Granular Activated Carbon Versus Carbon Molecular Sieve as an Adsorbent inthe Lightweight Contingency Water Recovery System
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Several different carbon-based materials are contenders for use as an absorbent in the first stage of the Lightweight Contingency Water Recovery System (LWC-WRS). Granular activated carbon has been proven as an effective adsorbent, and is commonly used in water filtration. However, studies have shown that carbon molecular sieve membranes outperform the activated carbon in adsorption capacity and efficiency. The adsorption capability of the carbon molecular sieve was examined to determine its ability to remove contaminants, primarily urea and ammonia, from wastewater through the LWCWRS. In addition, the endurance of both the activated carbon and the molecular sieve was tested to determine the volume of fluid that can be filtered through each matrix before adsorbent saturation. Preliminary data from column and batch tests run over a period between 4 to 12 hours showed the Total Organic Carbon (TOC) removal capability of the molecular sieve to be twenty times that of the activated carbon, with over 99% removal. After 11 hours and 1 L of urine processed, the molecular sieve continued to remove over 97% of the TOC in the initial urine volume. However, in line with its performance, the molecular sieve is ten times more expensive per kilogram, than the activated carbon. This must be taken into account in the creation of L WC-WRS, especially if it is to be further developed into a possible primary water treatment system for future spaceflight.
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