Study On Microbial Removal Mechanism And Physical Adsorption Of Phthalic Acid Esters (PAEs)

Phthalate Esters (PAEs) are a kind of widespread toxic organic compounds in the environment. Firstly, we studied the different degradation rates of PAEs with difference concentrations in the soil and its impact on different soil enzyme activities. The results showed that soil microorganisms played a major role in the degradation of PAEs. With initial concentrations increased and the extension of carbon chains, PAEs degradation rates were decreased. On the 40th day, the degradation efficiencies of DMP and DEP in different samples were all reach up to 99.8% regardless of initial concentration. In PAE1 samples, the degradation efficiency of DnBP and DnOP were 98.41%,93.43%, while in PAE30 samples were only 78.1%和73%, after 40 days. After adding the PAEs into soil, activities ofβ-glucosidase, phosphatase, urease and protease were changed. Activity decreased at first and then increased for phosphatase, decreased slowly forβ-glucosidase, increased at first and then decreased for protease, increased gradually for urease. After 20 days, the activities of most enzymes recovered gradually and higher than the control group exceptβ-glucosidase whose activity continued decreasing.BIOLOG method was used to study the effect of PAEs on microbial metabolic activity in this study. The results showed that, PAEs significantly inhibited the metabolic activity of soil. Shannon index indicated that the higher the concentration of PAEs, the greater impacts of PAEs to the metabolic diversity of soil. Principal component analysis showed that the three soil samples in the domestication process showed a similar trend, the samples which domesticated 5 and 15 days, whose principal components are highly related to the easy degradation carbohydrate and carboxyl acid, but after 40 days, with the polymer and other compounds which are not easy to degradation.Physical adsorption is one of the effective ways to remove PAEs in water. In adsorption process of DMP from aqueous solution onto TOC, the conditions of pH, carbon dosage and initial concentration of DMP and adsorption temperature were optimized firstly. In this study, the selected pH is 7, the optimal dosage is 2.0 g/100 ml. Freundlich isotherm gave a better fit to adsorption isotherms than Langmuir isotherm. Adsorption reached equilibrium in 300 minutes. The kinetic study confirmed that the adsorption followed pseudo-second-order model. The results of this study indicated that TOC can be employed as a low-cost adsorbent in wastewater treatment for the removal of DMP.