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首页> 外文期刊>Environmental Science & Technology >Ettringite-induced heave in chromite ore processing residue (COPR) upon ferrous sulfate treatment
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Ettringite-induced heave in chromite ore processing residue (COPR) upon ferrous sulfate treatment

机译：硫酸亚铁处理后铬铁矿在铬铁矿矿石加工残渣（COPR）中引起的隆起

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摘要

A pilot-scale treatment study was implemented at a deposition site of chromite ore processing residue (COPR) in New Jersey. Ferrous sulfate heptahydrate (FeSO4, 7H(2)O) was employed to reduce hexavalent chromium in two dosages with three types of soil mixing equipment. XANES analyses of treated samples cured for 240 days indicated that all treatment combinations failed to meet the Cr(VI) regulatory limit of 240 mg/kg. More importantly, the discrepancy between XANES and alkaline digestion results renders the latter unreliable for regulatory purposes when applied to ferrous-treated COPR. Regardless of Cr(VI), the introduction of reductant containing sulfate, mechanical mixing, water, acidity, and the resulting temperature increase in treated COPR promoted dissolution of brownmillerite (Ca2FeAlO5), releasing alumina and alkalinity. The pH increase caused initially precipitated gypsum (CaSO4 center dot 2H(2)O) to progressively convert to ettringite (Ca6Al2(SO4)(3)center dot 32H(2)O) and its associated volume expansion under both in situ and ex situ conditions, with a maximum of 0.8 m vertical swell within 40 days of curing. While Cr(VI) treatment remains a challenge, the intentional exhaustion of the heave potential of COPR by transforming all Al sources to ettringite emerges as a possible solution to delayed ettringite formation, which would hamper site redevelopment.
机译：在新泽西州的铬铁矿矿石加工残留物（COPR）沉积现场进行了中试规模的研究。七水合硫酸亚铁（FeSO4，7H（2）O）用于通过三种土壤混合设备以两种剂量还原六价铬。固化240天的处理样品的XANES分析表明，所有处理组合均未达到240 mg / kg的Cr（VI）法规限值。更重要的是，XANES与碱消解结果之间的差异使得后者在应用于含铁处理的COPR时，对于监管目的而言并不可靠。不论Cr（VI）如何，引入含硫酸盐的还原剂，机械混合，水，酸度以及所处理的COPR中所导致的温度升高均会促进褐煤（Ca2FeAlO5）的溶解，从而释放氧化铝和碱度。 pH值升高导致最初沉淀的石膏（CaSO4中心点2H（2）O）逐渐转变为钙矾石（Ca6Al2（SO4）（3）中心点32H（2）O）及其相关的在原位和非原位体积膨胀在固化的40天内，垂直膨胀最大为0.8 m。尽管Cr（VI）处理仍然是一个挑战，但通过将所有Al源转变为钙矾石来故意耗尽COPR的沉浮潜力，可能是解决延迟钙矾石形成的一种可能的解决方案，这将阻碍场地的重建。

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