Affiliations: Department of Environmental Engineering, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871,
Japan | Department of Environmental Systems Technology,
College of Technology, Toyama Prefectural University, 5180 Kurokawa, Kosugi,
Imizu, Toyama, 939-0398, Japan | Research Center for Environmental Preservation, Osaka
University, 2-4 Yamada-oka, Suita, Osaka 565-0871, Japan
Abstract: Nonylphenol (NP), nonylphenoxy acetic acid (NP1EC), nonylphenol
monoethoxy acetic acid (NP2EC), nonylphenol monoethoxylate (NP1EO) and
nonylphenol diethoxylate (NP2EO) are biodegradation end products (BEPs) of
nonionic surfactant nonylphenolpolyethoxylates (NP nEO). In this research,
sorption of these compounds onto model activated sludge was characterized.
Sorption equilibrium experiments showed that NP, NP1EO and NP2EO reached
equilibrium in about 12 h, while equilibrium of NP1EC and NP2EC were reached
earlier, in about 4h. In sorption isotherm experiments, obtained equilibrium
data at 28°C fitted well to Freundlich sorption model for all investigated
compounds. For NP1EC, in addition to Freundlich, equilibrium data also fitted
well to Langmuir model. Linear sorption model was also tried, and equilibrium
data of all NP, NP1EO, NP2EO and NP2EC except NP1EC fitted well to this model.
Calculated Freundlich coefficient (K_F) and linear sorption
coefficient (K_D) showed that sorption capacity of the
investigated compounds were in order NP > NP2EO > NP1EO > NP1EC ≈
NP2EC. For NP,NP1EO and NP2EO, high values of calculated K_F
and K_D indicated an easy uptake of these compounds from
aqueous phase onto activated sludge. Whereas, NP1EC and NP2EC with Iow values
of K_F and K_D absorbed weakly to
activated sludge and tended to preferably remain in aqueous phase.
