Journal
CHEMICAL ENGINEERING JOURNAL
Volume 365, Issue -, Pages 60-69Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2019.02.034
Keywords
Struvite; Heavy metal; Slow-release fertilizer; Heterogeneous nucleation; Sorption; Precipitation
Categories
Funding
- National Natural Science Foundation of China [51674305]
- Key Projects of Science and Technology of Hunan Province [2017SK2420]
- Innovation-Driven Project of Central South University [2017CX010]
- Opening Fund of Jiangsu Key laboratory of Anaerobic Biotechnology (Jiangnan University), China [JKLAB201706]
- Project of Creation of Life Innovation Materials for Interdisciplinary and International Researcher Development of the Ministry of Education, Culture, Sports, Science and Technology, Japan
- 2017 Huxiang Provincial Scholar Program [2017RS3005]
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During the struvite (MgNH4PO4 center dot 6H(2)O) recovery from agricultural or industrial wastewater, the extensive existence of heavy metals would pose great threats to the planting and environment. This work revealed the association of kinds of heavy metals, as possible substances in the wastewater, with the struvite. The struvite has been synthesized in situ and employed to contact with both high and low concentration heavy metal (including Cu, Ni, Pb, Zn, Mn, Cr(III)) wastewater. The heavy metal precipitation rates under different pH values from 6.0 to 10.0, and under a series of struvite addition amount have been investigated. The precipitation of heavy metals without addition of struvite is functioned as control experiments. The struvite's presence can enhance the heavy metal precipitation rate under all pH values. The Ni and Mn have relatively lower precipitation rate compared with other metals. For extremely low heavy metal concentration the precipitation rate is 99.1%, 97.9%, 99.9%, 98.9%, 96.9%, and 98.3%, which is much higher than that of control group (10.5%, 8.7%, 13.2%, 14.1%, 6.7%, and 10.5%). Through XPS and TEM & EDS analysis, the heavy metal hydroxides is found to be precipitated on the struvite surface. Based on TEM observations, it has been found the copper hydroxides had nucleation and growth on the struvite's surface. The heterogeneous nucleation mechanism has been proposed, which provides relationship model of sorption, nucleation, and precipitation of heavy metals in the form of hydroxides on struvite surfaces. It has been calculated that the Delta G(i) value that thermodynamic activation energy barrier constraints on the metal hydroxide formation can be intensively abated through heterogeneous nucleation on struvite.
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