Synthesis of chitosan-g-itaconic acid hydrogel as an antibacterial drug carrier: optimization through RSM-CCD

Deep removal of phosphate from electroplating wastewater using novel Fe-MOF loaded chitosan hydrogel beads

Since the electroplating industry is springing up, effective control of phosphate has attracted global concerns. In this study, a novel biosorbent (MIL-88@CS-HDG) was synthesized by loading a kind of Fe-based metal organic framework called MIL-88 into chitosan hydrogel beads and applied in deep treatment of phosphate removal in electroplating wastewater. The adsorption capacities of H2PO4- on MIL-88@CS-HDG could reach 1.1 mmol/g (corresponding to 34.1 mg P/g and 106.7 mg H2PO4-/g), which was 2.65% higher than that on single MOF powders and chitosan hydrogel beads. The H2PO4- adsorption was well described by the Freundlich isotherm model. Over 90% H2PO4- could be adsorbed at contact time of 3 h. It could keep high adsorption capacity in the pH range from 2 to 7, which had a wider pH range of application compared with pure MIL-88. Only NO3- and SO42- limited the adsorption with the reduction rate of 11.42% and 23.23%, proving it tolerated most common co-existing ions. More than 92% of phosphorus could be recovered using NaOH and NaNO3. Electrostatic attraction between Fe core and phosphorus in MIL-88@CS-HDG and ion exchange played the dominant role. The recovered MIL-88@CS-HDG remained stable and applicable in the treatment process of real electroplating wastewater even after six adsorption-regeneration cycles. Based on the removal properties and superb regenerability, MIL-88@CS-HDG is potentially applicable to practical production.

Agar and Chitosan Hydrogels' Design for Metal-Uptaking Treatments

In the field of cultural heritage, the use of natural gels is rising for the application of active agents. Here, two natural polymers are assessed: agar, a pioneer hydrogel for conservation treatments, and chitosan, a rather novel and metal-binding gel. For chitosan, a state-of-the-art based formulation (CS-ItA-LCys) is evaluated as it was reported for silver-complexing properties. It is evaluated whether these polymers can withstand the addition of the chelating compound deferoxamine, which is a bacterial siderophore. This allows for the obtainment of completely bio-sourced gel systems. A Fourier-transformed (FT) infrared spectroscopy characterization is performed, completed with rheological measurements and Cryo-Scanning Electron Microscopy (cryo-SEM) to investigate the physico-chemical properties of the gels, as well as their interaction with deferoxamine. Both polymers are also tested for their inherent complexing ability on silver ions using FT-Raman spectroscopy. A multi-analytical comparison shows different microstructures, in particular, the presence of a thick membrane for chitosan and different mechanical behaviors, with agar being more brittle. Neither hydrogel seems affected by the addition of deferoxamine; this is shown by similar rheological behavior and molecular structures in the presence or absence of the chelator. The intrinsic abilities of the chitosan formulation to make silver complex are demonstrated with the observation of two peaks characteristic of Ag-S and Ag-O bonds. Agar and chitosan are both proven to be reliable gels to act as carriers for bio-based active agents. This paper confirms the potential asset of the chitosan formulation CS-ItA-LCys as a promising gel for the complexation of soluble silver.