Using incinerated sewage sludge ash as a high-performance adsorbent for lead removal from aqueous solutions: Performances and mechanisms.

A substantial amount of ash is produced after the incineration of sewage sludge which is difficult to manage. Its potential use as a cost-effective adsorbent for heavy metals is beneficial to both waste management and wastewater treatment. In this study, the adsorption kinetics, isotherms as well as the factors influencing the adsorption performance were assessed through batch sorption experiments. The results show that incinerated sewage sludge ash (ISSA) was effective in adsorbing Pb(II) from aqueous solution in a wide pH range (3.00-6.00) due to the combined contributions of ion exchange, precipitation and complexation, which was confirmed by systematic investigation through XRD, SEM-EDX, FTIR, XPS and a sequential extraction procedure (SEP) for Pb(II). Nonetheless, the adsorption of Pb(II) by ISSA would be adversely affected by high ionic strength. The sorption process was fast, and the equilibrium data could be well described by the Langmuir model, the maximum uptake capacity for Pb(II) increased with temperature and the calculated adsorption capacities at 298, 308 and 318 K for Pb(II) were 58.28, 60.06 and 62.42 mg/g, respectively. These findings indicate the ISSA can be recognized as a high-performance adsorbent for Pb(II) removal in wastewater treatment applications.