Pine wood nematode, Bursaphelenchus xylophilus, is a plant parasitic nematode which causes severe damage to several Pinus species. Two natural compounds, dipropyl trisulfide (DPTS) and methyl propyl trisulfide (MPTS), showed strong nematicidal activity against the pine wood nematode, presenting 4.24 and 17.81 μg/mL LC₅₀ values, respectively. However, hydrophobicity and low stability have limited their practical use in the field as nematicides. To overcome these problems, chitosan-coated nanoemulsions of DPTS and MPTS were developed. The optimum chitosan concentration for the delivery system of the two sulfides was 0.5%. Optimized chitosan-coated nanoemulsions of sulfides have a uniform size distribution (mean diameter = 203.7 and 207.7 nm, mean polydispersity index = 0.176 and 0.178) with sufficient colloidal stability (mean zeta potential = +40 and +45 mV). The LC₅₀ values of DPTS and MPTS nanoemulsions coated with 0.5% chitosan against the pine wood nematode were 5.01 and 16.60 μg/mL, respectively. In addition, chitosan coating improved the long-term storage stability and persistence of nematicidal activity of the nanoemulsions. This study indicates that the chitosan-coated nanoemulsion is a suitable formulation for sulfides as novel nematicides against the pine wood nematode for field application.

Progesterone, an endocrine-disrupting chemical, has been frequently detected in wastewater for decades, posing a serious threat to ecological and human health. However, it is still a challenge to achieve the effective detection of progesterone in complex matrices water samples. In this study, a novel adsorbent CNT@CS/P(MAA) was prepared by grafting methacrylic polymers on the surface of modified carbon nanomaterials. Compared with other reported materials, the hybrid carbon nanomaterial could selectively identify the progesterone in the complex industrial pharmaceutical wastewater, and its adsorption performance is almost independent of the pH and environmental temperature. In addition, this nanomaterial could be reused with a good recovery rate. The prepared nanomaterials were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, nitrogen adsorption and desorption experiments, and thermogravimetric analysis. The results confirmed that the methacrylic polymers and chitosan layer were successfully grafted on the surface of carbon nanotubes. Adsorption isotherms, adsorption kinetics, and selectivity tests showed that CNT@CS/P(MAA) had a high adsorption capacity (44.45 mg·g⁻¹), a fast adsorption rate and a satisfied selectivity for progesterone. Then, CNT@CS/P(MAA) was used as solid phase extraction sorbent and combined with HPLC to enrich progesterone from the wastewater samples. Under the optimum conditions, a good linearity was obtained with the correlation coefficient was 0.9998, and the limit of detection was 0.003 ng·mL⁻¹. Therefore, this method could be used for the selective and effective detection of progesterone in industrial wastewater with complex substrates and provided a new method for the detection of progesterone in other environmental waters.

In this study, a novel slow release carrier for the controlled release of citric acid (CA), hydroxypropyl chitosan-graft-carboxymethyl-β-cyclodextrin (HPCS-g-CMCD) was synthesized by the grafting reaction of carboxymethyl-β-cyclodextrin (CMCD) with hydroxypropyl chitosan (HPCS), and the structural characteristics of HPCS-g-CMCD were confirmed by FT-IR, TGA, and NMR. Based on HPCS-g-CMCD and CA, slow release citric acid (SRCA) was prepared by a spray drying method. HPCS-g-CMCD carrier has a better slow release performance for CA compared to HPCS and CMCD, and CA release mechanism was attributed to a Fickian diffusion. Furthermore, the release behavior of uranium in contaminated soil could be effectively controlled by SRCA. The effects of SRCA on improving the phytoremediation capacity in uranium-contaminated soil were investigated using Brassica juncea, which were grown in pots containing soil with uranium at 56 mg kg⁻¹. After 50 days of growth, 5 mmol kg⁻¹ of CA, SRCA I, SRCA II, and SRCA III was applied, respectively. The results showed that slow release citric acid could enhance the uptake of uranium in Indian mustard. Uranium concentration in the root with SRCA I treatment was increased by 80.25% compared to the control, and the uranium removal efficiency of the SRCA I treatment was 1.66-fold greater than that of the control. Simultaneously, the leaching loss of uranium in SRCA I-treated soil was decreased by 37.35% compared to CA-treated soil. As a promising remediation strategy, SRCA-assisted phytoremediation may provide a kind of feasible technology with low leaching risk for remediation of uranium-contaminated soils.

A biocomposite system was developed and tested for the removal of the azo dye Reactive Red (RR195) from wastewater. The biocomposite was synthesized using ceramic particles containing 75% alumina which were coated using chitosan cross-linked with oxalic acid. The biocomposite showed high performance at low pH (maximum adsorption capacity = 345.3mg.g⁻¹ at pH=2.0). The physicochemical and structure characteristics of the matrix were evaluated by Z-potential, FTIR-ATR, SEM-EDS, XRD, and porosity. Langmuir sorption isotherm and pseudosecond-order model gave the best fit. The electrostatic interaction between RR195 (due to the sulfonate groups) and the free amino groups of chitosan, enabled successive desorption/regeneration cycles. The maximum removal percentage (>80%) occurred at pH=2.0 due to the cross-linking effect. Experiments at different temperatures allowed the calculation of thermodynamic parameters (ΔG, ΔS, ΔH); adsorption was spontaneous, exothermic, and enthalpy controlled. The presence of inorganic ions ([Formula: see text]) was analyzed during the adsorption process. This novel biocomposite can be applied as a cost-effective and environmentally friendly adsorbent for anionic azo dye removal from wastewater. The application of chitosan cross-linked with oxalic acid as a coating of the ceramic support enhanced the adsorption capacity and enabled its use under acidic conditions without solubilization.

Emerging contaminants (ECs) have been studied extensively because of the various damages they can cause to the environment, especially due to the non-treated domestic effluents, which contaminate the water bodies. Therefore, it is important to evaluate alternatives to remove these compounds. The objective of this work was to evaluate the potential of a new biosorbent from chitosan modified with vanillin (CTSV) to remove isoniazid, cortisol, bisphenol A, 17α-ethinylestradiol, and triclosan by competitive adsorption studies. Structural characterization of the biosorbents was performed by Fourier transform infrared spectroscopy, thermogravimetry, Brunauer-Emmett-Teller, zeta potential, scanning electron microscopy, and ¹H nuclear magnetic resonance. The adsorption for ECs were carried out in an aqueous medium, and quantitative analyzes were performed by HPLC. The effect of pH was evaluated in the pH range 5 to 10 and indicated that better results were found in pH 9 and 8 for CTS and CTSV, respectively. The salt concentrations effect was evaluated in 0.0 to 1.0 mol L⁻¹ and revealed better adsorption conditions in 0.7 mol L⁻¹ of NaCl. The adsorption kinetics pointed to an equilibrium condition reached quickly (with adjustment of data R² > 0.969) with adequacy to pseudo–second-order model for both biosorbents and ECs. The linear isothermal model was suitable for the adsorption isothermal data and distribution constant (KD) showed the highest values for 17α-ethinylestradiol (0.067 L g⁻¹) and triclosan (0.197 L g⁻¹) in CTSV adsorption. Thus, the results indicated that CTSV performed well in removal for the tested ECs, being an interesting alternative, due to the ease of obtaining and abundance of reagents employed in its preparation.

In order to endow alkaline Ca-bentonite (ACB) with magnetic separation ability, simultaneously obtain better magnetic stability and stronger removal capacity of heavy metal cations; magnetic alkaline Ca-bentonite/carboxymethylcellulose-chitosan film (MACB/C-C) was prepared by organic modification of magnetic alkaline Ca-bentonite (MACB) using non-toxic carboxymethylcellulose and chitosan. Textural characterization results revealed that magnetic Fe₃O₄ nanoparticles were successfully immobilized on ACB and modified with C-C. The functionalized layer of C-C concurrently enhanced the stability of Fe₃O₄ and removal performances of heavy metal cations. Adsorption results indicated that MACB/C-C exhibited thorough separation from aqueous solution and greater uptake ability for Pb(II) and Cd(II) (483 mg·g⁻¹ and 123 mg·g⁻¹) than the nascent MACB (335 mg·g⁻¹ and 76 mg·g⁻¹), respectively, at pH 5 and 25 °C temperature. The adsorption of Pb(II) and Cd(II) on MACB/C-C mainly occurred via surface precipitation and complexation when pH > 2. MACB/C-C could be efficiently recycled with marginal decrease in adsorption capacity. The current approach credited to the convenient operation, simplified synthesis, and high efficiency of MACB/C-C could be deemed as a promising alternative for the removal of heavy metal cations from wastewater.

Macroscopic utilization of nanomaterial provides a new idea for the research and development of novel adsorbent, which can enhance efficiency in the adsorption and elution process. In this paper, nano-polypyrrole (PPy) was dispersed into two inexpensive and renewable biomass materials, gelatin (Gel) and chitosan (CS), to fabricate a novel photo/electric-sensitive hydrogel, Gel/CS/PPy. The micro-network of Gel/CS/PPy shows a high adsorption rate of 94.2% for acid fuchsine (AF). Furthermore, with the addition of polypyrrole, Gel/CS/PPy has the characteristic of photo/electric response, which can improve the elution efficiency of AF from the adsorbent. The results showed that the elution efficiency could be increased by 4 times with photo-assistance, and about 2 times with electro-assistance. Predictably, using the methods described in this article, high-quality adsorbents can be designed for more organic pollutants. Graphical abstract

The rapid growth of human population and global industrialization has resulted in the generation of larger amounts of wastewater containing various pollutants, among which toxic heavy metals. Adsorption is efficient for this purpose, but its application is limited by the high cost of adsorbent materials. Chitosan (CS) and phosphorylated microcellulose (PMC) have a high potential as low-cost and effective adsorbents for water remediation. Nonwoven CS/PMC nanocomposite fiber mats were produced by electrospinning with up to 50% by weight of PMC. The thermal, chemical, and morphological properties of the mats were studied. Batch adsorption trials were carried out using Cd²⁺ ions. Kinetics and isotherm models were tested against experimental results and the thermodynamic properties were calculated. Results showed that the pseudo-second order model best fitted experimental data and suggested chemisorption as the mechanism for Cd²⁺ removal. Langmuir isotherm best described equilibrium data reaching the maximum adsorption capacity of 283 mg/g at 60 °C. This high value was attributed mainly to the large amount of phosphate groups, which require less energy to capture the metal cations. Thermodynamic evaluation suggested that the adsorption is a spontaneous endothermic reaction. These results confirm that CS/PMC mats are easy to produce, and provide high adsorption capacity in simulated wastewater containing Cd²⁺. These laboratory-based adsorption experiments will assist in selecting/ranking of potential candidate matrices, and scale-up development of technologies for complex wastewater applications.

In this work was studied the single-component and multi-component abatement of metals in water using a hydrogel based on chitosan. The maximum single-component abatement capacities of cadmium (Cd) and lead (Pb) were 234.84 and 482.83 mg of metal per g of dried hydrogel at pH 6 and 40 °C, according to the Sips isotherm. The value for iron (Fe) was 386.59 mg g⁻¹ at pH 4 and 40 °C, according to the Langmuir isotherm. The best kinetic fits were determined using the pseudo-second-order model, whereas the thermodynamic parameters inferred spontaneous, favorable abatement phenomena. Lower abatement capacities were determined for multi-component studies due to the hydrated ionic radius and electronegativity of the metals. The abatement processes were confirmed by scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectra, indicating reversible chemical interactions between the hydrogel binding groups and Cd, Pb, and Fe. Such hydrogel proved to be a potential functional biopolymer for the treatment of water and wastewater contaminated by heavy metals. Graphical abstract

Controlled-release fertilizers (CRFs) are an effective approach in providing essential nutrients for plant growth while minimizing the loss of nutrients in water and air, reducing contamination risks. However, commercial CRFs often release nutrients either too quickly or slowly due to the properties of their coating materials (polymer or sulfur). In this work, a novel CRF technology was developed using chitosan (CS) and graphene oxide (GO) nanocomposites as coating materials. CS and GO solutions were applied at varying ratios in preparing different nanocomposites. CS and GO formed homogeneous nanocomposite films through their interactions with each other. Fertilizer beads were successfully encapsulated by the CS-GO films using the simple dipping method. Resulting CRFs showed controlled-release behaviors, with nutrient release lasting for about a week. Although additional investigations are required for further evaluation and optimization, this method presents a promising concept for an alternative fertilizer-coating technology.