Initial Paraquat Concentration Research Articles

Magnetically recoverable steel slag/TiO2 visible‐light‐driven photocatalyst for paraquat degradation

AbstractParaquat is a bipyridylium herbicide with high solubility in water, which is widely used for aquatic weed control. The purposes of the present study were to introduce a navel TiO2‐based photocatalyst (SCS@Fe‐TiO2) and investigate its performance in paraquat degradation from aqueous solution under visible light. The response surface methodology (RSM) method was used to optimize pH, catalyst dose, initial concentration of paraquat, and irradiation intensity in the photocatalytic process. The characterization results of the photocatalyst revealed that coating Fe‐TiO2 onto the SCS has improved its photo‐degradation properties. Diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) results showed that not only doping TiO2 by Fe but also coating Fe‐TiO2 onto the SCS makes a reduction in the bandgap and electron–hole recombination. Totally, the performance of the photocatalytic process was high (90%–99%) and the effect of the parameters studied on the process was significant (p‐value <0.05). The concentration of paraquat and irradiation intensity variables had linear relationships, so increasing the concentration of paraquat reduced the efficiency but the light intensity had the opposite effect. On the other hand, pH and photocatalyst mass had optimum values of 7 and 0.7 g, respectively, so they were the most important variables. and h+ played a crucial role in the photo‐degradation of paraquat by SCS@Fe‐TiO2. SCS@Fe‐TiO2 exhibited excellent photocatalytic reactivity for paraquat over 10 cycles. Finally, the SCS@Fe‐TiO2 would be a promising photocatalyst for the photo‐degradation of paraquat from aqueous solutions under visible light.

Plasma Concentration After the First Hemoperfusion has a High Predictive Value in Medium Level Acute Paraquat-Poisoned Patients.

Paraquat ( PQ) is very poisonous to humans and animals and there is no effective clinical antidote . The efficacy of hemoperfusion (HP) treatment for PQ poisoning remains controversial. To explore new ways to predict the prognosis of patients with acute PQ poisoning and assist in the development of better hemopurification treatment strategies. The clinical data of patients who were intoxicated with PQ through contact were diagnosed with PQ poisoning by high-performance liquid chromatography. Samples were collected by the Emergency Intensive Care Unit of the First Affiliated Hospital of Wenzhou Medical University from January 2012 to November 2016. Based on the prognosis, the patients were grouped into survival and death groups. Comparisons of the differences in the clinical indexes were performed, including the initial concentration of PQ at admission, PQ concentration after first HP, the number of HP cartridges used for the first hemoperfusion, whether HP was combined with continuous renal replacement therapy, and the number of concurrent organ injuries between the 2 groups. In addition, data were analyzed using multivariate logistic regression models and receiver operating characteristic curves. Moreover, prognostic factors in patients with acute PQ poisoning were analyzed. Overall, 128 patients with acute PQ poisoning were enrolled in this study. The median plasma PQ concentrations of the patients at admission were 21 and 834 ng/mL (range: 50-1,099,118 ng/mL). The multiple logistic regression model revealed that the initial concentration of PQ and the PQ concentration after the first perfusion were independent risk factors for death in patients with acute PQ poisoning. The PQ concentration in the survival group after the first HP was <516 ng/mL and was mainly distributed at approximately 100 ng/mL. The percentage of patients whose concentration after the first HP was <516 ng/mL in the death group was only 19%. The initial plasma PQ concentration after admission and PQ concentration after the first HP are risk factors for death in patients with acute PQ poisoning. Moreover, PQ concentration after the first HP had a high predictive value for death. When the initial plasma PQ concentration after admission ranges from 50 ng/mL to 5000 ng/mL, the rapid reduction in plasma PQ concentration after HP treatment could improve the prognosis of patients with acute PQ poisoning.

Highly Stable Photocatalytic Removal of Paraquat Dichloride using ZnO/TiO2 supported on PVC

This study presents on ZnO/TiO2 supported on PVC (ZnO/TiO2@PVC) in the photocatalytic removal of paraquat dichloride. The ZnO/TiO2@PVC was characterized using XRD, FESEM-EDX, FTIR, and AFM. Findings indicated that ZnO/TiO2@PVC allowed degradation of paraquat dichloride under UV irradiation by the rate of up to 73%. XRD pattern indicated the presence of both TiO2(anatase) and ZnO (zincite) crystalline as well as PVC amorphous structures. FESEM and AFM results revealed the observed shape and surface of TiO2 interconnected nanowires with ZnO nanorods uniformly distributed according to EDX mapping. The reduced surface roughness was also shown in the supported photocatalyst. FTIR analysis clearly demonstrate the combined spectra of immobilised ZnO/TiO2 powder catalyst onto the PVC in the composite. Kinetic study of the degradation process was performed according to pseudo-first-order and the influence of ZnO/TiO2 coating onto PVC polymer and initial paraquat concentration were investigated on the treatment performance. Under optimized condition (pH = 7, PQ =20 mg/L and catalyst coating =15%), the stability and reusability of the supported catalyst was also evaluated over ten sequential treatment runs, and the catalyst maintain high reactivity. High recyclability of the ZnO/TiO2@PVC composites as catalyst in photodegradation processes are also reported in this study.

Experimental design for the optimization of paraquat removal from aqueous media using a fixed-bed column packed with Pinus Eldarica stalks activated carbon

In this study, a fixed-bed column packed with an activated carbon (Pinus eldarica stalks (PES-AC)) was used to evaluate the performance of paraquat removal from wastewater. The effect of bed height, initial paraquat concentration, contact time, flow rate on the removal of paraquat was investigated using response surface methodology (RSM) based on central composite design (CCD). From the RSM model, the optimum experimental conditions to achieve 94.65% removal of paraquat were solution pH of 8.0, 6 mg L−1 of paraquat, 4 mL min−1 of flow rate, 0.8 cm of the bed height, and 40 min of contact time. The breakthrough data were significantly fitted with Thomas, bed depth services time (BDST), and Yoon–Nelson models. The high values of NBD (14.33, 32.29, and 54.46 mg L−1) and critical bed depth (0.396, 0.370, and 0.330 cm) obtained from BDST model revealed the high efficiency and suitability of the adsorbent. Adsorption of paraquat on PES-AC was strongly dependent on solution pH, indicating an electrostatic attraction mechanism.

Ultrasound-assisted adsorption of paraquat herbicide from aqueous solution by graphene oxide/ mesoporous silica

In the present study, the graphene oxide (GO) nanosheets /mesoporous SiO2 nanocomposites were prepared from graphene oxide without any surfactant. The obtained GO/SiO2 was synthesized through a simple two-step reaction, including modified Hummer's method and sol-gel route using a mixture of tetraethylorthosilane (TEOS). The as-synthesized GO/SiO2 composite was characterized by FE-SEM, EDS, XRD, FTIR, BET and element mapping. The as-synthesized GO/SiO2 composite used as an adsorbent to remove herbicide paraquat (PQ) from aqueous solution by ultrasound-assisted. To investigate the influence of various variables including initial concentration of PQ, pH and mass of adsorbent in batch experiments based on CCD. The equilibrium data were better explained by Langmuir isotherm model and adsorption capacity of GO/SiO2 from Langmuir model was 31.34 mg g−1. The exothermic enthalpy change of −48.791 kJ mol−1 and the results indicated the spontaneous nature based on negative Gibbs free energy change for adsorption of PQ by GO/SiO2. The presence 0.1 M of NaCl, Na2CO3 and KNO3 salt in aqueous solution have a significant effect on the adsorption of PQ.

Capacitive Deionization for the Removal of Paraquat Herbicide from Aqueous Solution

In comparison to other conventional methods like adsorption and reverse osmosis (RO), capacitive deionization (CDI) has only been investigated extensively for the removal of inorganic pollutants from water, demonstrating limited practicality. Herein, the study investigated the use of CDI for the removal of paraquat (PQ) herbicide from water by using commercial activated carbon (AC) electrodes. The CDI performance was examined as a function of the initial PQ concentration, applied voltage, flowrate, treatment time, and cycle stability testing in the batch mode approach. The applied voltage had a beneficial effect on the removal efficiency, whereas the removal efficiency of PQ declined as the initial PQ concentration increased. However, the electrosorption capacity gradually increased with the increase of initial feed solutions’ concentration. The maximum removal efficiency and electrosorption capacity achieved at 5 mg/L and 20 mg/L PQ initial concentrations, an applied voltage of 1.2 V, and 5 mL/min flowrate were 100% and 0.33 mg/g and 52.5% and 0.7 mg/g, respectively. Washing the electrodes with distilled water achieved sequential desorption of PQ, and the process produces a waste stream that can be disposed of or treated further. Therefore, the CDI method is considered a promising and efficient method for removing organic pollutants from water including pesticides.

Water-insoluble cyclodextrin polymer crosslinked with citric acid for paraquat removal from water

The anionic water-insoluble cyclodextrin polymer (polyCTR-β-CD) was crosslinked between β-cyclodextrin (β-CD) and citric acid (CTR) at 180 °C during 30 minutes to eliminate paraquat (PQ) from water. The reaction yield was equal to 70.2%, the ionic exchange capacity corresponded to 3.29 mmol·g−1 and the β-CD content was 0.29 mmol·g−1. Then, samples were characterized by SEM, ATR-FTIR, TGA, BET and stereoscopic microscope. Adsorption experiments were investigated with different factors such as pH of the solution, contact time, initial concentration of paraquat and adsorption temperature. The relevant pH was equal to 6.5 and the optimal contact time was 120 minutes to attain adsorption equilibrium. At 30 °C, the adsorption capacity was increased (9.4, 17.4 and 20.8 mg·g−1) when the initial concentration of paraquat was raised (25, 50 and 200 mg·L−1 respectively). Adsorption kinetics was appropriated to the pseudo-second-order model and adsorption isotherm was fitted to the Langmuir model. For thermochemistry parameters at different temperatures, the negative ΔG° showed a spontaneous adsorption process, the negative ΔH° indicated an exothermic process and the positive ΔS° exhibited an increase disorder. Finally, the reusability of the insoluble polymer was reached 78.3% after four regeneration cycles in methanol.

Adsorption of paraquat from water by insoluble cyclodextrin polymer crosslinked with 1,2,3,4-butanetetracarboxylic acid

An insoluble polymer was elaborated by crosslinking reaction between β-CD (β-cyclodextrin) and BTCA (1,2,3,4-butanetetracarboxylic acid) and it was firstly applied in adsorption of paraquat (PQ) from water. This insoluble polymer was synthesized at 180 °C for 30 min which displayed 74.1% of reaction yield, 3.80 mmol g− 1 of ion exchange capacity (IEC) and 0.18 mmol g− 1 of β-CD content. Physicochemical properties were evaluated by attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR), carbon-13 nuclear magnetic resonance (13C NMR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) method and stereoscopic microscopy. The optimal pH was 8 and the equilibrium time was 120 min. At 30 °C, the adsorption capacity was enhanced (10.8, 19.7, and 25.8 mg g− 1) when the initial concentration of paraquat was increased (25, 50 and 200 mg L− 1, respectively). Adsorption kinetics was described by the pseudo-second-order model and adsorption isotherm was appropriated to the Langmuir model. The negative standard enthalpy change (∆Ho) showed an exothermic process, the positive standard entropy change (∆So) displayed an increased disorder and the negative standard Gibbs free energy change (∆Go) indicated a spontaneous adsorption method. Ultimately, the regeneration efficiency of polymer in methanol was 87.3% after four cycles. This polymer could be used as a potential adsorbent for removal of other cationic pesticides.

Removal of paraquat herbicide from water by textile coated with anionic cyclodextrin polymer

The coating of anionic cyclodextrin polymer on polyethylene terephthalate (PET) textile was achieved by crosslinking between β-cyclodextrin (β-CD) and citric acid (CTR) to adsorb paraquat herbicide from aqueous solution. This coating performance (30 min, 170 °C) was 22.18% of weight gain which was corresponded to 0.51 mmol/g of ion exchange capacity (IEC). Then, the samples were characterized by scanning electron microscopy (SEM), attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR) and thermogravimetric analysis (TGA). The appropriated pH was 6.5 and the equilibrium time was 420 min. At 30 °C, the adsorption capacity towards paraquat (PQ) was enhanced (4.5, 18.9 and 23.7 mg/g) when the initial concentration of paraquat was increased (10, 50 and 250 mg/L). The adsorption kinetics was fitted to the pseudo-second-order model and the adsorption isotherm was suitable to Langmuir model. For the thermodynamic studies, the negative ∆G° revealed a spontaneous process, the negative ∆H° showed an exothermic process and the positive ∆S° displayed an enhanced disorder. Finally, the reusability of functionalized textile in methanol was reached 78.6% after six regeneration cycles and the stability of sample in various solvents was also studied. Anionic cyclodextrin polymer coated on PET textile issued from the crosslinking between β-cyclodextrin and citric acid was used as an efficient adsorbent for paraquat removal from aqueous solution.

Coating of PET Textiles with Anionic Cyclodextrin Polymer for Paraquat Removal from Aqueous Solution

Polyethylene terephthalate (PET) textile was coated with anionic cyclodextrin polymer issued by crosslinking between β-CD (β-Cyclodextrin) and BTCA (1,2,3,4-butanetetracarboxylic acid) for paraquat (PQ) removal from aqueous solution. The polymer covering operated by the thermofixation method (170 oC and 30 minutes) comprised 23.52 % of weight gain, which was related to 0.76 mmol/g of ionic exchange capacity. The functionalized textile was also characterized by FTIR, SEM and TGA. Adsorption experiment was performed employing different parameters such as the pH of the solution, adsorption time, the initial concentration of paraquat and the adsorption temperature. The suitable pH was equal to 8 and the equilibrium time was 420 minutes. At 30 oC, the adsorption capacity of PQ was increased (5.0, 20.4, and 25.9 mg/g) when the initial concentration of paraquat was enhanced (10, 50, and 250 mg/l). Adsorption kinetics was appropriated to the pseudo-second-order model and adsorption isotherm was fitted to the Langmuir model. Thermodynamic parameters were studied at different temperatures (30, 40, and 50 oC), in which the negative ΔH displayed an exothermic adsorption process, the negative ΔG showed a spontaneous adsorption process and the positive ΔS revealed an enhanced disorder. Eventually, the recyclability of the modified textile in methanol reached 85 % after four reusability cycles.

A designed experimental approach for photocatalytic degradation of paraquat using α-Fe2O3@MIL-101(Cr)@TiO2 based on metal–organic framework

A new magnetic α-Fe2O3@MIL-101(Cr)@TiO2 photocatalyst was successfully prepared. The structural and morphological properties of synthesized photocatalyst were studied by FTIR, XRD, SEM, EDX and BET analysis. Optimizing of the removal of paraquat herbicide from aqueous solution was investigated by response surface methodology based on Box–Behnken design. The interactive effects of four parameters including the dosage of catalyst, pH, the initial concentration of paraquat and contact time, all have been studied on the photocatalytic degradation and COD reduction. A quadratic polynomial model was adjusted to the data with an R2 of 0.89 for photocatalytic degradation and R2 of 0.92 for COD reduction, respectively. The photocatalytic degradation and COD reduction were obtained 87.46% and 90.09% at the optimal conditions, after 45 min using 0.2 g L−1 of α-Fe2O3@MIL-101(Cr)@TiO2, pH 7 and the concentration of paraquat 20 mg L−1. The kinetics of paraquat adsorption on the surface of α-Fe2O3@MIL-101(Cr)@TiO2 photocatalyst were obtained by the pseudo-second-order and parabolic diffusion models.

Photocatalytic Decomposition of Paraquat Under Visible Light by Carbon Nitride and Hydrogen Peroxide

Carbon nitride is a newly discovered and probably only known organic photocatalyst that can be activated by visible light due to its relatively lower bandgap energy. In this research, carbon nitride was synthesized by thermal polymerization of dicyandiamide in air and in elevated temperature. Paraquat, or methyl viologen, is a commonly used herbicide that possesses several threats to the environment. In this research, photocatalytic decomposition of paraquat by pure carbon nitride in water and under visible light irradiation is observed to be negligible. Addition of only a small amount of hydrogen peroxide to the system remarkably enhances the overall photocatalytic decomposition of paraquat under visible light. The photodegradation of paraquat is also investigated as a function of the dose of photocatalyst, concentration of hydrogen peroxide, and initial concentration of paraquat. The dual role of hydrogen peroxide in enhancing the photocatalytic activity of carbon nitride can be attributed to the generation of additional amounts of highly reactive hydroxyl radical in the system and the prevention of recombination of electron-hole pairs in carbon nitride thereby stabilizing its prolonged photocatalytic activity. In this study, liquid chromatography-mass spectroscopy (LCMS) study was employed to understand the intermediate products of the photodegradation of paraquat. To the best of our knowledge, this is one of the few reports on the photocatalytic decomposition of paraquat under visible light irradiation and the results suggest that the carbon nitride-hydrogen peroxide system can be potentially used to decompose paraquat and its toxic effects in water.

PHOTOCATALYTIC DEGRADATION OF PARAQUAT USING N-TiO2/SiO2 UNDER VISIBLE LIGHT

In the present paper, photocatalytic degradation of paraquat using N-TiO2/SiO2 with different molar ratio of titanium: nitrogen (Ti:N) under visible light was investigated. The catalyst was prepared via immersed SiO2 in N-TiO2. N-TiO2 was synthesized by sol-gel method. The N-TiO2/SiO2 catalyst was characterized using X-ray diffraction, UV diffuse reflectance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy. The results from characterizations indicated that N-doped anatase TiO2 had a 20-25 nm size. Degradation of paraquat, at an initial concentration of 10 mg/L was determined by UV-Vis. Chemical oxygen demand (COD) was used for process performance. Based on the COD tests, the COD values in residual paraquat was lower than that in initial paraquat concentration after 8 hours illumination of visible light. Moreover, the experiment’s results indicated that 80% of paraquat was degraded within 8 h of illumination time. These results showed that N-TiO2/SiO2 with molar Ti:N=2:1 gives the highest degradation efficiency of paraquat under visible light. This catalyst was stable and reusable suggesting it can be applied to treat organic pollutant in water.

Catalytic activity of bimetallic Zn/TiO2 catalyst for degradation of herbicide paraquat: synthesis and characterization

The preparation and characterization of Zn/TiO2 catalysts were performed and the photocatalytic properties of the resulting catalysts were tested using the paraquat degradation reaction under UV and solar light irradiation. The effect of the preparation method, amount of Zn loading, the calcination temperature and the thermal annealing during the autoclave aging were studied as well as the light irradiation during the testing reaction. The initial concentration of paraquat was 400 ppm, the pH during the catalytic testing was seven and the reaction temperature was 30 °C. The characterization information were obtained from XRD, XPS, UV–vis diffuse reflectance, FTIR, TEM and BET techniques. They were used to explain the expressed catalytic activity of Zn/TiO2. The results showed that the Zn/TiO2 catalyst from the hydrothermal method could remove about 80% of the paraquat from the solution (using 4 g l−1 of catalyst). The characterization data showed that the surface area, porous structure and dispersion of Zn species could affect the ability of the paraquat removal rather than the crystallnity of the TiO2 in the catalyst. The XPS spectra suggested that the preparation method, between the sol gel and hydrothermal, could not affect the state of the Zn and Ti, which presented in the Zn2+ and Ti4+ forms. This primary result will lead us to further study to elucidate the main active site by the XPS technique. Moreover, it clearly showed that the lowering of the band gap energy in the Zn/TiO2 was achieved (compared to bare TiO2), and this phenomena was one of the factors that gave the higher photocatalytic activity of the Zn/TiO2 catalyst.

Adsorption of Paraquat Dichloride by Graphitic Carbon Nitride Synthesized from Melamine Scraps

In this research, graphitic carbon nitride (g-C3N4) was synthesized from useless melamine scraps. Mixture of melamine powder and urea was directly burned in the muffle furnace at 550 °C. Later as-synthesized g-C3N4 was modified with hydrochloric acid. The g-C3N4 powder was characterized by several techniques including X-ray diffraction, scanning electron microscope, and specific surface area analyser. Adsorption of the herbicide paraquat from an aqueous solution to suspended particles of g-C3N4 was investigated, taking into consideration several parameters such as initial concentration of paraquat, initial pH, and dosage of g-C3N4. The results showed that with the same amount of g-C3N4, the increase in the paraquat concentration caused the reduction in the removal efficiency and the higher the amount of g-C3N4, the less residual paraquat remained in the bulk solution. G-C3N4 showed better adsorption behaviour in the basic condition. Finally, Langmuir and Freundlich adsorption isotherms were also evaluated. Paraquat adsorption by g-C3N4 was in accordance with Langmuir more than Freundlich adsorption isotherm.

Producción de enzimas ligninolíticas durante la degradación del herbicida paraquat por hongos de la pudrición blanca

Paraquat is a widely used herbicide in agriculture. Its inappropriate use and wide distribution represents a serious pollution problem for soil and water. White rot fungi are capable of degrading pollutants having a similar structure to that of lignin, such as paraquat. This study evaluated the degradation effect of paraquat on the production of ligninolytic enzymes by white rot fungi isolated from the South of Mexico. Six fungal strains showed tolerance to the herbicide in solid culture. Three of the six evaluated strains showed levels of degradation of 32, 26 and 47% (Polyporus tricholoma, Cilindrobasidium laeve and Deconica citrispora, respectively) after twelve days of cultivation in the presence of the xenobiotic. An increase in laccase and manganese peroxidase (MnP) activities was detected in the strains showing the highest percentage of degradation. Experiments were done with enzyme extracts from the extracellular medium with the two strains showing more degradation potential and enzyme production. After 24hours of incubation, a degradation of 49% of the initial paraquat concentration was observed for D. citrispora. These results suggest that paraquat degradation can be attributed to the presence of extracellular enzymes from white rot fungi. In this work the first evidence of the biodegradation potential of D. citrispora and Cilindrobasidium leave is shown.

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 &amp; Sons, Ltd.

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.

Clearance rate and BP-ANN model in paraquat poisoned patients treated with hemoperfusion.

In order to investigate the effect of hemoperfusion (HP) on the clearance rate of paraquat (PQ) and develop a clearance model, 41 PQ-poisoned patients who acquired acute PQ intoxication received HP treatment. PQ concentrations were determined by high performance liquid chromatography (HPLC). According to initial PQ concentration, study subjects were divided into two groups: Low-PQ group (0.05–1.0 μg/mL) and High-PQ group (1.0–10 μg/mL). After initial HP treatment, PQ concentrations decreased in both groups. However, in the High-PQ group, PQ levels remained in excess of 0.05 μg/mL and increased when the second HP treatment was initiated. Based on the PQ concentrations before and after HP treatment, the mean clearance rate of PQ calculated was 73 ± 15%. We also established a backpropagation artificial neural network (BP-ANN) model, which set PQ concentrations before HP treatment as input data and after HP treatment as output data. When it is used to predict PQ concentration after HP treatment, high prediction accuracy (R = 0.9977) can be obtained in this model. In conclusion, HP is an effective way to clear PQ from the blood, and the PQ concentration after HP treatment can be predicted by BP-ANN model.

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.