Adsorption of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-metylphenoxyacetic acid onto activated carbons derived from various lignocellulosic materials

Adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-metylphenoxyacetic acid (MCPA) from aqueous solution onto activated carbons derived from various lignocellulosic materials including willow, miscanthus, flax, and hemp shives was investigated. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first order and pseudo-second order equations. The adsorption kinetics of both herbicides was better represented by the pseudo-second order model. The adsorption isotherms of 2,4-D and MCPA on the activated carbons were analyzed using the Freundlich and Langmuir isotherm models. The equilibrium data followed the Langmuir isotherm. The effect of pH on the adsorption was also studied. The results showed that the activated carbons prepared from the lignocellulosic materials are efficient adsorbents for the removal of 2,4-D and MCPA from aqueous solutions.     

Treatment of 2,4-D, mecoprop, and dicamba using membrane bioreactor technology

Phenoxyacetic and benzoic acid herbicides are widely used agricultural, commercial, and domestic pesticides. As a result of high water solubility, mobility, and persistence, 2,4-dichlorophenoxyacetic acid (2,4-D), methylchlorophenoxypropionic acid (mecoprop), and 3,6-dichloro-2-methoxybenzoic acid (dicamba) have been detected in surface and waste waters across Canada. As current municipal wastewater treatment plants do not specifically address chronic, trace levels of contaminants like pesticides, an urgent need exists for an efficient, environmentally friendly means of breaking down these toxic herbicides. A commercially available herbicide mix, WeedEx, containing 2,4-D, mecoprop, and dicamba, was subjected to treatment using membrane bioreactor (MBR) technology. The three herbicides, in simulated wastewater with a chemical oxygen demand of 745 mg/L, were introduced to the MBR at concentrations ranging from 300 μg/L to 3.5 mg/L. Herbicides and biodegradation products were extracted from MBR effluent using solid-phase extraction followed by detection using high-performance liquid chromatography coupled with mass spectrometry. 2,4-D was reduced by more than 99.0 % within 12 days. Mecoprop and dicamba were more persistent and reduced by 69.0 and 75.4 %, respectively, after 112 days of treatment. Half-lives of 2,4-D, mecoprop and dicamba during the treatment were determined to be 1.9, 10.5, and 28.3 days, respectively. Important water quality parameters of the effluent such as dissolved oxygen, pH, ammonia, chemical oxygen demand, etc. were measured daily. MBR was demonstrated to be an environmentally friendly, compact, and efficient method for the treatment of toxic phenoxyacetic and benzoic acid herbicides.     

Chlorinated Pesticides (2,4-D and DDT) Biodegradation at High Concentrations Using Immobilized Pseudomonas Fluorescens

Abstract

Degradation of two chlorinated pesticides (2,4-D and DDT) using a 54-mL glass column packed with tezontle (a low-cost basaltic scoria) was tested. Bacteria were cultured in YPG (yeast, peptone, and glucose) liquid medium at 32°C. The rich medium was pumped during 24 h through the column to inoculate it. Later, the wasted medium was discharged and the pesticide added. Optical densities, TOC, and pesticide concentration were determined. Pesticide removals for 2,4-D (with initial concentration between 100 and 500 mg/L) were about 99%. DDT removal (at initial concentration of up to 150 mg/L) was as high as 55–99%. TOC removals for 2,4-D was in the 36-87% interval, whereas for DDT they were as high as 36–78%.     

Spiking solvent, humidity and their impact on 2,4-D and 2,4-DCP extractability from high humic matter content soils

The 2,4-dichlorophenoxyacetic acid (2,4-D) is a hormone-like herbicide widely used in agriculture. Although its half life in soil is approximately two weeks, the thousands of tons introduced in the environment every year represent a risk for human health and the environment. Considering the toxic properties of this compound and its degradation products, it is important to assess and monitor the 2,4-D residues in agricultural soils. Furthermore, experiments of phyto/bioremediation are carried out to find economic and environmental friendly tools to restore the polluted soils. Accordingly, it is essential to accurately measure the amount of 2,4-D and its metabolites in soils. There is evidence that 2,4-D extraction from soil samples seriously depends on the physical and chemical properties of the soil, especially in those soils with high content of humic acids. The aim of this work was to assess the variables that influence the recovery and subsequent analysis of 2,4-D and its main metabolite (2,4-dichlorophenol) from those soils samples. The results showed that the recovery efficiency depends on the solvent and method used for the extraction, the amount and kind of solvent used for dissolving the herbicide and the soil water content at the moment of spiking. An optimized protocol for the extraction and quantification of 2,4-D and its main metabolite from soil samples is presented.     

Absorption and translocation of 2,4-D in plants of Memora peregrina

The objective of this work was to evaluate absorption and translocation of the herbicide 2,4-D in plants of Memora peregrina. The herbicide 2,4-D was used alone with the formulation DMA 806 BR and associated with the herbicide picloram in the commercial product Padron. Levels of radioactivity on the treated leaves were determined in sample obtained after washing them with methanol and chloroform at different times after the application of the radiolabelled formulation (1, 2, 4, 8, 24, and 48 h). Translocation was evaluated by cutting plants between stem and root. The parts obtained were: root, stem, leaf treated, leaves above the leaf treated, leaves below the leaf treated, and leaf opposite of the leaf treated. These parts were weighted, dried, ground, burnt, and radioactivity in the samples was determined. The results suggest that the translocation of the radioactive herbicide 2,4-D was insignificant in plants of M. peregrina in the two treatments evaluated. Absorption of 14C 2,4-D in the treatment with DMA 806 BR and the mixture of DMA 806 BR plus Padron had the same behavior. These observations explain the inefficient control obtained with this herbicide in plant species under study.     

2,4-Dichlorophenoxy Acetic Acid Mineralization in Amended Soil

The application of municipal biosolid or liquid hog manure to agricultural soils under laboratory conditions at 20°C influenced the fate of the herbicide 2,4-D [2,4-(dichlorophenoxy)acetic acid] in soil. When 2,4-D was added to soil at agronomic rates immediately after the addition of manure or biosolids to a coarse-textured soil, the percentage of 2,4-D mineralized at 100 days was about 47% for both treatments, compared to only 31% for control soils without amendments. The enhanced 2,4-D mineralization as a result of amendment addition was due to an increased heterotrophic microbial activity, with the greatest increases in soil respiration occurring for soils amended with biosolids. When additions of 2,4-D were delayed for one, two, or four weeks after the amendments were applied, the additions of amendments generally reduced 2,4-D mineralization in soil, particularly for manure, indicating that the effect of amendments on enhancing soil microbial activities diminished over time. In contrast, the mineralization of 2,4-D in control soils was less dependent on when 2,4-D was applied in relation to pre-incubations of soil for zero, one, two, or four weeks. The effect of manure on decreasing 2,4-D mineralization in specific soils was as large as the effect of soil texture on differences in 2,4-D mineralization across soils. Because manure was not found to impact 2,4-D sorption by soil, it is possible that 2,4-D mineralization decreased because 2,4-D transformation products were strongly sorbed onto organic carbon constituents in manure-amended soils and were therefore less accessible to microorganisms. Alternatively, microorganisms were less likely to metabolize the herbicide because they preferentially consumed the type of organic carbon in manure that is a weak sorbent for 2,4-D.     

Effect of different inorganic and organic compounds on sorption of 2,4-D and atrazine

In this study, the effects of size of adsorbent, temperature, pH of solution, ionic strength, presence of inorganic substances such as calcium ion, magnesium ions, chloride ions, fertilizers and presence of organic substances such as dissolved organic matter, surfactant, other herbicides on sorption of 2,4-D and atrazine onto rubber granules were investigated. The removal efficiency was more for fine adsorbent particles. Temperature played an important role in sorption process. Temperature effect was endothermic for 2,4-D and exothermic for atrazine, respectively. The removals were maximum at pH 4 for 2,4-D and at pH 6 for atrazine. The presence of other herbicide (butachlor) reduced sorption capacity of rubber granules by approximately 10% for both 2,4-D and atrazine. All other factors had insignificant effect on sorption capacity. The mathematical expressions were developed for predicting the overall percentage removal of 2,4-D and atrazine on the basis of major four controlling factors viz. adsorbent size, temperature, pH and presence of other herbicide.     

Preparation of Activated Carbons from Raw and Biotreated Agricultural Residues for Removal of Volatile Organic Compounds

ABSTRACT

Activated carbons with diverse physical and chemical properties were produced from four agriculture residues, including raw barley husk, biotreated barley husk, rice husk, and pistachio shell. Results showed that with adequate steam activation (30–90 min, 50% H₂O_(g)/50% N₂), activated carbons with surface areas between 360 and 950 m² g^?1 were developed. Further increases in the activation time destroyed the pore structure of activated carbons, which resulted in a decrease in the surface area and pore volume. Biotreated agricultural residues were found to be suitable precursors for producing mesoporous activated carbons. The oxygen content of activated carbons increased with increasing activation time. Results from X-ray photoelectron spectroscopy examination further suggested that H₂O molecules react with the carbon surface, enhancing the deconvoluted peak area of carbonyl and carboxyl groups. Equilibrium adsorption of toluene indicated that the adsorption capacities increased with an increase in the inlet toluene concentration and a decrease in temperature. The adsorption isotherms were successfully fitted with Freundlich, Langmuir, and Dubinin– Radushkevich equations. Activated carbons derived from agricultural residues appear to be more applicable to adsorb volatile organic compounds at a low concentration and high-temperature environment.

IMPLICATIONS This paper presents data on the preparation of activated carbons from agricultural residues, especially the waste from biohydrogen generation. Experimental results indicated that with proper carbonization and steam activation, activated carbons with diverse characteristics can be produced from various agricultural residues. The resulting activated carbons effectively adsorb toluene. This work provides useful information for reutilization of these agricultural residues, helping in decreasing the cost of biological waste treatment and providing a cost-effective alternative to conventional adsorbent production and application.     

Factors Influencing 2,4-D Sorption and Mineralization in Soil

Abstract

This study quantified 2,4-D [(2,4-dichlorophenoxy)acetic acid] sorption and mineralization rates in five soils as influenced by soil characteristics and nutrient contents. Results indicated that 2,4-D was weakly sorbed by soil, with Freundlich distribution coefficients ranging from 0.81 to 2.89 µg^1?1/n  g^?1 mL^{1/ n} . First-order mineralization rate constants varied from 0.03 to 0.26, corresponding to calculated mineralization half-lives of 3 and 22 days, respectively. Herbicide sorption generally increased with increasing soil organic carbon content, but the extent of 2,4-D sorption per unit organic carbon varied among the soils due to differences in soil pH, clay content and/or organic matter quality. Herbicide mineralization rates were greater in soils that sorbed more 2,4-D per unit organic carbon, and that had greater soil nitrogen contents. We conclude that the effect of sorption on herbicide degradation cannot be generalized without a better understanding of the effects of soil characteristics and nutrient content on herbicide behavior in soil.     

Determination of 2,4-Dichlorophenoxyacetic acid in food and water samples using a modified graphene oxide sorbent and high-performance liquid chromatography

Abstract

In the present work, dispersive micro-solid phase extraction (D-μ-SPE) method using magnetic graphene oxide tert-butylamine (GO/Fe₃O₄/TBA) nanocomposite, as an efficient sorbent, was applied for determining 2,4-dichlorophenoxyacetic acid (2,4-D) in water and food samples. Detection was carried out using high-performance liquid chromatography (HPLC) instrument. Influential parameters of D-μ-SPE such as sorbent and its amount, elution solvent and its volume, adsorption and desorption times and pH of sample solution were investigated and optimized. Under the optimized conditions, limit of detection and quantitation values were 0.007 and 0.02?μg/mL, respectively. Recovery data for several real samples were obtained within the range of 88.0–94.0% with a relative standard deviation (RSD) less than 7.5%. The proposed method was successfully applied to quantitative determination of 2,4-D in several vegetables and water samples.     

Sorption of 2,4-D on Natural and Organic Amended Soils of Different Characteristics

The effect of one organic amendment consisting of an urban waste compost (UWC) was assessed on the sorption properties of the herbicide 2,4-D on four soils of different physicochemical characteristics. The soils chosen were a Typic Haphorthod (ST), a Typic Endoaquept (SR), an Entic Pelloxerert (TO), and a Typic Eutrochrept (AL). Adsorption experiments were performed on the original soils, and on mixtures of these soils with UWC at a rate of 6.25% (w/w). These mixtures were used just after preparation, and after aging for 8 and 25 weeks. 2,4-D adsorption was the highest on ST soil, whereas the lowest adsorption was for SR soil. This behavior is related to the high amount of organic matter (OM) and amorphous iron and aluminum oxides content on soil ST, whereas soil SR had the lowest OM content and specific surface area of the soils of this study. Addition of exogenous OM to soils caused an increase in the 2,4-D adsorption by three of the soils treated with UWC, with the only exception being ST soil, due to an observed decrease in its specific surface area. The adsorbed amounts of the herbicide on aged organic fertilized soils diminished in three of the amended soils, but was still greater than on unamended soils. In contrast, the ST soil showed the largest adsorption for unamended soil.     

Mobility and efficacy of 2,4-D herbicide from slow-release delivery systems based on organo-zeolite and organo-bentonite complexes

This research aimed to develop slow-release formulations (SRFs) of 2,4-dichlorophenoxyacetic acid (2,4-D) using zeolite and bentonite minerals modified with cetyltrimethylammonium (CTMA) surfactant. Adsorption–desorption, greenhouse bioassay and column experiments were carried out to assess the potential of the SRFs to control weeds while reducing the herbicide leaching losses to deep layers of soil. The results showed that only 6.5 mmol 2,4-D kg^?1 was retained by Na-bent, and the herbicide was not adsorbed by Na-zeol at all. The surface modification with CTMA surfactant, however, improved the 2,4-D adsorption capacity of the zeolite and bentonite up to 207.5 and 415.8 mmol kg^?1, respectively. The synthesized organo-minerals slowly released the retained 2,4-D discharging 22 to 64% of the adsorbed 2,4-D to the solution phase within 7 days. The SRFs significantly (P = 0.05) reduced the herbicide mobility within the soil columns keeping a great portion of the herbicide active ingredient in the upper 5 cm soil layer. The SRFs were significantly (P = 0.05) as effective as the free technical herbicide in weed control without harming the ryegrass as the main plant. Therefore, the synthesized SRFs could be considered as useful tools for weed control in sustainable agriculture.     

The effect of propanil co-application on 2,4-D sorption by soil

The herbicide 2,4-D is often applied as a tank mixture in combination with other herbicide products. However, current information on 2,4-D sorption by soil is largely based on batch-equilibrium experiments without considering the competition of other herbicides for sorption sites by soil. This study quantified the effect of the herbicide propanil on the sorption of 2,4-D in soil. Results indicated that propanil competed with 2,4-D for sorption sites, particularly in soils with an organic carbon content greater than 3.6%. The decrease in 2,4-D sorption by soil, as a result of propanil competition, was most notably for herbicide concentrations that are typical of recommended field rates. We conclude that herbicide co-applications on agricultural fields have the potential to increase the mobility of herbicides in soil.     

Evaluating the degradation of the herbicides picloram and 2,4-D in a compartmentalized reactive biobarrier with internal liquid recirculation

Tordon is a widely used herbicide formulation of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram), and it is considered a toxic herbicide. The purposes of this work were to assess the feasibility of a microbial consortium inoculated in a lab-scale compartmentalized biobarrier, to remove these herbicides, and isolate, identify, and evaluate their predominant microbial constituents. Volumetric loading rates of herbicides ranging from 31.2 to 143.9 g m^?3 day^?1, for 2,4-D, and 12.8 to 59.3 g m^?3 day^?1 for picloram were probed; however, the top operational limit of the biobarrier, detected by a decay in the removal efficiency, was not reached. At the highest loading rates probed, high average removal efficiencies of 2,4-D, 99.56?±?0.44; picloram, 94.58?±?2.62; and chemical oxygen demand (COD), 89.42?±?3.68, were obtained. It was found that the lab-scale biofilm reactor efficiently removed both herbicides at dilution rates ranging from 0.92 to 4.23 day^?1, corresponding to hydraulic retention times from 1.087 to 0.236 days. On the other hand, few microbial strains able to degrade picloram are reported in the literature. In this work, three of the nine bacterial strains isolated cometabolically degrade picloram. They were identified as Hydrocarboniphaga sp., Tsukamurella sp., and Cupriavidus sp.     

Fungal bioconversion of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP)

Ninety strains of fungi from the collection of our mycology laboratory were tested in Galzy and Slonimski (GS) synthetic liquid medium for their ability to degrade the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and its by-product, 2,4-dichlorophenol (2,4-DCP) at 100 mg l(-1), each. Evolution of the amounts of each chemical in the culture media was monitored by HPLC. After 5 days of cultivation, the best results were obtained with Aspergillus penicilloides and Mortierella isabellina for 2,4-D and with Chrysosporium pannorum and Mucor genevensis for 2,4-DCP. The data collected seemed to prove, on one hand, that the strains responses varied with the taxonomic groups and the chemicals tested, and, on the other hand, that 2,4-D was less accessible to fungal degradation than 2,4-DCP. In each case, kinetics studies with the two most efficient strains revealed that there was a lag phase of 1 day before the onset of 2,4-D degradation, whereas there was none during 2,4-DCP degradation. Moreover, 2,4-DCP was detected transiently during 2,4-D degradation. Finally, M. isabellina improved its degradation potential in Tartaric Acid (TA) medium relative to GS and Malt Extract (ME) media.     

2,4-Dichlorophenoxyacetic acid (2,4-D) sorption and degradation dynamics in three agricultural soils

The fate and transport of 2,4-dichlorophenoxyacetic acid (2,4-D) in the subsurface is affected by a complex, time-dependent interplay between sorption and mineralization processes. 2,4-D is biodegradable in soils, while adsorption/desorption is influenced by both soil organic matter content and soil pH. In order to assess the dynamic interactions between sorption and mineralization, 2,4-D mineralization experiments were carried using three different soils (clay, loam and sand) assuming different contact times. Mineralization appeared to be the main process limiting 2,4-D availability, with each soil containing its own 2,4-D decomposers. For the clay and the loamy soils, 45 and 48% of the applied dose were mineralized after 10 days. By comparison, mineralization in the sandy soil proceeded initially much slower because of longer lag times. While 2,4-D residues immediately after application were readily available (>93% was extractable), the herbicide was present in a mostly unavailable state (<2% extractable) in all three soils after incubation for 60 days. We found that the total amount of bound residue decreased between 30 and 60 incubation days. Bioaccumulation may have led to reversible immobilization, with some residues later becoming more readily available again to extraction and/or mineralization.     

Adsorption characteristics of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solution on powdered activated carbon

The removal of 2,4-dichlorophenoxyacetic acid (2,4-D), one of the most commonly used phenoxy acid herbicides, from aqueous solution was studied by using acid-washed powdered activated carbon (PAC) as an adsorbent in a batch system. Adsorption equilibrium, kinetics, and thermodynamics were investigated as a function of initial pH, temperature, and initial 2,4-D concentration. Powdered activated carbon exhibited the highest 2,4-D uptake capacity of 333.3 mg g(-1) at 25 degrees C and an initial pH value of 2.0. Freundlich, Langmuir, and Redlich-Peterson isotherm models were used to express the equilibrium data of 2,4-D depending on temperature. Equilibrium data fitted very well to the Freundlich equilibrium model in the studied concentration range of 2,4-D at all the temperatures studied. Three simplified models including pseudo-first-order, pseudo-second-order, and saturation-type kinetic models were used to test the adsorption kinetics. It was shown that the adsorption of 2,4-D on PAC at 25, 35, and 45 degrees C could be best fitted by the saturation-type kinetic model with film and intraparticle diffusions being the essential rate-controlling steps. The activation energy of adsorption (EA) was determined as--1.69 kJ mole(-1). Using the thermodynamic equilibrium coefficients obtained at different temperatures, the thermodynamic constants of adsorption (deltaG degrees, deltaH degrees, and deltaS degrees) were also evaluated.     

Dissipation of 2,4-D in soils of the Humid Pampa region, Argentina: a microcosm study

Phenoxy herbicides like 2,4-dichlorophenoxyacetic acid (2,4-D) are widely used in agricultural practices. Although its half life in soil is 7-14d, the herbicide itself and its first metabolite 2,4-dichlorophenol (2,4-DCP) could remain in the soil for longer periods, as a consequence of its intensive use. Microcosms assays were conducted to study the influence of indigenous microflora and plants (alfalfa) on the dissipation of 2,4-D from soils of the Humid Pampa region, Argentina, with previous history of phenoxy herbicides application. Results showed that 2,4-D was rapidly degraded, and the permanence of 2,4-DCP in soil depended on the presence of plants and soil microorganisms. Regarding soil microbial community, the presence of 2,4-D degrading bacteria was detected even in basal conditions in this soil, possibly due to the adaptation of the microflora to the herbicide. There was an increment of two orders of magnitude in herbicide degraders after 15d from 2,4-D addition, both in planted and unplanted microcosms. Total heterotrophic bacteria numbers were about 1x10(8) CFUg(-1) dry soil and no significant differences were found between different treatments. Overall, the information provided by this work indicates that the soil under study has an important intrinsic degradation capacity, given by a microbial community adapted to the presence of phenoxy herbicides.     

Removal technology for pesticide contaminants in potable water

Abstract

Granular activated carbon adsorption is one of the reliable and effective means of removing organochlorine pesticides from water. Continuous stirred tank and fix bed reactor systems were used for the screening of indigenous granular activated carbons in the removal of organochlorine pesticides from water at low microgram levels in simulated samples. The carbon dose reguired to treat raw water at initial concentrations of 5–10 ug/1 of Y‐HCH, p,p'‐DDT and p,p'‐DDE to <2 ug/1 potable level was computed. Data leads to the development of a tap attachable water treatment unit for pesticides removal for applications on domestic scale.     

The system design of UV-assisted catalytic oxidation process--degradation of 2,4-D

Unlike the conventional first- or second-order model, a novel approach to design for the removal of 2,4-dichlorophenoxy (2,4-D) by the UV-catalytic oxidation process (UVCOP) was investigated. Two distinctive parameters, initial decay rate and maximum oxidative capacity, were characterized. By using these parameters, the performance of the degradation of 2,4-D by UVCOP regarding to the reagent dosages could be successfully predicted. Low concentrations of ferrous ion was found to be a rate-limiting factor for the process while the dosage of hydrogen peroxide was concluded as a dominant species in determining the maximum oxidation capacities. This information can be used to optimize the treatment process and achieve the expected performance target; an "optimal-dose model" was developed accordingly. The model is an intelligent and useful tool to evaluate the optimal doses of hydrogen peroxide with the minimum dose of ferrous ion, which leads to a better design of the treatment process.