Design of Flexible Film-Forming Polydopamine/Polypyrrole/Nanodiamond Hierarchical Structure for Broadband Microwave Absorption.

Microwave-absorbing materials are widely used in numerous fields, including the military, daily protection, etc. Currently, in addition to being lightweight and highly efficient, good film-forming processing characteristics and environmental stability are also required for the practical application of microwave-absorbing materials, which, in general, are difficult to make compatible. In this paper, a mulberry-like PDA/PPy/ND hierarchical structure was prepared by in situ polymerization. The hierarchical structure showed remarkably enhanced microwave absorption, as well as better flexible film-forming characteristics, thanks to the multiple roles PDA played in the system. The optimal RL peak for PDA/PPy/ND could reach -43.6 dB at 7.58 GHz, which is mainly attributed to the multiple dielectric loss paths and significantly improved impedance-matching characteristics. Furthermore, given the H-bond crosslink, the introduction of PDA also promoted the film formation and dispersion of PDA/PPy/ND in the PVA matrix, forming a water-resistant and flexible film. This work provides a referencing path for the design and practical applications of lightweight microwave-absorbing materials.

N-methylene phosphonic chitosan aerogels for efficient capture of Cu2+ and Pb2+ from aqueous environment.

In this paper, N-methylene phosphonic acid chitosan (NPCS-PEI) was synthesized from chitosan, phosphorous acid, formaldehyde and hyperbranched polyethyleneimine (PEI), and Cu2+ and Pb2+ removal performance was examined in aqueous solution. NPCS-PEI exhibited three-dimensional porous architectures, with a specific surface area of 490.61 m2/g. The effects of pH, initial concentration, adsorption time, temperature and ionic strength on the adsorption capacity were investigated. The adsorption kinetics indicated that Cu2+ and Pb2+ adsorption onto NPCS-PEI follows a pseudo-second-order model. The adsorption isotherms agree well with the Langmuir isotherm model, and the maximum adsorption capacities of Cu2+ and Pb2+ on the NPCS-PEI are approximately 276.12 and 645.16 mg/g, respectively. The adsorption efficiency of NPCS-PEI remained above 85% after 5 adsorption-desorption successive cycles. Moreover, the NPCS-PEI aerogels had selective adsorption toward Cu2+. The FTIR and XPS analysis proved that amino, hydroxyl, and phosphonic acid groups were involved in the chelation with metal ions.