Ca and Fe modified biochars as adsorbents of arsenic and chromium in aqueous solutions

• Published in: Journal of environmental management 2014-12, Vol.146, p.444-450
• Main Authors: Agrafioti, Evita, Kalderis, Dimitrios, Diamadopoulos, Evan
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Animal, plant and microbial ecology; Applied ecology; Aqueous solutions; Arsenic; Arsenic - chemistry; Biochar; Biological and medical sciences; Calcium; Calcium - chemistry; Cation Exchange Resins; Charcoal; Charcoal - chemistry; Chromium; Chromium - chemistry; Conservation, protection and management of environment and wildlife; Fe/Ca impregnation; Fundamental and applied biological sciences. Psychology; General aspects; Humans; Iron; Iron - chemistry; Water Pollutants, Chemical - chemistry; Water Purification - methods
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2014.07.029

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 Fe0 and Fe3+ 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 Fe0, 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 Fe3+, 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. •Biochars impregnated with Ca2+ and Fe3+ removed more than 95% of As(V).•Rice husk impregnated with Fe0 removed only 58% of As(V).•Higher As(V) removal rates were obtained as compared to non-impregnated biochars.•Removal rates for Cr(VI) were low.•Metal precipitation and electrostatic interactions are the main removal mechanisms.