Environmentally friendly chitosan/PEI-grafted magnetic gelatin for the highly effective removal of heavy metals from drinking water

Tannic acid adsorption properties of cellulose nanocrystalline/fish swim bladder gelatin composite sponge

Foods and beverages with excessive tannins acid (TA) content taste astringent and bitter. The overconsumption of TA could result in nutritional and digestive problems. In this study, the cellulose nanocrystals (CNC)/fish swim bladder gelatin (FG) composite sponge was prepared with glutaraldehyde as a crosslinking agent. The TA adsorption performance of the sponge was discussed. The freeze-dried CNC/FG composite sponge had a porous network structure. CNC was combined into the FG matrix as a reinforcing phase. The mechanical strength, thermal stability, and swelling properties of the composite sponge were improved with the addition of an appropriate amount of CNC. Although CNC decreased the porosity of composite sponge, the increase in active adsorption sites resulted in an overall positive effect on its TA adsorption properties. Under the optimal adsorption conditions, the TA removal rate of 1.0 % CNC composites reached 80.4 %. Furthermore, the sponge retained a TA removal rate of 54 % after five cycles of adsorption and desorption using 50 % ethanol. The results demonstrated that CNC/FG composite sponge has application potential in the field of adsorption materials for TA.

Enhanced systematic delivery of fluconazole-loaded biotin-glutathione functionalized chitosan-g-proline carrier into the infected retinitis treatment

BACKGROUND

The polymer-based facile and effective drug carrier approach was developed to treat superficial fungal infected retinopathy infections.

METHODS

Here, biotin-glutathione (B-GHS) functionalized with chitosan grafted proline (CS-g-P) moieties were fabricated with the loading of fluconazole (FLZ) for the treatment of retinopathy. FT-IR and XRD techniques were used to characterize chemical structural and phase changes of the prepared carriers The SEM results show that the sphere morphology with interconnection particle nature.

RESULTS

The particle diameter was found as ~ 6.5 and ~ 8.6 nm for CS-g-P/B-GHS and FLZ-loaded CS-g-P/B-GHS carriers, respectively. The negative surface charge was found as the values of CS-g-P/B-GHS and FLZ-loaded CS-g-P/B-GHS, such as -20.7 mV and - 32.2 mV, from zeta potential analysis. The in-vitro FLZ releases from the CS-g-P/B-GHS were investigated at pH 7.4 (PBS) as the tear fluid environment, and it was observed at 85.02% of FLZ release in 8 h reaction time. The sustained release was observed, leading to the necessity for prolonged therapeutic effects. The antifungal effect of the carrier was studied by the minimum inhibitory concentration (MIC) and the percentage inhibition of viable fungal count against Candida albicans, and it observed 81.02% of the zone of inhibition by the FLZ carrier.

CONCLUSION

FLZ-loaded CS-g-P/B-GHS carrier could inhibit the biofilm formation in a concentration-dependent inhibition. Hence, A novel FLZ/B-GHS-CS-g-P carrier is a hopeful approach for effectively treating superficial fungal contaminations of the retina region.

Chitosan-grafted hydrogels for heavy metal ion adsorption and catalytic reduction of nitroaromatic pollutants and dyes

Chitosan-grafted-poly(acrylic acid) (CS-g-PAA) and chitosan-grafted- poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (CS-g-P(AA-co-AMPS)) hydrogels were synthesized and then employed as adsorbents for the effective removal of Cu2+ and other heavy metal ions. The effect of hydrogel's composition on the Cu2+ adsorption was explored. The CS-g-PAA hydrogel demonstrated a superior adsorption capacity compared to pristine CS, PAA hydrogel, and CS-g-P(AA-co-AMPS) hydrogels. The adsorption followed the Langmuir isotherm model, and the pseudo-second order kinetic model. Additionally, the CS-g-PAA hydrogel exhibited relatively high adsorption performances toward Cr3+, Co2+, Ni2+, Pb2+, and Zn2+. Metal ions adsorbed within CS-g-PAA hydrogels underwent reduction to their corresponding metallic states and were reutilized as catalysts for the reduction of 4-nitrophenol. The comparative catalytic performances of the metal species in the hydrogel were in the order of Cu > Ni > Co > Zn. The reduction efficiency of Cu-CS-g-PAA increased with increased catalyst dosage, NaBH4 concentration, and temperature. A very low activation energy of 3.7 kJ/mol was observed. The catalyst maintained high catalytic performance even when subjected to real water samples and proved its reusability for up to three cycles. Moreover, the catalyst could effectively reduce 2-nitrophenol and methyl orange.

Myrica esculenta Leaf Extract-Assisted Green Synthesis of Porous Magnetic Chitosan Composites for Fast Removal of Cd (II) from Water: Kinetics and Thermodynamics of Adsorption

Heavy metal contamination in water resources is a major issue worldwide. Metals released into the environment endanger human health, owing to their persistence and absorption into the food chain. Cadmium is a highly toxic heavy metal, which causes severe health hazards in human beings as well as in animals. To overcome the issue, current research focused on cadmium ion removal from the polluted water by using porous magnetic chitosan composite produced from Kaphal (Myrica esculenta) leaves. The synthesized composite was characterized by BET, XRD, FT-IR, FE-SEM with EDX, and VSM to understand the structural, textural, surface functional, morphological-compositional, and magnetic properties, respectively, that contributed to the adsorption of Cd. The maximum Cd adsorption capacities observed for the Fe3O4 nanoparticles (MNPs) and porous magnetic chitosan (MCS) composite were 290 mg/g and 426 mg/g, respectively. Both the adsorption processes followed second-order kinetics. Batch adsorption studies were carried out to understand the optimum conditions for the fast adsorption process. Both the adsorbents could be regenerated for up to seven cycles without appreciable loss in adsorption capacity. The porous magnetic chitosan composite showed improved adsorption compared to MNPs. The mechanism for cadmium ion adsorption by MNPs and MCS has been postulated. Magnetic-modified chitosan-based composites that exhibit high adsorption efficiency, regeneration, and easy separation from a solution have broad development prospects in various industrial sewage and wastewater treatment fields.

Bisphosphonate-incorporated coatings for orthopedic implants functionalization

Bisphosphonates (BPs), the stable analogs of pyrophosphate, are well-known inhibitors of osteoclastogenesis to prevent osteoporotic bone loss and improve implant osseointegration in patients suffering from osteoporosis. Compared to systemic administration, BPs-incorporated coatings enable the direct delivery of BPs to the local area, which will precisely enhance osseointegration and bone repair without the systemic side effects. However, an elaborate and comprehensive review of BP coatings of implants is lacking. Herein, the cellular level (e.g., osteoclasts, osteocytes, osteoblasts, osteoclast precursors, and bone mesenchymal stem cells) and molecular biological regulatory mechanism of BPs in regulating bone homeostasis are overviewed systematically. Moreover, the currently available methods (e.g., chemical reaction, porous carriers, and organic material films) of BP coatings construction are outlined and summarized in detail. As one of the key directions, the latest advances of BP-coated implants to enhance bone repair and osseointegration in basic experiments and clinical trials are presented and critically evaluated. Finally, the challenges and prospects of BP coatings are also purposed, and it will open a new chapter in clinical translation for BP-coated implants.

Protein/Polysaccharide Composite toward Multi-in-One Toxin Removal in Blood with Self-Anticoagulation and Biocompatibility

Biocompatible adsorbents play an essential role in hemoperfusion. Nevertheless, there are no hemoperfusion adsorbents that can simultaneously remove small and medium toxins, including bilirubin, urea, phosphor, heavy metals, and antibiotics. This bottleneck significantly impedes the miniaturization and portability of hemoperfusion materials and devices. Herein, a biocompatible protein-polysaccharide complex is reported that exhibits "multi-in-one" removal efficacy for liver and kidney metabolism wastes, toxic metal ions, and antibiotics. Through electrostatic interactions and polysaccharide-mediated coacervation, adsorbents can be prepared by simply mixing lysozyme (LZ) and sodium alginate (SA) together in seconds. The LZ/SA absorbent presented high adsorption capacities for bilirubin, urea, and Hg2+ of up to 468, 331, and 497 mg g-1 , respectively, and the excellent anti-protein adsorption endowed LZ/SA with a record-high adsorption capacity for bilirubin in the interference of serum albumin to simulate the physiological environment. The LZ/SA adsorbent also has effective adsorption capacity for heavy metals (Pb2+ , Cu2+ , Cr3+ , and Cd2+ ) and multiple antibiotics (terramycin, tetracycline, enrofloxacin, norfloxacin, roxithromycin, erythromycin, sulfapyrimidine, and sulfamethoxazole). Various adsorption functional groups exposed on the adsorbent surface significantly contribute to the excellent adsorption capacity. This fully bio-derived protein/alginate-based hemoperfusion adsorbent has great application prospects in the treatment of blood-related diseases.

Preparation of chitosan/sodium alginate/nano cellulose composite for the efficient removal of cadmium (II) cations from wastewater and soil systems

In this study, chitosan/sodium alginate/nano cellulose (CSA-N) nanocomposite hydrogels were prepared using a completely green route and used as sorbents to adsorb Cd²⁺ ions from water and soil systems of an environmental aspect. The sorbents were characterized by FTIR, SEM, and XRD. The influences of initial Cd²⁺ concentration, the presence of nano cellulose, type of the polluted environment, and ionic strength on adsorption and desorption isotherms were investigated. The maximum adsorption capacity of cadmium onto CSA was significantly increased from 2264.9 to 4380.97 μmol/g when the system was changed from soil to water, respectively. While, the maximum adsorption capacity of cadmium onto CSA-N was almost the same in the soil and wastewater systems, i.e., 3419.5 and 3230.3 µmol/g, respectively. The results indicated that Langmuir and Freundlich models provided the best fit for the experimental adsorption data for CSA and CSA-N, respectively. By comparing the amounts of Δq, the difference between adsorption and desorption amounts, the CSA was not economically feasible sorbent at high initial concentrations of Cd²⁺ in the wastewater system, while, CSA-N was demonstrated to be a more efficient adsorbent than CSA for cadmium removal from both the soil and wastewater systems.

Functionalized dual modification of covalent organic framework for efficient and rapid trace heavy metals removal from drinking water

A key challenge in trace heavy metals removal from drinking water by adsorption technology is to achieve high adsorption capacity and rapid uptake speed of adsorbent. Herein, we report a functionalized double modified covalent organic framework (DMTD-COF-SH) bearing high-density sulfur and nitrogen chelating groups provided simultaneously by 2,5-dimercapto-1,3,4-thiadiazole (DMTD) and 1,2-ethanedithiol, which was prepared via a facile one-pot thiol-ene "click" reaction. PXRD, FTIR, XPS, SEM, BET and ¹³C MAS NMR confirmed their successful graft, and DMTD was found to be more easily grafted on the COF surface layer than 1,2-ethanedithiol. The as-prepared DMTD-COF-SH showed remarkable adsorption capacity and ultrafast uptake dynamics to trace heavy metals owing to the synergistic effects resulting from densely populated sulfur and nitrogen chelating groups within ordered COF mesopores and at the COF surface. On the basis of the drinking water treatment units standard NSF/ANSI 53-2020, when the adsorbent dosage was 10 mg/30 mL and 20 mg L^-1 calcium ions coexisted, the lead concentration decreased from initial 150 μg L^-1 to 2.89 μg L^-1 within 10 s, far below the allowable limit of world health organization (WHO) drinking water standard (10 μg L^-1), and the maximum adsorption capacity meeting the standard attained 14.22 mg g^-1. The adsorbent also exhibited excellent stability, wide applicable pH range and outstanding adsorption performance for coexisting trace lead, mercury, cadmium, chromium (VI) and copper in tap water, indicating that the DMTD-COF-SH material has excellent application prospect for trace heavy metals removal from drinking water.

Research progress of adsorption and removal of heavy metals by chitosan and its derivatives: A review

Chitosan has received widespread attention as an adsorbent for pollutants because of its low cost and great adsorption potentials. Chitosan has abundant hydroxyl and amino groups that can bind heavy metal ions. However, it has defects such as sensitivity to pH, low thermal stability, and low mechanical strength, which limit the application of chitosan in wastewater treatment. The functional groups of chitosan can be modified to improve its performance via crosslinking and graft modification. The porosity and specific surface area of chitosan in powder form are not ideal, therefore, physical modification has been attempted to generate chitosan nanoparticles and hydrogel. Chitosan has also been integrated with other materials (e.g. graphene, zeolite) resulting in composite materials with improved adsorption performance. This review mainly focuses on reports about the application of chitosan and its derivatives to remove different heavy metals. The preparation strategy, adsorption mechanism, and factors affecting the adsorption performance of adsorbents for each type of heavy metal are discussed in detail. Recent reports on important organic pollutants (dyes and phenol) removal by chitosan and its derivatives are also briefly discussed.

Removal of Cu(II) by Fixed-Bed Columns Using Alg-Ch and Alg-ChS Hydrogel Beads: Effect of Operating Conditions on the Mass Transfer Zone

The removal of Cu(II) ions from aqueous solutions at a pH of 5.0 was carried out using fixed-bed columns packed with alginate-chitosan (Alg-Ch) or alginate-chitosan sulfate (Alg-ChS) hydrogel beads. The effect of the initial Cu(II) concentration, flow rate, pH, and height of the column on the amount of Cu removed by the column at the breakpoint and at the exhaustion point is reported. The pH of the solution at the column's exit was initially higher than that at the entrance, and then decreased slowly. This pH increase was attributed to proton transfer from the aqueous solution to the amino and COO^- groups of the hydrogel. The effect of operating conditions on the mass transfer zone (MTZ) and the length of the unused bed (H_LUB) is reported. At the lower flow rate and lower Cu(II) concentration used, the MTZ was completely developed and the column operated efficiently; by increasing column height, the MTZ has a better opportunity to develop fully. Experimental data were fitted to the fixed-bed Thomas model using a non-linear regression analysis and a good correspondence between experimental and Thomas model curves was observed.

Nano@lignocellulose intercalated montmorillonite as adsorbent for effective Mn(II) removal from aqueous solution

This paper describes the preparation of nano@lignocellulose (nano@LC) and a nano@lignocellulose/montmorillonite (nano@LC/MT) nanocomposite, as well as the capacity of the nano@LC/MT for adsorbing manganese ions from aqueous solution. The structure of nano@LC and nano@LC/MT was characterised by Fourier-transform infrared spectroscopy, X-ray diffraction, Scanning electron microscopy, and Transmission electron microscopy, which revealed that the diffraction peak of montmorillonite almost disappeared, infrared bands of the functional groups shifted, and morphology of the material changed after the formation of the composite. The optimum conditions for the adsorption of Mn(II) on the nano@LC/MT nanocomposite were investigated in detail by changing the initial Mn(II) concentration, pH, adsorption temperature, and time. The results revealed that the adsorption capacity of the nano@LC/MT nanocomposite for Mn(II) reached 628.0503 mg/g at a Mn(II) initial concentration of 900 mg/L, solution pH 5.8, adsorption temperature 55 °C, and adsorption time 160 min. Adsorption kinetics experiments revealed good agreement between the experimental data and the pseudo-second order kinetic model. The experimental data was satisfactorily fitted to the Langmuir isotherm. Adsorption-desorption results showed that nano@LC/MT exhibited excellent reusability. The adsorption mechanism was investigated through FT-IR and EDX spectroscopic analyses. The results suggested that nano@LC/MT have great potential in removing Mn(II) from water.

Large-scale preparation of a 3D patchy surface with dissimilar dendritic amphiphiles

We show here the first example of the large-scale surface decoration of a macroscopic and porous monolith with dissimilar micropatches. Branched polyethylenimine (PEI) is alkylated with poly(propylene glycol) (PPG), leading to a reverse-micelle-like dendritic amphiphile of PEI@PPG. Peralkylation and partial quaternization of the residual amino groups of PEI@PPG produces a cationic dendritic amphiphile of PEI-N⁺@PPG. The two dendritic amphiphiles jointly stabilize a water-in-oil high-internal-phase emulsion to prepare open-cellular monoliths of macroscopic size, with the monolith pore surface dictated by the cationic and neutral dendritic amphiphiles. The amino groups of the neutral amphiphile are further derivatized into anionic dithiocarbamates. The resulting monolith, along with the dissimilar functional patches on the surface, simultaneously eliminates multiple anionic and cationic micropollutants from water to very low residues, and affords the pH-triggered sequential release. Our strategy of using dissimilar dendritic amphiphiles rather than block copolymers as surface building blocks can confer the resulting surface with robust and predesigned microenvironments besides the conventional coacervate structure, and thus can afford more functions.

Three-channel capillary NF membrane with PAMAM-MWCNT-embedded inner polyamide skin layer for heavy metals removal

MWCNTs-PAMAM were incorporated into the polyamide layer of NF membranes and the prepared membranes showed good permeation and rejection performances.

Inhibition of advanced glycation endproducts during fish sausage preparation by transglutaminase and chitosan oligosaccharides induced enzymatic glycosylation

A non-antioxidative method in which glycosylation induced by transglutaminase “replaced” glycation to inhibit the formation of AGEs in real foods.