Nitrate removal from aqueous solutions by magnetic cationic hydrogel:Effect of electrostatic adsorption and mechanism

Excessive nitrate(NO3-)is among the most problematic surface water and groundwater pollutants.In this study,a type of magnetic cationic hydrogel(MCH)is employed for NO3-adsorption and well characterized herein.Its adsorption capacity is considerably pHdependent and achieves the optimal adsorption(maximum NO3--adsorption capacity is95.88±1.24 mg/g)when the pH level is 5.2-8.8.The fitting result using the homogeneous surface diffusion model indicates that the surface/film diffusion controls the adsorption rate,and NO3-approaches the center of MCH particles within 30 min.The diffusion coefficient(Ds)and external mass transfer coefficient(kF)in the liquid phase are1.15×10-6 cm2/min and 4.5×10-6 cm/min,respectively.The MCH is employed to treat surface water that contains 10 mg/L of NO3-,and it is found that the optimal magnetic separation time is 1.6 min.The high-efficiency mass transfer and magnetic separation of MCH during the adsorption-regeneration process favors its application in surface water treatment.Furthermore,the study of the mechanism involved reveals that both-N+(CH3)3 groups and NO3-are convoluted in adsorption via electrostatic interactions.It is further found that ion exchange between NO3-and chlorine occurs.

Mechano-responsive hydrogel for direct stem cell manufacturing to therapy

Bone marrow-derived mesenchymal stem cell(MSC)is one of the most actively studied cell types due to its regenerative potential and immunomodulatory properties.Conventional cell expansion methods using 2D tissue culture plates and 2.5D microcarriers in bioreactors can generate large cell numbers,but they compromise stem cell potency and lack mechanical preconditioning to prepare MSC for physiological loading expected in vivo.To overcome these challenges,in this work,we describe a 3D dynamic hydrogel using magneto-stimulation for direct MSC manufacturing to therapy.With our technology,we found that dynamic mechanical stimulation(DMS)enhanced matrix-integrinβ1 interactions which induced MSCs spreading and proliferation.In addition,DMS could modulate MSC biofunctions including directing MSC differentiation into specific lineages and boosting paracrine activities(e.g.,growth factor secretion)through YAP nuclear localization and FAK-ERK pathway.With our magnetic hydrogel,complex procedures from MSC manufacturing to final clinical use,can be integrated into one single platform,and we believe this‘all-in-one’technology could offer a paradigm shift to existing standards in MSC therapy.

Combining material characterization with single and multi-oxyanion adsorption for mechanistic study of chromate removal by cationic hydrogel

Cationic hydrogel with magnetic property was synthesized via radical polymerization and its removal capacity of chromate from contaminated water was found to be 200 mg/g.Using Fourier transform infrared spectroscopy（FT-IR） study,the mechanism of chromate removal by hydrogel was found to be non-specific adsorption,mainly due to ion exchange,as evidenced by the positively charged functional group,trimethyl ammonium-N＋（CH3）3,in the monomer.Verifications were accordingly determined by testing di？erent oxyanion adsorption onto the hydrogel.The results of the chromate adsorption experiments illustrated that the amount of chromate adsorbed was nearly equal to that of the chloride released from the hydrogel,which is part of the evidence for ion exchange.Single and multi-oxyanion adsorption experiments were also performed,and it was demonstrated that ion removal was species independent,but charge dependent,another characteristic of the ion exchange process.It was found that the same Langmuir model can be applied to best fit the findings of single and multi-oxyanion adsorption,which further indicates the mechanism of chromate removal is attributed to ion exchange.In view of the above,the background anions compete for adsorption sites with chromate,evidenced by inhibitive chromate removal in the presence of background electrolytes in the batch studies,further echoing the ion exchange mechanism.