Selective heavy metal removal and water purification by microfluidically-generated chitosan microspheres: Characteristics, modeling and application

Many industrial wastewater streams contain heavy metals, posing serious and irreversible damage to humans and living organisms, even at low concentrations due to their high toxicity and persistence in the environment. In this study, high-performance monodispersed chitosan (CS) microspheres were prepared using a simple microfluidic method and evaluated for metal removal from contaminated water. Batch experiments were carried out to evaluate the adsorption characteristics for the removal of copper ions, one representative heavy metal, from aqueous solutions. The inherent advantages of microfluidics enabled a precise control of particle size (CV = 2.3%), while exhibiting outstanding selectivity towards target ions (adsorption capacity 75.52 mg g−1) and fair regeneration (re-adsorption efficiency 74% after 5 cycles). An integrated adsorption mechanism analytic system was developed based on different adsorption kinetics and isotherms models, providing an excellent adsorption prediction model with pseudo-second order kinetics (R2 = 0.999), while the isotherm was fitted best to the Langmuir model (R2 = 0.998). The multi-step adsorption process was revealed via quantitative measurements and schematically described. Selective adsorption performance of CS microspheres in the present of other competitive metal ions with different valence states has been demonstrated and studied by both experimental and density functional theory (DFT) analysis

Effect of macrophage transfusion on corneal wound healing.

<p>Forty-eight hours after penetrating keratoplasty in mice injected with Cl₂MDP-LIP, 10⁵ peritoneal macrophages from naïve Balb/c mice were transfused into conjunctiva. After 21 and 28 days later, the mice with macrophage transfusion into conjunctiva showed significant enhanced wound healing (C, F), almost similar to the control mice injected with PBS-LIP (A, D), while the macrophage-depleted mice still showed significant defective wound healing and even the disclosure of eye content (B, E).</p

Sub-conjunctival Cl₂MDP-LIP injection prevented the infiltration of macrophages.

<p>Corneal flat mount staining after 14 days of penetrating keratoplasty showed a number of F4/80⁺ macrophages near the suture sites and around the junction between the graft and recipient cornea (A, B). Section staining primarily revealed staining clustered in the superficial corneal stromal layer (C), while few macrophages could be found in the junction and suture area in Cl₂MDP-LIP-injected mice (D–F).</p

Effect of macrophage depletion on myofibroblast differentiation.

<p>Corneal flat mount staining after 14 days of penetrating keratoplasty showed that α-SMA was strongly expressed in the junction area between the graft and recipient cornea (A) and parallel to the corneal surface (B, C) in the PBS-LIP-injected mice, while in the Cl₂MDP-LIP-treated mice, α-SMA expression was significantly lower (D), and the fibers in the junction area were more disorganized than in the control mice (E,F).</p

Sub-conjunctival Cl₂MDP-LIP injection depleted corneal resident macrophages.

<p>Immunofluorescence staining of cornea after 2 days of liposome injection showed a few F4/80⁺CD11b⁺ macrophages in the central cornea of mice injected with PBS-LIP, while there was no specific staining in mice injected with clodronate liposomes.</p

Effect of macrophage depletion on corneal wound healing.

<p>In mice injected with PBS-LIP, the graft healed well at 14 days after surgery (A), with apparent inflammatory cells and fibroblasts in the junction region between the graft and recipient cornea (B, C), and the collagen fibers were dense and distributed parallel to stromal layers (C). However, the graft showed apparent edema (D) and space between the recipient bed (E) in Cl₂MDP-LIP-treated mice. Few inflammatory cells and fibroblasts were recruited into the junction, the collagen fibers were irregularly distributed (F), the onset of wound dehiscence was observed, with the graft detached from the recipient cornea (G, H), and there was ingrowth of corneal epithelial cells into the junction (I).</p