M. Socías-Viciana

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.

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

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 chloridazon from water by kerolite/stevensite and bentonite: a comparative study.

The adsorption of chloridazon (5-amino-4-chloro-2-phenylpyridazin-3(2H)-one) on a new type of material formed by kerolite/stevensite bearing lithofacies and on a bentonite, 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 these samples using aqueous solutions of chloridazon at a concentration (C) of 45 × 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 0.072 cmol kg−1 for bentonite up to 1.30 cmol kg−1 for kerolite. The removal efficiency, R, ranged from 17.1% for bentonite up to 85.1% for kerolite. The batch experiments show that the kerolite is more effective than bentonite in adsorbing chloridazon. The column experiments show that kerolite might be reasonably used in removing chloridazon, the data indicating that a readily available and inexpensive Spanish kerolite can be employed as a filter for contaminated waters with chloridazon, so controlling its release to the environment. © 2000 Society of Chemical Industry

Adsorption of chloridazon from aqueous solution on modified kerolite-rich materials

The adsorption of chloridazon (5-amine-4-chloro-2-phenylpyridazin-3(2H)-one) on kerolite samples heated at 110°C (K-110), 200°C (K-200), 400°C (K-400), 600°C (K-600) and acid-treated with H2SO4 solutions of two different concentrations (0.25 and 0.5 M) (K-0.25 and K-0.5, respectively) from pure water at 25°C has been studied by using batch and column experiments. The adsorption experimental data points were fitted to the Freundlich equation in order to calculate the adsorption capacities (Kf) of the samples; Kf values ranged from 184.7 mg kg−1 (K-0.5) up to 2253 mg kg−1 (K-600). This indicated that the heat treatment given to the kerolite greatly increases its adsorption capacity for the herbicide whereas the acid treatment produces a clear decrease in the amount of chloridazon adsorbed. The removal efficiency (R) was also calculated; R values ranging from 52.8% (K-0.5) up to 88.3% (K-600). Thus, the results showed that the 600°C heat-treated kerolite was more effective in relation to adsorption of chloridazon and it might be reasonably used in removing this herbicide from water.