Adsorption Of Picloram Research Articles

Adsorption of picloram on clays nontronite, illite and kaolinite: equilibrium and herbicide-clays surface complexes

The picloram (PCM) adsorption on nontronite, illite and kaolinite was studied at pH 3, 5 and 7. The adsorption isotherms had well-fitted to Langmuir and Freundlich models equations. The interactions of PCM with the clay mineral surfaces exhibited an anionic profile adsorption, with a decrease in adsorption when the pH increases. The PCM adsorption capacity increases in the following order: kaolinite < illite < nontronite. The X-ray diffraction (XRD) analysis of PCM-clay samples revealed that the picloram molecule does not enter into the clays basal space. The interaction of PCM with clays surface sites through nitrogen of the pyridine ring was confirmed by X-ray photoelectron spectroscopy (XPS). Due to the anionic form of PCM, the adsorption onto the external and edges surface sites of the clay minerals was proposed.

Sequential Injection Analysis with Square Wave Voltammetry (SI-SWV) Detection for Investigation of Adsorption of Picloram on a Clay Soil

This paper describes a sequential injection analysis method, with detection by square wave voltammetry using a hanging mercury drop electrode, to determine the herbicide picloram in soil extracts (0.010 mol L-1 CaCl2). The method was applied for determination of the Freundlich parameters related to adsorption of picloram on a tropical soil sample. The major advantage of the proposed method over the conventional chromatographic methods is the high sampling throughput of 190 analyses per hour, with detection and quantification limits of 0.036 and 0.12 mg L-1, respectively. The Kf (0.0016 ± 0.0005 µmol1-1/n L1/n kg-1) and 1/n (0.85 ± 0.06) obtained by the proposed method did not differ from those determined by liquid chromatography with UV detection.

Adsorption of picloram herbicide on montmorillonite: Kinetic and equilibrium studies

The kinetics of the adsorption of picloram (PCM) onto montmorillonite (Mt) was studied in situ by attenuated total reflectance Fourier-transform infrared spectra (ATR-FTIR). Pseudo-first-order, pseudo-second-order, intra-particle diffusion and mixed surface reaction intra-particle diffusion-controlled kinetic models were applied to the experimental results. The latter was the model that best represented the experimental results. The adsorption equilibrium isotherms revealed the presence of two independent adsorption processes on different surface sites. The adsorption isotherms normalized by the surface area were fitted with the Langmuir and Freundlich models to obtain the respective parameters.Due to the anionic form of PCM, the adsorption onto the external clay mineral surface sites followed by the entrance of the PCM molecule into the Mt basal space in a less energetically favorable pathway was proposed. The interaction of PCM with montmorillonite surface sites through nitrogen of the pyridine ring and carboxylic group by forming an inner sphere complex was confirmed by ATR-FTIR.

Adsorption of picloram herbicide on iron oxide pillared montmorillonite

The adsorption of picloram on Fe Oxide Pillared Clays (PILC) as a possible basis for the development of adsorbent materials for the remediation of polluted environments was studied. To this end, after characterizing PILC obtained from raw clay from Wyoming, USA by XRD, elemental analysis, Mössbauer spectroscopy, DTA, TGA and N2 adsorption (BET), the picloram adsorption was studied at constant pH and ionic strength after 48h equilibration with an aqueous solution of PCM. PCM adsorbed samples were characterized by SEM, zeta-potential vs pH functions, FTIR and TGA-DTA and the adsorption was modellated using Langmuir and Freundlich models.The results reveal that the surface area and interlayer space of PILC are bigger than those of raw montmorillonite. An analysis of the adsorption isotherms of picloram on the PILC showed that picloram adsorption increases with decreasing pH. The adsorption of PCM on PILC was 150 times higher than that found for raw montmorillonite under similar conditions. The zeta-potential vs pH functions shape and FTIR indicated that PCM coordinates the surface iron centers throughout pyridinic nitrogen atom forming inner-sphere complexes. The much greater PCM adsorption on PILC turns the process into an excellent candidate to be used for dosing or remediation of pesticides.

Adsorption of acidic pesticides 2,4-D, Clopyralid and Picloram on calcined hydrotalcite

Calcined hydrotalcite, HT500, a Mg–Al mixed oxide with NaCl-structure of composition Mg 3AlO 4.5 was shown to be an effective adsorbent for the acidic pesticides: 2,4-D, Clopyralid and Picloram. Adsorption experiments were conducted using three procedures: time-dependent (kinetic), pH-dependent and concentration-dependent (isotherm). Results indicate that the intensity of the adsorption is related to the acidity of the pesticides. The characterization of the adsorption products by XRD and FT-IR spectroscopy confirm the adsorption of the three pesticides in the anionic form in the hydrotalcite interlayer by reconstruction of the layered structure. There was evidence of the adsorption of Picloram also in molecular form.

Contaminación de las aguas subterráneas por el uso de picloram en pastos

Se realizó un estudio de adsorción de picloram en 28 suelos de pastoreo bajo condiciones de laboratorio. Las capacidades de estos suelos para adsorber el picloram se expresaron en términos de las constantes de K y 1/n de la ecuación de Freundlich. Las constantes de adsorción (K) de estos suelos variaron desde 0.269 a 1.842 en el suelo Espinosa limo arenoso y en el Bajura arcilloso, respectivamente. Se hizo un análisis de correlación entre los valores de K de suelos para pastoreo y sus respectivas propiedades físicas y químicas. Los valores de K de los suelos se correlacionaron negativamente con su contenido de arena y positivamente con su contenido de materia orgánica, arcilla, limo y capacidad de intercambio de cationes. En un estudio de campo sobre la contaminación de agua subterránea con picloram, éste se aplicó dos veces a la dosis de 2.47 L/ha a dos parcelas de pasto (Mabí limo arcilloso), cada una de ellas adyacente a un pozo de agua. Las muestras de agua se recogieron semanalmente por un periodo de tres meses. Se analizaron las muestras con un cromatógrafo de gas. No se detectó picloram después de la primera aplicación Sin embargo, se detectó una concentración de 2 µg/L en uno de los pozos 10 semanas después de la segunda aplicación. Este hallazgo sugiere que hay poca posibilidad de contaminar agua subterránea con picloram en los suelos pesados parecidos al Mabí limo arcilloso.

Exchangeable Cations and Picloram Sorption by Soil and Model Adsorbents

The adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) was determined on an Aiken silt loam, on three cation exchange resins and on a single anion exchange resin. Adsorption data were evaluated using parameters in the Freundlich equation and their dependance upon cationic composition of the exchange complex, the ionic composition of the equilibrium solution, and the equilibrium solution pH. For the Aiken soil saturated with metallic cations the order of decreasing picloram adsorptive capacity was Fe+3= Cu+2&gt; Al+3&gt; Zn+2&gt; Ca+2&gt; native soil. Increases in adsorption compared to the native Aiken soil could be explained on the basis of decreases in the equilibrium solution pH except for Fe+3, Zn+2, and especially the Cu+2treatments. The adsorptive capacity of the Aiken soil was altered by the addition of several salts simulating addition of fertilizer salts. The Cu+2and Zn+2salts were the only treatments showing increased adsorption which could not be explained readily by pH changes. KH2PO4and NH2CONH2(urea) reduced picloram adsorption. Dowex 50-1 × 4, a strongly acidic cation exchange resin, showed increased picloram adsorptive capacity in the order Cu+2&gt; Al+3&gt; Ca+2&gt; Zn+2= H+. Cellex CM, a weakly acidic cellulose exchanger had increased adsorptive capacities in the order of Cu+2&gt; Ca+2&gt; Al+3&gt; Na+&gt; Fe+3&gt; Zn+2. Picloram adsorption by an anion exchange resin at pH 6.1 was nearly 100%. These results suggest that complex formation of picloram with polyvalent cations on the exchange complex is likely especially for Cu+2and to a lesser extent Fe+3and Zn+2. In soils such complex reactions would most probably involve organic matter, polyvalent cations, and picloram. The formation of chelate ring species is proposed.

Equilibrium and kinetics of adsorption of picloram and parathion with soils

Equilibrium and kinetics of adsorption of picloram and parathion with soils

Surfactant Effects on Picloram Adsorption by Soils

The effects of soil organic matter, clay, extractable Al, cation exchange capacity, and pH on the adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) from aqueous and surfactant solutions were investigated. Linear adsorption isotherms for the soils were obtained with the Freundlich equation. Of the five soil properties investigated, Freundlich K values correlated with extractable Al and clay content. Picloram adsorption from aqueous solutions and from the non-ionic and anionic surfactant solutions was greater on the soils at pH 5 than at pH 7. The anionic surfactant competed with picloram for adsorption sites on the soils at pH 5. Picloram adsorption from solutions containing 0.1 and 1% cationic surfactant was greater than that from aqeuous and anionic and nonionic surfactant solutions. Picloram adsorption from the 10% cationic surfactant solution was similar on soils with pH 5 and 7 and increased with decreased organic matter content.

A Two‐Phase Model for the Miscible Displacement of Reactive Solutes in Soils

AbstractMiscible displacement is studied by considering the flow regime to be composed of separate mobile and stationary phases. Solute transfer through the mobile phase occurs only by convection, whereas adsorption or reaction by the soil matrix is diffusion limited and occurs normal to the mobile‐stationary interface. The model is unique in that a specific rate law is not assumed, but the solution is exact. Results are presented graphically as a function of two parameters which are compared with experimental results of other workers. The displacement of calcium by magnesium was more closely in agreement with theoretical predictions than was adsorption of picloram.

Adsorption of Picloram (4‐Amino‐3,5,6‐Trichloropicolinic Acid) on Panoche, Ephrata, and Palouse Soils: A Thermodynamic Approach to the Adsorption Mechanism

AbstractThe adsorption of picloram (4‐amino‐3,5,6‐trichloropicolinic acid) was studied on Panoche clay loam (at pH 4.2 and 1.2), Ephrata sandy loam, and Palouse silty loam. The adsorption processes could be described by the Freundlich equation with Freundlich constants, K, 1/n, and percentage of adsorption at 25C: respectively, 0.210, 0.92, and 3–5.6% for Panoche at pH 4.2; 2.5, 0.93, and 30% for Panoche at pH 1.2; 0.172, 0.99, and 1.9–3.6% for Ephrata; and 1.74, 0.92, and 26–33% for Palouse. Also evaluated were the standard free energy, entropy, and enthalpy associated with the adsorption processes. The values of ΔG° (kcal/mol), ΔS° (cal/mol per degree), and ΔH° (kcal/mol) were: respectively, −1.2±0.1, −14±2, and −5.3±0.6 for Panoche at pH 4.2; −2.98±0.05, −59±2, and −20±1 for Panoche at pH 1.2; −1.80±0.06, −24±3, and −9±1 for Ephrata; and −3.11±0.05, −3.3±1.5, and −4.1±0.4 for Palouse. Thermodynamic parameters were useful in assigning adsorption mechanisms to the four picloram‐adsorbent‐water systems.

Adsorption of Picloram by Soil Colloids and Various Other Adsorbents

The adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) was studied for several Canadian prairie soils and for various other adsorbents. The kd values for the soils ranged from 0.09 to 0.75 and were correlated only with soil organic matter. The kd values for other adsorbents varied from 0 to 232, the order of adsorption being activated charcoal &gt; anion exchange resin &gt; peat moss &gt; cellulose triacetate. There was no adsorption of picloram on montmorillonite and kaolinite clays, cation exchange resin, wheat straw (Triticum aestivumL.), or cellulose powder. The differences in the adsorption of picloram were explained on the basis of the relative affinities of the various adsorptive surfaces for the molecular or the ionized forms of the acid.