To remove benzo[a]pyrene (BaP) that has accumulated in the Jiaozhou Bay wetland sediment, two strains (JB1 and JB2) were selected from the BaP-contaminated the wetland sediment and immobilized in coal cinder and chitosan beads using entrapping and surface adsorption methods. Biodegradation of BaP in sediment was carried out in pots. The results showed that, supported by the coal cinder and chitosan beads, 71.9, 65.5, 58.9 and 66.1% of the BaP in the immobilized cells was degraded after 40d. These percentages were clearly higher than the 47.7% that degraded from free cells. Kinetic analysis indicated that the immobilized gel-beads might remove BaP by multiple control steps. Compared to the chitosan, coal cinder-entrapping beads exhibited a higher removal rate for BaP; however, the degradation rates from coal cinder- and chitosan-surface adsorption beads were almost the same. This result indicates that in addition to the BaP-degrading bacteria, carrier materials and immobilizing methods play an important role in determining the success of a biodegradation strategy.

Anaerobic digestion (AD) and dewatering are the most common and widely applied sludge treatment methods in wastewater treatment plants (WWTPs). However, sludge dewatering has been recognised as one of the most expensive and least understood processes. Therefore, this study investigated the dewatering performance of synthetic sludge in comparison with anaerobically digested sludge when conditioned with chitosan, organic polyelectrolytes and inorganic metal cations. Capillary suction time (CST), turbidity, electrical conductivity, zeta potential, cake solids content and particle size were used to assess sludge dewatering performance and to determine the optimum conditioner dose. The effectiveness of sludge conditioning was evaluated by batch experiments using a series of 250-mL jar test beakers. Both synthetic sludge and AD sludge exhibited similar trend but little different extent of dewaterability when conditioned with low molecular weight (MW) chitosan. The low MW and medium MW chitosans, commercial cationic polyelectrolytes and trivalent metal cations (Al³⁺, Fe³⁺) demonstrated as effective conditioning agents with good sludge dewaterability. When assessing the dewaterability measurement parameters using synthetic sludge, the optimal dosage was found at the range of 15 to 20 g-chitosan/kg-dry sludge where the values of CST, turbidity and cake solids content were attained between 6.6 and 11.0 s, 35.4–40.6 NTU, and 24.3–25.3%, respectively. The application of cationic polyelectrolytes and trivalent metal cations generally improved the sludge dewaterability via charge neutralisation and polymer bridging. This study also demonstrated that less complex chemically controlled synthetic sludge can be used for studying the final properties of complex real digested sludge.

A magnetic chitosan-modified Fe₃O₄@SiO₂ with sodium tripolyphosphate adsorbent (MTPCS) was synthesized by surface modification of Fe₃O₄@SiO₂ with chitosan using sodium tripolyphosphate (STPP) as the cross-linker in buffer solution for the adsorption of Cu(II) ions from aqueous solution. The structure and morphology of this magnetic nanoadsorbent were examined by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), BET surface area measurements, Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS). The effects of initial pH, adsorbent amount, and initial concentration of heavy metal ions were investigated by batch experiments. Moreover, adsorption isotherms, kinetics, and thermodynamics were studied to understand the mechanism of adsorbing metal ions by synthesized MTPCS. The results revealed that adsorption kinetics was best depicted by the pseudo-second-order rate mode and intraparticle-diffusion models. The adsorption isotherm fitted well to the Langmuir model. Moreover, thermodynamic study verified the adsorption process was endothermic and spontaneous in nature. The maximum adsorption occurred at pH 5 ± 0.1, and the adsorbent could be used as a reusable adsorbent with convenient conditions.

Mosquitoes (Diptera: Culicidae) are vectors of important parasites and pathogens causing death, poverty and social disability worldwide. The overuse of synthetic insecticides to control mosquito vectors lead to resistance, adverse environmental effects and high operational costs. Therefore, the development of eco-friendly control tools is an important public health challenge. In this study, two different essential oils (EO) (geranium, Geranium maculatum, and bergamot, Citrus bergamia) loaded polymeric nanoparticle (PN) were elaborated using polyethylene glycol (PEG) and chitosan (Qx) as the polymeric matrix/coating. In addition, the mosquito larvicidal acute and residual activity of the PN was evaluated on Culex pipiens pipiens. The physicochemical characterization of PN revealed that PEG-PN had sizes <255 nm and encapsulation efficiency between 68 and 77%; Qx-PN showed sizes <535 nm and encapsulation efficiency between 22 and 38%. From the toxicological test, it was observed that Qx-PN produced higher acute and residual activity than PEG-PN. Overall, this study highlights that polymer nanoparticles containing essential oil are a promising source of eco-friendly mosquito larvicidal products.

A new commercial cationic polyelectrolyte chitosan (CM), obtained from the waste of mushroom production, was examined using models of water and wastewater namely kaolin and palm oil mill effluent (pome). As it is biocompatible, widely available, and economically feasible, chitosan mushroom has high potential to be a suitable replacement for alum. Also, it can be a promising alternative to chitosan obtained traditionally from Crustaceans due to its higher zeta potential and homogeneity based on the raw material required for its production. A wide range of coagulant dose (5–60 mg l⁻¹) and wastewater pH (2–12) were taken into account to find the optimal conditions of coagulation. The optimal doses are 10 and 20 mg l⁻¹ at best pH (11 and 3) when treated with kaolin and palm oil mill effluent, respectively, while 1200 mg l⁻¹ of alum was not enough to reach the efficiency of chitosan mushroom. On the other hand, the optimum dose of chitosan mushroom (20 mg l⁻¹) at pH 3 of pome produced (75, 73, and 98%) removal of chemical oxygen demand (COD), biological oxygen demand (BOD), and total suspended solids (TSS), respectively. The significant potential of chitosan mushroom was proved by zeta potential measurement. Indeed, it possesses the highest zeta potential (+70 mV) as compared to the traditional chitosan produced from crustaceans. In short, chitosan mushroom as a biocoagulant is eco-friendly and it enhances water quality that meets the requirements of environmental conservatives.

Peroxidases (EC 1.11.1.7) have enormous biotechnological applications. Usage of more abundant, basic isoforms of peroxidases in diagnostic kits and/or in immunochemistry has led to under exploitation and disregard of horseradish peroxidase (HRP) acidic isoforms. Therefore, acidic horseradish peroxidase (HRP-A) isoenzyme was used for the preparation of a biocatalyst with improved ability in dye decolorization. Ten biocatalysts were prepared by covalent binding of enzyme to chitosan and alginate, adsorption followed by cross-linking on inorganic support (aluminum oxide), and encapsulation in spherical calcium alginate beads via polyethylene glycol. Model dyes of 50 to 175 mg l⁻¹ were removed by the biocatalysts. Among the tested biocatalysts, the three with the highest specific activity and biodegradation rate were further studied (Chitosan-HRP, Al-Gel-HRP and Al-HRP-Gel). The impact of hydrogen peroxide concentration on dye decolorization was examined on the Chitosan-HRP biocatalyst, since the HRP is susceptible to inhibition/inactivation by high H₂O₂. On the other hand, H₂O₂ is needed as a co-substrate for the HRP, and the H₂O₂/dye ratio can greatly influence decolorization efficiency. Concentrations of H₂O₂ ranging from 0.22 to 4.4 mM showed no difference in terms of impact on the biocatalyst decolorization efficiency. The high decolorization efficiency of the biocatalysts was validated by the removal of 25 and 100 mg l⁻¹ anthraquinone (Remazol Brilliant Blue R (RBBR)), triphenylmethane (Coomassie Brilliant Blue (CBB)), acridine (Acridine Orange (AO)), and formazan metal complex dye (Reactive Blue 52 (RB52)). After the seven consecutive decolorization cycles, the decolorization was still 53, 78, and 67% of the initial dye for the Al-HRP-Gel, Al-Gel-HRP, and Chitosan-HRP immobilizate, respectively. The results obtained showed potential of otherwise neglected acidic HRP isoforms as a cost-effective biocatalyst with significant potential in wastewater dyestuff treatment.

Adsorption of copper ions onto chitosan films was studied, and the matrix effect was evaluated using a synthetic solution and a real effluent from closed copper mine. Chitosan films were prepared by casting technique and characterized. The adsorption study was carried out by equilibrium isotherms, thermodynamics, and kinetics. The thermodynamic parameters indicated that the copper adsorption onto chitosan film was favorable, spontaneous, and exothermic, suggesting an increased randomness at the solid/solution interface. The matrix effect was evaluated in kinetic assays, where a synthetic solution and a real system were carried out at different stirring rates. The highest values of adsorption capacity reached in all stirring rates were about 20% lower in the real effluent, and this reduction in the competitiveness was due to the presence of other ions in the matrix of the real effluent. The maximum adsorption capacity of copper ions onto chitosan films for the synthetic solution was of 450 mg g⁻¹, and the removal percentage was in the range from 78 to 96%, and these values for the real effluent were of 360 mg g⁻¹ and removal ranging from 62 to 76%. The mapping done of ions present in the water adsorbed of the mine in the films showed that the same was homogeneously distributed in the films’ surfaces.

A highly sensitive, specific, simple, and rapid chemiluminescence enzyme immunoassay (CLEIA) was developed for the determination of microcystin-LR (MC-LR) by using strategies for oriented immobilization of functionally intact polyclonal antibodies on chitosan surface. Several physicochemical parameters such as metal ion adsorption, hexahistidine-tagged Protein G sorption, the dilution ratio polyclonal antibody concentration, and peroxidase-labeled MC-LR concentration were studied and optimized. The sorption in batch system of G-histidine and G-proteins was studied on a novel sorbent consisting of chitosan/divalent metal ions. Transition metals as Ni⁺⁺ and Zn⁺⁺ were immobilized through interaction with –NH₂ groups of chitosan in order to supply a material capable to efficiently remove the proteins from aqueous solutions. The maximum uptake of divalent metals onto the chitosan material was found to be 230 mg g⁻¹ for Zn⁺⁺ and 62 mg g⁻¹ for Ni⁺⁺. Experimental data were evaluated using the Langmuir and Freundlich models; the results were well fitted with the Langmuir model; chitosan/Ni⁺⁺ foam was found to be the best sorbent for G-protein, maximum sorption capacity obtained was 17 mg g⁻¹, and chitosan/Zn⁺⁺ was found to be the best for G-histidine with a maximum sorption capacity of 44 mg g⁻¹. Kinetic data was evaluated with pseudo-first- and pseudo-second-order models; the sorption kinetics were in all cases better represented by a pseudo-second-order model. Under optimum conditions, the calibration curve obtained for MC-LR gave detection limits of 0.5 ± 0.06 μg L⁻¹, the 50 % inhibition concentration (IC50) was 2.75 ± 0.03 μg L⁻¹, and the quantitative detection range was 0.5–25 μg L⁻¹. The limit of detection (LOD) attained from the calibration curves and the results obtained demonstrate the potential use of CLEIA with chitosan support as a screening tool for the analysis of pollutants in environmental samples.

Synthesis and controlled release study of polymeric nanoformulation of carbendazim (2-benzimidazole carbamic acid methyl ester) using chitosan and pectin is reported in this article. The formulation was subjected to morphological, physiological, in vitro fungicide release and bio-efficacy evaluation studies. The average size of nanoparticles was found to be in the range of 70–90 nm as confirmed by transmission electron microscopy. The in vitro fungicide release of nanoformulated carbendazim was compared with pure carbendazim at different pH values. The results confirmed sustained release of nanoformulated carbendazim. The bio-efficacy evaluation of the carbendazim nanoformulation was carried out against Fusarium oxysporum and Aspergillus parasiticus. The nanoformulation showed 100 % inhibition of test fungi at both concentrations (0.5 and 1.0 ppm) while pure carbendazim showed 80 ± 0 % and 97.2 ± 1.1 % inhibition at 0.5 and 1.0 ppm concentration respectively against Fusarium oxysporum and 86.0 ± 0.6 % inhibition and 100.0 % inhibition at 0.5 and 1.0 ppm concentration respectively against Aspergillus parasiticus. The commercial formulation (WP 50) showed 42 % and 58.0 ± 0.1 % inhibition at 0.5 and 1 ppm concentration respectively against Aspergillus parasiticus and 50.5 ± 0.7 % and 70.0 ± 0 % inhibition at 0.5 and 1.0 ppm concentrations respectively against Fusarium oxysporum. Phytotoxicity evaluation of nanoformulated fungicide confirmed that the nanoformulated carbendazim is safer for germination and root growth of the seeds of Cucumis sativa, Zea mays, and Lycopersicum esculantum.

This research focuses on the removal of heavy metal ions from aqueous solutions using magnetic chitosan hydrogel beads as a potential sorbent. Highly porous magnetic chitosan hydrogel (PMCH) beads were prepared by a combination of in situ co-precipitation and sodium citrate cross-linking. Fourier transform infrared spectroscopy indicated that the high sorption efficiency of metal cations is attributable to the hydroxyl, amino, and carboxyl groups in PMCH beads. Thermogravimetric analysis demonstrated that introducing Fe₃O₄ nanoparticles increases the thermal stability of the adsorbent. Laser confocal microscopy revealed highly uniform porous structure of the resultant PMCH beads, which contained a high moisture content (93%). Transmission electron microscopy micrographs showed that the Fe₃O₄ nanoparticles, with a mean diameter of 5 ± 2 nm, were well dispersed inside the chitosan beads. Batch adsorption experiments and adsorption kinetic analysis revealed that the adsorption process obeys a pseudo-second-order model. Isotherm data were satisfactorily described by the Langmuir equation, and the maximum adsorption capacity of the adsorbent was 84.02 mg/g. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectra analyses were performed to confirm the adsorption of Pb²⁺ and to identify the adsorption mechanism.