Poly(ethylene oxide) -poly(propylene oxide) -poly-(ethylene oxide) block copolymers (PEO-PPO- PEO) are encapsulated with sodium alginate hydrogel. The apparent partition coefficients of naphthalene based on inside and outside hydrogel beads of encapsulating six block copolymers are measured

the results indicate that hydrogel encapsulating L122 black copolymer has the largest capacity to extract naphthalene. The extrsction capacity of hydrogel is enhanced by increase temperature. The alginate hydrogel can be reused through a process of dryness

reverse-extraction and regeneration.