Arsenate(V) removal from aqueous system by using modified incinerated sewage sludge ash (ISSA) as a novel adsorbent

Adsorption methods have been widely used in wastewater treatment due to its high removal efficiency, easy operation and handling, economic efficiency and little secondary pollution to the environment. In this paper, a high-iron containing incineration sewage sludge ash (ISSA) was modified by combined acid leaching and precipitation processes to improve its adsorption capacity of As(V). The effects of pH, time, temperature and ionic strength on the adsorption of As(V) were investigated by batch adsorption experiments. The results indicated that iron (mainly present as hematite) in the ISSA was rearranged to Fe(SO₄)OH. The modified ISSA showed an excellent adsorption potential for As(V) under acidic conditions and the adsorption capacity was around 9 times of the unmodified ISSA at pH 2–3. The adsorption process was fast during the first 2 h and reached an equilibrium at around 6 h. The Freundlich model could well fit the adsorption isotherm data, the presence of NO₃⁻ and Cl⁻ had a negligible influence on the As(V) removal by the modified ISSA, while PO₄³⁻ and SO₄²⁻ could significantly suppress As(V) removal via competitive adsorption. After 3 cycles of regeneration, the modified ISSA still showed a satisfying adsorption capacity. As(V) was removed by the modified ISSA mainly through ligand exchange reaction with hydroxyl oxygen (OH-) to form inner-sphere complexes. Therefore, the modified ISSA can be a promising material for As(V) removal from wastewater in particular due to the waste recycling potential.