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Phosphate recovery from wastewater using calcium silicate hydrate (C-S-H): sonochemical synthesis and properties

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Abstract

In this study, a novel ultrasound-assisted sol–gel method was developed for the room-temperature synthesis of single-phase calcium silicate hydrate (C-S-H). The optimum synthesis conditions and the phosphate recovery properties of C-S-H were investigated by batch experiments. Samples were characterized by scanning electron microscopy (SEM), specific surface area analysis, 29Si magic-angle spinning nuclear magnetic resonance (29Si MAS-NMR) spectroscopy, and X-ray diffraction (XRD). The results showed that ultrasound irradiation played a vital role in the rapid and effective synthesis of C-S-H at room temperature, and the Ca/Si ratio of 1.2 was the most appropriate raw material ratio. In the process of phosphate recovery, C-S-H acted as the seed crystal, the calcium ion donor, and the pH adjuster at the same time, and therefore phosphate could be recovered in one-step crystallization without adding other chemicals. The adsorption kinetics and adsorption isotherms of phosphate recovery could be well described by the pseudo-second-order model and the Langmuir model, respectively. The thermodynamic parameters indicated that the phosphate recovery process was endothermic and spontaneous. The phosphate adsorption capacity on C-S-H could reach 109.4 mg g−1 when the initial pH was 5.0 and the temperature was 298 K. Unlike the case of using Ca(OH)2, only a slight degree of carbonate inhibition was observed for the phosphate recovery by C-S-H. All the results indicate that the ultrasound-assisted sol–gel synthesis is a valuable method for C-S-H synthesis.

Graphical abstract: Phosphate recovery from wastewater using calcium silicate hydrate (C-S-H): sonochemical synthesis and properties

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Publication details

The article was received on 14 Sep 2018, accepted on 19 Nov 2018 and first published on 22 Nov 2018


Article type: Paper
DOI: 10.1039/C8EW00643A
Citation: Environ. Sci.: Water Res. Technol., 2019, Advance Article
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    Phosphate recovery from wastewater using calcium silicate hydrate (C-S-H): sonochemical synthesis and properties

    Z. Zhang, X. Wang and J. Zhao, Environ. Sci.: Water Res. Technol., 2019, Advance Article , DOI: 10.1039/C8EW00643A

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