A Novel Technique for Determining the Adsorption Capacity and Breakthrough Time of Adsorbents Using a Noncontact High-Resolution Microwave Resonator Sensor.

A newly developed noncontact high-resolution real-time microwave sensor was used to determine the breakthrough time and adsorption capacity of adsorbents/adsorbates with different dielectric properties. The sensor is a microwave microstrip planar resonator with an enhanced quality factor using a regenerative feedback loop operating at 1.4 GHz and an adjustable quality factor of 200-200000. Beaded activated carbon (BAC, microwave-absorbing) and a polymeric adsorbent (V503, microwave transparent) were completely loaded with 1,2,4-trimethylbenzene (nonpolar) or 2-butoxyethanol (polar). During adsorption, variations in the dielectric properties of the adsorbents were monitored using two microwave parameters; quality factor and resonant frequency. Those parameters were related to adsorption breakthrough time and capacity. Adsorption tests were completed at select relative pressures (0.03, 0.1, 0.2, 0.4, and 0.6) of adsorbates in the influent stream. For all experiments, the difference between the breakthrough time (t5%) and the settling time of the quality factor variation (time that the quality factor was 0.95 of its final value) was <5%. Additionally, a linear relationship between the final value of the resonant frequency shift and adsorption capacity was observed. The proposed noncontact sensor can be used to determine the breakthrough time and adsorption capacity.

Automotive Wastes.

A review of the literature from 2014 related to automotive wastes is presented. Topics include solid wastes from autobodies and tires as well as vehicle emissions to soil and air as a result of the use of conventional and alternative fuels. Potential toxicological and health risks related to automotive wastes are also discussed.

Using microwave heating to improve the desorption efficiency of high molecular weight VOC from beaded activated carbon.

Incomplete regeneration of activated carbon loaded with organic compounds results in heel build-up that reduces the useful life of the adsorbent. In this study, microwave heating was tested as a regeneration method for beaded activated carbon (BAC) loaded with n-dodecane, a high molecular weight volatile organic compound. Energy consumption and desorption efficiency for microwave-heating regeneration were compared with conductive-heating regeneration. The minimum energy needed to completely regenerate the adsorbent (100% desorption efficiency) using microwave regeneration was 6% of that needed with conductive heating regeneration, owing to more rapid heating rates and lower heat loss. Analyses of adsorbent pore size distribution and surface chemistry confirmed that neither heating method altered the physical/chemical properties of the BAC. Additionally, gas chromatography (with flame ionization detector) confirmed that neither regeneration method detectably altered the adsorbate composition during desorption. By demonstrating improvements in energy consumption and desorption efficiency and showing stable adsorbate and adsorbent properties, this paper suggests that microwave heating is an attractive method for activated carbon regeneration particularly when high-affinity VOC adsorbates are present.