| Dispersion, sedimentation, conversion and migration way of nanomaterials can affect their fates in seawater. In this paper, we chose nano-Al2O3for the research, established the method of detecting nano-Al2O3content in artificial seawater by Ultraviolet-visible Spectrophotometry(UV-vis), and discussed the sedimentation behavior in seawater. And then we discussed the adsoiption characteristics of nano-Al2O3in perspectives of dynamics and isothermal adsoiption, analyzed the effects of initial content, pH, salinity and so on. The behavior and end-result of nano-Al2O3in seawater had been preliminarily revealed. Main contents and conclusions of this paper were as follows:(1) Nano-Al2O3dispersion can be detected reliably by UV-vis under100mg/L, and the detection limit was0.93×10-3mg/L. In artificial seawater(ASW), nano-Al2O3dispersion had the fastest sedimentation rate when pH was7.31, which was1.1,1.3and2.1times higher than that when pH were8.03,6.57and8.97respectively. With increasing salinity from0.20%o to31.50%o, sedimentation rate of nano-Al2O3increased3.2times. As the concentration of nano-Al2O3increased from10.00mg/L to100.00mg/L, sedimentation rate increased2.7times. Sedimentation rate of nano-Al2O3in natural seawater(NSW) was1.1times faster than it was in ASW.(2) The kinetic studies showed that the pseudo second-order rate equation could fit the adsorption of phosphate or humic acid by nano-Al2O3as well as the adsorption of phosphate by compounds of humic acid and nano-Al2O3very well(R2>0.99). In ASW, the equilibrated adsorption capacity(ge) from nano-Al2O3to phosphate was0.13mg/g, and to HA1and HA2were75.19mg/g and62.50mg/g respectively. qe from30%HAl-Al2O3and30%HA2-Al2O3to phosphate were0.085mg/g and0.079mg/g respectively.(3) The adsorption of phosphate or humic acid by nano-Al2O3as well as the adsorption of phosphate by compounds of humic acid and nano-Al2O3fitted well with Langmuir adsorption model(R>0.99), indicated that the adsorptions conformed to the mechanism of monolayer adsorption. (4) The adsorption of phosphate by nano-Al2O3was a exothermic process, and adsorption of humic acid by nano-Al2O3was endothermic. Adsorption of phosphate by compounds of humic acid and nano-Al2O3were not much affected by temperature.(5)As the dosages of adsorbents increased160times, adsorbing capacities of phosphate by nano-Al2O3,30%HAl-Al2O3and30%HA2-Al2O3decreased10,6.7and4.3times, and adsorption rates increased13.8,26.5and41.1times respectively. The dosages of nano-Al2O3increased100times, adsorbing capacities of HA1and HA2decreased64.5and63.1times, and adsorption rates increased1.5and1.6times respectively.(6) With increased pH of6.05～6.95, adsorbing capacity of phosphate by nano-Al2O3decreased of28.5%, and the adsorption was mainly controlled by electrostatic forces. As pH increased from6.95to8.91, adsorbing capacity only decreased of6.7%, van der Waals’ forces played a main role in the adsorption. With pH of5.75-9.17, adsorbing capacities of HA1and HA2decreased of20.5%and27.7%respectively, the adsorptions were mainly controlled by electrostatic forces and ligand exchange. With increased pH of5.75-8.03, adsorbing capacities of phosphate by30%HAl-Al2O3and30%HA2-Al2O3decreased of32.1%and31.7%respectively, and the adsorptions were mainly controlled by electrostatic forces. As pH increased from8.03to9.17, adsorbing capacities only decreased of0.7%and0.2%, van der Waals’ forces played a main role in the adsorptions.(7) With increasing salinity from0.20%o to31.50%o, adsorbing capacities of phosphate by nano-Al2O3,30%HAl-Al2O3and30%HA2-Al2O3decreased of50.0%,46.1%and45.3%respectively. Results indicated that the physical adsorption was the dominating factor. With salinity of0.20%o-10.00%o, adsorbing capacities of HA1and HA2by nano-Al2O3increased2.9times and8.0times respectively. With salinity of10.00%o-31.50%o, adsorbing capacities of HA1and HA2both increased1.1times, the mechanism of adsorptions included electrostatic interactions. |
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