Abstract Brick-red clay mineral with palygorskite (PAL) as the main ingredient has huge reserves in the nature, but the congenital brick-red color limits its applications in industrial fields. In light of the prospective application value of such mineral, researchers have been looking for a feasible way to turn it into white one. Herein, a simple one-step reaction process in the presence of hydroxylammonium chloride (HAC) was developed and used to turn brick-red PAL into white one. The change of textural structure and physicochemical features of the brick-red PAL was investigated. It was shown that the brick-red PAL was converted to white after the reaction in 5 mol/L of aqueous solution of HAC at 80 °C. The rod-like crystal morphology of PAL still remain well after the reaction, and the associated minerals such as quartz, feldspar and muscovite did not change obviously. The dissolution of associated hematite (α-Fe2O3) and the leaching of Fe(III) and Fe(II) in acidic and reductive HAC solution mainly contributed to the whitening of brick-red PAL, as confirmed by Mossbauer spectroscopy. This research would lay a theoretical basis for extending the industrial application of naturally abundant brick-red clay minerals.

中文翻译：

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氯化羟铵诱导砖红色坡缕石结构演化

摘要 以坡缕石（PAL）为主要成分的砖红色粘土矿物在自然界中储量巨大，但先天的砖红色限制了其在工业领域的应用。鉴于这种矿物的潜在应用价值，研究人员一直在寻找一种可行的方法将其变白。在此，开发了一种在氯化羟铵 (HAC) 存在下的简单一步反应过程，并将其用于将砖红色 PAL 变成白色。研究了砖红色PAL的质构结构和理化特征的变化。结果表明，砖红色的 PAL 在 5 mol/L 的 HAC 水溶液中在 80 ℃下反应后转变为白色。反应后 PAL 的棒状晶体形态仍保持良好，伴生矿物如石英、长石和白云母没有明显变化。Mossbauer 光谱证实，伴生赤铁矿 (α-Fe2O3) 的溶解和 Fe(III) 和 Fe(II) 在酸性和还原性 HAC 溶液中的浸出主要促成了砖红色 PAL 的发白。该研究将为扩大天然丰富的砖红色粘土矿物的工业应用奠定理论基础。