<p>In this study, Mn-Ni-layered double hydroxides (Mn-Ni-LDHs) were synthesized and utilized to activate peroxymonosulfate (PMS) for degrading reactive brilliant blue KN-R (KN-R) in aqueous solutions. The characterization results demonstrate that the catalysts synthesized are layered structures, and the surface area is 169.3 m²/g. The Mn-Ni-LDHs exhibited significant efficiency effective for the degradation of KN-R via activating PMS, achieving 96.5% degradation of KN-R within 90 min under optimal conditions (0.20 g/L catalyst, 10 mM PMS, pH=10.0 and 25°C). The reaction followed pseudo-first-order kinetics with a rate constant of 0.0351 min^-1, and the apparent activation energy was calculated to be 11.94 kJ/mol. Electron paramagnetic resonance (EPR) and free radical scavenging experiments identified ·O₂⁻ and ¹O₂ as the primary reactive species involved in the reaction for KN-R degradation. The proposed catalytic mechanism suggests that redox cycling between Mn⁴⁺/Mn³⁺ and Ni³⁺/Ni²⁺ within Mn-Ni-LDHs plays a critical role in enhancing PMS activation, thereby promoting the continuous generation of active oxygen species.</p>