Un‐restricted diffusion channels for ions and molecules within catalytic composites is of practical significance for environmental remediation with aqueous reaction systems. Herein, hierarchical Co/N‐co‐doped carbonaceous beads with diffusion‐promoting nanostructures for activating peroxymonosulfate (PMS) were prepared through a seaweed‐based hydrogel strategy. Several technologies were applied to characterize resultant samples including XRD, SEM, TEM, XPS and N2 adsorption‐desorption. The degradation was carefully tested in simulations of real conditions such as in running water, laboratory waste liquid, and seawater, which indicated that the catalyst/PMS system has a practical and a wide range of degradation capacity. Moreover, SA/N−CoxOy could also prepared with waste cobalt solution, and also showed relatively good catalytic performance. In contrast to other works which mostly concentrated on the study of static testing, this research is mainly concerned with dynamic degradation. Batch and fixed‐bed column degradation experiments were simultaneously carried out to evaluate the efficiency and potential industrial applications, which revealed that the as‐prepared sample led to the fast removal of 90.26% of MB within 400 minutes and continuously degraded the dye for 25 h at 298 K. The recycling performance was also investigated by means of dynamic degradation tests, which only showed a slight decline with time.