Study On Deposition Characteristics Of Reduced Graphene Oxide On NOM Surface And Its Cogulation Removal

Graphene-family nanomaterials(GFNs) are likely to release into aquatic environments at significant level and cause adverse effects to the water system, with the discovery, production and widespread application of them. But there a re few published reports about the fate and transport of GFNs. Thus, human have little knowledge about the potential pollution of GFNs. In order to have clearer understand about the mobility and transport behaviors of GFNs and their influence to water ecosystem, this study focused on reduced graphene oxide(r GO) of GFNs, and firstly investigated its depositon characteristics on the HA and FA surface in different ionic strength by quartz crystal microbalance with dissipation(QCM-D) and then analyzed their interaction mechanism. The deposition characteristics of r GO on NOM and PLL were compared synthetically. On the other hand, the study firstly explored the influence of r GO to aquatic organism, selecting microcystis aeruginosa as a tested target. On the basi s of the investigation, preliminary study about the removal of r GO by coagulation was carried out, selecting the polyaluminium chloride(PAC) as coagulant.Firstly, the study investigated the deposition behaviors of r GO on HA and FA surface in Na Cl and Ca Cl2 electrolyte at p H=7.4 using QCM-D, the deposition of r GO on surface of HA, FA, PLL were also compared, among them deposition on the PLL viewed as favorable. The results of total deposition, initial deposition rate and deposition efficiency consistently show that both ionic strength and ion valence had notable impact on the interactions of r GO with different surfaces. The deposition interactions of r GO increased at first and decreased subsequently with increasing Na Cl concentrations. At lower ionic strengths(<25m M), the deposition interactions of r GO increased gradually due to charge-screening of Na+, following classical DLVO theory. At higher ionic strengths, the deposition behavior of r GO decreased due to aggregate formation which reduced diffusion rates of r GO to the deposition surface. Ca2+ was more effective than Na+ in contributing to the deposition of r GO. The deposition of r GO on FA surface was higher than on HA surface, but both lower than on PLL surface. higher carboxyl functional group concentr ation on FA may be responsible for increased interaction with few functional groups on r GO. In addition, Characteristics of r GO layers deposited on surfaces can be determined from the |ΔD/Δf| value. Higher |ΔD/Δf| values of deposition on HA surface indicated a dissipative and soft deposited layer of r GO than FA.Moreover, this study also firstly explored the influence of r GO to aquatic organism, selecting microcystis aeruginosa as the tested target. The algal cell number、surface morphology and chlorophyll-a content were analyzed.The results indicated that r GO could inhibit the growth of microcystis aeruginosa by shading effect and physical contact damage,showing that r GO will pose potential pollution to aquatic ecosystem.On the basis of the potential pollution of r GO to aquatic system analyzed, a preliminary study was made about further removal of r GO nanoparticles from water system. The study examined the influence of HA to the coagulation removal of r GO nanoparticles and the optimum dosage of coagulant wer e determined without or with the presence of HA. With the presence of HA, the optimum dosage of PAC was merely 3 mg/L, and the main coagulation mechanism was adsorption bridging action; with the presence of HA, the optimum dosage of PAC reached 40 mg/L and charge-neutralization dominated the coagulation mechanism in this case.