This paper reports the effect of several competing anions on arsenate adsorption with maghemite nanoparticles.Sulphate(as SO

4

)

nitrate(as NO

3

-N)

phosphate(as PO

4

-P) ions and silicate(as SiO

2

) were studied in dual solution with arsenate.Moreover

the combined effect of ions and other water characteristics were examined with a natural groundwater sample which was spiked with a certain amount of arsenate.Arsenate batch adsorption experiments were carried out with two different kinds of maghemite—a commercially available one and a homemade one using the sol-gel process.Sulphate(≤250 mg·L

-1

) and nitrate(≤12 mg·L

-1

) had a negligible effect on the arsenate(0.5 mg·L

-1

) adsorption at pH 3.However

both phosphate(≤2.9 mg·L

-1

) and silicate(≤50 mg·L

-1

) had an adverse impact on arsenate(≤3 mg·L

-1

) adsorption at pH 7.Phosphate(≤1.5 mg·L

-1

) showed minimal competition with arsenate(0.5 mg·L

-1

)

while silicate(≤10 mg·L

-1

) inhibition was insignificant for all studied As(V) concentrations at pH 3.The removal of arsenate from the groundwater sample was as efficient as from laboratory water for 0.5 mg·L

-1

As(V) both at pH 3 and pH 7.