Study On Microbial Adsorbtion By Nano-iron And Mechanism Of Microbial Degradation Of PAHs

Naphthalene and phenanthrene are the typical polycyclic aromatic hydrocarbons (PAHs) with low-molecular-weight, and are persistent organic pollutants (POPs) with higher detection rate. They have carcinogenic, teratogenic and mutagenic effects, and have toxic effects on the liver and kidney, cardiovascular, gastrointestinal, and other organs; naphthalene and phenanthrene can easily migrate into the organisms, sediment and organic matter, or accumulate in the human body through the food chain. Therefore, the research on the naphthalene and phenanthrene migration and transformation in the environment can provide reference for the bioremediation of pollution with PAHs. The degradation characteristics of naphthalene and phenanthrene by two kinds of Bacillus brevis strains were studied. The effects of various environmental factors on degradation, the reaction enzymatic of the degradation, and the absorption properties of these two micro-organisms on the nano-iron were discussed. Another main research is that the impact of Nano-iron on gram-positive bacteria and gram-negative bacteria adsorption, the adsorption isotherms and adsorption kinetics, and the microbial nano-iron absorption mechanism. The results of the study are as follows:(1) Microorganisms and inorganic materials react with the same amount of nano-iron under the same conditions. Microbial reaction can be balanced in shorter time and higher efficiency.(2) At certain pH, the charges of microorganisms to some extent affect the microbial adsorption; the gram-negative bacterium requires the less activation energy than the gram-positive bacterium;(3) By using Fraundlich isotherm equation, the adsorption process of bacteria and nano-iron is suitable for this adsorption model, and it turns out that it is single-layer absorption;(4) The activity of microorganisms at 20℃is lower than at 30℃and 40℃, but apparently this three have no significant impact to the character of microorganism.(5) The experimental outcomes of the degradation of naphthalene and Phenanthrene by both of the strains could be fit well with the first-order biodegradation kinetics model; at 28℃, The completely removal time of the naphthalene degradation by strains Na-B、Na-S for 43.0 mg/L of naphthalene were 120 h and 74 h, respectively; the completely removal time of the Phenanthrene degradation by strains Na-B、Na-S for 1.03 mg/L of naphthalene were 48 h and 56 h, respectively; Temperature and pH value had great impacts on the degradation.(6) The naphthalene and Phenanthrene degradation rate constant, half-life and Michaelis-Menten enzymatic reaction kinetics equation of two strains of naphthalene Philippines at different temperatures can be obtained.