Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China.
Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China.
Environ Pollut. 2018 Jan;232:505-513. doi: 10.1016/j.envpol.2017.09.078. Epub 2017 Oct 5.
The implications of humic acid (HA) regarding surface properties of graphene materials and their interactions with phthalic acid esters (PAEs) are not vivid. We report the role of HA on graphene oxide (GO) and reduced graphene oxide (RGO) for sorption-desorption behavior of PAEs. Besides higher surface area and pore volume, the hydrophobic π-conjugated carbon atoms on RGO ensured prominent adsorption capacity towards PAEs in comparison to hydrophilic GO, highlighting the hydrophobic effect. After adjusting for the hydrophobic effect by calculating the hexadecane-water partition coefficient (K) normalized adsorption coefficient (K/K), the dimethyl phthalate (DMP) molecule portrayed a higher adsorption affinity towards RGO by π-π electron donor-acceptor (EDA) interaction for active sites on graphene interface via sieving effect. In contrast to RGO, the weak π-π EDA interactions and H-bonding was observed between the carbonyl groups of PAEs and oxygen containing functional groups on GO. There was no obvious change in morphologies of GO and RGO before and desorption as revealed by SEM and TEM images, as desorption hysteresis did not occur in all conditions. The presence of HA also resulted in shielding effect thereby decreasing the adsorption rate and capacity of diethyl phthalate (DEP) on GO and RGO, while it had little effect on DMP, probably due to the adsorbed HA as new active sites. The desorption of DMP and DEP on RGO in presence of HA was quick and enhanced. These results should be important for evaluating the fate and health risk of graphene materials and PAEs in the environment.
腐殖酸（HA）对石墨烯材料表面性质及其与邻苯二甲酸酯（PAEs）相互作用的影响尚不清楚。我们报告了腐殖酸（HA）在氧化石墨烯（GO）和还原氧化石墨烯（RGO）上对 PAEs 吸附-解吸行为的作用。与亲水性 GO 相比，RGO 上较高的疏水性π共轭碳原子具有较高的 PAEs 吸附能力，这是由于疏水性效应所致。通过计算十六烷-水分配系数（K）归一化吸附系数（K/K）来调整疏水性效应后，二甲基邻苯二甲酸酯（DMP）分子通过筛分效应通过石墨烯界面上的活性位点，表现出对 RGO 更高的吸附亲和力的π-π电子供体-受体（EDA）相互作用。与 RGO 不同，在 GO 上，PAEs 的羰基与含氧官能团之间观察到较弱的π-π EDA 相互作用和氢键。正如 SEM 和 TEM 图像所揭示的，GO 和 RGO 的形态在吸附和解吸前后都没有明显变化，因为在所有条件下都没有出现解吸滞后。HA 的存在还导致了屏蔽效应，从而降低了 DEP 和 DMP 在 GO 和 RGO 上的吸附速率和容量，而对 DMP 的影响较小，这可能是由于吸附的 HA 作为新的活性位点。在 HA 存在下，RGO 上 DMP 和 DEP 的解吸迅速增强。这些结果对于评估环境中石墨烯材料和 PAEs 的命运和健康风险非常重要。
