Liberation of Adsorbed and Co-Precipitated Arsenic from Jarosite, Schwertmannite, Ferrihydrite, and Goethite in Seawater

Minerals

Rodrigo Alarcón¹  Jenny Gaviria² 

[1] Geology Department, University of Chile, Plaza Ercilla #803, Casilla 13518, Correo 21, Santiago 8320000, Chile;Institute of Applied Economic Geology (GEA), University of Concepcion, Casilla 160-C, Concepción 4030000, Chile; E-Mail:

关键词: arsenic;    desorption;    marine;    coastal mine tailings;    climate change;    pollution;    ferrihydrite;    schwertmannite;    mobility;    environment;    mining;   

DOI  :  10.3390/min4030603

来源: mdpi

【 摘 要 】

Sea level rise is able to change the geochemical conditions in coastal systems. In these environments, transport of contaminants can be controlled by the stability and adsorption capacity of iron oxides. The behavior of adsorbed and co-precipitated arsenic in jarosite, schwertmannite, ferrihydrite, and goethite in sea water (common secondary minerals in coastal tailings) was investigated. The aim of the investigation was to establish As retention and transport under a marine flood scenario, which may occur due to climate change. Natural and synthetic minerals with co-precipitated and adsorbed As were contacted with seawater for 25 days. During this period As, Fe, Cl, SO₄, and pH levels were constantly measured. The larger retention capability of samples with co-precipitated As, in relation with adsorbed As samples, reflects the different kinetics between diffusion, dissolution, and surface exchange processes. Ferrihydrite and schwertmannite showed good results in retaining arsenic, although schwertmannite holding capacity was enhanced due its buffering capacity, which prevented reductive dissolution throughout the experiment. Arsenic desorption from goethite could be understood in terms of ion exchange between oxides and electrolytes, due to the charge difference generated by a low point-of-zero-charge and the change in stability of surface complexes between synthesis conditions and natural media.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.