Dredged sediment poses significant challenges for transportation and subsequent treatment due to its high water content and large volume. Coagulation, a common method of dewatering, can significantly enhance the dewatering performance of dredged sediment. This study synthesized a cationic starch-based flocculant [starch-3-chloro-2-hydroxypropyl trimethylammonium chloride (St-CTA)] through etherification for the flocculation dewatering of dredged sediment. The effectiveness and mechanism of St-CTA as a dewatering flocculant for dredged sediment were investigated. The results demonstrated that when the dosage of St-CTA was 12 mg g−1 TSS (total suspended solids), the dehydration property of dredged sediment substantially improved, with the specific resistance to filtration (SRF) decreasing by 93.3%, the capillary suction time (CST) by 93.5%, and the water content of the filter cake (WC) by 9.7%. The removal rate of turbidity of the supernatant from the conditioned dredged sediment reached 99.6%, accelerating the settling speed and effectively capturing and separating fine particles from the sediment. St-CTA significantly increased the median particle size (D50), altered the microstructure and extracellular polymeric substances (EPS) of the flocs, and increased the fractal dimension of the flocs, making them more compact and conducive to the formation of drainage channels. These findings confirm the feasibility of using potentially environmentally friendly St-CTA as a rapid dewatering conditioning agent for sediment.
Carbon materials are widely used as catalysts or supports due to their excellent properties. In this paper, the tungsten carbide-activated carbon (WC-AC) composite support was successfully prepared by in-situ carburizing on AC matrix, which is characterized by the covalent anchoring of WC on the AC support. The active metal Co was supported on WC-AC for dry reforming of methane (DRM). Samples were analyzed by N 2 physisorption measurements, XRD , XPS , H 2 -TPR, H 2 -TPD, CH 4 &CO 2 -TPSR, TG-DTG. The WC-AC stabilizes the disturbance of C in AC, alleviates the gasification effect of CO 2 and increases the active sites for CH 4 cracking. Moreover, WC provides a resistance-less bridge suitable for the Co 3+ → Co 2+ , resulting in a high Co 2+ /Co 3+ ratio on the catalyst surface . This enhances the interaction between the Co species and the WC-AC, thereby enhancing the CH 4 activation. In the process of WC-AC promoting Co 3+ →Co 2+ , the catalyst surface is accompanied by the generation of oxygen vacancies . This can enhance the dissociative adsorption of CO 2 on surface of the WC-cobalt oxide, and at the same time increase the relative proportion of adsorbed oxygen on the catalyst surface, thereby effectively inhibiting the formation of coke. However, the small amount of graphitic carbon generated due to the strong coupling of WC and Co is the main reason for deactivation of Co/WC-AC.
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