Initial Pesticide Concentration Research Articles

Study of the Adsorption Efficiency of an Eco-Friendly Carbohydrate Polymer for Contaminated Aqueous Solution by Organophosphorus Pesticide

The removal of pesticide (ethoprophos) from aqueous solution using a natural biosorbent such as chitosan (CH) prepared from a biopolymer waste obtained from marine industry was studied. The Fourier Transform Infrared Spectroscopy (FTIR), Scanning electron microscopy (SEM), and X-ray diffraction spectroscopy (XRD) were used to study the structure of the adsorbent. The biosorption studies were carried out under various parameters, such as biosorbent dose, initial pesticide concentration and contact time. The experimental results show that the removal percentage of ethoprophos increased from 85.693% to 89.234%, as adsorbent dose (CH) increased from 0.02 to 0.1 g/100ml. The equilibrium uptake was increased with an increase in the initial pesticide concentration in solution. Biosorption kinetic data were fitted well with the pseudo-second order kinetic model. The experimental isotherms data were analyzed using Freundlich, Langmuir, Temkin and Dubinin-Radushkevich (D-R) isotherm equations. The best fit was obtained by Freundlich isotherm with high correlation coefficients. That the value of energy calculated from the D-R isotherm was 5.56 KJ/mol suggests the adsorption of ethoprophos on Chitosan is physical. All the results indicating CH was chosen as low-cost biosorbent could be applied for the removal of organophosphorous pesticide from aqueous solutions.

Chlorine dioxide treatment for the removal of pesticide residues on fresh lettuce and in aqueous solution

The effectiveness of chlorine dioxide (CD) to remove phorate and diazinon residues on fresh lettuce and in aqueous solution was investigated. The results indicated that CD (20 mg/L) added in tap water can significantly improve the removal of phorate and diazinon on lettuce (p < 0.05), as compared to tap water wash. The study in aqueous solutions suggested that addition of CD could increase the removal rates of phorate and diazinon by 40–80% and 10–20% more than that in tap water without CD, respectively, indicating CD can result in the degradation of the both pesticides. The removal of the both pesticides in aqueous solutions was influenced by concentration of CD, pH value, treatment time, initial concentration and kind of pesticides. The degradation efficiency increased with the concentration of CD and treatment time, and the least removal rates of the both pesticides were obtained in the aqueous solution at pH 4.6. Furthermore, the lower initial concentration of pesticides, the higher degradation rate would be obtained. The degradation kinetics of both pesticides were fitted to the first-order kinetics model well, and the kinetics parameters indicated that phorate was much easier to be degraded than diazinon. The degradation products of both pesticides were identified by GC–MS, phorate and diazinon were oxidized to phorate sulfoxide and phoratoxon sulfoxide, diazoxon, respectively. The present study validates the application of CD treatment as a safe and promising method for the removal of pesticides on fresh fruits and vegetables.

Removal of organochlorine pesticides by chitosan loaded with silver oxide nanoparticles from water

Silver oxide nanoparticles embedded chitosan beads were studied to remove pesticides from water. A simple and an effective approach was used in regard to preparing AgO nanoparticles on the surface of chitosan. The chitosan–AgO nanoparticles (CS–AgONPs) composite was characterized by infrared spectroscopy (FTIR), X-ray diffraction, and scanning electron microscopy. The CS–AgONPs composite beads were optimized to remove maximum permethrin as the model pesticide, with amount of sorbent, agitating time, initial concentration of pesticide, and pH parameters. In optimum conditions, room temperature, pH 7, and the CS–AgONPs beads could recover 99 % pesticides of permethrin solution (0.1 mg L-1) which were characterized by using UV spectrophotometer at 272 nm. In comparison with the pure chitosan, the removal capacity of CS–AgONPs beads has been increased to 49 %. The CS–AgONPs composite beads have high capacity as an adsorbent which could explore a new biocompatible and eco-friendly strategy for pesticide removal, and appears to be the new promising material in water treatment application.

Comparative study on photocatalytic degradation of methomyl and parathion over UV-irradiated TiO2 particles in aqueous solutions

Photodegradation of methomyl and parathion, the representatives of carbamate and organophosphorus pesticides, respectively, over TiO2 particles under 400-W UV irradiation was investigated and compared at 40°C. All experiments were conducted at different initial pH values (4.0–10.0), initial pesticide concentrations (10–30mg/L), and TiO2 doses (0–1.5g/L). The Langmuir–Hinshelwood kinetic model was used to evaluate the apparent first-order rate constants of both pesticides at their initial stages of degradation processes. It was seen that methomyl was degraded much faster than parathion under comparable conditions, primarily due to more complicated structures of parathion molecules. The mineralization processes of methomyl and parathion by TiO2/UV were also studied on the basis of the measured total organic carbon (TOC) data. Finally, the possible degradation paths of methomyl and parathion were inferred by following the variations of the concentrations of final mineralized products with time.

Influence of Different Planting Seasons of Six Leaf Vegetables on Residues of Five Pesticides

To investigate the influence of different planting seasons on the dissipation of pesticides, field experiments of thiophanate-methyl, metalaxyl, fluazifop-P-butyl, chlorpyrifos, and λ-cyhalothrin on six crops including pakchoi, rape, crown daisy, amaranth, spinach, and lettuce were designed and conducted. In this study, a high-performance liquid chromatography and electrospray ionization-tandem mass spectrometer with multiple reaction monitoring was used to simultaneously determine thiophanate-methyl and its metabolite carbendazim, metalaxyl, and fluazifop-P-butyl in various samples; gas chromatography with an electron capture detector was used to detect chlorpyrifos and λ-cyhalothrin. The limits of quantitation (LOQs) of these six pesticides were in the range of 0.001-0.01 mg kg(-1) for all samples, and the average recoveries of all pesticides ranged from 60.1 to 119.1% at 0.01 and 0.1 mg kg(-1) spiked levels. The relative standard deviation (RSD) ranged from 1.1 to 13.9%. All maximal concentrations of the six pesticides in six leaf vegetables in autumn were higher than in summer in Beijing. For most pesticides half-lives in autumn were longer than in summer. The results showed that the initial concentration, maximal concentration, and half-lives of pesticides were influenced not only by environmental factors such as light, heat, moisture, and rainy climate but also by plant matrices.

Removal of Mixed Pesticides from Aqueous Solutions using Organoclays: Evaluation of Equilibrium and Kinetic Model

Removal of mixed pesticides, namely alachlor, metolachlor, chlorpyriphos, fipronil, α-endosulfan, β-endosulfan, p,p'-DDT and two metabolites p,p'-DDE and endosulfan sulphate from aqueous solution by batch adsorption onto three commercial organo-modified montmorillonite clays [modified with octadecylamine (ODA-M), modified with dimethyl- dialkylamine (DMDA-M) and modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M)] were investigated. Effect of process variables, mainly contact time and initial concentration of mixed pesticides, on adsorption phenomenon were evaluated. To understand the adsorption kinetic pseudo-first-order and pseudo-second-order models were tested. The pseudo-second-order model provided the best fit for explaining adsorption kinetics, on the basis of high correlation coefficient (r) and normalized percent deviation values. The adsorption equilibrium was explained by the Freundlich isotherm (r = 0.951-0.992). High values (0.17-0.52 mg g⁻¹) of Freundlich constant (K(f)) indicated higher affinity of pesticides towards all three organoclays, as a result of hydrophobic interaction between the adsorbent/adsorbate systems. Pesticides with high octanol-water partition coefficient (K(ow)) and low water solubility showed faster adsorption with higher K(f) values as compared to the pesticides with low K(ow) and high water solubility. The order of organoclays for removal efficiency of mixed pesticide was ODAAPS-M > DMDA-M > ODA-M. These findings may find application to decontaminate or treat mixed pesticide contaminated industrial/agricultural waste waters.

Influence of initial pesticide concentrations in water on chlorpyrifos toxicity and removal by Iris pseudacorus

For understanding the influence of initial concentrations of pesticides in the water body on removal efficiency of the contaminant by aquatic plants, one hydroponics experiment was used to investigate the influence of initial concentration (1-16 mg L(-1)) on toxicity and chlorpyrifos removal potential of Iris pseudacorus for 20 days under greenhouse conditions. An increased sensitivity to and reduced removal rate for chlorpyrifos were observed with increasing chlorpyrifos concentration. The relative growth rate (RGR) of I. pseudacorus was significantly inhibited in the presence of 4, 8 and 16 mg L(-1) chlorpyrifos, and a negative relationship was also found between RGR and initial pesticide concentration. The half-life of chlorpyrifos was shortened in the hydroponic system with plants, indicating that I. pseudacorus accelerated chlorpyrifos removal from water. But the contribution of the plant to chlorpyrifos removal in the hydroponic phytoremediation system decreased with the increase of initial concentration of chlorpyrifos. The results also indicated that I. pseudacorus can efficiently eliminate chlorpyrifos and may ultimately serve as phytoremediation agents in the natural water body.

Fabrication of two perovskite-type oxide nanoparticles as the new adsorbents in efficient removal of a pesticide from aqueous solutions: Kinetic, thermodynamic, and adsorption studies

The perovskite-type LaFe0.9Co0.1O3 (LFCO1) and LaFe0.1Co0.9O3 (LFCO2) nanoparticles (NPs) were prepared via sol–gel method. The structure and morphology of NPs were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), scanning tunneling microscopy (STM), energy dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET). The average particle size of NPs is approximately between 20 and 40nm. The ability of calcined NPs to remove vitavax as a typical pesticide in aqueous solutions was assessed. The removal kinetic studies were conducted on LFCOs NPs with different contact time, temperatures, initial pesticide concentrations, and adsorbent doses to find the optimum conditions. The results showed both NPs can remove the vitavax from aqueous solution with a very high adsorption capacity. The removal process follows first-order kinetics and the Langmuir adsorption isotherm model. The activation energy and Arrhenius factor were obtained from temperature dependence of the rate constant. The thermodynamic parameters of the adsorption were also determined.

Removal of Malathion Pesticide from Polluted Solutions by Electrocoagulation: Modeling of Experimental Results using Response Surface Methodology

The main purpose of this work was to assess the removal of the pesticide malathion from aqueous solution in batch mode using the electrocoagulation process. The effects of operational parameters such as initial pH, initial pesticide concentration, current density, salt concentration, and distance between electrodes on the malathion removal efficiency have been investigated in a laboratory scale study. The effects of current density and the supporting electrolyte on electrical energy consumption were also investigated. A phenomenological model was proposed using the response surface methodology method. The model indicated that the studied parameters have no effect on the experiment's design which had been established to give the final result. The other operating factors had both positive and negative effects. With an initial pH of 6, an initial pesticide concentration of 40 mg/L, current density of 10 mA/cm2, salt concentration of 2500 mg/L, temperature of 27°C, and distance between electrodes of 2 cm, over 90% of the malathion was removed after 10 min of electrolysis.

Removal of Carbaryl Pesticide from Aqueous Solution by Adsorption on Local Clay in Agadir

This study was conducted to assess the removal efficiency of pesticide (Carbaryl) used in Souss Massa region (Agadir city), on a clay originated from barrage situated in Agadir. The adsorption of Carbaryl from aqueous solution by local clay as a low-cost, natural and eco-friendly adsorbent was investigated. Different physicochemical parameters were analyzed: adsorbent mass, ionic strength (NaNO3), initial concentration of pollutant, temperature, and pH. The empirical results showed that all these parameters have an impact on the retention of pesticide on the clay. The equilibrium uptake was increased with an increase in the initial pesticide concentration in solution. The results of adsorption were fitted to the Langmuir and Freundlich isotherms. The Freundlich model represented the adsorption process better than Langmuir model, with correlation coefficients (R2) values ranged from 0.97 to 0.99. This study has shown that the natural clay is a solid that has got an important adsorption capacity, which may be used in treatment and depollution of water.

Photocatalytic degradation of five sulfonylurea herbicides in aqueous semiconductor suspensions under natural sunlight

In the present study, the photocatalytic degradation of five sulfonylurea herbicides (chlorsulfuron, flazasulfuron, nicosulfuron, sulfosulfuron and triasulfuron) has been investigated in aqueous suspensions of zinc oxide (ZnO), tungsten (VI) oxide (WO3), tin (IV) oxide (SnO2) and zinc sulfide (ZnS) at pilot plant scale under natural sunlight. Photocatalytic experiments, especially those involving ZnO photocatalysis, showed that the addition of semiconductors in tandem with the oxidant (Na2S2O8) strongly enhances the degradation rate of the herbicides in comparisons carried out with photolytic tests. The degradation of the herbicides follows a first order kinetics according to the Langmuir–Hinshelwood model. In our conditions, the amount of time required for 50% of the initial pesticide concentration to dissipate (t½) ranged from 8 to 27min (t30W=0.3–1.2min) for sulfosulfuron and chlorsulfuron, respectively in the ZnO/Na2S2O8 system. None of the studied herbicides was found after 120min of illumination (except chlorsulfuron, 0.2μgL−1).

Degradation of Organophosphorus Pesticides in Water during UV/H2O2 Treatment: Role of Sulphate and Bicarbonate Ions

The photodegradation of two organophosphorus pesticides, malathian and diazinon, by sulfate radicals and bicarbonate radicals in aqueous solution were studied. The effect of the operational parameters such as pH, salt concentration, water type, H2O2 concentration and initial concentration of pesticides was studied. Gas chromatography mass spectroscopy (GC–MS) was used for analyses of pesticides. When salt effect was studied, it was found that sodium bicarbonate was the most powerful inhibitor used, while sodium sulfate was the weakest one. The highest degradation in UV/H2O2 process for malathion was found in alkaline condition and for diazinon in acidic condition. The photodegradation in all waters used in this work exhibited first order kinetics. Photodegradation rate in distilled water was higher than real water. The degradation of pesticides increased with increasing of H2O2 concentration.

Photocatalytic Degradation of Dichlorvos in Visible Light byMg2+-TiO2Nanocatalyst

Photocatalytic activity of TiO2was studied by doping with magnesium (Mg2+-TiO2) with varying magnesium weight percentages ranging from 0.75–1.5 wt%. The doped and undoped samples were synthesized by sol-gel method and characterized by X-ray diffraction (XRD), N2adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), and scanning electron microscopy (SEM). The XRD data has shown that anatase crystalline phase in Mg2+-TiO2catalysts, indicating that Mg2+ions did not influence the crystal patterns of TiO2. The presence of magnesium ions in TiO2matrix has been determined by XPS spectra. DRS spectra showed that there is a significant absorption shift towards the visible region for doped TiO2. The SEM images and BET results showed that doped catalyst has smaller particle size and highest surface area than undoped TiO2. The photocatalytic efficiency of the synthesized catalysts was investigated by the photocatalytic degradation of aqueous dichlorvos (DDVP) under visible light irradiation, and it was found that the Mg2+-doped catalysts have better catalytic activity than undoped TiO2. This can be attributed that there is a more efficient electron-hole creation in Mg2+-TiO2in visible light, contrary to undoped TiO2which can be excited only in UV irradiation. The effect of dopant concentration, pH of solution, dosage of catalysts, and initial pesticide concentration has been studied.

Treatment of Pesticides in Wastewater by Heterogeneous and Homogeneous Photocatalysis

The effect of different heterogeneous and homogeneous photocatalytic systems on the oxidative degradation of mepiquat chloride in aqueous solutions was investigated. In the case of heterogeneous reactions, the influence of five factors was studied: the type of catalyst, photocatalyst concentration, pH, pesticide concentration, and the presence of H2O2and/or Fe3+. For homogeneous catalysis, other factors were studied: the oxidising agent and the light source. Nearly complete degradation of mepiquat chloride was obtained after about 180 minutes in the presence of an acid medium (pH3) using a UV-A lamp and TiO2P-25 catalyst (0.5 g/L), for an initial pesticide concentration of 10 ppm. Degradation rates corresponding to homogeneous photocatalysis were lower compared to those corresponding to the use of TiO2as the photocatalyst.

Pesticides Removal Using Conventional and Low‐Cost Adsorbents: A Review

AbstractWorldwide pesticide usage has increased dramatically during the last three decades, coinciding with changing practices and increasing by intensive agriculture. This widespread use of pesticides for agricultural and non‐agricultural purposes has resulted in the presence of their residues in various environmental matrices. The occurrence of pesticides and their metabolite transported in rivers, channels, lakes, sea, air, soils, groundwater, and even drinking water, proves the high risk of these chemicals to human health and the environment. Therefore, pesticide removal is of an increasing concern. In this study, a review of the published literature dealing with pesticides removal process is presented. Firstly, pesticide removal by conventional means is briefly considered. Secondly, the use of the low‐cost sorbent through biosorption process is discussed comprehensively. The effect of factors such as pH, contact time, sorbent dosage, initial pesticide concentration, and optimization of biosorption conditions is also discussed. Kinetic, thermodynamic, and mechanism studies are also given. This study shows that both microorganisms and other materials with biological origin like agricultural by‐products may be used to this end. There is a significant potential for pesticide uptake by the use of various pristine and especially modified biosorbents. In the case of living organisms used as removal agents, degradation may also play a role in the total removal observed.

Organo/layered double hydroxide nanohybrids used to remove non ionic pesticides

The preparation and characterization of organo/layered double hydroxide nanohybrids with dodecylsulfate and sebacate as interlayer anion were studied in detail. The aim of the modification of the layered double hydroxides (LDHs) was to change the hydrophilic character of the interlayer to hydrophobic to improve the ability of the nanohybrids to adsorb non-ionic pesticides such as alachlor and metolachlor from water. Adsorption tests were conducted on organo/LDHs using variable pH values, contact times and initial pesticide concentrations (adsorption isotherms) in order to identify the optimum conditions for the intended purpose. Adsorbents and adsorption products were characterized several physicochemical techniques. The adsorption test showed that a noticeable increase of the adsorption of the non-ionic herbicides was produced. Based on the results, the organo/LDHs could be good adsorbents to remove alachlor and metolachlor from water. Different organo/LDHs complexes were prepared by a mechanical mixture and by adsorption. The results show that HTSEB-based complex displays controlled release properties that reduce metolachlor leaching in soil columns compared to a technical product and the other formulations. The release was dependent on the nature of the adsorbent used to prepare the complexes. Thus, it can be concluded that organo/LDHs might act as suitable supports for the design of pesticide slow release formulations with the aim of reducing the adverse effects derived from rapid transport losses of the chemical once applied to soils.

Biosorption of 2,4‐d, 2,4‐DP, and 2,4‐DB from aqueous solution by using thermophilic anoxybacillus flavithermus and analysis by high‐performance thin layer chromatography: Equilibrium and kinetic studies

AbstractIn this study, the potential biosorption characteristics of the thermophilic Anoxybacillus flavithermus (A. flavithermus) was investigated for the removal of the chlorophenoxy acid derivates, namely, 2,4‐dichlorophenoxy acetic acid (2,4‐D), 2,4‐dichlorophenoxy propanoic acid (2,4‐DP or dichlorprop), and 2,4‐dichlorophenoxy butyric acid (2,4‐DB). The experiments were performed for the simultaneous biosorption of the studied pesticides. Optimum biosorption conditions were determined as a function of contact time, pH of the solution, amount of biomass, and initial pesticides concentrations. The concentrations of the pesticides in the remaining solutions were simultaneously analyzed by high performance thin layer chromatography. The optimum parameters were found as pH: 4.0 for biosorption medium, 60 min of contact time, 50 mg of bacteria, and 50 mg L−1 of initial pesticides concentrations. Langmuir and Freundlich models were applied to describe the biosorption isotherm of the pesticides by A. flavithermus as biomass. Biosorption of pesticides on to A. flavithermus showed pseudo first‐order rate kinetics at different initial concentration of pesticides and different temperatures. The experimental adsorption data were fitted both the Langmuir and Freundlich adsorption models. Fourier‐transform Infrared spectroscopy was used to understand the bonding mechanism of pesticides to biosorbent and surface functionality of the biosorbent The highest pesticide uptake was calculated from Langmuir isotherm and found to be 24.15 mg g−1 for 2,4‐D. Among the studied pesticides, 2,4‐DP showed difference adsorption behavior. According to in your comments the reason of this that 2,4‐DP contain an asymmetric carbon atom, which provide a molecular chirality. © 2011 American Institute of Chemical Engineers Environ Prog, 2011

Assessing the cleanability of a direct nozzle injection system

A direct injection system that injects pesticides locally at all nozzles on a boom was assembled and investigated under laboratory conditions with regards to its ability to be cleaned. The system was contaminated with a safe-to-use polyvinylpyrrolidone-water solution as a test pesticide before cleaning. The cleaning process was divided into two steps: 1) reclaiming the simulated pesticide by pushing it back into the pesticide tank using pressurised air (pre-cleaning) and 2) rinsing the contaminated part of the hydraulic system with water. Cleaning performance was investigated systematically to ascertain the initial dynamics of the rinsing process as well as long term cleaning. Evaluations included variation of 1) pre-cleaning time and 2) water inlet position. Measurements showed that the concentration of the simulated pesticide in the rinsing water could initially be as high as 30%. As the pre-cleaning time was extended the initial concentration was reduced by one third. Changing the water inlet position reduced the initial concentration of the simulated pesticide in the rinsing water to 5%. These concentrations were much higher than in most common spray solutions. This means that if an active pesticide was used further dilution of the pesticide concentration in the rinsing water would be required for it to be sprayed on a crop. In some cases it took more than 10 min to dilute simulated pesticide residues in a 3 m test section down to 0% which clearly shows the need for more research on factors influencing the cleaning process and more development of cleaning processes.

Pesticides removal from waste water by activated carbon prepared from waste rubber tire

Waste rubber tire has been used for the removal of pesticides from waste water by adsorption phenomenon. By applying successive chemical and thermal treatment, a basically cabonaceous adsorbent is prepared which has not only a higher mesopore, macropore content but also has a favorable surface chemistry. Presence of oxygen functional groups as evidenced by FTIR spectra along with excellent porous and surface properties were the driving force for good adsorption efficiency observed for the studied pesticides: methoxychlor, methyl parathion and atrazine. Batch adsorption studies revealed maximum adsorption of 112.0 mg g −1, 104.9 mg g −1 and 88.9 mg g −1 for methoxychlor, atrazine and methyl parathion respectively occurring at a contact time of 60 min at pH 2 from an initial pesticide concentration of 12 mg/L. These promising results were confirmed by column experiments; thereby establishing the practicality of the developed system. Effect of various operating parameters along with equilibrium, kinetic and thermodynamic studies reveal the efficacy of the adsorbent with a higher adsorption capacity than most other adsorbents. The adsorption equilibrium data obey Langmuir model and the kinetic data were well described by the pseudo-first-order model. Applicability of Bangham’s equation indicates that diffusion of pesticide molecules into pores of the adsorbent mainly controls the adsorption process. Spontaneous, exothermic and random characteristics of the process are confirmed by thermodynamic studies. The developed sorbent is inexpensive in comparison to commercial carbon and has a far better efficiency for pesticide removal than most other adsorbents reported in literature.

Removal of bentazone from micro-polluted water using MIEX resin: Kinetics, equilibrium, and mechanism

The contamination of surface and ground water by bentazone has attracted increasing global concern in recent years. We conducted a detailed investigation using MIEX resin to eliminate bentazone from waters. Batch experiments were carried out to evaluate the effect of process parameters, such as retention time, resin amount, and initial pesticide concentration, on removal efficiency of bentazone. Results showed the sorption process was fast and bentazone could be efficiently removed in 30 minutes. The kinetic process of bentazone sorption on MIEX resin was well described by pseudo second-order model and intraparticle diffusion was the rate controlling step. The MIEX resin possessed the highest sorption capacity of 0.2656 mmol/mL for bentazone according to Langmuir fitting. Bentazone is a hydrophobic ionizable organic compound, and both ionic charge and hydrophobic aromatic structure governed the sorption characteristics on MIEX resin. The different removal efficiencies of ionic and non-ionic pesticides, combined with the charge balance equations of bentazone, SO 4 2−, NO 3 − and Cl −, indicated that removal of bentazone using MIEX resin occurred primarily via ion exchange.