Facilely Synthesized, Highly Permeable, and Efficiently Recyclable Polycationic Gel with Cohesive State Transformations for Purifying Dyeing Wastewater.

A highly permeable polycationic gel (PPG) was designed as a new type of absorbent material, which was prepared by a facile cross-linking copolymerization of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride and dimethyldiallylammonium chloride at 45 °C for 3.0 h. When the PPG absorbent was used for purifying dyeing wastewater, it showed high permeability so that the dyes could fully penetrate into the PPG more easily to be absorbed. Moreover, through Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, optical microscopy, and scanning electron microscopy technologies, the structures of PPG before and after absorption were analyzed, showing that the cohesive states of PPG underwent a great transformation during PPG absorption, and the binding energy of N 1S of PPG increased from 401.66 to 402.15 eV. Because of the new absorption effects of the cohesive state transformations of PPG, the absorption capacity of PPG for absorbing a large-sized dye of Reactive Scarlet 3BS reached 1371.04 mg·g, which was 2.07-56.35 times than those of other structural forms of similar cationic absorbents and was 761.69 times higher than that of the frequently used activated carbon. This was the greatest improvement level on the absorption ability of PPG versus the existing absorbents. In addition, PPG achieved excellent recyclability with a mild room-temperature desorption technology, and the absorption capacity of the recycled PPG was 606.76 times higher than that of activated carbon.