The effect of co-existing solutes on arsenate removal with hydrotalcite compound

摘要

Hydrotalcite (HTAL-Cl), an inorganic anion exchanger, is of use as an adsorbent for the removal ofnarsenate (As(V)) in water systems. The adsorption properties of HTAL-Cl for As(V) and the effectsnof co-existing anions on the As(V) removal performance were investigated in this work. Under thenconditions of pH $ 4, the adsorption capacity for As(V) gradually decreased with an increase ofnpH, but As(V) was removed effectively within the range of pH ¼ 5–8. Co-existing anionsninterfered As(V) removal, and the effect decreased in the order of HPO22n4 . HCO23n. SO22n4 . Cl2.nIn binary solute systems containing phosphate and As(V), the maximum adsorption capacity ofnHTAL-Cl was 0.95mmolg21 for phosphate and 0.65mmol g21 for As(V): the total of these valuesncorresponded to the maximum adsorption capacity for As(V) in single solute systems.nThe adsorption isotherms in these binary solute systems were approximated by the followingnmodified Langmuir equations:nAsðVÞ : qAs ¼n18:7 ffiCffiAffiffisffinpn1 þ 21:5 ffiCffiPffiffinpnþ 12:8 ffiCffiAffiffisffinp ; phosphate : qP ¼n33:1 ffiCffiPffiffinpn1 þ 21:5 ffiCffiPffiffinpnþ 12:8 ffiCffiAffiffisffinpnThe column adsorption experiments showed that the adsorbed As(V) was released by thenphosphate adsorption, because phosphate was adsorbed more strongly on HTAL-CL than As(V).