Investigation Of Factors That Affect Cationic Surfactant Loading On Activated Carbon And Perchlorate Adsorption

Activated carbon modification for removal of specific contaminants has been a significant part of recent studies in activated carbon. 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 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 loading 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. The virgin and modified activated carbon were also characterized by BET, the characterization results indicated that specific surface area and pore volume have decreased by different degree after surfactant loading, and the degree is related to the amount of surfactant loading. What’s more, modified activated carbon presented a much positively charged surface, which means the net positive charge carried on carbon surface increased, which is favorable to the adsorption of anions, such as perchloarte. The obvious improvement in perchlorate adsorption by activated carbon proved that. Specifically, the maximum adsorption capacity was 5.52 mg/g for virgin activated carbon, while those of activated carbon modified by CTAC and CPC were 32.26, and 50 mg/g, respectively. Also, surfactant-loaded activated carbon was much robust again pH changes than virgin ones.In addition, this study also studied other materials modified by surfactant(represented by CTAC), these materials included activated carbon, granular ferric hydroxide(GFH), chitosan, zeolite and bentonite. For example, in the case of perchlorate adsorption, the performance of these materials was compared with activated carbon. The results showed that surfactant loading varied with adsorbent. Surface porosity and ion exchange capacity played key role during surfactant loading, also made contribution to adsorption capacity of perchlorate. In general, these experiments further verified that activated carbon is the most suitable carrier for cationic surfactant loading among all selected materials, also modified activated carbons shows superiority in perchlorate adsorption.The mechanism of perchlorate adsorption by surfactant-modified adsorbents was also investigated, the results shows the dominant mechanism of perchlorate adsorption for all adsorbent is ion exchange. In summary, more adsorption reaction sites for perchlorate interaction were provided through surfactant loading.