Effect Of Organic Substrate On The Adsorption Of Uranyl Ion By Extracellular Polymeric Substances From Activated Sludge

The effect of different organic substrates on the adsorption of uranyl ion byextracellular polymeric substances (EPS) from activated sludge is studied in this paper.There are mainly three parts, the first one is the culture and acclimation of activated sludge;the second one is the extraction, analysis and characterization of EPS; the third one is thestudy of adsorption of uranyl ion by EPS.Part one, the culture and acclimation of activated sludge. Use the sewage treatmentplant sludge as bacteria, four kinds of activated sludge (1to4) were cultivated by fourkinds of organic substrates (glucose, sodium acetate, soluble starch, peptone), during theculture and acclimation of activated sludge, the determination of the parameters of the fourkinds of activated sludge and electron microscopy is accomplished, the influence oforganic substrates for activated sludge is studied. Part Two, the extraction, analysis andcharacterization of EPS. Different EPS were extracted from activated sludge throughNaOH extraction method and marked by EPS1,EPS2,EPS3and EPS4. By studying thepolysaccharide, protein, DNA and the amount variation of EPS under different pHconditions, the best pH for extracting is determined. By analyzing the four kinds of EPS’scomponent content, element and infrared spectrum, the influence of organic substrates forEPS is studied.Part three, the study of adsorption of uranyl ion by EPS. Theadsorption behaviour of EPS on uranyl ion is studied by static method. Theadsorption behaviour of EPS on uranyl ion were studied by static method. The influence oftemperature, pH, adsorption time, the dosage of the EPS, initial concentration of uranyl ionand ionic strength on the effect of adsorption of uranyl ion are discussed,thermodynamic sorption and kinetic study. And the infrared spectra of four kinds of EPSbefore and after absorbing uranyl ion are compared.The experimental results indicate that four kinds of activated sludge all have looseand porous flocculent structure, good flocculation and sedimentation property. And the best activated sludge performance is cultivated by sodium acetate. The worst activated sludgeperformance was cultivated by soluble starch,the other activated sludge between sodiumacetate and soluble starch. The best pH condition for extracting by NaOH extractionmethod is11. Although organic substrates exerted a little influence on the amounts of EPS,impacting on generation rate and content of EPS’s each component. The ratio between fourkinds of polysaccharide content and protein content is15.628,10.355,15.367,2.631,respectively. The ratio between C element and N element is8.925,5.475,9.057,2.679,respectively. They have the same infrared spectra roughly, including a variety offunctional groups (hydrocarbonyl, phosphate, carboxyl, sulfonic acid and peptide linkage).The best adsorbent temperature is25℃,the best pH is3and the best adsorbent time is120min.The best dosage of the four kinds of EPS were350mg/L、300mg/L、400mg/L、350mg/L. The study showed that as the initial concentration of uranyl ion and adsorptionquantity added, the adsorption rate was decline.And ionic concentration impact onadsorption strongly. The study of adsorption thermodynamics indicate that the adsorptionprocess conform to the Freundlich adsorption model and the study of adsorption kineticsindicate that the adsorption process conform to second order reaction kinetics model.