Preparation of amino/hydroxy dual-functionalized hypercrosslinked polymers for effective removal of organic dyes from...

Given the pervasive existence and toxicity of organic dyes, it is imperative to develop effective methods for their removal and detection. High-performance adsorbents competent for broad spectrum removal of organic dyes are highly expected. In this manuscript, we demonstrate the preparation of porous hypercrosslinked polymers (MAP-BCMBP-HCP) for the removal of anionic dyes, cationic dyes, and amphoteric dyes from water, through a simple Friedel-Crafts alkylation using m-aminophenol as a monomer and 4,4'-bis(chloromethyl)biphenyl (BCMBP) as a cross-linking agent. It exhibits high capacity for adsorption of the organic dyes, with maximum adsorption capacity of 299, 254, 388, 521, 111, 86, 962, 329, 173, and 153 mg/g to bromothymol blue, chromium black T, alizarin red S, chromium azurite S, methylene blue, crystal violet, rhodamine B, congo red, methyl orange, and caustic bright blue, which is superior to the majority of previously reported adsorbents. The removal efficiency of these dyes can reach 91-99 %, this may be attributed to the high specific surface area of the adsorbent, the rich pore structure, and the presence of abundant functional groups on the surface. Furthermore, MAP-BCMBP-HCP exhibited fast adsorption kinetics, enabling the rapid and highly efficient removal of organic dyes within 10-40 min. Chemisorption plays a predominant role in the overall adsorption process. Additionally, the analysis of adsorption thermodynamics demonstrates that this process occurs spontaneously. A combination of experimental and density functional theory (DFT) studies revealed that the dye adsorption on MAP-BCMBP-HCP was governed by hydrogen bonding interaction, hydrophobic interaction, π-π interaction, and pore-filling. The adsorption of the dyes did not change remarkably with variation in pH and salt concentration, as well as the coexistence of various anions and cations. The good performance of MAP-BCMBP-HCP for organic dye removal was validated using simulated wastewater. In addition, the polymer shows a good ability to remove other pollutants including naphthalene and its derivatives, bisphenols, and polyfluorinated benzoic acids, indicating its potential for broad-spectrum organic pollutants. MAP-BCMBP-HCP can be readily reused at least six times without a notable decline in adsorption efficacy. All these features lay a solid foundation for the application of MAP-BCMBP-HCP in practical industrial wastewater treatment.