title: Accuracy and application of quantitative X-ray diffraction on the precipitation of struvite product.
abstract: Struvite (MgNH4PO4·6H2O) crystallization from wastewater can gain a great advantage for phosphorus recovery and recycling. Although the recovery process and reaction modeling have been investigated, few studies have been conducted to quantify the different phases in recovered phosphorus products. The quantitative X-ray diffraction (QXRD) technique was employed in the present study to quantitatively determine the crystal phases and amorphous content of recovered struvite-containing products. Substantial mixed phase samples (i.e. struvite, newberyite and amorphous phase) were prepared to perform quantitative analysis to calibrate against known phase composition information by Rietveld refinement on powder X-ray diffraction data. The results showed a high level of accuracy (mean error = ∼3%) in our quantification model and validated the use of the Rietveld method to quantify the amorphous and crystal phases in the struvite-containing products. In addition, the influence of N:P molar ratio on struvite crystallization suggested that the weight percentage of struvite increased from 52% to 93%, when the N:P molar ratio was elevated from 0.2:1 to 1.2:1. This finding suggested the effectiveness of QXRD in facilitating the recovery of quality struvite products from waste streams.
authors.affiliation: Research Centre for Environmental Health and Pollution Control, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China; Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong.
authors.forename: Xingwen
authors.initials: X
authors.lastname: Lu
authors.affiliation: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong.
authors.forename: Kaimin
authors.initials: K
authors.lastname: Shih
authors.affiliation: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong.
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Li
authors.affiliation: School of Environment and Guangzhou Key Laboratory of Environmental Exposure and Health, Jinan University, Guangzhou 510632, China.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Liu
authors.affiliation: School of Environment and Guangzhou Key Laboratory of Environmental Exposure and Health, Jinan University, Guangzhou 510632, China.
authors.forename: Eddy Y
authors.initials: EY
authors.lastname: Zeng
authors.affiliation: School of Environment and Guangzhou Key Laboratory of Environmental Exposure and Health, Jinan University, Guangzhou 510632, China. Electronic address: feiwang1984@gmail.com.
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
mesh_terms: D011232:Chemical Precipitation; D003460:Crystallization; D017616:Magnesium Compounds / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D000069877:Struvite; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000737:chemistry; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D017616:Magnesium Compounds; D010710:Phosphates; D000069877:Struvite; D062065:Wastewater; C030781:magnesium phosphate
keywords: Phosphorous recovery; Precipitation; Quantitative X-ray diffraction; Rietveld refinement; Struvite