Adsorption Of Herbicides Research Articles

Biochar Decreases Atrazine and Pendimethalin Preemergence Herbicidal Activity

Biochar and vinasse are by-products of biofuel production that can be used as soil amendments. However, their addition to the soil might affect PRE herbicide activity. Although studies have shown that biochar has a high herbicide adsorption capacity, there is little information available about biochar effect on weed control especially under field conditions. Therefore, the objective of this study was to determine the influence of biochar and vinasse application on atrazine and pendimethalin availability and herbicide activity underin vitroand field conditions.In vitroatrazine and pendimethalin herbicidal activities were not influenced by vinasse addition, but biochar application reduced atrazine and pendimethalin injury for all evaluated species. A sorption experiment confirmed high affinity of biochar for atrazine and pendimethalin. Linear regression analysis showed that the slope for atrazine and pendimethalin adsorption was 16 and 4 times higher in soil with biochar than in soil alone. Under field conditions, biochar at 0.5 kg m−2reduced atrazine and pendimethalin weed control 75% and 60%, respectively. These results suggested that the use of biochar as a soil amendment in cropping system could decrease PRE herbicide efficacy. Therefore, mitigating practices such as the use of higher rates or reliance on POST herbicides and cultivation might be necessary to ensure proper weed control.

Effect of wheat and rice straw biochars on pyrazosulfuron-ethyl sorption and persistence in a sandy loam soil

The objective of this research was to investigate the effect of wheat and rice biochars on pyrazosulfuron-ethyl sorption in a sandy loam soil. Pyrazosulfuron-ethyl was poorly sorbed in the soil (3.5–8.6%) but biochar amendment increased the herbicide adsorption, and the effect varied with the nature of the feedstock and pyrolysis temperature. Biochars prepared at 600°C were more effective in adsorbing pyrazosulfuron-ethyl than biochars prepared at 400°C. Rice biochars were better than wheat biochars, and higher herbicide adsorption was attributed to the biochar surface area/porosity. The Freundlich constant 1/n suggested nonlinear isotherms, and nonlinearlity increased with increase in the level of biochar amendment. Desorption results suggested sorption of pyrazosulfuron-ethyl was partially irreversible, and the irreversibility increased with increase in the level of biochar. Both sorption and desorption of pyrazosulfuron-ethyl correlated well with the content of biochars. The free energy change (ΔG) indicated that the pyrazosulfuron-ethyl sorption process was exothermic, spontaneous and physical in nature. Persistence studies indicated that biochar (0.5%) amendment did not have significant effect on herbicide degradation, and its half-life values in the control, 0.5% WBC600- and RBC600-amended rice planted soils were 7, 8.6, and 10.4 days, respectively.

Interactions of triazine herbicides with biochar: Steric and electronic effects

We studied the adsorption of triazine herbicides and several reference heteroaromatic amines from water onto a temperature series of hardwood biochars (300–700 °C, labeled B300–B700). Adsorption on biochars correlated poorly with pyrolysis temperature, H/C, O/C, mean minimum fused ring size, surface area (N2 or CO2), microporosity, and mesoporosity, but correlated well with a weighted sum of microporosity and mesoporosity. Steric effects were evident by the negative influence of solute molecular volume on adsorption rate. For a given compound, adsorption rate maximized for the biochar with the greatest mesoporosity-to-total-porosity ratio, suggesting that mesopores are important for facilitating diffusion into pore networks. The cationic forms of amines adsorb more slowly than the neutral forms. To further probe steric and electronic effects, adsorption on a biochar (B400) was compared to adsorption on graphite—a nonporous reference material with an unhindered, unfunctionalized graphene surface—and in comparison with reference compounds (benzene, naphthalene, pyridine, quinoline and 1,3-triazine). Relative to benzene, the surface area-normalized adsorption of the triazine herbicides was disfavored on B400 (favored on graphite) by 11–19 kJ/mol, depending on concentration. It is estimated that steric suppression of B400 adsorption comprises 6.2 kJ/mol of this difference, the remainder being the difference in polar electronic effects. Based on the behavior of the reference amines, the difference in polar effects is dominated by π−π electron donor–acceptor (EDA) interactions with sites on polyaromatic surfaces, which are more electropositive and/or more abundant on graphite. Overall, our results show that mesoporosity is critical, that adsorption rate is a function of solute molecular size and charge, that steric bulk in the solute suppresses equilibrium adsorption, and that π−π EDA forces play a role in triazine polar interactions with biochar.

Montmorillonite Functionalized with Zwitterionic Surfactant as a Highly Efficient Adsorbent for Herbicides

A novel adsorbent (DHAPS-Mt) was prepared with Na montmorillonite (Na-Mt) and a zwitterionic surfactant (3-(N,N-dimethylhexadecylammonio)propanesulfonate, DHAPS). Then DHAPS-Mt was characterized by a series of characterization techniques and applied in herbicide adsorption. Two representative herbicides in agriculture, paraquat (PQ, 1,1′-dimethyl-4,4′-dipyridinium dichloride) and amitrole (AMT, 3-amino-1,2,4-triazole), were removed by DHAPS-Mt varying with different experimental conditions. The adsorption mechanisms, obtained from a comparison of adsorption capacities of DHAPS-Mt and two other kinds of organomontmorillonite (CTAB-Mt and SDS-Mt), suggested that the surface electrostatic adsorption and electrostatic attraction between herbicide cations and negatively charged group of DHAPS were the main interaction in PQ and AMT removal. The results of anionic dye (methyl orange) removal onto these three kinds of clay indicated that DHAPS-Mt might be applied in the treatment of mixed-ion wastewater. The kinetic study indicated that the adsorption of herbicides onto DHAPS-Mt followed the pseudo-second-order model, and the Langmuir isotherm model agreed well with the experimental data. Furthermore, thermodynamic parameters illustrated that PQ removal by DHAPS-Mt was more spontaneous at higher temperature, and the process was endothermic and randomness increasing in nature, while the AMT removal presented an opposite tendency.

Adsorption of 2,4-dichlorophenoxyacetic acid by mesoporous activated carbon prepared from H3PO4-activated langsat empty fruit bunch

The removal of toxic herbicide from wastewater is challenging due to the availability of suitable adsorbents. The Langsat empty fruit bunch is an agricultural waste and was used in this study as a cheap precursor to produce activated carbon for the adsorption of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) at different initial concentrations ranging from 50 to 400 mg/L. The produced Langsat empty fruit bunch activated carbon (LEFBAC) was mesoporous and had high surface area of 1065.65 m2/g with different active functional groups. The effect of shaking time, temperature and pH on 2,4-D removal were investigated using the batch technique. The adsorption capacity of 2,4-D by LEFBAC was decreased with increase in pH of solution whereas adsorption capacity increased with temperature. The adsorption data was well described by Langmuir isotherm followed by removal capacity of 261.2 mg/g at 30 °C. The results from this work showed that LEFBAC can be used as outstanding material for anionic herbicide uptake from wastewater.

Study on adsorption of herbicide onto functionalized cellulose extracted from Juncusacutus L. plant: Experimental results and theoretical modeling

Static equilibrium measurements were performed for the study of linuron adsorption on amine functionalized cellulose fiber extracted from Juncusacutus L. plant (Smar) at pH 7. We have noticed that the retention capacities of loaded aminated smar support were 64.8, 51.8, 38.9 and 32.3mg/g at 20, 40, 60 and 80°C, respectively. While for the non saturated support, these capacities were 31, 28.5, 26.4 and 23.5mg/g at 20, 40, 60 and 80°C, respectively. The obtained adsorption isotherms cannot be evaluated by using the Freundlich or Langmuir equations. New equation has been derived by making use of the grand canonical ensemble in statistical physics and some working hypotheses. The characteristic model parameters of the adsorption isotherm such as the number or fraction of adsorbed molecule(s) per site, n, the number of receptor sites per gram of adsorbent, NM, and the energetic parameter, w, were estimated for the studied systems by a non-linear least square regression. The calculated curves fit well to the experimentally obtained isotherms and the parameters of the model can be used for the characterization of the herbicide–adsorbent interactions. Thermodynamic parameters of adsorption process, i.e., entropy, Gibbs free energy and internal energy were computed and their negative values indicate that the adsorption was exothermic and favorable nature.

Application of organo-beidellites for the adsorption of atrazine

The surfaces of natural beidellite were modified with cationic surfactant octadecyl trimethylammonium bromide at different concentrations. The organo-beidellite adsorbent materials were then used for the removal of atrazine with the goal of investigating the mechanism for the adsorption of organic triazine herbicide from contaminated water. Changes on the surfaces and structure of beidellite were characterised by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and BET surface analysis. Kinetics of the adsorption studies were also carried out which show that the adsorption capacity of the organoclays increases with increasing surfactant concentration up until 1.0 CEC surfactant loading, after which the adsorption capacity greatly decreases. TG analysis reveals that although the 2.0 CEC sample has the greatest percentage of surfactant by mass, most of it is present on external sites. The 0.5 CEC sample has the highest proportion of surfactant exchanged into the internal active sites and the 1.0 CEC sample accounts for the highest adsorption capacity. The goodness of fit of the pseudo-second order kinetic confirms that chemical adsorption, rather than physical adsorption, controls the adsorption rate of atrazine.

Pillar[5,6]arene-functionalized silicon dioxide: synthesis, characterization, and adsorption of herbicide.

A layer of synthetic supramolecular macrocycles, that is, perhydroxyl-pillar[5]arene and perhydroxyl-pillar[6]arene, has been covalently attached to hydrophilic silica supports through Si-O-Si linkages with a coverage of up to 250 μmol pillar[5,6]arenes/g to form novel absorbent hybrid materials. Their adsorption toward a typical herbicide, namely, paraquat, from its aqueous solution has been investigated. Kinetic studies disclosed that paraquat adsorption fits a first-order kinetic model. Equilibrium adsorption data could be explained very well by the Langmuir equation. The pillar[6]arene-modified materials showed more obvious adsorption as compared with pillar[5]arene-modified ones and the saturation adsorption quantity reached about 0.20 mmol of paraquat per gram of materials. The entire process of adsorption was endothermic, and significantly an elevated temperature led to an increase in the adsorption quantity. This new type of pillarene-based adsorbent materials can be considered as a potential adsorbent for harmful substances removal from wastewaters.

Adsorption of herbicide 2-(2,4-dichlorophenoxy)propanoic acid by electrochemically generated aluminum hydroxides: an alternative to chemical dosing

Flow diagram of pilot plant scale studies for the removal of 2,4-DP.

A high-performance "sweeper" for toxic cationic herbicides: an anionic metal-organic framework with a tetrapodal cage.

This communication reports a novel metal-organic framework exhibiting an excellent performance in adsorbing small toxic cationic herbicides, i.e. methyl viologen and diquat, with large adsorption capacities and ultratrace residue levels. To the best of our knowledge, this is the first example of high-performance MOFs trapping toxic cationic herbicides.

Sorption equilibrium prediction of competitive adsorption of herbicides 2,4-D and MCPA from aqueous solution on activated carbon using ANN

The simultaneous adsorption of two herbicides—2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA)—from their aqueous binary mixtures onto granular activated carbon was studied. The quantities adsorbed were determined by HPLC with UV detection. The experimental data were analysed using the Freundlich adsorption isotherm. The high correlation coefficients indicated that the adsorption equilibrium fitted the Freundlich isotherm well. A multilayer perceptron (MLP) (an artificial neural network model—ANN) was applied to describe the adsorption equilibrium in multicomponent systems. This enabled sorption isotherms to be predicted for all possible combinations of the two herbicides. The experimental results and the calculated data obtained from MLP for the solutions of the individual components and their mixtures suggest that MCPA is better adsorbed onto activated carbon than 2,4-D.

Adsorption of Herbicide onto Fly Ash Sample from Aqueous Solution

Applying of low cost adsorbent for herbicide capturing is an important area of research in environmental field. The present work reports the adsorption potential of fly ash, a waste from power stations, for removal of herbicides namely paraquat and alachlor from aqueous solution. Batch experiment was employed to investigate the adsorption of herbicide in aqueous solution. The maximum capacity of the fly ash to adsorb paraquat and alachlor was found to be 2.02 and 1.70 mmole.g-1, respectively. The coefficient of adsorption on the basis of 3 models: Freundlich, Langmuir and Sips isotherm models were found. The results shown that the equilibrium data are better fitted by three-parameter models than two-parameter models. The experimental data agree to adsorption isotherms in the order of Sips > Langmuir > Freundlich isotherms.

Effect of soil properties on pure and formulated mesotrione adsorption onto vertisol (Limagne plane, Puy-de-Dôme, France)

The fate of ionisable pesticides in the environment is complex as it is importantly related to many soil properties: pH, mineralogy, organic matter content and other soil characteristics. The adsorption of a weak acid herbicide, mesotrione, was studied in detail on whole and peroxide-treated vertisol topsoil and also on its granulometric fractions (clay, silt, sand) to evaluate the role of mineralogy and different organic matter pools. The soil studied is alkaline silty loam with smectite as the main clay mineral. It contains 1.7% organic carbon, mostly stabilized as a complex with smectite. Humus is of fulvic type. Mesotrione adsorption occurs on both mineral and organic constituents. Adsorption is weak and mesotrione can be easily and totally desorbed. As shown with 13C NMR experiments, adsorption best correlates with the alkyl and carboxylic carbon content, and occurs on both bound and free organic matter. No difference of mesotrione sorption was observed with the formulation Callisto®.

Reduced Herbicide Leaching by in Situ Adsorption of Herbicide–Micelle Formulations to Soils

Aiming to reduce herbicide leaching, "in situ" adsorption of herbicide-micelle formulations to soils was explored. Sulfentrazone or metolachlor were solubilized in cationic micelles, and these herbicide-micelle formulations were applied to sandy and alluvial soils. Sulfentrazone adsorption to the soils was negligible; however, its adsorption via its solubilization in micelles and their adsorption to the soil was significant and in good agreement with the Freundlich and Langmuir models. Adsorption of solubilized herbicide to the sandy soil was higher than to the alluvial soil. The low ratio between the surfactant concentration and the cation exchange capacity (CEC) of the alluvial soil brought upon micelle decomposition and reduction in herbicide adsorption. Therefore, an optimized ratio between surfactant and soil CEC was chosen to maximize herbicide retention. Even upon adding relatively low loadings of surfactant (0.075-0.3% w/w soil), herbicide leaching through the soils was significantly reduced (2-5-fold) in comparison with the commercial formulations.

Online Sequential-Injection Chromatography with Stepwise Gradient Elution: A Tool for Studying the Simultaneous Adsorption of Herbicides on Soil and Soil Components

The adsorption of triazine herbicides simazine (SIM), atrazine (ATR), and propazine (PRO) as well as the metabolites deisopropylatrazine (DIA), deethylatrazine (DEA), and 2-hydroxyatrazine (HAT) on soil, humic acid, and soil modified with humic acidic was studied by sequential-injection chromatography with UV detection at 223 nm. An online monitoring system was assembled, which was composed of a tangential filter and a peristaltic pump for the circulation of the soil (25 g L(-1)) or humic acid (2.5 g L(-1)) suspensions. A stepwise gradient elution separated the compounds using three mobile phases whose compositions were 28, 40, and 50% (v v(-1)) methanol in 1.25 mmol L(-1) ammonium acetate buffer, pH 4.7. The sampling throughput was about six analyses per hour; the linear dynamic range was between 100 and 1000 μg L(-1) for all of the studied compounds. The detection limits varied from 9 μg L(-1) for ATR to 36 μg L(-1) for DEA. At contact times <2 h, humic acid was the material with a higher adsorptive capacity (from 1470 ± 43 μg g(-1) for DIA to 2380 ± 51 μg g(-1) for PRO). In soil, HAT exhibited the highest adsorption (23.8 ± 0.2 μg g(-1)). The presence of humic acid in the soil increased the adsorption of ATR (14 ± 1 to 23 ± 2 μg g(-1)) and PRO (21.5 ± 0.5 to 24.0 ± 0.2 μg g(-1)), decreased the adsorption of HAT (23.8 ± 0.2 to 18 ± 2 μg g(-1)), and did not affect DIA and DEA. The adsorption of SIM was negligible in all of the sorbents studied. Simazine is the herbicide with the greatest potential for leaching to water bodies followed by DEA and DIA.

Fe-pillared clay mineral-based formulations of imazaquin for reduced leaching in soil

Slow release formulations of the herbicide imazaquin (2-(4-isopropyl-4-methyl-5-oxo-4,5-dihydro-1H-imidazol-2-yl)quinoline-3-carboxylic acid) were prepared by its adsorption on Fe-pillared clay minerals (Fe PILCs). Fe PILCs were synthesized by the reaction of Na+-montmorillonite (SWy-2) with base-hydrolyzed solutions of Fe and Al. The Fe/(Fe+Al) ratios used were 0, 0.05, 0.15 and 0.50. Fe PILCs showed basal spacing values of 5.2 and 1.8nm which were due to iron clusters between delaminated clay layers, and intercalated aluminum polyoxocations, respectively. As iron content increased, the pillaring process yielded PILC with lower microporosity and larger mesoporosity. The affinity of imazaquin on Fe PILCs was very high relative to Al PILC, as revealed in its higher herbicide adsorption values and lower desorption percents. Competitive adsorption of anions such as sulfate, phosphate and chloride provided evidence of formation of inner sphere complexes of imazaquin on Fe PILCs. Slow release formulations were prepared by enhanced adsorption of the herbicide from imazaquin–cyclodextrin (CD) complexes in solution. CDs were able to enhance up to 8.5-fold the solubility of imazaquin, by the formation of inclusion complexes where the quinolinic moiety of the herbicide was partially trapped within the CD cavity. Release of the herbicide in sandy soil was about 1/2-fold lower from Fe PILC formulations relative to the commercial formulation.

Adsorption of paraquat herbicide on deposits from drinking water networks

Although forbidden in Europe, paraquat is still largely used worldwide as herbicide. Therefore, the hypothesis of an accidental or deliberate contamination of drinking water distribution systems (DWDSs) may be posed. The interactions between paraquat and three typical deposits (S2, S3 and S4 deposits) from DWDS were investigated in order to understand the fate of this chemical in such systems in case of contamination. Additionally, these materials can be valorized as adsorbents in wastewater treatment applications. The effect of stirring speed, adsorbent dose, initial paraquat concentration and temperature on the adsorption kinetics was evaluated. Good adherence was observed between experimental data and both kinetic (pseudo-second order) and equilibrium (Langmuir) models. The interaction between paraquat and the deposits is extremely weak when compared to those established in the paraquat-clay system, where irreversible sorption was observed. It was found that S2 and S3 may represent potential adsorbents regarding the treatment of paraquat-contaminated waters.

Adsorption of atrazine in packed beds

The adsorption of the herbicide atrazine in packed beds filled with solids modelling soil components, (silica and humic acid), was studied at conditions simulating the adsorption of atrazine in cultivated soils. The choice of only two constituents of soil in the experimental study was based on the assumption that these two compounds contribute significantly to the adsorption of herbicides in soil relative to others, like alumina, calcium carbonate, etc. Packed beds were filled with inorganic material (silica gel grains) and solid organic compounds (humic acid). Adsorption data were fitted to the Freundlich isotherm. The presence of humic acid, even in small quantities, increases considerably the amount of adsorbed atrazine. Increasing humic acid content in the packed beds, the amount of adsorbed atrazine increased. Reversibility tests showed that the adsorption of atrazine was reversible. Two steps for adsorption and desorption were observed. The first fast step is attributed to the physical adsorption on the free adsorption sites of the substrates washed by the solution, while the second slow step is attributed to the diffusion of the molecules of atrazine within the structure of the silica and of the humic acid. Study of the hydrodynamics of atrazine containing solutions flow in the packed beds filled with silica and humic acid showed that the morphology of insoluble humic acid upon hydration changed its shape resulting in its transport through the bed and clogging of the narrow pores of the medium. As a result the packed bed permeability was reduced by 99%.

Kinetic and equilibrium studies of simultaneous adsorption of monochlorophenols and chlorophenoxy herbicides on activated carbon

Adsorption on activated carbon is one of the well-established and effective techniques for the removal of chloroorganic pollutants from surface water, groundwater, and drinking water. Since these water contaminants occur often together in the present study, kinetics and equilibria of simultaneous adsorption of selected chlorophenols and chlorophenoxy herbicides from aqueous solutions are investigated and described. For investigations, three monochlorophenols (2-chlorophenol, 3-chlorophenol, and 4-chlorophenol), as well as chlorophenoxy hebicides (2,4-dichlorophenoxyacetic acid and 2-methyl-4-chlorophenoxyacetic acid), are chosen. As adsorbent granular-activated carbon Filtrasorb 300 (938 m2/g) was used. Adsorption quantities were determined by HPLC method. Kinetics of adsorption was described by pseudo-second-order model and adsorption equilibria by Freundlich equation. Proposed method can be used for adsorption from multicomponent aqueous solutions.

Removal of Atrazine, Metribuzin, Metolachlor and Alachlor by Granular Carbon

Adsorption-desorption of atrazine, metribuzin, alachlor and metolachlor on granular carbon were studied in a batch study. All herbicides were highly sorbed on the granular carbon (93.8-100%). Adsorption data were subjected to the Langmuir and the Freundlich adsorption isotherms, and fitted well to the Freundlich adsorption isotherm (r2>0.96). Except alachlor, where the isotherm was nearly linear, 1/n values for atrazine, metribuzin and metolachlor isotherms were <1, suggesting a decrease in herbicide adsorption with increasing concentration in the aqueous phase. The Freundlich adsorption parameter [Kf(1/n)] values were 6813.6, 2981.8, 1420.7 and 5661.4 for atrazine, metribuzin, metolachlor and alachlor, respectively. Thus, granular carbon showed the highest adsorption capacity for atrazine followed by alachlor, metribuzin and metolachlor. However, a desorption study suggests that, except alachlor (<3%), none of the herbicides were desorbed during three desorption cycles. Although alachlor adsorption coefficients were higher than those of metribuzin and metolachlor, it was desorbed. The Freundlich constant Kf showed a positive correlation with solubility (S) while no correlation was observed with the octanol-water partition coefficient (Kow). Results of three sequential adsorption studies suggest that the order of herbicide adsorption was: atrazine>metribuzin>metolachlor>alachlor. This is in agreement with the desorption results, which suggested that granular carbon had poor retention capacity for alachlor. Among the herbicides used in this study, granular carbon has maximum retention capacity for atrazine.