Arsenate adsorption onto iron oxide amended rice husk char

•Produced rice husk char (RHC) and measured its specific surface area (SSA).•Amended RHC with iron oxide (IO) and measured As(V) adsorption isotherms.•Compared amended RHC with IO-amended sand and IO-based material.•Evaluated SSA of RHC as function of charring temperature.•Evaluated As(V) adsorption on IO-amended RHC with higher SSA than above RHC medium.

In this study, rice husks were charred at 550 °C in a partially sealed ceramic vessel for 30 minutes to create a high specific surface area (SSA) rice husk char (RHC). The RHC was then amended with iron oxides using dissolved ferric nitrate, Fe(NO3)3 ⋅ 9H2O, to provide a surface chemistry conducive to arsenic adsorption. The 550 °C iron oxide amended rice husk char's (550 IOA-RHC's) SSA was nearly 2.5 orders of magnitude higher and the arsenate adsorptive level was nearly 2 orders of magnitude higher than those reported for iron oxide amended sand, thus indicating a positive relationship between post-amendment SSA and arsenate adsorptive levels.Rice husks were then charred at temperatures ranging from 450 °C to 1050 °C to create an even higher SSA material, which might further increase arsenate adsorptive levels. The 950 °C RHC was chosen for amendment due to its high SSA and feasibility of being produced in the field. Once amended, the 950 °C iron oxide amended rice husk char (950 IOA-RHC) improved the arsenate adsorption capacity by thus confirming a positive relationship, though not a linear relationship, between post-amendment SSA and arsenic adsorptive capacity. Further study demonstrated that post-amendment mesoporous volume and mesoporous surface area appear to be better indicators of arsenic adsorptive capacity than SSA or iron content.