title: Carbon dioxide adsorption in chemically activated carbon from sewage sludge.
abstract: In this work, sewage sludge was used as precursor in the production of activated carbon by means of chemical activation with KOH and NaOH. The sludge-based activated carbons were investigated for their gaseous adsorption characteristics using CO2 as adsorbate. Although both chemicals were effective in the development of the adsorption capacity, the best results were obtained with solid NaOH (SBA(T16)). Adsorption results were modeled according to the Langmuir and Freundlich models, with resulting CO2 adsorption capacities about 56 mg/g. The SBA(T16) was characterized for its surface and pore characteristics using continuous volumetric nitrogen gas adsorption and mercury porosimetry. The results informed about the mesoporous character of the SBA(T16) (average pore diameter of 56.5 angstroms). The Brunauer-Emmett-Teller (BET) surface area of the SBA(T16) was low (179 m2/g) in comparison with a commercial activated carbon (Airpel 10; 1020 m2/g) and was mainly composed of mesopores and macropores. On the other hand, the SBA(T16) adsorption capacity was higher than that of Airpel 10, which can be explained by the formation of basic surface sites in the SBA(T16) where CO2 experienced chemisorption. According to these results, it can be concluded that the use of sewage-sludge-based activated carbons is a promising option for the capture of CO2.
  
  
  CONCLUSIONS
  Adsorption methods are one of the current ways to reduce CO2 emissions. Taking this into account, sewage-sludge-based activated carbons were produced to study their CO2 adsorption capacity. Specifically, chemical activation with KOH and NaOH of previously pyrolyzed sewage sludge was carried out. The results obtained show that even with a low BET surface area, the adsorption capacity of these materials was comparable to that of a commercial activated carbon. As a consequence, the use of sewage-sludge-based activated carbons is a promising option for the capture of CO2 and an interesting application for this waste.
authors.affiliation: Department of Chemical and Environmental Engineering, Technical University of Madrid (UPM), c/José Gutiérrez Abascal 2, 28006 Madrid, Spain. jdeandres@etsii.upm.es
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: de Andrés
authors.forename: Luis
authors.initials: L
authors.lastname: Orjales
authors.forename: Adolfo
authors.initials: A
authors.lastname: Narros
authors.forename: María del Mar
authors.initials: Mdel M
authors.lastname: de la Fuente
authors.forename: María
authors.initials: M
authors.lastname: Encarnación Rodríguez
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry; D002245:Carbon Dioxide / Q000032:analysis / Q000737:chemistry*; D002606:Charcoal / Q000737:chemistry*; D006358:Hot Temperature; D006878:Hydroxides / Q000737:chemistry*; D017680:Potassium Compounds / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods*; D012722:Sewage / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry*; D013030:Spain
chemical_list: D006878:Hydroxides; D017680:Potassium Compounds; D012722:Sewage; D002245:Carbon Dioxide; D002606:Charcoal; D012972:Sodium Hydroxide; D002244:Carbon; C029943:potassium hydroxide