The dominant adsorption mechanism of ionizable organic chemicals (IOCs) on carbonaceous materials is still unclear. This study used benzoic acid (BA), o-chlorobenzoic acid (2-CBA) and p-chlorobenzoic acid (4-CBA) as representatives of IOCs to investigate the dominant adsorption mechanism on graphene oxide (GO) and graphite (GP), with a specific emphasis on the impact of pH-dependent K_OW. The order of apparent adsorption of the investigated chemicals changed with pH, which could not be explained by their constant K_OW. According to our measurement, K_OW varied greatly with pH. The pH-dependent adsorption of BA, 2-CBA and 4-CBA were significantly correlated with pH-dependent K_OW for both GO and GP. Our observations indicated that the hydrophobic effects may dominate the apparent adsorption of BA, 2-CBA and 4-CBA on GO and GP. Electrostatic repulsion played a minor role in their reduced adsorption at high pH. Negative charge-assisted H-bond and π-π interactions may explain the adsorption of negatively charged BA, 2-CBA and 4-CBA on negatively charged GO. This study implied that pH-dependent K_OW rather than constant K_OW should be incorporated to understand IOC adsorption as affected by pH.

含碳材料上可电离的有机化学物质（IOC）的主要吸附机理仍不清楚。本研究使用苯甲酸（BA），邻氯苯甲酸（2-CBA）和对氯苯甲酸（4-CBA）作为IOC的代表，研究了氧化石墨烯（GO）和石墨（GP）的主要吸附机理，特别强调pH依赖性K _OW的影响。所研究化学物质的表观吸附顺序随pH的变化而变化，这不能用其常数K _OW来解释。根据我们的测量，K _OW随pH值变化很大。对于GO和GP ，BA，2-CBA和4-CBA的pH依赖性吸附与pH依赖性K _OW显着相关。我们的观察结果表明，疏水作用可能主导着BA，2-CBA和4-CBA在GO和GP上的表观吸附。静电排斥作用在高pH下降低吸附力方面起着次要作用。负电荷辅助的H键和π-π相互作用可以解释带负电荷的GO上带负电荷的BA，2-CBA和4-CBA的吸附。这项研究暗示应该结合pH依赖性的K _OW而不是恒定的K _OW来理解受pH影响的IOC吸附。