Investigation of factors that affect cationic surfactant loading on activated carbon and perchlorate adsorption

Five cationic surfactants were employed to modify activated carbon for the purpose of comparing the impacts of surfactant properties and operational parameters on modification. Surfactants under study included cetylpyridinium chloride monohydrate (CPC), hexadecyltrimethylammonium bromide (HDTMA), cetyltrimethylammonium chloride (CTAC), myristyltrimethylammonium bromide (MTAB), and decyltrimethylammonium bromide (DTAB). Results revealed that, properties of surfactants (critical micelle concentration, chemical configuration), initial loading concentration, pH of solution and carbon type all had significant impacts on surfactant loading. In general, surfactants with smaller micelle structures were more easily loaded than those with larger micelles. For all cationic surfactants tested here, loading is optimal around neutral pH. After surfactant loading, activated carbon presented a much positively charged surface and this is manifested in obvious improvement in perchlorate adsorption. Perchlorate was mainly adsorbed through ion exchange with surfactant-loaded activated carbon.