This paper demonstrates that digested sludge can be reclaimed as an adsorbent for the removal of organic vapors (MEK, TOL and TCE) through the use of a pyrolysis. The manufactured adsorbent products were characterized by Brunauer, Emmentt and Teller (BET) surface area, carbon tetrachloride activity (ANSI/ASIM D3467–76'), and an elemental analysis test. Both the determination of CCl4 activity and BET surface area were regarded as the useful means for estimation of the adsorption capacity of organic vapors on the reclaimed adsorbents.
From the view point of specific surface area (CCl4 activity number or adsorption capacity), it was concluded that the optimum condition for manufacturing the reclaimed adsorbent was by adding 5 kmols/m3 ZnCl2 to the treated sludge and then heating the mixture at 550°C for 1 hour.
The global ecological crisis of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in drinking water has gradually shifted from long-chain to short-chain PFASs; however, the widespread established PFAS adsorption technology cannot cope with the impact of such hydrophilic pollutants given the inherent defects of solid–liquid mass transfer. Herein, we describe a reagent-free and low-cost strategy to reduce the energy state of short-chain PFASs in hydrophobic nanopores by employing an in situ constructed confined water structure in activated carbon (AC). Through direct (driving force) and indirect (assisted slip) effects, the confined water introduced a dual-drive mode in the confined water–encapsulated activated carbon (CW-AC) and completely eliminated the mass transfer barrier (3.27 to 5.66 kcal/mol), which caused the CW-AC to exhibit the highest adsorption capacity for various short-chain PFASs (C-F number: 3-6) among parent AC and other adsorbents reported. Meanwhile, benefiting from the chain length– and functional group–dependent confined water–binding pattern, the affinity of the CW-AC surpassed the traditional hydrophobicity dominance and shifted toward hydrophilic short-chain PFASs that easily escaped treatment. Importantly, the ability of CW-AC functionality to directly transfer to existing adsorption devices was verified, which could treat 21,000 bed volumes of environment-related high-load (~350 ng/L short-chain PFAS each) real drinking water to below the World Health Organization’s standard. Overall, our results provide a green and cost-effective in situ upgrade scheme for existing adsorption devices to address the short-chain PFAS crisis.
Volatile organic compounds (VOCs) emitted from industrial manufacturing processes are commonly controlled by combustion and condensation methods: however, the most promising method is through adsorption by activated carbon. Ozone is used to oxidize activated carbon thus increasing the specific surface area, pore volume, and functional groups. As the results indicate, the specific surface area of activated carbon was increased from 783 m 2 /g to 851 m 2 /g. Pore size distribution analysis found the specific surface area on the activated carbon increases mainly at micropores. Oxygen functional group increases from 196 ueq/g to 240 ueq/g after ozone treatment. The adsorption capacity of benzene on activated carbon (AC) and on oxidized activated carbon (AO 3 ) at various temperatures was decreased from 268 mg/g (10°C) to 179 mg/g(120°C) at AC and from 262 mg/g to 158 mg/g, at the same respective temperatures, for AO 3 . The results show that reaction temperature has a greater effect on AO 3 than on AC. According to factor analysis and correspondence analysis, we found physical characteristics (BET surface area and micropore area) on the AC could consider as the major factor affecting the adsorption rate.
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