The incorporation of Pb2+ during struvite precipitation: Quantitative, morphological and structural analysis. (15th December 2020)

• Record Type: Journal Article
• Authors: Lu, Xingwen; Zhong, Ren; Liu, Yuxin; Li, Zhe; Yang, Jiani; Wang, Fei
• Is Part Of: Journal of environmental management. Volume 276(2020)
• Publication Date: 2020-12-15
• Subjects: Lead -- Struvite -- Precipitation -- Adsorption -- Recovery; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2020.111359
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Struvite precipitated from wastewaters is an important fertilizer. However, struvite derived from wastewater usually contains toxic Pb, which can bring contamination to soil and even plants. Thus, understanding the incorporation mechanisms of Pb 2+ during struvite precipitation is critical to its safe application. Here the influence of Pb concentration on struvite precipitation was assessed. When the initial Pb concentrations were at the range of 0.1–1 mg/L, the formation of pitting and roughening on struvite crystal surfaces was observed by scanning electron microscopy (SEM), indicating a surface interaction between Pb and struvite. Combined with X-ray photoelectron spectra (XPS), the results confirmed that the formed Pb-enriched layer with Pb–OH and Pb-PO4 bonds was absorbed on struvite surface during precipitation. When Pb concentrations were increased to 10–100 mg/L, the precipitation of dominating Pb phase, crystalline Pb10 (PO4 )6 (OH)2, was confirmed by X-ray diffraction (XRD). Combined with XPS, the amorphous Pb hydroxide/phosphate and Mg phosphate were also detected in struvite solids. Our findings revealed that at low concentrations (0.1–1 mg/L), Pb can affect the mineral surface by surface absorption, whereas Pb precipitated as separated phase(s) (e.g. Pb10 (PO4 )6 (OH)2, Pb hydroxide and/or phosphate) at high Pb concentrations (10–100 mg/L). Thus, the initial Pb 2+ concentrations in wastewater will dictate final struvite contents and Pb-bearing phases in recovered solids. Highlights: > 99% of Pb was incorporated into struvite solids at 0.1–100 mg/L of Pb. Pb bound with PO4 and OH adsorbs on struvite surface at 0.1–1 mg/L of Pb. Pb precipitated as Pb10 (PO4 )6 (OH)2 and Pb hydroxide/phosphate at 10–100 mg/L of Pb.