The release of chlorophenoxyherbicides agrochemicals, namely 2-chloro- (2CPA), 4-chloro and 2,4,5-trichloro (TCPA) phenoxyacetates from their nanohybrids into various aqueous solutions; carbonate, sulfate and chloride was found to be controlled by pseudo-second order rate expression. The percentage saturated released was found to be anionic-dependent, in the order of carbonate>sulfate>chloride for the release media and 2CPA>4CPA>TCPA for the anionic guests. This study demonstrates that the release of the phenoxyherbicides agrochemicals from the nanohybrid compounds can be tuned by choosing the right combination of exchangeable anions both the incoming and the outgoing anions.
An artificial neural network (ANN) model was developed to simulate the biodegradation of herbicide glyphosate [2-(Phosphonomethylamino) acetic acid] in a solution with varying parameters pH, inoculum size and initial glyphosate concentration. The predictive ability of ANN model was also compared with Monod model. The result showed that ANN model was able to accurately predict the experimental results. A low ratio of self-inhibition and half saturation constants of Haldane equations (< 8) exhibited the inhibitory effect of glyphosate on bacteria growth. The value of K(i)/K(s) increased when the mixed inoculum size was increased from 10(4) to 10(6) bacteria/mL. It was found that the percentage of glyphosate degradation reached a maximum value of 99% at an optimum pH 6-7 while for pH values higher than 9 or lower than 4, no degradation was observed.
Herbicides, namely 4-(2,4-dichlorophenoxy) butyrate (DPBA) and 2-(3-chlorophenoxy) propionate (CPPA), were intercalated simultaneously into the interlayers of zinc layered hydroxide (ZLH) by direct reaction of zinc oxide with both anions under aqueous environment to form a new nanohybrid containing both herbicides labeled as ZCDX. Successful intercalation of both anions simultaneously into the interlayer gallery space of ZLH was studied by PXRD, with basal spacing of 28.7 Å and supported by FTIR, TGA/DTG and UV-visible studies. Simultaneous release of both CPPA and DPBA anions into the release media was found to be governed by a pseudo second-order equation. The loading and percentage release of the DPBA is higher than the CPPA anion, which indicates that the DPBA anion was preferentially intercalated into and released from the ZLH interlayer galleries. This work shows that layered single metal hydroxide, particularly ZLH, is a suitable host for the controlled release formulation of two herbicides simultaneously.
The removal of toxic herbicide from wastewater is challenging due to the availability of suitable adsorbents. The Langsat empty fruit bunch is an agricultural waste and was used in this study as a cheap precursor to produce activated carbon for the adsorption of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) at different initial concentrations ranging from 50 to 400 mg/L. The produced Langsat empty fruit bunch activated carbon (LEFBAC) was mesoporous and had high surface area of 1065.65 m(2)/g with different active functional groups. The effect of shaking time, temperature and pH on 2,4-D removal were investigated using the batch technique. The adsorption capacity of 2,4-D by LEFBAC was decreased with increase in pH of solution whereas adsorption capacity increased with temperature. The adsorption data was well described by Langmuir isotherm followed by removal capacity of 261.2 mg/g at 30 °C. The results from this work showed that LEFBAC can be used as outstanding material for anionic herbicide uptake from wastewater.
This paper reports on the direct ability of two positively charged organic polyelectrolytes (natural-based and synthetic) to reduce the atrazine concentration in water. The adsorption study was set up using multiple glass vessels with different polymer dosing levels followed by ultrafiltration with a 1 kDa membrane. The addition of polymers exhibited a capability in reducing the atrazine concentration up to a maximum of 60% in surface-to-volume ratio experiments. In the beginning, the theoretical L-type of the isotherm of Giles' classification was expected with an increase in the dosage of the polymer. However, in this study, the conventional type of isotherm was not observed. It was found that the adsorption of the cationic polymer on the negatively charged glass surface was necessary and influential for the removal of atrazine. Surface-to-volume ratio adsorption experiments were performed to elucidate the mechanisms and the polymer configuration. The glass surface area was determined to be a limiting parameter in the adsorption mechanism.
This study was carried out to determine the sorption-desorption, degradation and leaching of napropamide in selected Malaysian soils. The sorption capacities of the selected Malaysian soils for napropamide were the following in descending order: Linau > Teringkap > Gunung Berinchang > Jambu > Rudua > Baging soil. The results indicate that napropamide degradation decreased with increasing soil sorption capacity. Napropamide was leached out earlier in the Baging soil than the other soils. Overall, the application of napropamide in the selected Malaysian soils would not pose a threat to the environment except in soil with low organic matter and clay content and high hydraulic conductivity, such as the Baging soil.
This study examined the performance of nanofiltration membranes to retain atrazine and dimethoate in aqueous solution under different pH conditions. Four nanofiltration membranes, NF90, NF200, NF270 and DK are selected to be examined. The operating pressure, feed pesticide and stirring rate were kept constant at 6x10(5) Pa, 10 mg/L and 1000 rpm. It was found that increasing the solution's pH increased atrazine and dimethoate rejection but reduced the permeate flux performance for NF200, NF270 and DK. However, NF90 showed somewhat consistent performance in both rejection and permeate flux regardless of the solution's pH. NF90 maintained above 90% of atrazine rejection and approximately 80% of dimethoate rejection regardless of the changes in solution's pH. Thus, NF90 is deemed the more suitable nanofiltration membrane for atrazine and dimethoate retention from aqueous solution compared to NF200, NF270 and DK.
Triazine-2-(14)C metsulfuron-methyl is a selective, systemic sulfonylurea herbicide. Degradation studies in soils are essential for the evaluation of the persistence of pesticides and their breakdown products. The purpose of the present study was to investigate the degradation of triazine-2-(14)C metsulfuron-methyl in soil under laboratory conditions. A High Performance Liquid Chromatograph (HPLC) equipped with an UV detector and an on-line radio-chemical detector, plus a Supelco Discovery column (250 x 4.6 mm, 5 μm), and PRP-1 column (305 x 7.0 mm, 10 μm) was used for the HPLC analysis. The radioactivity was determined by a Liquid Scintillation Counter (LSC) in scintillation fluid. The soil used was both sterilized and non-sterilized in order to observe the involvement of soil microbes. The estimated DT50 and DT90 values of metsulfuron-methyl in a non-sterile system were observed to be 13 and 44 days, whereas in sterilized soil, the DT50 and DT90 were 31 and 70 days, respectively. The principal degradation product after 60 days was CO2. The higher cumulative amount of (14)CO2 in (14)C-triazine in the non-sterilized soil compared to that in the sterile system suggests that biological degradation by soil micro-organisms significantly contributes to the dissipation of the compound. The major routes of degradation were O-demethylation, sulfonylurea bridge cleavage and the triazine "ring-opened."
The persistence of metsulfuron-methyl (methyl 2-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl]aminosul fonyl]benzoate) in nonautoclaved and autoclaved Selangor, Lating, and Serdang series soils incubated at different temperatures and with different moisture contents was investigated under laboratory conditions using cucumber (Cucumis sativus L.) as the bioassay species. Significant degradation of metsulfuron-methyl was observed in nonautoclaved soil compared with the autoclaved soil sample, indicating the importance of microorganisms in the breakdown process. At higher temperatures the degradation rate in nonautoclaved soil improved with increasing soil moisture content. In nonautoclaved Selangor, Lating and Serdang series soils, the half-life was reduced from 4.79 to 2.78 days, 4.9 to 3.5, and from 3.3 to 1.9 days, respectively, when the temperature was increased from 20 degrees to 30 degrees C at 80% field capacity. Similarly, in nonautoclaved soil, the half-life decreased with an increasing soil moisture from 20% to 80% at 30 degrees C in the three soils studied. In the autoclaved soil, the half-life values were slightly higher than those obtained in the nonautoclaved soils, perhaps indicating that the compound may be broken down by nonbiological processes. The fresh weight of the bioassay species was reduced significantly in Serdang series soil treated with metsulfuron-methyl at 0.1 ppm. However, the reduction in fresh weight of the seedlings was least in Lating series soil, followed by Selangor series soil.
The adsorption, desorption, and mobility of permethrin in six tropical soils was determined under laboratory and greenhouse conditions. The six soils were selected from vegetable growing areas in Malaysia. Soil organic matter (OM) was positively correlated (r2 = 0.97) with the adsorption of permethrin. The two soils, namely, Teringkap 1 and Lating series with the highest OM (3.2 and 2.9%) released 32.5 and 30.8% of the adsorbed permethrin after four consecutive repetitions of the desorption process, respectively, compared to approximately 75.4% of the Gunung Berinchang soil with the lowest OM (1.0%) under the same conditions. The mobility of permethrin down the soil column was inversely correlated to the organic matter content of the soil. Permethrin residue penetrated only to the 10-15 cm zone in the Teringkap 1 soil with 3.2% OM but penetrated to a depth of more than 20 cm in the other soils. The Berinchang series soil with the lowest OM (1.0%) yielded leachate with 14.8% permethrin, the highest level in leachates from all the soils tested. Therefore, the possibility for permethrin to contaminate underground water may be greater in the presence of low organic matter content, which subsequently allows a higher percentage of permethrin to move downwards through the soil column.
In this study, the performance of glyphosate removal in an electrocoagulation batch with two electrodes formed by the same metal type, consisting of aluminum, iron, steel and copper have been compared. The aim of this study intends to remove glyphosate from an aqueous solution by an electrocoagulation process using metal electrode plates, which involves electrogeneration of metal cations as coagulant agents. The production of metal cations showed an ability to bind together to form aggregates of flocs composed of a combination of glyphosate and metal oxide. Electrocoagulation using aluminum electrodes indicated a high percentage removal of glyphosate, 94.25%; followed by iron electrodes, 88.37%; steel electrodes, 62.82%; and copper electrodes, 46.69%. The treated aqueous solution was then analyzed by Fourier Transform Infrared Spectroscopy. Percentages of Carbon, Hydrogen, Nitrogen, Sulfur remaining in the treated aqueous solution after the electrocoagulation process have been determined. The treated water and sludge were characterized and the mechanism of the overall process was concluded as an outcome. An X-Ray Diffraction analysis of dried sludge confirmed that new polymeric compounds were formed during the treatment. The sludge composed of new compounds were also verified the removals. This study revealed that an electrocoagulation process using metal electrodes is reliable and efficient.
The present study revealed the optimization of nanoemulsion containing palm oil derivatives and Parthenium hysterophorus L. crude extract (PHCE) as pre-emergence herbicide formulation against Diodia ocimifolia. The nanoemulsion formulation was prepared by high energy emulsification method, and it was optimized by mixture experimental design (MED). From the optimization process, analysis of variance (ANOVA) showed a fit quadratic polynomial model with an optimal formulation composition containing 30.91% of palm kernel oil ester (PKOE), 28.48% of mixed surfactants (Tensiofix and Tween 80, 8:2), 28.32% of water and 12.29% of PHCE. The reading of both experimental and predicted particle size in the verification experiment were acceptable with a residual standard error (RSE) was less than 2%. Under the optimal condition, the smallest particle size obtained was 140.10 nm, and the particle was shown by morphology analysis to be spherical and demonstrated good stability (no phase separation) under centrifugation and different storage conditions (25 ± 5°C and 45°C). Nanoemulsion stored for 60 days exhibits monodisperse emulsion with a slight increase of particle size. The increase in particle size over time might have contributed by Ostwald ripening phenomenon which is shown by a linear graph from Ostwald ripening rate analysis. In the in vitro germination test, P. hysterophorus nanoemulsion (PHNE) was shown to cause total inhibition of D. ocimifolia seed at lower concentration (5 g L-1) as compared to PHCE (10 g L-1). The finding of the research could potentially serve as a platform for the development of palm oil based formulation containing plant crude extract for green weed management.
Imidazolinones as a persistent and active herbicides group have potential risks to non-target organisms in the environment. Biochar is a carbon-rich sorbent used as an amendment to change soil properties and its microbial communities effective on pesticides degradation rate. The present study was the first to compare empty fruit bunch (EFB) of oil palm and rice husk (RH) biomasses as biochar feedstock for remediation of imidazolinones-contaminated soils. Degradations of imazapic, imazapyr, and a mixture of them (Onduty®) was investigated in the presence of the optimized biochars in the soil during a 70-days incubation. Based on the results, the polar herbicides were resistant to hydrolysis degradation. Photolysis rates of the herbicides reduced significantly in the presence of the biochars in the soil. EFB biochar had greater effects due to its chemical compositions and surface functional groups. Photo-degradation of imazapyr was more affected by biochars amendment. The imidazolinones bio-degradation, however, accelerated significantly with the presence of EFB and RH biochars in soil with the greater effects of RH biochar. It was concluded that the application of the optimized EFB and RH biochars as an innovative sustainable strategy has the potential to decrease the persistence of the imidazolinones and minimize their environmental hazards.
Hybridization of beneficial organic guest with inorganic host affords scientists an opportunity to synthesize various combinations of new organic-inorganic nanohybrids with various potential applications, especially for controlled delivery of beneficial agent and storage. A new layered organic-inorganic nanohybrid material containing an agrochemical, 4-(2,4-dichlorophenoxy)butyrate (DPBA) in Zn-Al-layered double hydroxide inorganic interlayer was synthesised by direct and indirect methods. Both methods yielded mesoporous-type, phase pure, well-ordered layered nanohybrids with similar basal spacing of 28.5-28.7 angstroms and organic loading of around 54.3%. Compared to the material prepared by direct method, the ion exchanged product inherited more of the host's properties especially the pore structure and the organic moiety is also more easily released. This shows that the method of preparation plays an important role in determining the resulting physicochemical properties, in particular the release property and therefore can be used as a means to tune up the release property of the beneficial agent.
A new electric-field driven extraction approach based on the integration of a bubbleless electrode into the electromembrane extraction (EME) across hollow polymer inclusion membranes (HPIMs) was demonstrated for the first time. The bubbleless electrode was prepared based on an in-situ synthesised polyacrylamide within a fused silica capillary. The electrode functions as a salt bridge, which conducts the electrical current between the acceptor phase in the lumen of the HPIM and the acceptor solution in the reservoir connected to a high voltage supply through a platinum electrode. Two types of HPIMs were employed, which consisted of desired proportions of cellulose acetate as base polymer, tris(2-ethylhexyl)phosphate as plasticizer, and di-(2-ethylhexyl)phosphoric acid as anionic carrier or Aliquat 336 as cationic carrier, respectively. The EME strategy was evaluated for the simultaneous determination of cationic quaternary ammonium and anionic chlorophenoxy acetic acid herbicides present in the river water, respectively. The analysis was carried out using capillary electrophoresis coupled with UV and contactless conductivity detection. Under the optimised conditions, enrichment factors in the range of 152-185-fold were obtained from 4mL of river water sample with a 20min extraction time and an applied voltage of 3000V. The proposed method provided good linearity with correlation coefficients ranging from 0.9982 to 0.9997 over a concentration range of 1-1000μg/L. The detection limits of the method for the herbicides were in the range of 0.3-0.4μg/L, with relative standard deviations of between 4.8% and 8.5%. The relative recoveries obtained when analysing the spiked river water ranged from 99.1% to 100%. A comparison was also made between the newly developed approach with the conventional EME setup by placing the platinum electrode directly in the lumen of the HPIMs.
Weed infestation is a persistent problem for centuries and continues to be major yield reducing issue in modern agriculture. Chemical weed control through herbicides results in numerous ecological, environmental, and health-related issues. Moreover, numerous herbicides have evolved resistance against available herbicides. Plant extracts are regarded as an alternative to herbicides and a good weed management option. The use of plant extracts is environmentally safe and could solve the problem of herbicide resistance. Therefore, laboratory and wire house experiments were conducted to evaluate the phytotoxic potential of three Fabaceae species, i.e., Cassia occidentalis L. (Coffee senna), Sesbania sesban (L.) Merr. (Common sesban) and Melilotus alba Medik. (White sweetclover) against seed germination and seedling growth of some broadleaved weed species. Firstly, N-hexane and aqueous extracts of these species were assessed for their phytotoxic effect against lettuce (Lactuca sativa L.). The extracts found more potent were further tested against germination and seedling growth of four broadleaved weed species, i.e., Parthenium hysterophorus L. (Santa-Maria), Trianthema portulacastrum L. (Pigweed), Melilotus indica L (Indian sweetclover). and Rumex dentatus L. (Toothed dock) in Petri dish and pot experiments. Aqueous extracts of all species were more toxic than their N-hexane forms for seed germination and seedling growth of lettuce; therefore, aqueous extracts were assessed for their phytotoxic potential against four broadleaved weed species. Aqueous extracts of all species proved phytotoxic against T. portulacastrum, P. hysterophorus, M. indica and R. dentatus and retarder their germination by 57, 90, 100 and 58%, respectively. Nevertheless, foliar spray of C. occidentalis extract was the most effective against T. portulacastrum as it reduced its dry biomass by 72%, while M. alba was effective against P. hysterophorus, R. dentatus and M. indica and reduced their dry biomass by 55, 68 and 81%, respectively. It is concluded that aqueous extracts of M. alba, S. sesban and C. occidentalis could be used to retard seed germination of T. portulacastrum, P. hysterophorus, M. indica and R. dentatus. Similarly, aqueous extracts of C. occidentalis can be used to suppress dry biomass of T. portulacastrum, and those of M. alba against P. hysterophorus, R. dentatus. However, use of these extracts needs their thorough testing under field conditions.
The non-ionic silicone surfactant (OFX 0309) has been applied in cloud point extraction for the extraction of triazine herbicides in food samples. Evidence has shown that the non-ionic silicone surfactant demonstrated a good performance as an extractor toward triazine herbicides. In this present study, OFX 0309 surfactant was combined with activated charcoal (AC) due to their valuable properties. Activated charcoal modified with non-ionic silicone surfactant coated with magnetic nanoparticles (AC-OFX MNPs) was synthesized and characterized by FT-IR, VSM, SEM, TEM and BET. This novel material was applied as a magnetic adsorbent for the pre-concentration and separation of triazine herbicides due to hydrophobic interaction between polysiloxane polyether of OFX 0309 surfactant and triazine herbicides. Under optimal conditions, the proposed magnetic solid phase extraction method using AC-OFX MNPs adsorbent was applied to extract triazine herbicides from selected milk and rice samples using high performance liquid chromatography coupled with diode array detector. The validation method revealed a good linearity (1 - 500 μg L-1) with the coefficient of determination (R2) in the range of 0.992-0.998 for the samples. The limits of detection (LOD) of the developed method were 0.04 - 0.05 µg L-1 (milk sample) and 0.02 - 0.05 µg L-1 (rice sample). The limits of quantification (LOQ) were 0.134 - 0.176 µg L-1 (milk sample) and 0.075 - 0.159 µg L-1 (rice sample). The recoveries of the triazine compounds ranged from 81% to 109% in spiked milk samples and from 81% to 111% in spiked rice samples, with relative standard deviations (RSD) values lower than 13.5% and 12.1% for milk and rice samples, respectively. To the best of our knowledge, this is the first study that have investigated the use of magnetic nanoparticles coated activated charcoal modified with OFX 0309 surfactant for pretreatment of triazine herbicides in food samples analysis for simultaneous separation of organic pollutants.
Pesticides are developed with carriers to improve their physicochemical properties and, accordingly, the bioefficacy of the applied formulation. For foliar-applied herbicide, generally less than 0.1% of the active ingredient reaching the target site could reduce pesticide performance. Recently, a carrier of nanoemulsion consisting of oil, surfactant and water, with a particle size of less than 200 nm, has been shown to enhance drug permeability for skin penetration in pharmaceutical delivery systems. In the present work, the aim was to formulate a water-soluble herbicide, glyphosate isopropylamine (IPA), using a green nanoemulsion system for a biological activity study against the weeds creeping foxglove, slender button weed and buffalo grass.