Regeneration of Carbon Based Adsorbents through Thermal and Microwave Treatment

There has been increasing interest in the use of single-wall carbon nanotubes (SWCNTs) for water treatment purposes. Recent studies have looked into using a hybrid of carbon nanotubes and graphene combined in a ratio of 2:1 as a more effective adsorbent than single-wall carbon nanotubes alone. The problem with using these adsorbents is that they are expensive and cannot practically be replaced often like the traditional adsorbent, activated carbon. This study examines a method of regenerating the hybrid papers exhausted with 2,4-dichlorophenoxyacetic acid (2,4-D) through heat and microwave treatments. Optical (absorption) spectroscopy is used to measure the solution concentrations and adsorption rates. Samples are prepared from a stock solution of 100 µg 2,4-D/mL and are tested at concentrations of 65 µg/mL, 55 µg/mL, 45 μg/mL, 35 μg/mL, and 25 µg/mL. Adsorption isotherms are generated from solution concentrations after a saturation period of 1 day showing the maximum adsorption capacity of the adsorbents. Saturated papers then undergo heat treatment at 550°C for 5 minutes followed by microwave treatment at 1200 watts for 15 minutes. The regenerated hybrid papers are then saturated in the same way. A comparison of the maximum adsorption capacities shows that the desorption process was effective in completely removing the 2,4-D as well as improving the adsorbent material to achieve a 5% increase in capacity. Adsorption kinetics of the adsorbent also improved from a linear short time adsorption to an exponential short time adsorption.