Nano-MgO is a good bactericide but with strong alkalinity in water due to its rapid hydrolysis. To control
its hydrolysis rate and keep its bactericidal properties, we synthesized nano-MgO microspheres using
chitosan–alginate system in this study. The synthesized nano-MgO release-controlled microspheres
(nMgO-RCM) were with 0.98–1.20 mm of particle sizes. Also, their embedding ratio and loading percentage
was 63.52% and 12.27%, respectively. Based on the characterization results, nano-MgO was only
observed on surface of the nMgO-RCM. Its release rate from the nMgO-RCM could be controlled by the
chitosan–alginate system, and the observed rate constant (kobs) increased from 0.0289 h1 to
0.0358 h1 with the increment of the dosage from 10 mg L1 to 80 mg L1. Furthermore, the nMgORCM
could maintain pH value lower than 8.5 and colony counts less than 20 CFU mL1 for at least 120 h.