Homo-aggregation And Hetero-agglomeration With Algal Cells Of Nanoparticles In Water

Since nanotechnology is developing rapidly, nanoparticles which are discharged into the aquatic environment will aggregate and unavoidably interact with the microorganism in water, but the mechanism of the interactions required more research. This research studies homo-aggregation of nanoparticles (NPs) and the hetero-agglomeration between NPs and Chlorella Pyrenoidosa, and analyze the influence of pH, ionic strength and natural organic matter (NOM). The research content and conclusions are as follows:1) The homo-aggregation of CeO2, Ag, anatase (HR3) and rutile (DJ3) were studied, and the influence of ionic strength, NOM and pH were analyzed. The homo-aggregation of HR3, DJ3and CeO2were similar, and where strengthened as the concentration and valence of added cations increased. The critical coagulation concentrations (CCC) of Na+and Ca2+to NPs were inversely proportional to the valence of cations, following the Schulze-Hardy law. NOM could increase the electronegativity of TiO2and CeO2under various pHs, hence inhibited the homo-aggregation of the NPs. Athough the homo-aggregation of Ag was also strengthened as the concentration and valence of cations increased, the relationship between CCC and valence of cations didn’t follow the Schulze-Hardy law. NOM could only slightly increase the CCC of CaCl2for AgNPs and decreased the CCC of NaCl. Cl-and the released Ag+could form AgCl precipitation on the surfaces of Ag NPs and resulted in the core-shell structure of Ag-AgCl colloids. Cl-would be excessively adsorbed and increase the electronegativity of the Ag-AgCl colloids, and thereby inhibited the homo-aggregation of Ag NPs in the presence of NaCl and CaCl2; furthermore, the excessively adsorbed Cl-would screen the sorption sites for the NOM and weaken its role in the dispersion and suspension of Ag NPs.2) The hetero-agglomeration between HR3, DJ3, SiO2(DP1、SP1、DS1、SS1) and Al2O3(MC2R、MC2A) with Chlorella Pyrenoidosa cells were studied. Type of NPs, pH (5.6,7.0and8.0) and ionic strength (5,50,100,250and500mM) could influence the hetero-agglomeration between the NPs and the cells. The hetero-agglomeration of the cells with DJ3and MC2A were so weak that pH and ionic strength showed very limited influence on the interaction. The hetero-agglomeration between HR3and the cells was the strongest under neutral pH and low ionic strength (5mM), while the hetero-agglomeration was weak under the other pHs and ionic strengths. The strong homo-aggregation of HR3under the higher ionic strengths (>50mM) and lower pH (5.6) may inhibit the hetero-agglomeration between HR3and Chlorella Pyrenoidosa. The hetero-agglomeration between the4kinds of SiO2and MC2R with Chlorella Pyrenoidosa were driven by the DLVO forces, and on the whole became stronger as ionic strength increased. The hetero-agglomerations between DPI and MC2R with Chlorella Pyrenoidosa were the strongest at pH5.6, while the hetero-agglomerations between the other3kinds of SiO2and Chlorella Pyrenoidosa were insensitive to pH.