title: Ca and Fe modified biochars as adsorbents of arsenic and chromium in aqueous solutions.
abstract: This work investigated the production of Ca and Fe modified biochars in order to use them for the removal of arsenic As(V) and chromium Cr(VI) from aqueous solutions. Rice husk was impregnated with CaO at an impregnation ratio 0.114, while both rice husk and the organic fraction of municipal solid wastes were impregnated with Fe(0) and Fe(3+) at impregnation ratios 0.114 and 0.23. The modified biochars exhibited high As(V) removal capacity (>95%), except for the case of rice husk impregnated with Fe(0), whose removal capacity reached only 58%. All modified biochars exhibited much better As(V) removal capacity compared to the non-impregnated biochars. However, the Cr(VI) removal rates were not as high as the As(V) ones. The maximum Cr(VI) removal was observed in the case of rice husk biochar impregnated with 2.3% w/w Fe(3+), whereas the majority of impregnation agents examined did not manage to enhance the biochars' Cr(VI) removal ability. The equilibrium study showed that the Freundlich model can adequately describe the sorption process for the majority of samples examined. Analysis of the amount of Fe present in the equilibrium solutions suggested that the main mechanisms of As(V) and Cr(VI) removal were possibly metal precipitation and electrostatic interactions between the modified biochars and the adsorbate.
authors.affiliation: Department of Environmental Engineering, Technical University of Crete, 73100 Chania, Greece.
authors.forename: Evita
authors.initials: E
authors.lastname: Agrafioti
authors.affiliation: Department of Natural Resources and the Environment, Technological Educational Institute of Crete, 73100 Chania, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Kalderis
authors.affiliation: Department of Environmental Engineering, Technical University of Crete, 73100 Chania, Greece. Electronic address: diamad@dssl.tuc.gr.
authors.forename: Evan
authors.initials: E
authors.lastname: Diamadopoulos
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D002411:Cation Exchange Resins; D002606:Charcoal / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D006801:Humans; D007501:Iron / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D002411:Cation Exchange Resins; D014874:Water Pollutants, Chemical; C540010:biochar; D002857:Chromium; D002606:Charcoal; D007501:Iron; D001151:Arsenic; D002118:Calcium
keywords: Adsorption; Arsenic; Biochar; Chromium; Fe/Ca impregnation