High-strength hydrogels:Fabrication,reinforcement mechanisms,and applications

With the continuous appearance and expansion of high-strength hydrogels in emerging fields such as industry,medicine,and green development,the synthesis and application of high-strength hydrogels have developed dramatically and achieved remarkable results from the aspects of raw materials,preparation methods,and reinforcement mechanisms.However,there is still a lack of systematic reviews on high-strength hydrogels.Herein,we first discuss the advantages of natural and synthetic materials,and the characteristics of high-strength hydrogels prepared from different raw materials;we then expound on the influence mechanism of physical interactions or chemical bonds on the strength of the hydrogel from three aspects:physical cross-linking,chemical cross-linking,and dynamic chemical cross-linking;at last,we systematically expound the strengthening strategies,including double network/multi-network,nanocomposite,topology,supramolecular polymerization,and characteristics and strengthening mechanisms of such high-strength hydrogels.In addition,based on the development status of high-strength hydrogels,we combined the application requirements and the existing drawbacks of high-strength hydrogels to propose their possible development directions in the future.

Crosslinking acrylamide with EDTA-intercalated layered double hydroxide for enhanced recovery of Cr(Ⅵ)and Congo red:Adsorptive and mechanistic study

We prepared ethylenediaminetetraacetic acid(EDTA)-intercalated MgAl-layered double hydroxide(LDH-EDTA),then grafted acrylamide(AM)to the LDH-EDTA by a cross-linking method to yield a LDH-EDTA-AM composite;we then evaluated its adsorptive ability for Congo red(CR)and hexavalent chromium(Cr(Ⅵ))in single and binaiy adsorption systems.The adsorption process on LDH-EDTA-AM for CR and Cr(Ⅵ)achieved equilibrium quickly,and the removal efficiencies were minimally affected by initial pH.The maximum uptake quantities of CR and Cr(Ⅵ)on LDH-EDTAAM were 632.9 and 48.47 mg/g,respectively.In mixed systems,chromate removal was stimulated by the presence of CR,while the adsorption efficiency of C R was almost not influenced by coexisting Cr(Ⅵ).The mechanisms involved electrostatic attraction,surface complexation,and anion exchange for the adsorption of both hazardous pollutants.In the Cr(Ⅵ)adsorption process,reduction also took place.The removal efficiencies in real contaminated water were all higher than those in the laboratory solutions.