BACKGROUND: This work explored a complete evolutionary process, from discovering a new reaction and synthesizing a new crosslinker intermediate, to product application in the purification of dyeing wastewater.RESULTS: A new micro-polycondensation reaction between propylacryloyloxypropyldimethylamine and epichlorohydrin was first observed, forming a new polyunsaturated cationic crosslinker (poly (2-hydroxypropylacryloyloxypropyldimethylammonium chloride) (PHPAC), abbreviating HPAC unit as the repeating unit); meanwhile, this new PHPAC crosslinker was just a critical modifier of a polycationic flocculant. When the thimbleful of PHPAC crosslinkers containing only 0.2% molar percentage of HPAC units were incorporated into a polycationic skeleton of poly (acryloyloxyethyltrimethylammonium chloride) (PDAC), the application properties of the obtained modified product (known as SC-PDAC) were greatly improved compared to the unmodified product of PDAC. The cost for preparing the modified product of SC-PDAC was hardly increased because the quantity of HPAC modifier used was minimal. The multi-dimension flocculation interactions of SC-PDAC with the anionic dyes allowed the SC-PDAC to realize a more efficient purification of dyeing wastewater than the unmodified PDAC. The obtained SC-PDAC could remove 99.10% of the dyes Reactive Scarlet 3BS and 96.69% of the dyes Methyl Blue when used for purifying the dyeing wastewater. In real engineering applications, the further complex interactions of SC-PDAC with certain inorganic flocculants and coagulant aids would allow the flocs to be quickly formed, condensed, and aggregated, so as to realize a fast purification of dyeing wastewater within 10 s. The successful implementation of a simulation amplification experiment for treating a 4.0 L dye solution further confirmed that the SC-PDAC had good potential to be applied in real water treatment engineering. CONCLUSIONS: Therefore, as expected, it could be regarded as an economic and facile modification way to obtain the efficient organic cationic flocculant by selecting the PHPAC crosslinker as a critical modifier.

To address the efficient resourcefulness of papermaking wastewater, this study designed a super-efficient gel material (SGPQG/SGPQ) that could remove over-10-times masses of lignins from wastewater, and subsequently realized the highly-efficient reuse of wastes. The mass of lignin removed by per unit mass of SGPQG/SGPQ was 10,157.71 mg•g-1, i.e., the mass of lignin removed was 10.16 times that of the mass of SGPQG/SGPQ itself, which was 1.23-50.55 times better than the existing similar materials, showing a super-efficient lignin removal ability. Meanwhile, the average lignin removal rate of SGPQG/SGPQ was 1.85-3.34 times higher than those of the pre-products. Moreover, the extended application of SGPQG/SGPQ in the purification of a complex wastewater and a real papermaking wastewater had been also successfully carried out. The mechanism investigations confirmed an integrated skeleton-space effect mechanism, which is the key factor for SGPQG/SGPQ to achieve the super-efficient lignin removal in the purification of papermaking wastewater. In addition, the SGPQG/SGPQ wastes after treating lignins, could be directly used for adsorption treatment of dyeing wastewater, and had 443.9 times adsorption capacity compared to the widely-used activated carbon, demonstrating an efficient resourcefulness reuse.