Dissolved silica is ubiquitous in impaired waters, resistant to existing antiscalants, and difficult to remove from power plant feed waters, thereby inhibiting long term reuse of industrial water. Herein is presented a fast, energy efficient and low cost material for the removal of silica ions from industrial waters: the high selectivity anion-exchanger hydrotalcite (Mg6Al2(OH)16(CO3) . 4H2O, HTC) material. HTCs exist in two different forms: crystalline uncalcined and amorphous calcined (550°C) phases. The results indicated that the calcined amorphous HTC removes &gt;90% silica from batch solutions as compared to uncalcined HTC. Materials characterization studies indicate that in the calcined HTC the silica anions have easy access to the oxide exchange sites. XRD and FTIR confirm both the recrystallization of the HTC when mixed with silica containing waters; SEM-EDS confirms the conclusion of the silica in the HTC. The single path flow through tests point to rapid uptake of silicate and an overall uptake capacity of ~45 mg SiO2/g HTC. Preliminary research shows the HTC can be regenerated and reused multiple times. Ongoing studies into techno-economic modeling and scale-up analysis will help direct this research toward real word implementation of hydrotalcite.

Selective silica separations from waste water using ion-exchange media

253rd National Meeting (2017)

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