Study On Aerobic Biodegradation Of Nonylphenol Ethoxylates

A fast and simple porphyrin method for determining primary biodegradabilities ofnonylphenol ethoxylates(NPEOs) was built, and the method did not require extraction. Themethod resolved the problem that absorbance of Pb(II)-T(DBHP)P-NPEOs complex at 478nm was restrained by NH₄⁺ in culture medium through adding NaOH. Average recoveries ofNP₁₀EO mass concentrations were between 96%¹01%, and relative standard deviations wereless than 3%, and detect limit was 0.2 mg·L^-1. And CTAS method was applicable for NPEOswith EO number more than 10, while porphyrin method was more fitted to NPEOs with EOnumber between 5 and 20.Aerobic biodegradation of NPEOs was tested in shaking-flask. Mass concentrations ofNP5²0EO changed with time were determined using porphyrin method, and all massconcentrations of NP_5²0EO decreased to 98% of initial concentrations in 2 days. After 2 day,mass concentrations of NP₅EO and NP₁₀EO remained unchanged, but concentrations oflong-EO-chain NPEOs increased firstly and decreased again. Mass concentration of NP15EOdecreased 98% again after 7 days, and those of NP18EO and NP₂₀EO decreased 90% after 14days. These phenomena were related to increasing-absorption effect of complex aroused bypolyglycol produced by long EO chain NPEOs during biodegradation. After the effects werededucted, all biodegradabilities of NPEOs were excess of 90% in 14 days, indicating primarybiodegradation of NPEOs were readily carried out.The biodegradation of benzene rings in NPEOs molecular was determined using UVspectrophotometer. The results shown that more than 80% of benzene rings were removedafter 8¹0 days of degradation. NP₂EO sample was also determined using HPLC, and thechanges of concentration of NPEOs were coincident with those determined by UV method.Biodegradation intermediates of NPEOs were also analyzed by ESI-MS. Long-EO-chainNPEOs was degraded to short-EO-chain by ω/β-oxidation or central fission pathway. Then,alkyl-chains of short-EO-chain NPEOs were shorted by ω/β-oxidation. The substance ofHOOC-C₆H₄-(OC₂H₄)_1²OH was detected during degradation, which indicated alkyl-chains ofNPEOs took place and degraded ultimately. A complete aerobic biodegradation pathway ofNPEOs was proposed on the basis of UV, HPLC and ESI-MS results.Nine strains were obtained by step of selection, separation and purification. 40% benzenerings in NPEOs were removed by a relative high-effected strain (Pseudomonas sp.). The strainof benzene rings biodegraded could be applied to wastewater plants, and it is meaningful toour society.