The development of efficient and inexpensive boron removal techniques is required to treat wastewater from many industrial processes. We investigated the removal mechanism of boron from wastewater by calcinated ettringite, a concrete sludge, and compared the advantage of this method to coprecipitation with ettringite. The amount of boron remaining in solution decreased slightly from an initial concentration of 2.3 mmol/dm³ to 1.3–1.4 mmol/dm³ after reaction for 60 min with ettringites calcinated at 55 and 65 °C. The boron removal efficiency increased greatly, with only 0.30 mmol/dm³ remaining in solution after treatment for 60 min with samples calcinated at 75 °C, but samples calcinated at 95 and 175 °C removed slightly less boron than those calcinated at 75 °C. This enhancement of boron removal performance is due to the amorphization of the ettringite structure by calcination. However, excess heating inhibits ion exchange between the sulfate ions in the ettringite and the borate ions in the solution. The coprecipitation method also achieved efficient boron removal at high Al/B molar ratio (0.44 mmol/dm³ boron remaining after 60 min). However, uptake by a different amorphous precipitant became the dominant removal mechanism. Large amounts of sludge are generated by this method. Adsorption using calcinated ettringite is therefore the optimal method for the efficient and inexpensive removal of boron from wastewater.

中文翻译：

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煅烧钙矾石去除废水中硼的实验研究

为了处理来自许多工业过程的废水，需要开发有效且廉价的除硼技术。我们研究了煅烧钙矾石（一种混凝土污泥）从废水中去除硼的机理，并比较了该方法与钙矾石共沉淀的优势。与在55和65°C下煅烧的钙矾石反应60分钟后，溶液中残留的硼量从最初的2.3 mmol / dm ³轻微降低到1.3–1.4 mmol / dm ³。硼去除效率大大提高，仅0.30 mmol / dm ³在75°C下煅烧的样品处理60分钟后仍保留在溶液中，但在95和175°C下煅烧的样品中硼的含量比在75°C下煅烧的样品略少。除硼性能的提高是由于煅烧使钙矾石结构非晶化。但是，过度加热会抑制钙矾石中的硫酸根离子与溶液中的硼酸根离子之间的离子交换。共沉淀法还可以在高Al / B摩尔比（0.44 mmol / dm ³60分钟后剩余的硼）。但是，另一种无定形沉淀物的吸收成为主要的去除机理。这种方法会产生大量的污泥。因此，使用煅烧钙矾石进行吸附是从废水中高效，廉价去除硼的最佳方法。