Development of chitosan/Spirulina sp. blend films as biosorbents for Cr6+ and Pb2+ removal

Biohybrid microrobots with a Spirulina skeleton and MOF skin for efficient organic pollutant adsorption

Wastewater treatment is a key component in maintaining environmental health and sustainable urban life, and the rapid development of micro/nanotechnology has opened up new avenues for more efficient treatment processes. This work developed a novel biohybrid microrobot for the efficient adsorption of a series of organic pollutants in water-the microrobot with a biodegradable Spirulina skeleton and biocompatible ZIF-8 skin. The microrobot not only has a low-cost and simple preparation method but also shows attractive propulsion in various contaminant solutions (including rhodamine B, methylene blue, and methyl orange) under a low-intensity (3 mT) rotating magnetic field and has excellent directional control. Our research results show that the biohybrid microrobot can significantly improve the adsorption performance of various organic pollutants in the moving state, thereby improving the purification rate. In addition, the microrobot also has good swarming motion control to achieve directional and efficient adsorption of organic pollutants in the microspace. Such Spirulina@ZIF-8 microrobots can be prepared in large quantities as highly controllable, biocompatible, and wireless tools, showing great potential for water treatment.

Adsorption of haem by magnetic chitosan microspheres: Optimal conditions, adsorption mechanisms and density functional theory analyses

Magnetic chitosan microspheres (Al@CTS@Fe3O4) were prepared for haem separation via chemical cross-linking of chitosan, Fe3O4 and AlCl3·6H2O. The properties of the Al@CTS@Fe3O4 microspheres were investigated through techniques including XRD, TEM, FTIR, BET analysis, SEM, TG, VSM, XPS and pHpzc analysis. The haem adsorption of Al@CTS@Fe3O4 was optimized via a Box-Behnken design (BBD) with three operating factors: Fe3O4 dose (0.5-1.3 g), AlCl3·6H2O concentration (0.25-1.25 mol/L) and glutaraldehyde dose (2-6 mL). The optimal haem adsorption effect was achieved with 1.1 g of Fe3O4, 0.75 mol/L AlCl3·6H2O, and 3 mL of glutaraldehyde. The adsorption kinetics and isotherms demonstrated that haem adsorption by the Al@CTS@Fe3O4 microspheres was best described by the pseudo-second-order model. The maximum adsorption capacity is 33.875 mg/g at pH 6. After six adsorption-desorption cycles, the removal of haem still reached 53.83 %. The surface adsorption mechanism of haem on Al@CTS@Fe3O4 can be attributed to electrostatic, hydrogen bonding, and n-π interactions. Thermodynamic calculations indicated that the adsorption process is spontaneous, with the microspheres preferentially accepting electrons and haem preferentially providing electrons. Consequently, the Al@CTS@Fe3O4 microspheres exhibit considerable potential as adsorbents for haem separation.

Green synthesis of chitosan/glutamic acid/agarose/Ag nanocomposite hydrogel as a new platform for colorimetric detection of Cu ions and reduction of 4-nitrophenol

In this study, the green synthesis of chitosan/glutamic acid/agarose/Ag (Chi/GA/Aga/Ag) nanocomposite hydrogel was obtained via in situ reduction of Ag ions during the crosslinking process of chitosan-agarose double network hydrogels. The rich hydroxyl, carboxyl and amino groups in both agarose, chitosan, and glutamic acid can effectively control the growth, dispersion and immobilization of nearly spherical Ag nanoparticles (70 nm) in the Chi/GA/Aga/Ag composite hydrogel. Glutamic acids can act as the structure-directing agents to induce the formation of chitosan/glutamic acid hydrogel. The mechanical strength of the Chi/GA/Aga/Ag composite hydrogel can be enhanced by the introduction of chitosan-agarose double network hydrogels, which guarantees that it can be directly used as a visual test strip of the Cu ions with a lower detection limit of 1 μM and an active catalyst for the reduction of 4-nitrophenol within 18 min. The quantitative and semi-quantitative measurement of Cu ions can be carried out by UV-visible absorption spectroscopy and visual measurement, which provided a convenient, portable, and "naked-eye" solid-state detection methodology.

Visualized adsorption and enhanced photocatalytic removal of Cr6+ by carbon dots-incorporated fluorescent nanocellulose aerogels

In this study, carbon dots (CDs) and titanate nanofibers (TNs) were mixed with TEMPO-oxidized nanocellulose (TOCNC) to prepare fluorescent nanocellulose aerogels (FNAs) by a Schiff base reaction. The resulting FNA can detect the adsorption of Cr6+ through the fluorescence quenching in CDs and promote the removal of Cr6+ through the synergistic effect of CDs in photocatalysis. The optimized FNA has a maximum adsorption capacity of 543.38 mg/g, higher than most reported Cr6+ adsorbents. This excellent performance is due to the porous structure of the aerogel, which gives it a high specific surface area of 20.53 m2/g and provides abundant adsorption sites. Simultaneously, CDs can enhance the amino-induced Cr6+ adsorption, improve the photocatalytic performance of TNs, and expose more adsorption sites through electrostatic adsorption of amino-induced reduction products (Cr3+). This study explores the preparation of visualized nanosorbents with enhanced photocatalytic removal of Cr6+ and provides a new direction for nanoscale photocatalysts.

Crosslinked modified chitosan biopolymer for enhanced removal of toxic Cr(VI) from aqueous solution

Two new crosslinked modified chitosan biopolymers, namely (CTS-VAN) and (Fe₃O₄@CTS-VAN) bioadsorbents were prepared starting from chitosan and 4-hydroxy-3-methoxybenzaldehyde (VAN) in presence of epichlorohydrin. The analytical techniques FT-IR, EDS, XRD, SEM and XPS besides BET surface analysis were utilized for full characterization of the bioadsorbents. Batch experiments were conducted to study the effect of various influencing parameters in Cr (VI) removal such as initial pH, contact time, adsorbent amount and initial Cr (VI) concentration. The adsorption of Cr (VI) was found out to be maximum at pH = 3 for both bioadsorbents. Langmuir isotherm fit well the adsorption process with a maximum adsorption capacity of 188.68 and 98.04 mg/g for CTS-VAN and Fe₃O₄@CTS-VAN, respectively. The adsorption process followed pseudo second-order kinetics with R² values of 1 and 0.9938 for CTS-VAN and Fe₃O₄@CTS-VAN, respectively. X-ray photoelectron spectroscopy (XPS) analysis showed that Cr(III) accounted for 83 % of the total Cr bound to bioadsorbents surface, which indicated reductive adsorption was responsible for Cr(VI) removal by the bioadsorbents. Cr(VI) was initially adsorbed on the positively charged surface of the bioadsorbents and reduced to Cr(III) by electrons provided by oxygen-comprising functional groups (e.g., CO), and consequently part of the converted Cr(III) stayed on the surface and the rest released into solution.

Research Progress of Treatment Technology and Adsorption Materials for Removing Chromate in the Environment

Cr is used extensively in industry, so the number of Cr (VI) hazards is increasing. The effective control and removal of Cr (VI) from the environment are becoming an increasing research priority. In order to provide a more comprehensive description of the research progress of chromate adsorption materials, this paper summarizes the articles describing chromate adsorption in the past five years. It summarizes the adsorption principles, adsorbent types, and adsorption effects to provide methods and ideas to solve the chromate pollution problem further. After research, it is found that many adsorbents reduce adsorption when there is too much charge in the water. Besides, to ensure adsorption efficiency, there are problems with the formability of some materials, which impact recycling.

Dietary chitooligosaccharide supplementation improves mineral deposition, meat quality and intramuscular oxidant status in broilers

BACKGROUND

The present study aimed at evaluating the in vitro adsorption capability of chitooligosaccharide (COS) with some metal elements (Fe, Zn, Cd, Pb) at different pH values along with potential effects of dietary COS supplementation on growth performance, mineral content, meat quality and oxidant status in broilers. Day-old male chicks were randomly distributed into two groups and offered a basal diet supplemented with or without 30 mg kg^-1 COS for 42 days.

RESULTS

In vitro trials demonstrated that Fe levels were higher (P < 0.001) in the COS-treated group compared with the non-treated group at pH of 2.5. However, these levels became lowered when pH values were raised to 5 (P < 0.01) or 6 (P < 0.001). Similarly, COS adsorbed more (P < 0.05) Zn at pH values of 2.5 and 6, and Cd contents at pH of 2.5 for 70 min when compared with the control. For in vivo trial, the feed-to-gain ratio, serum Cu (P < 0.01), hepatic Mn, Cr (P < 0.05) and intramuscular Cd (P < 0.01) were lower in response to COS treatment. Supplementation of COS improved (P < 0.05) meat quality of broilers in terms of lower drip loss, cooking loss and malondialdehyde content with a concomitant increase (P < 0.01) in the pH of breast meat at 24 h post mortem.

CONCLUSION

COS adsorbed heavy metal ions not only in vitro but also in broilers, and dietary supplementation with 30 mg kg^-1 COS improved growth performance, breast meat quality and oxidant status in broilers. © 2022 Society of Chemical Industry.

Chitosan-the miracle biomaterial as detection and diminishing mediating agent for heavy metal ions: A mini review

Proliferation of heavy metal ions as aquatic pollutants has been a matter of growing concern now a days. Several anthropogenic activities have fueled higher concentration of heavy metal ions in aquatic bodies above threshold values, as set by World Health Organization. Of late, chitosan for its exquisite properties has been widely used in tackling this burning problem of aquatic pollution caused by heavy metal ions. Accordingly, this mini review appraises the detection as well as diminution activities where chitosan plays the major contributing part. Starting from the intrinsic properties of chitosan, the detection strategy via chitosan composites is comprehensively delineated. Likewise, the removal activities via chitosan mediating agents are also overviewed, followed by future recommendations. It is believed that this mini review will give researchers a brief appraisal of two prominent activities related to controlling of heavy metal ion pollution.

Removal of p-nitrophenol from simulated sewage using MgCo-3D hydrotalcite nanospheres: capability and mechanism

4-Nitrophenol (4-NP) is an organic pollutant found in the wastewater discharged from coking and petrochemical industries, and it is highly toxic, persistent, and bioaccumulative. 4-NP is difficult to degrade and causes serious damage to human health and the ecological environment. In this study, MgCo-3D hydrotalcite nanospheres were synthesized via the hot solvent method using ZIF-67 as a template for 4-NP removal from wastewater. The composition and structure of MgCo-3D hydrotalcite nanospheres were characterized via X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission Electron Microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Energy Dispersive Spectroscopy (EDS), and BET analyses. The maximum adsorption capacity was 131.59 mg g-1 under the optimized conditions (pH = 7, t = 298 K, C 0 = 50 mg L-1, dose = 0.4 g L-1). The adsorption obeyed the Langmuir, Redlich-Peterson and Sips models and pseudo-second-order kinetics, and the adsorption activation energy was 29.4 kJ mol-1, indicating a monolayer physical adsorption phenomenon. The adsorption of 4-NP on the MgCo-3D hydrotalcite nanospheres mainly involved hydrogen bonding and electrostatic interactions. The nanospheres were regenerated using the hot-air purging method. After five adsorption-desorption cycles, the adsorption capacity reached 107.6 mg g-1, indicating the good regeneration performance of the MgCo-3D hydrotalcite nanospheres.

Photocatalytic degradation of paracetamol and bisphenol A by chitosan supported covalent organic framework thin film with visible light irradiation

Covalent Organic Frameworks (COFs) have attracted extensive attention for the photocatalytic degradation of emerging organic contaminants. The difficulty in separation and recovery after use yet would hinder the practical application of COFs in powder form. In present study, COFs in film form were fabricated via using chitosan as the film-substrate to support COFs (CSCF). We found that CSCF could effectively degrade two types of emerging organic contaminants under visible light irradiation. Particularly, CSCF could effectively degrade 99.8% of paracetamol (PCT) and 94.0% of bisphenol A (BPA) within 180 min under visible light irradiation. •O₂^- and h⁺ played dominant roles during the photocatalytic degradation process. Hydroxylation and cleavage were the main degradation processes. CSCF exhibited good photocatalytic degradation performance in a broad range of ionic strengths, in the presence of common coexisting ions including Cl^-, NO₃^- and SO₄^2-, in a wide range of pH (5-11), and in real water samples including tap water, river water and lake water. Moreover, CSCF could be easily collected after use and exhibited excellent degradation performance in five successive cycles. CSCF has potential applications to treat water with either PCT or BPA contamination. This study provided a new insight into the practical application of COFs.

Highly Porous Hydroxyapatite/Graphene Oxide/Chitosan Beads as an Efficient Adsorbent for Dyes and Heavy Metal Ions Removal

Dye and heavy metal contaminants are mainly aquatic pollutants. Although many materials and methods have been developed to remove these pollutants from water, effective and cheap materials and methods are still challenging. In this study, highly porous hydroxyapatite/graphene oxide/chitosan beads (HGC) were prepared by a facile one-step method and investigated as efficient adsorbents. The prepared beads showed a high porosity and low bulk density. SEM images indicated that the hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanosheets were well dispersed on the CTS matrix. FT-IR spectra confirmed good incorporation of the three components. The adsorption behavior of the obtained beads to methylene blue (MB) and copper ions was investigated, including the effect of the contact time, pH medium, dye/metal ion initial concentration, and recycle ability. The HGC beads showed rapid adsorption, high capacity, and easy separation and reused due to the porous characteristics of GO sheets and HA nanoparticles as well as the rich negative charges of the chitosan (CTS) matrix. The maximum sorption capacities of the HGC beads were 99.00 and 256.41 mg g⁻¹ for MB and copper ions removal, respectively.

Graphene-Based Materials Immobilized within Chitosan: Applications as Adsorbents for the Removal of Aquatic Pollutants

Graphene and its derivatives, especially graphene oxide (GO), are attracting considerable interest in the fabrication of new adsorbents that have the potential to remove various pollutants that have escaped into the aquatic environment. Herein, the development of GO/chitosan (GO/CS) composites as adsorbent materials is described and reviewed. This combination is interesting as the addition of graphene to chitosan enhances its mechanical properties, while the chitosan hydrogel serves as an immobilization matrix for graphene. Following a brief description of both graphene and chitosan as independent adsorbent materials, the emerging GO/CS composites are introduced. The additional materials that have been added to the GO/CS composites, including magnetic iron oxides, chelating agents, cyclodextrins, additional adsorbents and polymeric blends, are then described and discussed. The performance of these materials in the removal of heavy metal ions, dyes and other organic molecules are discussed followed by the introduction of strategies employed in the regeneration of the GO/CS adsorbents. It is clear that, while some challenges exist, including cost, regeneration and selectivity in the adsorption process, the GO/CS composites are emerging as promising adsorbent materials.

Recent Developments in Chitosan-Based Adsorbents for the Removal of Pollutants from Aqueous Environments

The quality of water is continuously under threat as increasing concentrations of pollutants escape into the aquatic environment. However, these issues can be alleviated by adsorbing pollutants onto adsorbents. Chitosan and its composites are attracting considerable interest as environmentally acceptable adsorbents and have the potential to remove many of these contaminants. In this review the development of chitosan-based adsorbents is described and discussed. Following a short introduction to the extraction of chitin from seafood wastes, followed by its conversion to chitosan, the properties of chitosan are described. Then, the emerging chitosan/carbon-based materials, including magnetic chitosan and chitosan combined with graphene oxide, carbon nanotubes, biochar, and activated carbon and also chitosan-silica composites are introduced. The applications of these materials in the removal of various heavy metal ions, including Cr(VI), Pb(II), Cd(II), Cu(II), and different cationic and anionic dyes, phenol and other organic molecules, such as antibiotics, are reviewed, compared and discussed. Adsorption isotherms and adsorption kinetics are then highlighted and followed by details on the mechanisms of adsorption and the role of the chitosan and the carbon or silica supports. Based on the reviewed papers, it is clear, that while some challenges remain, chitosan-based materials are emerging as promising adsorbents.

Adsorption of ibuprofen, ketoprofen, and paracetamol onto activated carbon prepared from effluent treatment plant sludge of the beverage industry

The presence of emerging contaminants such as pharmaceuticals in aquatic means presents as a serious threat, since their real consequences for the environment and human health are not well known. Therefore, this work consisted of preparing and characterize sludge-derived activated carbons (beverage sludge activated carbon - BSAC and acid-treated beverage sludge activated carbon - ABSAC) to investigate their use in the pharmaceuticals adsorption in aqueous media. The morphology study has demonstrated that ABSAC, unlike BSAC, exhibited an abundant porous structure, with smaller particles and bigger roughness. Adsorption results indicated that the ABSAC was more effective that BSAC, since it presented superior surface area (642 m² g^-1) and total pore volume (0.485 cm³ g^-1) values. Pseudo-second-order kinetic model was more suitable to predict experimental data. Sips model best described the equilibrium data, with maximum adsorption capacities of 145, 105, and 57 mg g^-1 for paracetamol, ibuprofen, and ketoprofen, respectively. Besides, the sludge-derived adsorbent was highly efficient in the treatment of a simulated drug effluent, removing 85.16% of the pharmaceutical compounds. Therefore, the material prepared in this work possesses intrinsic characteristics that make it a remarkable adsorbent to be applied in the treatment of pharmaceutical contaminants contained in industrial wastewater.