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Manufactured Nanomaterials' Dispersion and Study of Inhibiting and Adsorption Characteristics with Activated Sludge

Author: WuZuoZuo
Tutor: ShiHanChang
School: Tsinghua University
Course: Environmental Science and Engineering
Keywords: nanoparticles activated sludge activity inhibition disperse adsorption
CLC: X703
Type: Master's thesis
Year: 2013
Downloads: 5
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Abstract


With a lot of special physical and chemical properties, manufacturednanoparticles are widely used in cosmetics, paints, pigments etc. in recent years.That makes them easily go into the city’s sewage biological treatment systemthrough rain washing, scouring and other ways and may cause some influencesand even biological toxicities on the micro-organisms in the system. Thus, toprotect the safety of urban sewage treatment plant operation, it’s urgentlyneeded to do research on the relathionship and impact between nanomaterialsand biological aggregates in the system.Five kinds of common artificial nanoparticles, namely SiO2, Ag, TiO2,Al2O3, ZnO and activated sludge mixed liquor taken from Xiaohongmenwastewater treatment plant in Beijing were used for the study of the adsorptioncharacteristics and inhibiting effect between them. Through dynamic laser lightscattering particle size analyses, the dispersion and agglomeration behaviors ofnanoparticles under different ultrasonication conditions, differentconcentrations and different solvent were studied. The results showed that: withthe growth of the time under ultrasonication, nanoparticles have an averageparticle diameter decreasing. Different types of nanoparticles’ minimum averageparticle sizes were shown in different concentrations after ultrasonicating for2h.Nano Ag, nano TiO2are generally easier to disperse and stabilize. The averageparticle sizes of nanoparticles in the supernatant are bigger than that in the highpurity water. Under the experimental conditions, the optimum concentration ofthe dispersing agent to disperse nanoTiO2suspension liquid is: SDBS=10mM,PVP=0.5g/l, SDS=2mM.Through oxygen uptake rate experiment, the instantaneous and lastingactivity inhibition effects which different concentrations of variousnanoparticles suspension liquid and the corresponding metal ion solution causedon aerobic activated sludge under endogenous and exogenous respiration statewere studied. The results showed that: under endogenous respiration state, theorder of the1mg/l nanoparticles suspension liquids’ instantaneous biologicalactivity inhibition effect on3g/l sludge mixture is: SiO2> Ag> TiO2> Al2O3> ZnO, more significant than under exogenous respiration state. Under somecondition,1mg/l nano Ag has more significant biological activity inhibition thanAg+. Nano ZnO showed biological activity inhibition caused by the leaching ofmetal ions at30mg/l, which has the similar lasting activity inhibition effect withZn2+. Among the other three kinds of metal ions of corresponding concentrations,Ag+and Ti4+have lasting activity inhibition effects; Al3+does not.Through static and dynamic adsorption experiments, mechanism andinfluencing factors, including endogenous and exogenous respiration state,nanoparticle type, sludge type, and sludge concentration were studied aboutactivated sludge’s adsorption of nanoparticles. The results showed that: pseudosecond-order kinetic equation, Freundlich model are better models which arecapable of simulating the nano TiO2and nano ZnO’s adsorption process on theactivated sludge. Anoxic sludge has bigger adsorption capacity of nanoparticlesthan aerobic sludge. The bigger the aerobic sludge’s concentration is, theelements content of the nanoparticles in supernatant are less when reaching theadsorption equilibrium state. When the activated sludge adsorbed four kinds ofnanoparticles, the order of the content of elements in the supernatant is always:Al> Ti> Zn> Ag.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization
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