Removal of phthalate esters from water using immobilized lipase on chitosan beads

Lipase immobilized on chitosan beads was investigated as a possible efficient and cost-effective method of removing phthalate esters (PAEs) from water, under the hypothesis that the immobilized lipase could degrade PAEs and the amino group of chitosan could adsorb the degraded products. Three immobilization methods, namely crosslinking using glutaraldehyde (GLA), activation with 1-ethyl-3(3-dimethyl-aminopropyl) carbodiimide hydrochloride (EDC) and a binary method using both GLA and EDC, were compared. The results showed that lipase immobilized by crosslinking with GLA exhibited a higher degradation ability for PAEs with lower molecular weights. It removed 100% of dimethyl phthalate and 93.86% of diethyl phthalate. On the other hand, lipase immobilized by EDC activation exhibited efficient degradation of PAEs with higher molecular weights, such as diethylhexyl phthalate (removal efficiency 100%). However, lipase immobilized by the binary method unexpectedly showed less than 50% removal efficiency for all five PAEs. The PAE solutions treated with different immobilized lipases were characterized using high-performance liquid chromatography, and the mechanism of the removal of PAEs by the lipase immobilized on chitosan beads using different methods is further discussed.