Controlled release of herbicide acetochlor from clay/carboxylmethylcellulose gel formulations

Herbicidal weed management practices: History and future prospects of nanotechnology in an eco-friendly crop production system

Weed management is an important aspect of crop production, as weeds cause significant losses in terms of yield and quality. Various approaches to weed management are commonly practiced by crop growers. Due to limitations in other control methods, farmers often choose herbicides as a cost-effective, rapid and highly efficient weed control strategy. Although herbicides are highly effective on most weeds, they are not a complete solution for weed management because of the genetic diversity and evolving flexibility of weed communities. The excessive and indiscriminate use of herbicides and their dominance in weed control have triggered the rapid generation of herbicide-resistant weed species. Moreover, environmental losses of active ingredients in the herbicides cause serious damage to the environment and pose a serious threat to living organisms. Scientific advances have enabled nanotechnology to emerge as an innovation with real potential in modern agriculture, adding a new dimension in the preparation of controlled release formulations (CRF) of herbicides. Here the required amount of active ingredients is released over longer periods of time to obtain the desired biological efficacy whilst reducing the harmful effects of these chemicals. Various organic and inorganic carrier materials have been utilised in CRF and researchers have a wide range of options for the synthesis of eco-friendly carrier materials, especially those with less or no toxicity to living organisms. This manuscript addresses the history, progress, and consequences of herbicide application, and discusses potential ways to reduce eco-toxicity due to herbicide application, along with directions for future research areas using the benefits of nanotechnology.

Multifunctional Nanoparticles and Nanopesticides in Agricultural Application

The unscientific application of pesticides can easily cause a series of ecological environmental safety issues, which seriously restrict the sustainable development of modern agriculture. The great progress in nanotechnology has allowed the continuous development of plant protection strategies. The nanonization and delivery of pesticides offer many advantages, including their greater absorption and conduction by plants, improved efficacy, reduced dosage, delayed resistance, reduced residues, and protection from natural enemies and beneficial insects. In this review, we focus on the recent advances in multifunctional nanoparticles and nanopesticides. The definition of nanopesticides, the types of nanoparticles used in agriculture and their specific synergistic mechanisms are introduced, their safety is evaluated, and their future application prospects, about which the public is concerned, are examined.

Superabsorbent hydrogel as a formulation to promote mineralization and accelerate degradation of acetochlor in soils

The excessive use of herbicides had caused serious environmental pollution and ecological problems. Therefore, it is imperative to explore an effective method to reduce herbicide residues and pollution. In the present study, we used superabsorbent hydrogels coated ¹⁴C-acetochlor (SH-ACE) to investigate its behavior in different soils under oxic conditions. After 100 days, the mineralization by SH-ACE was increased by 2.3%, 2.5% and 3.3% in the red clay soils, fluvio-marine yellow loamy soils and coastal saline soils, respectively, compared to the control group. This result indicated that the SH-ACE treatment resulted in more complete degradation and detoxification of acetochlor. In addition, the dissipation rates of acetochlor were significantly faster in the SH-ACE treatment, which reduced the persistence of acetochlor. The probable degradation pathways of acetochlor involved dechlorination, hydroxylation, deethoxymethylation, and the formation of thioacetic acid derivatives in the two treatments, but the contents of transformation products were completely different. These findings suggest that the SH-ACE treatment has a significant effect to accelerate the degradation of acetochlor. When developing green pesticides, we emphasize that superabsorbent hydrogel coating treatment should be considered as a promising method for ecological safety in the environment.

Bio-efficacy of imidazolinones in weed control in a tropical paddy soil amended with optimized agrowaste-derived biochars

Biochar is a black carbon sorbent that has the ability to stabilize organic substances in soil and, therefore, the potential to reduce their bio-availability. This sustainable material can be produced from locally-available agro wastes. The present study, for the first time, investigated the effects of biochars produced from oil palm empty fruit bunches (EFB) and rice husk (RH) on the efficiency of imazapic and imazapyr (two polar members of imidazolinone herbicides) as well as Onduty®, a mixture of them. It was executed in a Malaysian paddy field soil during a 30-day greenhouse experiment. The presence of optimized EFB and RH biochars in the heavy soil generally increases weed seeds germination and plants growth due to stabilization of the herbicides. The effect of EFB biochar was found higher than RH biochar having a higher affinity to the herbicides. An increase in the biochars application rates enhanced their effects as a soil modifier. Differences were more significant in the higher herbicides doses. Efficacies of all the herbicides were generally decreased in the biochar-amended soils. In the presence of 0.5% biochar in soil, the GR₅₀ values for all herbicides were almost similar to biochar-free soil. In a 1.0% biochar-soil mixture, GR₅₀ values of the herbicides increased by about 1.5 times. Bio-efficacies of the herbicides decreased by around 2.0 times as the biochar application rate enhanced to 2.0%. The greatest GR₅₀ values were obtained in the presence of 4.0% biochar in the soils and were about 7.0-8.5 folds, indicating the high capability of amended soil in the stabilization of the herbicides. The findings of this study can help to reduce imidazolinones' pollution and, in this way, prevent the threats of their residues to the environment.

Gel Carriers for Plant Extracts and Synthetic Pesticides in Rodent and Arthropod Pest Control: An Overview

Insecticides and rodenticides form the basis of integrated pest management systems worldwide. As pest resistance continues to increase and entire groups of chemical active ingredients are restricted or banned, manufacturers are looking for new options for more effective formulations and safer application methods for the remaining pesticide ingredients. In addition to new technological adaptations of mainstream formulations in the form of sprays, fumigants, and dusts, the use of gel formulations is becoming increasingly explored and employed. This article summarizes information on the current and potential use of gel (including hydrogel) and paste formulations against harmful arthropods or rodents in specific branches of pest management in the agricultural, food, stored product, structural wood, urban, medical, and public health areas. Due to the worldwide high interest in natural substances, part of the review was devoted to the use of gels for the formulation of pesticide substances of botanical origin, such as essential or edible oils. Gels as emerging formulation of so called “smart insecticides” based on molecular iRNA disruptors are discussed.

Cellulose-based functional hydrogels derived from bamboo for product design

Hydrogels have outstanding research and application prospects in the field of product design. Among them, the design and preparation of cellulose-based functional hydrogels derived from bamboo have attracted increasing research interest. Cellulose-based hydrogels not only have the skeleton function of hydrogels, but also retain excellent specificity, smart structural design, precise molecular recognition ability, and superior biocompatibility. Cellulose-based hydrogels show important application prospects in various fields, such as environmental protection, biomedicine, and energy. What's more, they are potentially viable for application in food packaging and plant agriculture, such as fertilizers release and crop production. Recently, researchers have extracted cellulose from bamboo and generated a variety of cellulose-based functional hydrogels with excellent properties by various cross-linking methods. In addition, a variety of multifunctional hybrid cellulose-based hydrogels have been constructed by introducing functional components or combining them with other functional materials, thus expanding the breadth and depth of their applications. Herein, we elaborate on advances in the field of cellulose-based hydrogels and highlight their applications in food packaging and plant agriculture. Meanwhile, the existing problems and prospects are summarized. The review provides a reference for the further development of cellulose-based hydrogels.

Cellulose: A Fascinating Biopolymer for Hydrogel Synthesis

The growing environmental concerns and increasing demands for eco-friendly materials have obliged researchers worldwide to explore naturally occurring biopolymers for various applications. Cellulose is a non-exhaustible polysaccharide biopolymer available almost...

Translational Applications of Hydrogels

Advances in hydrogel technology have unlocked unique and valuable capabilities that are being applied to a diverse set of translational applications. Hydrogels perform functions relevant to a range of biomedical purposes-they can deliver drugs or cells, regenerate hard and soft tissues, adhere to wet tissues, prevent bleeding, provide contrast during imaging, protect tissues or organs during radiotherapy, and improve the biocompatibility of medical implants. These capabilities make hydrogels useful for many distinct and pressing diseases and medical conditions and even for less conventional areas such as environmental engineering. In this review, we cover the major capabilities of hydrogels, with a focus on the novel benefits of injectable hydrogels, and how they relate to translational applications in medicine and the environment. We pay close attention to how the development of contemporary hydrogels requires extensive interdisciplinary collaboration to accomplish highly specific and complex biological tasks that range from cancer immunotherapy to tissue engineering to vaccination. We complement our discussion of preclinical and clinical development of hydrogels with mechanical design considerations needed for scaling injectable hydrogel technologies for clinical application. We anticipate that readers will gain a more complete picture of the expansive possibilities for hydrogels to make practical and impactful differences across numerous fields and biomedical applications.

Application of Nanocellulose Derivatives as Drug Carriers; A Novel Approach in Drug Delivery

BACKGROUND

The production of nanocellulose for drug delivery systems has achieved increased attention in the past decade. High capacity for swelling and absorption of the liquid phase, high flexibility in creating different derivatives, economical cost, and ease of access to the primary source, all of these properties have encouraged researchers to use nanocellulose and its derivatives as a high-performance drug carrier.

OBJECTIVE

The recent progress summary of cellulose-based nanocarriers designing and practical approaches in drug delivery.

METHODS

We conducted a literature review on the development of the nanocellulose and its derivatives as a high-performance drug carrier.

RESULTS

In this review, we have attempted to present the latest advances in cellulose modifications for the design of pharmaceutical nanocarriers. At first, cellulose properties and structural classification of nanocellulose were introduced. Then, focusing on medical applications, some efforts and laboratory trials in cellulose-based nano designing were also discussed. The findings demonstrate the benefits of nanocellulose in drug delivery and its potential for modifying by adding functional groups to enhance drug delivery efficiency. Due to the physical and chemical properties of cellulose and its high flexibility to interact with other compounds, a broad perspective can be imagined in the diverse research and novel forms of nanocarriers.

CONCLUSION

The cellulose nanocarriers can be considered as an attractive platform for researchers to design new structures of pharmaceutical carriers and increase the efficiency of these nanocarriers in drug delivery for the treatment of diseases such as cancer.

Bioformulation of Microbial Fertilizer Based on Clay and Alginate Encapsulation

This study aims to develop new formulations for microbial fertilizers Pseudomonas fluorescens Ms-01 (Pf) and Azosprillum brasilense DSM1690 (Ab) using two kinds of clay minerals. The studied formulations were prepared as hybrid materials based on halloysite and alginate [Ha-Ag] or montmorillonite and alginate polymers [Mt-Ag] and were applied to the bacterial strains to develop low cost, efficient, and slow-release capsules. Their efficiency was evaluated in comparison with alginate [Ag] as the control. The produced capsules were spherical in shape and were chemically and physically characterized and further analyzed for their swelling ratios, soil biodegradability, release kinetics of microbial cells, and their survival stability over 3 months of storage under different conditions (room temperature vs 4 °C). The effect of the capsules on the growth of wheat plants was also investigated. Results showed that both formulations were able to preserve bacterial survival which reached 14.8 log CFU g^-1 after 3 months storage in the halloysite formulation. The swelling ratios were ranged between 61.5 ± 1.35% and 36.5 ± 5% for the montmorillonite and the halloysite formulations, respectively. The release kinetics revealed the slow-release capacity of the capsules mainly with the halloysite formulation which significantly released bacterial cells after 15 days of incubation in saline water (15.24 log CFU mL^-1). The application of the capsules to wheat plants significantly increased root and shoot biomasses and nitrogen content in the roots. In conclusion, halloysite minerals seem to be more adapted as additive to alginate in microbial encapsulation.

Coumarin-Containing Light-Responsive Carboxymethyl Chitosan Micelles as Nanocarriers for Controlled Release of Pesticide

Currently, controlled release formulations (CRFs) of pesticides in response to biotic and/or abiotic stimuli have shown great potential for providing “on-demand” smart release of loaded active ingredients. In this study, amphiphilic biopolymers were prepared by introducing hydrophobic (7-diethylaminocoumarin-4-yl)methyl succinate (DEACMS) onto the main chain of hydrophilic carboxymethylchitosan (CMCS) via the formation of amide bonds which were able to self-assemble into spherical micelles in aqueous media and were utilized as light-responsive nanocarriers for the controlled release of pesticides. FTIR and NMR characterizations confirmed the successful synthesis of the CMCS-DEACMS conjugate. The critical micelle concentration (CMC) decreased with the increase in the substitution of DEACMS on CMCS, which ranged from 0.013 to 0.042 mg/mL. Upon irradiation under simulated sunlight, the hydrodynamic diameter, morphology, photophysical properties and photolysis were researched by means of dynamic light scattering (DLS), transmission electron microscopy (TEM), UV-vis absorption spectroscopy and fluorescence spectroscopy. Moreover, 2,4-dichlorophenoxyacetic acid (2,4-D) was used as a model pesticide and encapsulated into the CMCS-DEACMS micelles. In these micelle formulations, the release of 2,4-D was promoted upon simulated sunlight irradiation, during which the coumarin moieties were cleaved from the CMCS backbone, resulting in a shift of the hydrophilic–hydrophobic balance and destabilization of the micelles. Additionally, bioassay studies suggested that this 2,4-D contained which micelles showed good bioactivity on the target plant without harming the nontarget plant. Thereby, the light-responsive CMCS-DEACMS micelles bearing photocleavable coumarin moieties provide a smart delivery platform for agrochemicals.

Plant growth regulation by seed coating with films of alginate and auxin-intercalated layered double hydroxides

Auxins are a class of organic substances known as plant-growth regulators, which act on plant physiology, promoting its full development. However, due to the great instability of these substances among the diversity of crops and cultivation environments, it is necessary to seek more efficient modes of application, which lead to a homogeneous distribution and promote a sustained release according to the plants demand. Seed coating, using films containing a biodegradable polymer and auxins intercalated into layered compounds, emerges as a very promising approach to a new form of growth regulator application. Thus, the presented work had three aims: (i) the synthesis and characterization of an organic-inorganic hybrid material containing a layered double hydroxide (LDH) of zinc and aluminum and the synthetic auxin 1-naphthalenoacetic acid (ZnAl-NAA-LDH), (ii) the coating of bean seeds (Phaseolus vulgaris L.) with composite films produced from mixtures of alginate polymer and ZnAl-NAA-LDH, and (iii) the evaluation of the plant response by bioassays. The hybrid ZnAl-NAA-LDH was characterized by a set of analytical techniques, including powder X-ray diffraction, thermogravimetric analysis coupled to differential scanning calorimetry and mass spectrometry, specific surface area measurement, and scanning electron microscopy. Bioassays were performed with the seeds coated with the composite film to assess the germination rate and germination speed index of the seeds, as well as biometric analyses including measurements of root area, root fresh matter, and shoot length of the plants. The bioassay performed in soil pots showed that the alginate film containing ZnAl-NAA-LDH yields an enhancement regarding root area, fresh root matter and shoot length of plants. Thus, films produced from a mixture of alginate and the hybrid material containing the growth regulator intercalated into LDH can be a viable alternative to enhance plant development, which can be included in seed management.

Cellulose based materials for controlled release formulations of agrochemicals: A review of modifications and applications

Controlled release formulations (CRFs) of agrochemicals have been attracted considerable attention due to their friendliness to environment. The commercial supporting materials for CRFs of agrochemicals are non-degradable, leading to secondary pollution issue. Cellulose, as the most abundant natural materials in the world, is regarded as one of the most ideal substitutes for non-degradable supporting materials thanks to its good biocompatibility and biodegradability. As raw cellulose materials suffer several problems, such as poor mechanical strength, fast release rate, etc., chemical modifications are commonly performed to improve their properties. In this review, modification methods of cellulose materials for CRFs of agrochemicals were introduced. The relationships between release rate and cellulose based materials were discussed in detail. The applications of cellulose materials for CRFs of agrochemicals were also expounded.

Controlled Release of Biological Control Agents for Preventing Aflatoxin Contamination from Starch⁻Alginate Beads

For the wise use of fungal biocontrol and metalaxyl fungicide, starch-alginate-based formulations have been developed by encapsulating metalaxyl and non-toxigenic Aspergillus flavus spores simultaneously in the form of microspheres using calcium chloride as a cross-linking agent. The formulations were characterized by Fourier transform infrared spectroscopy (FTIR), a scanning electron micrograph (SEM), and thermogravimetry (TGA). Formulation characteristics, including the bead size, entrapment efficiency, swelling ratio of the beads, and rheological properties, were analyzed. The release behavior of beads with different formulations was evaluated. The addition of kaolin and rice husk powder in starch-alginate beads retarded the release profile of spores and metalaxyl. The release of the active ingredient from starch-alginate-kaolin beads and starch-alginate-rice husk powder beads occurred in both a controlled and sustained manner. Additionally, the release rate decreased with the increase of kaolin or rice husk powder content. The beads added with kaolin were slower than the release of rice husk powder. In comparison, spores released slower and lasted longer than metalaxyl. The starch-alginate-kaolin formulations could be used as controlled release material in the field of biocontrol and reduce the harm of fungicides to the environment.

Cellulose-based hydrogel materials: chemistry, properties and their prospective applications

Hydrogels based on cellulose comprising many organic biopolymers including cellulose, chitin, and chitosan are the hydrophilic material, which can absorb and retain a huge proportion of water in the interstitial sites of their structures. These polymers feature many amazing properties such as responsiveness to pH, time, temperature, chemical species and biological conditions besides a very high-water absorption capacity. Biopolymer hydrogels can be manipulated and crafted for numerous applications leading to a tremendous boom in research during recent times in scientific communities. With the growing environmental concerns and an emergent demand, researchers throughout the globe are concentrating particularly on naturally derived hydrogels due to their biocompatibility, biodegradability and abundance. Cellulose-based hydrogels are considered as useful biocompatible materials to be used in medical devices to treat, augment or replace any tissue, organ, or help function of the body. These hydrogels also hold a great promise for applications in agricultural activity, as smart materials and some other useful industrial purposes. This review offers an overview of the recent and contemporary research regarding physiochemical properties of cellulose-based hydrogels along with their applications in multidisciplinary areas including biomedical fields such as drug delivery, tissue engineering and wound healing, healthcare and hygienic products as well as in agriculture, textiles and industrial applications as smart materials.

Examination of the influence of phenyltrimethylammonium chloride (PTMA) concentration on acetochlor adsorption by modified montmorillonite

The results presented in this paper show an impact of the concentration of the aromatic organic cation on the adsorption of acetochlor on the surface of the organic-modified montmorillonite. Natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification in this experiment. Cation exchange capacity of this montmorillonite (86 mmol 100 g^-1 of clay) was determined using the methylene blue method. In pretreatment, montmorillonite was modified with NaCl. For the purpose of organic modification, three different concentrations of phenyltrimethylammonium chloride (PTMA) have been selected, based on calculated CEC value: 43 mmol 100 g^-1 of clay (0.5 CEC), 86 mmol 100 g^-1 of clay (1 CEC) and 129 mmol 100 g^-1 of clay (1.5 CEC). The changes in the properties of the inorganic and organic modified montmorillonite were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and batch equilibrium method. Freundlich coefficients show higher uptake of the herbicide by montmorillonite modified with PTMA, compared to inorganic-modified montmorillonite. The results also indicate the influence of the organic cation concentration on the adsorption of the selected herbicide.

Herbicide/Zn-Al-layered double hydroxide hybrid composite: synthesis and slow/controlled release properties

The herbicide glyphosate (GLY) or 2,4-dichlorophenoxyacetic acids (2,4D) was intercalated in the interlayer region of a Zn-Al-layered double hydroxide (LDH) to obtain LDH-GLY or the LDH-2,4D hybrid composite because of its controlled release. Compared to the physically mixed herbicides, the LDH-herbicide hybrid composite displayed slow-release properties in decarbonated distilled water. The release rate of herbicides was found to be dependent on the carbonate and chloride anion concentrations in solution. The time at which 50% of the herbicides were released from the hybrid composite into solution, t ₅₀, ranged from 6.5 to 18.6 h for LDH-GLY and from 10 to 21.5 h for LDH-2,4D. Our results indicate that the application of LDH-GLY or LDH-2,4D hybrid composite to agricultural areas could reduce the maximum 2,4D or GLY contamination and result in the retardation of herbicides leaching through the soil. This study demonstrates the potential applicability of LDHs as supports for the slow release of acid herbicides.

Release behavior and bioefficacy of imazethapyr formulations based on biopolymeric hydrogels

Controlled release formulations of imazethapyr herbicide have been developed employing guar gum-g-cl-polyacrylate/bentonite clay hydrogel composite (GG-HG) and guar gum-g-cl-PNIPAm nano hydrogel (GG-NHG) as carriers, to assess the suitability of biopolymeric hydrogels as controlled herbicide release devices. The kinetics of imazethapyr release from the developed formulations was studied in water and it revealed that the developed formulations of imazethapyr behaved as slow release formulations as compared to commercial formulation. The calculated diffusion exponent (n) values showed that Fickian diffusion was the predominant mechanism of imazethapyr release from the developed formulations. Time for release of half of the loaded imazethapyr (t_1/2) ranged between 0.06 and 4.8 days in case of GG-NHG and 4.4 and 12.6 days for the GG-HG formulations. Weed control index (WCI) of GG-HG and GG-NHG formulations was similar to that of the commercial formulation and the herbicidal effect was observed for relatively longer period. Guar gum-based biopolymeric hydrogels in both macro and nano particle size range can serve as potential carriers in developing slow release herbicide formulations.

Influence of the organic complex concentration on adsorption of herbicide in organic modified montmorillonite

This study was undertaken to determine the impact of the organic complex concentration on the adsorption of herbicide (acetochlor) at the surface of the organic modified montmorillonite. In this work, natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification. Cation-exchange capacity of this montmorillonite was determined using a methylene blue method (86 mmol/100 g of clay). Montmorillonite has been modified first with NaCl and then with hexadecyltrimethylammonium bromide (HDTMA-bromide) organic complex. Saturation of cation exchange capacity (CEC) was 50%, 100%, and 150%. Changes in the properties of the inorganic and organic montmorillonite have been examined using the X-ray diffraction, Fourier transform infrared spectroscopy, and batch equilibrium method. Montmorillonite modified with HDTMA-bromide demonstrated higher uptake of the herbicide, compared to the inorganic montmorillonite. Comparing the values Freundlich coefficients in batch equilibrium method, it can be seen that the adsorption of acetochlor decreased in the series: 0.5 CEC HM > 1 CEC HM > 1.5 CEC HM > NaM.

Managing invasive plants on sub-Antarctic Macquarie Island

The Antarctic region is one of the most inhospitable frontiers on earth for weed invasion. On Australia’s world heritage sub-Antarctic Macquarie Island only three species of invasive weeds are well established (Poa annua L., Stellaria media (L.) Vill. and Cerastium fontanum Baumg.), although isolated occurrences of other species have been found and removed. These weed species are believed to have initially been introduced through human activity, a threat which is likely to increase, although strict biosecurity is in place. All three weeds are palatable and may have been suppressed to some extent by pest herbivore (rabbit) grazing. Given the high conservation value of Macquarie Island and threats to ecosystem structure and function from weed proliferation following rabbit eradication, well targeted invasive plant control management strategies are vital. We propose that a successful restoration program for Australia’s most southerly rangeland ecosystem should integrate both control of non-native plants as well as non-native herbivores. Of the non-native plants, S. media may most easily be managed, if not eradicated, because of its more limited distribution. Little, however, is known about the soil seed bank or population dynamics after rabbit eradication, nor the effect of herbicides and non-chemical control methods in cold conditions. A current research project on this non-grass species is helping to fill these knowledge gaps, complementing and building on data collected in an earlier project on the ecology and control of the more widespread invasive grass, P. annua. With an interest in off-target herbicide impacts, our work also includes a study of the movement and fate of herbicides in the cold climate Macquarie Island soils. Research in such a remote, cold, wet and windy place presents a range of logistical challenges. Nevertheless, outcomes are informing the development of effective, low-impact control or eradication options for sub-Antarctic weeds.

Constructing Slow-Release Formulations of Metribuzin Based on Degradable Poly(3-hydroxybutyrate)

Experimental formulations of herbicide metribuzin embedded in matrices of degradable natural polymer poly(3-hydroxybutyrate) (P3HB) and its composites with poly(ethylene glycol) (PEG), poly-ε-caprolactone (PCL), and wood powder have been prepared in the form of pressed pellets containing 75% polymeric basis (pure P3HB or its composite with a second component at a ratio of 7:3) and 25% metribuzin. Incubation of formulations in soil laboratory systems led to the degradation of the matrix and herbicide release. The most active release of metribuzin (about 60% of the embedded herbicide over 35 days) was detected for the P3HB/PEG carrier compared to the P3HB, P3HB/wood, and P3HB/PCL forms (30-40%). Thus, the study shows that herbicide release can be controlled by the matrix formulation. Metribuzin formulations exerted a significant herbicidal effect on the plant Agrostis stolonifera, used as a weed plant model. Application of these long-term formulations will make it possible to reduce environmental release of chemicals, which will restrict the rate of their accumulation in trophic chains of ecosystems and abate their adverse effects on the biosphere.

Imazamox-clay complexes with chitosan- and iron(III)-modified smectites and their use in nanoformulations

BACKGROUND

Imazamox is an ionisable herbicide, weakly retained and with high soil vertical mobility, that is used for the control of the root-parasitic plants Orobanche spp. A natural smectite (SW) modified with the biopolymer chitosan (Ch) or with Fe(3+) cation was assayed as adsorbent or carrier for imazamox controlled-release formulations (CRFs).

RESULTS

The greatest adsorption (74%) was observed for SWFe at high initial concentration (500 µM) and low pH (4.3). The interaction mechanism of imazamox on SWFe implies interlayer polar adsorption, followed by protonation of the imidazolinone ring, whereas ionic, polar and hydrophobic interactions seemed to occur in imazamox adsorption on SWCh. The herbicide release into water was inversely related to the strength of the imazamox-clay interactions and ranged in the first 10 min for imazamox-SWFe and imazamox-SWCh complexes from 27 to 75%, whereas commercial imazamox released 86%. The imazamox-SWCh weak complex (SWCh6 WC) showed similar herbicidal activity to the commercial formulation but produced a reduction of 15% in the total soil leaching losses and a reduction of 40% in the peak maximum concentration in soil column leachates.

CONCLUSION

The imazamox-clay weak complex (WC) of SWFe and SWCh and the strong complex (SC) with SWCh showed appropriate behaviour as nanopesticides or smart delivery systems to be incorporated in CRFs. © 2015 Society of Chemical Industry.

Development and employment of slow-release pendimethalin formulations for the reduction of root penetration into subsurface drippers

Subsurface drip irrigation supplies water directly to the root zone and is an efficient irrigation technology. One of the main challenges is preventing plant roots from clogging the drippers. With the aim of inhibiting root penetration, slow-release pendimethalin formulations based on its solubilization in micelles adsorbed and unadsorbed to clay were developed. In the past unadsorbed micelles were considered inadequate for slow release, because release was too fast. In contrast, the advantage of a two-mode release formulation, composed of adsorbed and unadsorbed micelles, is demonstrated. A bioassay to study pendimethalin leaching at a refined scale of 1-2 cm was developed and reduced leaching from the micelle-clay formulations in comparison to the commercial formulation (Stomp) was exhibited. In a greenhouse study the application of the formulations by injection into an irrigation system was extremely efficient with 0-10% root penetration in comparison to 100% penetration upon Stomp injection.

Microorganism-based monodisperse microcapsules: encapsulation of the fungicide tebuconazole and its controlled release properties

A controlled release system was prepared, it based on UF modified PCC cells in which TEB are loaded into cells. It can control the drug release rate, depress the initial “burst effect”, and was efficacious in controlling wheat powdery mildew.

Advances in cellulose-based superabsorbent hydrogels

This contribution provides a brief overview of recent progress in cellulose-based superabsorbent hydrogels, fabrication approaches, materials and promising applications.

Reduced herbicide leaching by in situ adsorption of herbicide-micelle formulations to soils

Aiming to reduce herbicide leaching, "in situ" adsorption of herbicide-micelle formulations to soils was explored. Sulfentrazone or metolachlor were solubilized in cationic micelles, and these herbicide-micelle formulations were applied to sandy and alluvial soils. Sulfentrazone adsorption to the soils was negligible; however, its adsorption via its solubilization in micelles and their adsorption to the soil was significant and in good agreement with the Freundlich and Langmuir models. Adsorption of solubilized herbicide to the sandy soil was higher than to the alluvial soil. The low ratio between the surfactant concentration and the cation exchange capacity (CEC) of the alluvial soil brought upon micelle decomposition and reduction in herbicide adsorption. Therefore, an optimized ratio between surfactant and soil CEC was chosen to maximize herbicide retention. Even upon adding relatively low loadings of surfactant (0.075-0.3% w/w soil), herbicide leaching through the soils was significantly reduced (2-5-fold) in comparison with the commercial formulations.

Nanocomposite PAAm/methyl cellulose/montmorillonite hydrogel: evidence of synergistic effects for the slow release of fertilizers

In this work, we synthesized a novel series of hydrogels composed of polyacrylamide (PAAm), methylcellulose (MC), and calcic montmorillonite (MMt) appropriate for the controlled release of fertilizers, where the components presented a synergistic effect, giving very high fertilizer loading in their structure. The synthesized hydrogel was characterized in relation to morphological, hydrophilic, spectroscopic, structural, thermal, and kinetic properties. After those characterizations, the application potential was verified through sorption and desorption studies of a nitrogenated fertilizer, urea (CO(NH2)2). The swelling degree results showed that the clay loading considerably reduces the water absorption capability; however, the hydrolysis process favored the urea adsorption in the hydrogel nanocomposites, increasing the load content according to the increase of the clay mass. The FTIR spectra indicated that there was incorporation of the clay with the polymeric matrix of the hydrogel and that incorporation increased the water absorption speed (indicated by the kinetic constant k). By an X-ray diffraction technique, good nanodispersion (intercalation) and exfoliation of the clay platelets in the hydrogel matrix were observed. Furthermore, the presence of the montmorillonite in the hydrogel caused the system to liberate the nutrient in a more controlled manner than that with the neat hydrogel in different pH ranges. In conclusion, excellent results were obtained for the controlled desorption of urea, highlighting the hydrolyzed hydrogels containing 50% calcic montmorillonite. This system presented the best desorption results, releasing larger amounts of nutrient and almost 200 times slower than pure urea, i.e., without hydrogel. The total values of nutrients present in the system show that this material is potentially viable for application in agriculture as a nutrient carrier vehicle.

Enhanced reduction of chlorophenols by nanoscale zerovalent iron supported on organobentonite

The reactivity of nanoscale zerovalent iron (NZVI) on removing chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) was remarkably enhanced by using a hydrophobic support of organobentonite (CTMA-Bent), namely the bentonite modified with organic cetyltrimethylammonium (CTMA) cations. The complete dechlorination of chlorophenols and total conversion into phenol using this novel NZVI/CTMA-Bent combination was observed in batch experiments. The kinetic studies suggested that the reduction of chlorophenols by NZVI was accelerated due to the enhanced adsorption onto CTMA-Bent, which facilitated the mass transfer of chlorophenols from aqueous to iron surface. The enhanced reduction rate by NZVI/CTMA-Bent was positively related to the hydrophobicity of chlorophenols, and an increasing linear relationship was obtained between the relative enhancement on reaction rate constants (k2/k1) and logKow values of chlorophenols. XPS results suggested there were fewer precipitates of ferric (hydro)xides formed on the surface of NZVI/CTMA-Bent, which may also lead to the improved reactivity and repetitive usability of NZVI/CTMA-Bent on removing chlorophenols.

Controlled release and retarded leaching of pesticides by encapsulating in carboxymethyl chitosan /bentonite composite gel

A novel composite gel composed of carboxymethyl-chitosan (CM-chit) and bentonite (H-bent) was used as the carrier for encapsulating atrazine and imidacloprid to control their release in water and retard their leaching in soil. Strong interactions between CM-chit and H-bent in the composite were confirmed by FT-IR, and good dispersion of pesticides in the carrier was observed by SEM. According to the results of release experiments in water, the CM-chit/H-bent composite carrier showed double advantages of both encapsulation by the polymer and sorption by the bentonite. The time taken for 50 % of active ingredients to be released, t₅₀, was prolonged to 572 h for atrazine and 24 h for imidacloprid, respectively. The difference between the two pesticides on release behavior was related to their hydrophobicity and water solubility. Leaching experiments through a soil layer showed that this novel carrier reduced the amount of pesticides available for leaching, and would be useful for diminishing the environmental pollution of pesticides.

Use of rice straw biochar simultaneously as the sustained release carrier of herbicides and soil amendment for their reduced leaching

The sustained release and reduced leaching of herbicides is expected for enhancing their efficacy and minimizing their pollution. For this purpose, the rice straw biochar made at a relatively low temperature (350 °C) (RS350) was used simultaneously as the carrier for incorporating herbicides besides as the soil amendment. In this way, the sustained release of herbicides acetochlor and 2,4-D was obtained in the release experiments, due to the high and reversible sorption by RS350 biochar. Besides, the RS350 biochar significantly reduced the leached amount of herbicides by 25.4%-40.7% for acetochlor, and by 30.2%-45.5% for 2,4-D, depending on the depth (50 or 100 mm) of biochar-amended soil horizon. The high retention of both herbicides in the biochar-amended topsoil makes it possible to extend their efficacy. The results suggest a potential way of using low temperature biochars to reduce the leaching of herbicides without impacting their efficacy.

Enhanced removal of pentachlorophenol by a novel composite: nanoscale zero valent iron immobilized on organobentonite

Nanoscale zero valent iron (NZVI) was immobilized on the organobentonite (CTMA-bent), so as to enhance the reactivity of NZVI and prevent its aggregation. This novel composite (NZVI/CTMA-Bent) was characterized by transmission electron microscope and X-ray diffraction. Good dispersion of NZVI particles on the bentonite was observed. Its performance on removing pentachlorophenol (PCP) was investigated by batch experiments. Results showed NZVI/CTMA-Bent could rapidly and completely dechlorinate PCP to phenol with an efficiency of 96.2%. It was higher than the sum (54.5%) of reduction by NZVI (31.5%) and adsorption by CTMA-Bent (23.0%) separately. The kinetic studies indicated the removal rate of PCP was positively related to the adsorption. We proposed that the adsorption of PCP by CTMA-Bent enhanced the mass transfer of PCP from aqueous to iron surface. Besides, NZVI/CTMA-Bent exhibited good stability and reusability, and CTMA-Bent could also reduce the amount of iron ions released into the solution.

Removal of atrazine by nanoscale zero valent iron supported on organobentonite

The organobentonite (CTMA-Bent) was prepared from Na(+)-saturated bentonite (Na-Bent) by intercalation with cetyltrimethylammonium bromide (CTMA), and used as a carrier of nanoscale zero valent iron (NZVI) for the removal of atrazine. The NZVI/CTMA-Bent composite was characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), and good dispersion of nanoscale iron particles on the carrier was observed. The removal efficiency of atrazine by this composite was compared with that by commercial iron powder and NZVI itself. For both treatments by NZVI and NZVI/CTMA-Bent, the removal efficiency increased as the pH of the solution decreased, and the removal percentage of atrazine by NZVI/CTMA-Bent reached 63.5% at initial pH=5.0 after 120 min. It is not only much higher than that (26.6%) by NZVI containing the same amount of iron, but also superior to the sum (32.1%) of reduction by NZVI plus adsorption by CTMA-Bent (5.5%). Besides, the NZVI/CTMA-Bent has a good long-term stability, and the carrier CTMA-Bent could prevent the iron ions (the byproduct of dechlorination) from leaching into the solution.

Multifunctional slow-release organic-inorganic compound fertilizer

Multifunctional slow-release organic-inorganic compound fertilizer (MSOF) has been investigated to improve fertilizer use efficiency and reduce environmental pollution derived from fertilizer overdosage. The special fertilizer is based on natural attapulgite (APT) clay used as a matrix, sodium alginate used as an inner coating and sodium alginate-g-poly(acrylic acid-co-acrylamide)/humic acid (SA-g-P(AA-co-AM)/HA) superabsorbent polymer used as an outer coating. The coated multielement compound fertilizer granules were produced in a pan granulator, and the diameter of the prills was in the range of 2.5-3.5 mm. The structural and chemical characteristics of the product, as well as its efficiency in slowing the nutrients release, were examined. In addition, a mathematical model for nutrient release from the fertilizer was applied to calculate the diffusion coefficient D of nutrients in MSOF. The degradation of the SA-g-P(AA-co-AM)/HA coating was assessed by examining the weight loss with incubation time in soil. It is demonstrated that the product prepared by a simple route with good slow-release property may be expected to have wide potential applications in modern agriculture and horticulture.

Addition of modified bentonites in polymer gel formulation of 2,4-D for its controlled release in water and soil

Carboxymethylcellulose (CMC) gel was used for encapsulating anionic herbicide 2,4-D for its controlled release. The slower release rate of 2,4-D in water and soil was obtained by adding in the gel formulation some modified bentonites, which were prepared by intercalating inorganic or organic cations in interlayers of Na(+)-saturated bentonite. The higher encapsulation efficiencies of 2,4-D were observed on the bentonite/CMC gel formulations due to the sorption of 2,4-D on modified bentonites. The time taken for 50% of 2,4-D to be released in water, t(50), showed a variation (8.8-19.8 h) for these gel formulations, the largest value corresponding to the formulation incorporated with hydroxy-iron intercalated bentonite that has the highest sorption capacity to 2,4-D. The gel formulations could also control the release of 2,4-D when applied to a thin soil layer and demonstrated potential to reduce leaching of such anionic herbicides in soil.