Lead stabilization by Polonite and phosphate amended Polonite: Modeling

• Published in: Journal of environmental chemical engineering 2016-09, Vol.4 (3), p.3562-3569
• Main Authors: Butkus, Michael A., Riegner, Dawn E.
• Format: Article
• Language: English
• Subjects: Freundlich; Hill; Immobilization; Isotherm; Surface complexation chemical equilibrium; Water
• ISSN: 2213-3437; 2213-3437
• DOI: 10.1016/j.jece.2016.07.022

•The ability of Polonite & PO4 amended Polonite (Polonite-P) to bind Pb was modeled.•Freundlich, Hill, and Linear models best fit isotherm data.•Surface complexation models (SCM) predicted a wide pH range of Pb solids.•Polonite-P SCM predicted that solid Pb4O(PO4)2 increased with initial Pb loading. Polonite is an alkaline material that is used to remove nutrients from domestic wastewater and it has been evaluated as a fertilizer. Stabilization of Pb by Polonite and Polonite amended with orthophosphate, PO4, (Polonite-P) was evaluated and modeled with isotherm and chemical equilibrium models. Uptake of Pb at low Pb loading for each sorbent (sorbate to sorbent mass ratios of less than 0.6mg Pb/g Polonite and less than 4mg Pb/g Polonite-P) was best-fit with the Freundlich isotherm model. Lead sorption by Polonite, at high Pb loading, was best-fit with the Freundlich isotherm model and Pb sorption by Polonite-P, at high Pb loading, was best-fit with the Hill isotherm model. The Polonite chemical equilibrium model predicted that the primary form of Pb above pH 7.5 was comprised of Pb-oxides. The Polonite-P chemical equilibrium model predicted that Pb formed a stabilized solid over a wider pH range than Polonite and the percentage of solid Pb4O(PO4)2 increased with increasing initial Pb loading above approximately 65mg Pb/L. The Polonite and Polonite-P models have been used to develop a framework that can aid in design of Pb remediation systems and they can serve as a foundation for more complex models in natural and engineered systems.