Boron Removal Through Precipitation Softening in Presence of Ettringite

Boron is frequently present in wastewater from hydrocarbon production, briefly referred as produced water. Boron at high levels is toxic, especially to plants. It makes challenging produced water reuse. State-of-the-art boron removal processes need specific operations resulting in an increase of water treatment train complexity and cost. Among these, we recall reverse osmosis, adsorption on chelating resins and precipitation softening in presence of magnesium in large excess. Ettringite is a calcium-aluminum sulfate hydroxide, Ca6Al2(SO4)3(OH)12 center dot 26H2O, reported as an effective boron adsorbent. The experimentation described in this paper deals to boron removal through precipitation softening in conditions promoting the formation of ettringite. The first-stage-reverse-osmosis permeate from an Italian oil-and-gas site was used as raw water.