Adsorption Of Paraquat Research Articles

Modeling, kinetic, and equilibrium characterization of paraquat adsorption onto polyurethane foam using the ion-pairing technique

We studied the adsorption of paraquat onto polyurethane foam (PUF) when it was in a medium containing sodium dodecylsulfate (SDS). The adsorption efficiency was dependent on the concentration of SDS in solution, because the formation of an ion-associate between the cationic paraquat and the dodecylsulfate anion was found to be a fundamental step in the process. A computational study was carried out to identify the possible structure of the ion-associate in aqueous medium. The obtained data demonstrated that the structure is probably formed from four units of dodecylsulfate bonded to one paraquat moiety. The results showed that 94% of the paraquat present in 45 mL of a solution containing 3.90 × 10−5 mol L−1 could be retained by 300 mg of PUF, resulting in the removal of 2.20 mg of paraquat. The experimental data were reasonably adjusted to the Freundlich isotherm and to the pseudo-second-order kinetic model. Also, the application of Morris–Weber and Reichenberg models indicated that both film-diffusion and intraparticle-diffusion processes were active during the control of the adsorption kinetics.

Adsorption behavior of herbicide paraquat from aqueous solutions using starfish particles: kinetic, isotherm, and thermodynamic studies

AbstractThe adsorption of paraquat (PQ) on starfish particles was investigated to calculate the kinetic, isotherm, and thermodynamic parameters. The experiments were carried out as a function of particle size of adsorbent, adsorbent dosage, contact time, initial PQ concentration, stirring speed, and temperature. The kinetic data followed the pseudo‐second‐order kinetic model, and the equilibrium data were well fitted by the Langmuir isotherm model with the maximum adsorption amount of 10.235 mg g−1 at 288 K. Thermodynamic parameters, including standard Gibbs free energy changes (ΔG0), standard entropy changes (ΔS0), and standard enthalpy changes (ΔH0) were also calculated. The results demonstrated that PQ was adsorbed onto starfish particles spontaneously and exothermically in nature. The adsorption process followed a physisorption mechanism. In addition, the starfish particles were successfully utilized to real sample. Hence, starfish particles are eligible for treating the wastewater containing PQ as an effective and low‐cost adsorbent. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

ADSORPTION OF PARAQUAT DICHLORIDE TO KAOLIN PARTICLES AND TO MIXTURES OF KAOLIN AND HEMATITE PARTICLES IN AQUEOUS SUSPENSIONS

Deliberate contamination with pesticides is a potential risk to water security, due to the availability of these contaminants and the fact that they do not need special expertise to handle or apply. Adsorption of the herbicide paraquat from an aqueous solution to suspended particles of kaolin and kaolin/hematite mixture was investigated by kinetic and equilibrium assays, taking into consideration several parameters such as initial pH, sorbent dosage and agitation speed. The results showed that the adsorption process is quite fast, reaching an 18% reduction in paraquat concentration in a very short period of time. The addition of hematite particles to kaolin suspension had no apparent effect on the maximum amount of paraquat adsorbed. Kinetic parameters were determined by fitting the pseudo-second order model to the experimental data (correlation coefficients close to 1). Isotherm studies indicate an inhibitory effect, promoted by hematite particles, that was not detected in the adsorption assays. Equilibrium data was best adjusted using the Langmuir model which yielded higher correlation coefficient values and smaller normalized standard deviations.

Removal of Paraquat from Aqueous Solutions Using Multi-Walled Carbon Nanotubes: Kinetic, Isotherm and Thermodynamic Studies

Multi-walled carbon nanotubes (MWCNT) were used as an efficient adsorbent to remove Paraquat (PQ) molecules from its aqueous solutions. The initial PQ concentration, adsorption time and temperature had considerable effect on the removal of PQ onto MWCNT. The adsorption of PQ onto MWCNT followed the pseudo second-order kinetic model involving the particle-diffusion mechanism. The adsorption isotherms were fitted by the Langmuir isotherm, with the maximum adsorption capacity based on the former of 79.365 mg·g-1. Thermodynamic parameters, including Gibbs free energy changes (ΔG0), as well as changes in enthalpy (ΔH0) and entropy (ΔS0), were also calculated. The results demonstrated that PQ was adsorbed onto MWCNT spontaneously and endothermically in nature.

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.

Sorption and Infiltration Potential of a Cationic Herbicide (Paraquat) in Three Cocoa Growing Soils in Nigeria

Despite the ban of paraquat, its use among Nigerian farmers for weed control is still popular. Larger proportion of applied herbicide ends up in the soil matrix. Off-site transfer of the residual paraquat as contaminant to other environmental compartment depends on sorption process. In order to study the influence of soil characteristics on retention and infiltration of paraquat in cocoa soils, adsorption of paraquat in selected cocoa soils was carried out. In the course of the experiment, Owena, Ibadan and Ikom soils were equilibrated with paraquat solutions of different concentrations ranging from 100 to 800 mg paraquat kg -1 soil. Result showed that, Freundlich model gave better description of paraquat adsorption in the investigated soils than Langmuir model. The pseudo second order kinetic equation gave better description of the adsorption mechanism than pseudo first order. Statistical analysis showed that, aluminium oxide and clay mineral contents were the main soil physicochemical parameters that influenced paraquat sorption in the soils. The low values of groundwater ubiquity score obtained from the adsorption data showed that, the investigated soils were non leacher of paraquat. Hence, its guided and appropriate use may not cause underground water contamination. Original Research Article Aikpokpodion et al.; BJAST, 6(1): 62-76, 2015; Article no.BJAST.2015.067 63

Synthesis of acrylic-acid-modified shorea sawdust and application in adsorbing toxic organic materials

Shorea sawdust grafted with poly(acrylic acid) (SD-g-PAA) is synthesized and characterized as an adsorbent of toxic organic compounds. SD-g-PAA copolymers are prepared using Fenton’s reagent (Fe+2–H2O2) as the redox initiator. The graft copolymerization is examined to determine the effects of temperature, concentrations of Fe(aq)+2 and H2O2(aq), and AA/SD ratio. The obtained maximum grafting percentage of the grafted copolymer is 13.0 ± 0.2%. The grafted copolymer is characterized using Fourier transform infrared spectroscopy and solid-state 13C NMR. A representative SD-g-PAA copolymer is neutralized to a sodium salt (SD-g-PANa) and used in the adsorption of malachite green (MG), methyl violet (MV), and paraquat (PQ). The monolayer adsorption capacities of these substances are 233.7, 312.9, and 164.8 mg/g adsorbent, respectively. The high adsorption capacity of SD-g-PANa for toxic matter indicates its potential in the treatment of wastewater that contains MG, MV, or PQ.

Removal of paraquat from drinking water by activated carbon prepared from waste wood

In this study, activated carbon was produced from the chips of two wood species, namely Ayous (Triplochiton schleroxylon) and Sapelli (Entandrophragma cylindricum) and characterized for its texture by scanning electron microscopy, granulometry using a master sizer, and the structure by determining the iodine and methylene blue indices. The obtained carbon was used to study the adsorption of paraquat in aqueous solution. Results from the characterization of carbon revealed that it consist essentially of micropores and mesopores, a tubular structure, and a fine coating of very small granules on the surface (Ayous) and elongated fibers (Sapelli). The adsorption kinetics of paraquat in solution followed a maximum exponential growth model with three stages: the first, which corresponds to an increase adsorption of the molecule on sites located on the outer surface of the carbon, the second phase, which correspond to the diffusion of the molecules on the internal pores, and the third constant phase corresponding to the adsorption equilibrium. The equilibrium time obtained was 10 min for Ayous with 87% of paraquat adsorbed and 20min for Sapelli with 90% of paraquat adsorbed. The biosorption kinetics of paraquat in the solution followed a pseudo-first order and intra-particle diffusion model. Result from the influence of paraquat concentration and mass of carbon showed that, an increase in concentration and mass of the adsorbent impel respectively in the amount of the paraquat molecule adsorbed. Change of solution pH does not affect the amount of paraquat adsorbed whatever the type of carbon. The adsorbed amounts of paraquat decreased (from 88 to 60 mg g−1) as the ionic strength increased from 5 × 10−3 to 5 × 10−2 M. This study shows that activated carbon products obtained from Sapelli and Ayous wood chips, which are wastes released into the environment, can be used as low-cost biosorbents for the removal of organic micropollutants in drinking water.

Effect of the surfactant benzalkonium chloride in the sorption of paraquat and cadmium on montmorillonite

Pesticides, heavy metals and surfactants can share the same region or site in the environment and thus they may compete for the surface of minerals. A competitive study of the adsorption between the cationic surfactant benzalkonium chloride (BAC) with the heavy metal cadmium (Cd(II)) and the cationic herbicide paraquat (PQ) on montmorillonite is presented. Adsorption isotherms for BAC, PQ and Cd(II) were performed in single solute systems and also in binary solute systems, PQ+BAC and Cd(II)+BAC to evaluate the effects of BAC on the adsorption of the other two substances. The affinities of BAC and PQ were strong and similar, thus BAC affected significantly the adsorption of PQ and vice versa. The affinity of Cd(II) for the montmorillonite surface was low, thus BAC affected appreciably Cd(II) adsorption, but the heavy metal did not modify BAC adsorption. XRD data show that BAC molecules control the magnitude of the basal spacing.

A Highly Efficient Activated Carbon by Chemical Activation Method for Adsorption of Paraquat (Toxin)

The optimum condition for preparing a highly efficient activated carbon has been investigated in this work. The effects of different activation temperatures on the pore structure and surface morphology of highly efficient activated carbon (AC) derived from waste palm shell by chemical activation method using phosphoric acid as activating agent were studied. For activation, different activation temperatures in the range of 550 °C-650 °C were carried out. Activated carbon with well developed pore size were produced at activation temperature of 600 °C for 2 hours. At this temperature the Brunauer , Emmett and Teller (BET) surface areas are 1287 m2g-1, the total pore volume for adsorption and desorption are 0.742 cm3 g-1. Scanning Electron Microscope also confirmed the porosity of the highly efficient activated carbon. Finally it was tested in vitro to determine its adsorbing capacity for paraquat as a toxin. For optimum adsorption ability of activated carbon for paraquat, 0.9% NaCl solution is the most suitable solvent. The paraquat preferentially adsorbed onto the activated carbon in NaCl solution. The adsorption ability of the activated carbon (the amount adsorbed) for paraquat observed to be 99.9 mg g-1.

Paraquat adsorption on porous materials synthesized from rice husk silica

The goal of this work was to utilize rice husk silica (RHS) and porous materials synthesized with RHS, including mesoporous material (MCM-41) and microporous materials (zeolite NaY and NaBEA), for adsorption of herbicide paraquat. The adsorption occurred although cation exchange and the capacity decreased in the following order: NaY > NaBEA > MCM-41 > RHS, consistent with the amount of Al. The adsorption on all adsorbents fitted well with the Langmuir model and the maximum adsorption capacity of 185.2 mg/g-adsorbent was obtained on NaY. In addition, blue dye in commercial grade paraquat did not interfere with paraquat adsorption. Although MCM-41 was the most efficient adsorbent for the blue dye, RHS was favorable in terms of production cost. A mixture of NaY and RHS is recommended for simultaneous adsorption of paraquat and blue dye.

Synthesis and characterization of large pore cubic mesoporous silicas functionalized with high contents of carboxylic acid groups and their use as adsorbents

Well-ordered cubic FDU-12 type mesoporous silicas functionalized with various contents of carboxylic acid group (COOH), up to 40mol% based on silica, were synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and carboxyethylsilanetriol sodium salt (CES) under acidic conditions using Pluronic F127 triblock copolymer as template. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), 13C and 29Si solid-state nuclear magnetic resonance (NMR) measurements. The materials were used as adsorbents for removal of methylene blue (MB) in aqueous solutions and as an antidote for intoxication of herbicide paraquat (PQ). Due to the COOH functionalization, three-dimensional pores, high surface areas, and electrostatic interactions between the adsorbent and the adsorbates, the prepared adsorbents possessed very high adsorption capacities and extremely rapid rates for MB and PQ adsorption. The kinetic regression results revealed that the overall adsorption process was controlled by external mass transfer and intra-particle diffusion jointly. The Langmuir isotherm model showed better fit with the experimental adsorption data than the Freundlich isotherm model, implying a monolayer adsorption mechanism. The present results show that the prepared COOH functionalized cubic mesoporous silicas have great potentials for removing pollutants and herbicides from aqueous solutions in environmental and clinical applications.

Silica Adsorbents and Peroxide Functionality for Removing Paraquat from Wastewater

To treat wastewater containing paraquat, the interaction of the herbicide with unmodified and modified (i.e., chemically treated) proprietary silicas is explored using liquid chromatography—mass spectrometry and ultraviolet-visible spectrometry. Strong adsorption and rapid exchange kinetics (i.e., more than 80% within 30 s) of the contaminant onto both unmodified and modified silica surfaces indicate that paraquat adsorption is inherent to the unmodified silica. Although activated carbon sequesters paraquat more effectively than silica at long times (i.e., after 2 h), considering both constant mass and constant area approaches in loading the adsorbents, the best performance in the short-term (i.e., at least up to 150 s) interaction was achieved by using unmodified silicas. Comparison of data fitting to a competitive binding model with or without consideration of homogeneous solid diffusion indicates that, at least for times relevant to water-treatment applications, the competitive binding model is an appropriate mathematical tool to explain experimental adsorption data. Addition of H2O2 is also attempted to initiate paraquat decomposition; however, silica is not an effective catalyst for peroxide decomposition paraquat.

Adsorption of paraquat from aqueous medium by Amberlite XAD-2 and XAD-4 resins using dodecylsulfate as counter ion

A study is reported about the adsorption of the herbicide paraquat (PQT2+) by the polymeric resins Amberlite XAD-2 and XAD-4, in a medium containing sodium dodecylsulfate (SDS). The strategy employed in this study was based on the adsorption of the ion-associate complex, formed between the cationic PQT2+ and the dodecylsulfate anion, which presents high affinity by the hydrophobic resins. The effect of several parameters that could affect the efficiency of adsorption (SDS concentration, pH, mass of adsorbent and initial concentration of PQT2+) was investigated. Also, a detailed kinetic characterization of the system was performed. The SDS concentration added to the medium affected the adsorption efficiency, while the pH of the solution did not present any effect on the efficiency in the range of 2–9.5. The mass of adsorbent was studied in the range of 100–500mg and did not influence the adsorption efficiency, changing only the adsorption rate. The kinetic evaluation of the system indicated that the adsorption of the PQT2+ followed a pseudo first-order model and that the adsorption rate was controlled by an intraparticle diffusion mechanism.

Preparation of acrylic acid-modified chitin improved by an experimental design and its application in absorbing toxic organic compounds

Chitin grafted poly (acrylic acid) (chi-g-PAA) is synthesized and characterized as an adsorbent of toxic organic compounds. Chi-g-PAA copolymers are prepared using of ammonium cerium (IV) nitrate (Ce4+) as the initiator. The highest grafting percentage of AA in chitin obtained using the traditional technique is 163.1%. A maximum grafting percentage of 230.6% is obtained using central composite design (CCD). Experimental results are consistent with theoretical calculations. The grafted copolymer is characterized by Fourier transform Infrared spectroscopy and solid state 13C NMR. A representative chi-g-AA copolymer is hydrolyzed to a type of sodium salt (chi-g-PANa) and used in the adsorption of malachite green (MG), methyl violet (MV), and paraquat (PQ) in aqueous. The monolayer adsorption capacities of these substances are 285.7, 357.1, and 322.6mg/g-adsorbent, respectively. Thermodynamic calculations show that the adsorption of MG, MV, and PQ are more favored at diluted solutions. The high adsorption capacity of chi-g-PANa for toxic matter indicates its potential in the treatment of wastewater and emergency treatment of PQ-poisoned patients.

Experimental improvement of preparation of acrylic acid-modified middle deacetylated chitosan and its application in absorbing paraquat

Chitosan with 45% deacetylation (CS45) grafted poly (acrylic acid) (CS45-g-PAA) was synthesized and characterized as an adsorbent of paraquat. CS45-g-PAA copolymers were prepared using H2O2(aq) as an initiator and NH4OH(aq) as a promoter. The highest grafting percentage of 44.2% was obtained using the traditional kinetic method. However, a maximum grafting percentage of 52.6% was calculated for the central composite design (CCD). Experimental results based on the reaction conditions that were predicted from the CCD are consistent with theoretical calculations. The grafted copolymer was characterized by FTIR, BET, and SEM. A representative CS45-g-PAA copolymer was hydrolyzed to a salt type (CS45-g-PANa) and used in the adsorption of paraquat. The adsorption equilibrium data correlate more closely with the Langmuir isotherm than with the Freundlich equation. The maximum adsorption capacity of CS45-g-PANa is 396.7 mg/g-adsorbent. This value clearly exceeds that of Fuller's earth and the activated carbon which is the most commonly used binding agent for paraquat. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Adsorption of paraquat on soil organic matter: Effect of exchangeable cations and dissolved organic carbon

Herbicides that interact with soil organic matter do so with both the solid and the dissolved fractions, so that the distribution of herbicide between the soil solution and solid phases is determined by competitive effects. In the present study, adsorption experiments were carried out with the cationic herbicide paraquat and untreated and acid-washed samples of a peat soil, at different values of pH and ionic strength. Less herbicide was adsorbed onto the untreated peat than onto the acid-washed peat; the difference was due to the presence of exchangeable cations, as demonstrated in experiments carried out by adding Ca2+ to suspensions of acid-washed peat. The results were interpreted by an electrostatic model and the fitting parameters indicated that the adsorption constants were the same for both samples of peat, although the number of binding sites available was different. Simultaneous resolution of the adsorption equilibrium of paraquat for the soil organic matter (SOM) and of the binding equilibrium between paraquat and dissolved organic matter (DOM) enabled the distribution of paraquat between the solid and solution phases to be determined. The increased solubility of the SOM with increasing pH led to a decrease in the fraction of paraquat retained on the peat surface above pH 5.5, which favors the mobility of the herbicide in the soil.

Effect of salinity on adsorption and desorption of paraquat in Pak Phanang river sediment, Thailand

Batch experiments were conducted to study the effect of salinity (0–30 g L−1) on adsorption and desorption of paraquat (1, 1′-dimethyl-4, 4′-dipyridylium dichloride), one of the most widely used herbicides in the world, in sediment of Pak Phanang River Basin, Thailand. Sediments from five locations were used in the studies (two from freshwater sites and three sites under saline environment). The adsorption capacity (Kf) of the sediments was positively correlated with CEC (r = 0.81**) and clay content (r = 0.70*). Paraquat adsorption by sediment was faster under fresh water (0 g L−1) versus saline conditions (10 and 20 g L−1). The adsorption coefficient (Kf) at low salinity (0 g L−1) was 17,302 whereas the Kf at 10 and 20 g L−1 were 5,344 and 4,263, respectively. Paraquat desorption was greater at higher salinity, which is similar to the salinity of estuarine or seawater. Approximately 12–31 % of sorbed paraquat in fresh water and saline sediment (7.67 and 7.98 mg kg−1) were released when leaching with 20 g L−1 salinity. The amount of paraquat released was in proportion to the amount sorbed. Results show that increases in salinity resulting from salt water intrusion from the lower estuary into the Pak Phanang River Basin would result in release of adsorbed paraquat from sediment into the water column.

Determination of Paraquat and Diquat by Combination of Nanoparticles‐Based Extraction with Capillary Electrophoresis

AbstractSilica nanoparticles (SiNPs) have been used as concentrating probes to extract paraquat and diquat from aqueous solution before capillary electrophoretic analysis. Adsorption of paraquat and diquat onto SiNPs is mainly through electrostatic interaction. After extraction and centrifugation, the analytes were eluted from the surface of SINPs by rinsing with acetic acid solution. The extract was directly analyzed by capillary electrophoresis with UV absorption detection. Using SiNPs to concentrate the analytes from 10 mL of aqueous solution, the enrichment factors for paraquat and diquat were 75 and 192, respectively. The limits of detection (LODs) at signal‐to‐noise ratio of 3 were 0.03 and 0.05 μM for paraquat and diquat, respectively. This developed method was applied to the determination of paraquat in mung bean. The LOD of paraquat in mung bean was 0.1 μg/g.

Adsorption of paraquat on mesoporous silica modified with titania: Effects of pH, ionic strength and temperature

The adsorption of the herbicide paraquat (PQ 2+) on the binary system titania–silica has been studied in batch experiments by performing adsorption isotherms under different conditions of pH, supporting electrolyte concentration, and temperature. Adsorption kinetic on the studied material has also been carried out and discussed. PQ 2+ adsorption is very low on the bare silica surface but important on the composed TiO 2–SiO 2 adsorbent. In this last case, the adsorption increases by increasing pH and decreasing electrolyte concentration. There are no significant effects of temperature on the adsorption. The increase of the adsorption in TiO 2–SiO 2 seems to be related to an increase in acid sites of the supported titania and to the homogenously dispersion of the TiO 2 nanoparticles over the silica support. The adsorption takes place by direct binding of PQ 2+ to TiO 2 leading to the formation of surface species of the type SiO 2–TiO 2–PQ 2+. Electrostatic interactions and charge-transfer and outer-sphere complexes formations seem to play a key role in the adsorption mechanism. The analysis of thermodynamic parameters suggests that the adsorption on TiO 2–SiO 2 is endothermic and spontaneous in nature.