Switch Effect, Water‐Like State, and New Interaction Mechanism of an H‐Bonded Polycation–Polyacrylamide System to Realize Instant Decolorization of Dyeing Wastewater

Abstract

technologies have been developed in the research literature, such as flocculation, adsorption, and oxidation decomposition. [12][13][14][15][16][17][18] Of these, flocculation is still more advantageous than the other technologies in the engineering applications of large-scale water treatment due to its simplicity, high efficiency, and cost-effectiveness. In engineering applications for dealing with dyeing wastewater, polycationic flocculants have been widely used as effective decolorization materials since their cations can produce electrostatic interactions with the watersoluble anionic dyes to form insoluble flocs for removing the colored dyes from water. [13,[19][20][21] According to the current understanding, the flocculation decolorization of dyeing wastewater primarily depends on the two basic processes of charge neutralization and bridging. [22][23][24] Small precipitations are first formed by the electrostatic interactions (i.e., charge neutralization) between the polycationic flocculants and the anionic dye (it takes a relatively long time as a rate-controlling step). Subsequently, the small precipitations can be gradually aggregated into the larger flocs by the bridging interactions (as the final structure assumes flocs). [25][26][27] The facts indicate that the formation, growth, and settlement of flocs in flocculation decolorization take more than 48 h, which is a very slow process. [28,29] Thus, an important breakthrough will be realizing fast decolorization for dealing with dyeing wastewater.To deal with the abovementioned problems, in essence, we deduce that if the attractive forces of the formed flocs of the flocculation decolorization could be further strengthened, then the stronger attractive forces would accelerate the formation, growth, and settlement of flocs so that the decolorization rate would be faster. Meanwhile, we also notice that the hydrogen bond is a strong interaction force that is not disturbed by the charge factors, suggesting that the incorporation of effective hydrogen bonding interactions within and between the formed flocs of the flocculation decolorization could be a good way to realize fast decolorization during the purification of dyeing wastewater. However, the roles of hydrogen bonds in the improvement of decolorization of dyeing wastewater have not been reported until now. As a preliminary exploration, as designed in this work, we selected the commonly existing A switch for controlling hydrogen bonds is incorporated into a polymerbased system of polyamine polycation and polyacrylamide, with an ultrahigh molecular weight of 18 million; a surprising process results whereby the apparent viscosity of the whole system suddenly plunges from 321 cps to below 6.5 cps, forming a new water-like phase state (WLPS) of an H-bonded polymer-based system. When WLPS products are used as decolorant materials to purify dyeing wastewater, they can flow similar to water during mass transfer and be quickly dissolved, immediately interacting with the anionic dyes in water. This observation i...

A Highly Expanded Polycarboxylate Gel and New Environmental Response Effects for Efficiently Adsorbing and Recovering Cu(II) from Water

“…The results showed that the Cu (II) removal percentages for EPCG adsorption were increased with the increase of EPCG dosages from 0.20 to 0.30 g, indicating a saturated adsorption state at the EPCG dosages of 0.20–0.35 g. However, when the EPCG dosages were above 0.35 g, the Cu­(II) removal percentages for EPCG adsorption maintained an ultimate limit level and changed a little, indicating that the EPCG dosages were excessive. The maximal adsorption capacity ( Q max ) for EPCG adsorption was represented by the average values of the equilibrium adsorption capacities ( q e ) under the saturated adsorption states with the EPCG dosages being 0.20–0.35 g. The results showed that the maximal adsorption capacity ( Q max ) of EPCG adsorption was calculated to be 261.70 mg/g, which was higher than that of most of the selected existing adsorbents reported in the recent years ,− and was also lower than that of a few existing adsorbents , (Table ). However, the existing adsorbent materials are usually difficult to prepare due to the complex and expensive preparation process, or some of them are likely to cause another waste disposal problem after the water treatment process. − In contrast, the EPCG preparation process was very facile, which was only through a facile cross-linking copolymerization and then a simple neutralization treatment.…”

“…Our work assumption was derived from a series of fundamental researches developing new water purification materials for treating various types of wastewater (e.g., heavy-metal wastewater, dyeing wastewater, and papermaking wastewater) in our past contributions. − In one of our previous contributions, we designed a novel polycarboxylate-based polyanionic gel (PAG) adsorbent material and discovered that it showed a higher adsorption capacity for Cu­(II) than the existing adsorbent materials. For the reasons, the polycarboxylate skeletons of PAG could form strong complex bonds with Cu­(II) so that the adsorption ability of PAG toward Cu­(II) could improve .…”

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

“…Dyeing wastewater has high toxicity, high chroma, and high chemical oxygen demands and is regarded as one of the main pollution sources for the global water environments. − To purify the dyeing wastewater, it is key to remove the highly toxic and highly colored anionic dyes in the water. Absorption, flocculation, and oxidation decomposition have already been proved to be useful methods for purifying industrial wastewater. − Of which, absorption is one of the most widely used and convenient methods for water treatment. − The authors have observed that several traditional absorbent materials, for example, activated carbon absorbent, clay mineral (or solid waste) absorbent, and natural product absorbent, are usually used in the field of water treatment. , However, the absorption forces of these traditional absorbents are usually weak intermolecular forces, resulting in their relatively weak absorption abilities when being used for water treatment. , Thus, it is necessary to search for new absorbent materials for purifying dyeing wastewater.…”