Design of Efficient Carbon-Based Adsorbents for the Removal of Organic and Inorganic Water Contaminants

Granular activated carbon (AC) and biochar (BC) are two carbon-based adsorbents commonly used for water and wastewater treatment. However, these adsorbents have drawbacks that suppress their aqueous contaminants removal efficiency. Their major disadvantages are that AC has low selectivity and reusability potential, and BC has a hydrophobic nature. The scope of this dissertation is to enhance the performance of commonly-used carbon-based adsorbents for the removal of organic and inorganic water contaminants and to understand the interactive mechanism of contaminants’ ions/molecules with adsorbents. Hexavalent chromium (Cr(VI)) and trichloroethylene (TCE) are two types of inorganic and organic water contaminants, respectively, which are introduced to receiving waters mainly by anthropogenic activities. Both Cr(VI) and TCE have been categorized as primary water contaminants by the United States Environmental Protection Agency (US EPA). In this work, AC and BC were modified, and their modification conditions were optimized. Activated carbon was modified through two different approaches. The first approach was coating granular activated carbon with polysulfide rubber, and the second approach was impregnating activated carbon with zero-valent iron nanoparticles. Modified and unmodified ACs were then compared for aqueous Cr(VI) removal efficiency. Biochar was also modified through two procedures. The first BC modification procedure is heat treatment aiming to make it hydrophilic, and the second approach is impregnating biochar with zero-valent iron nanoparticles. In the case of biochar modification, two modification procedures are finally combined to take advantage of the benefits of both. Modified and unmodified biochars were compared for the removal of p-nitrosodymethylanilin and TCE removal from aqueous phase. Adsorbents, before and after modification, were well characterized using various materials analysis techniques for surface morphology, surface chemistry, elemental composition, pore structure, surface charge, etc. Enhanced performances of the modified adsorbents were demonstrated by comparing contaminants’ adsorption capacity and removal rate. Kinetics studies were performed to investigate mechanisms and rates of the aqueous contaminant removal. Results of this study would benefit water treatment engineers and materials scientists to gain a better understanding of adsorbents’ drawbacks, correlate these characteristics to adsorbents’ physical and chemical properties, and purposefully modify them for adsorbents’ specific applications. This study helps to design highly-efficient materials by employing practical modification procedures on conventional adsorbents