society of Chemical Industry

Mobility of atrazine from alginate-bentonite controlled release formulations in layered soil

The mobility of atrazine [6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine] from alginate-bentonite-based controlled release (CR) formulations was investigated by using soil columns. Two CR formulations based on sodium alginate (14.0 g kg(-1), atrazine (6.0 g kg(-1), natural or acid-treated bentonite (50 g kg(-1), and water (924 g kg(-1) were compared to technical grade product and commercial liquid (CL) formulation (Gesaprim 500FW). All herbicide treatments were applied to duplicate layered bed systems simulating the typical arrangement under a plastic greenhouse, which is composed of sand (10 cm), peat (2 cm), amended soil (20 cm) and native soil (20 cm). The columns were leached with 39 cm (1500 ml) and 156 cm (6000 ml) of 0.02 M CaCl2 solution to evaluate the effect of water volume applied on herbicide movement. When 39 cm of 0.02 M CaCl2 solution was applied, there was no presence of herbicide in the leachate for the alginate-bentonite CR treatments. However, 0.11% and 0.14% of atrazine appeared in the leachate when the treatment was carried out with technical grade and CL formulations, respectively. When 156 cm of 0.02 M CaCl2 solution was applied, the use of the alginate-acid treated bentonite CR formulation retards and reduces the presence of atrazine in the leachate as compared to technical product. Analysis of the soil columns showed the highest atrazine concentration in the peat layer. Alginate-bentonite CR formulations might be an efficient system for reducing atrazine leaching in layered soil and thus, it could reduce the risks of pollution of groundwater.