Acid leaching of blast furnace slag for enhanced zeolite synthesis

Cleaner Waste Systems Pub Date : 2025-01-13 DOI:10.1016/j.clwas.2025.100207

Nhlanhla Nyembe, Yusuf M. Isa

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Abstract

The iron- and steelmaking industry generates a substantial amount of waste in the form of blast furnace slag (BFS). Previous studies have highlighted the potential of utilizing BFS, composed of SiO₂ and Al₂O₃, for synthesizing zeolitic materials. However, impurities such as Ca and Mg have been found to hinder the hydrothermal synthesis process by inhibiting zeolite crystallization. To address this, acid leaching of BFS has been proposed as a viable pretreatment method. However, the influence of acid-leaching conditions on the hydrothermal synthesis technique remains unclear. Therefore, the study aims to evaluate the effectiveness of leaching conditions in reducing Ca and Mg from BFS, thereby improving zeolite synthesis from BFS. The BFS under investigation contained significant amounts of SiO₂ (35.1 wt%), Al₂O₃ (16.1 wt%), CaO (30.6 wt%) and MgO (10.5 wt%). The results revealed that the optimal leaching conditions were achieved at a solids concentration of 8 wt%, an HCl concentration of 3 mol/L, and a leaching time of 90 min. Under these conditions, Ca and Mg were successfully solubilized from BFS with a maximum leaching efficiency of 80.4 % and 71.1 %, respectively. X-ray diffraction analysis revealed the mineral phase in the BFS as akermanite, while the products derived from the raw slag and leached slag consisted of augite and zeolite ZSM-5, respectively. It was observed that acid leaching of BFS resulted in a transformation of the mineral phase to augite. The initial composition of CaO and MgO in the starting material significantly influenced the formation of zeolite ZSM-5 during the hydrothermal treatment. With reduced impurities, the leached slag demonstrated successful conversion into zeolite ZSM-5. However, the resultant crystals exhibited a distinctive ball-shaped morphology. The environmental impact of the acidic leachate was minimized by neutralization, ensuring safe disposal and enhancing the sustainability of the leaching process.

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高炉渣酸浸强化沸石合成

钢铁工业以高炉渣的形式产生了大量的废物。先前的研究强调了利用由SiO2和Al2O3组成的BFS合成沸石材料的潜力。然而，Ca和Mg等杂质通过抑制沸石结晶而阻碍了水热合成过程。为了解决这个问题，BFS的酸浸被提出作为一种可行的预处理方法。然而，酸浸条件对水热合成技术的影响尚不清楚。因此，本研究旨在评价浸出条件对BFS中Ca和Mg的还原效果，从而提高BFS合成沸石的效率。所调查的BFS含有大量的SiO2（35.1 wt%）、Al2O3（16.1 wt%）、CaO（30.6 wt%）和MgO（10.5 wt%）。结果表明，最佳浸出条件为固体浓度为8 wt%， HCl浓度为3 mol/L，浸出时间为90 min。在此条件下，Ca和Mg从BFS中成功溶出，最大浸出率分别为80.4 %和71.1 %。x射线衍射分析表明，BFS中的矿物相为角长石，而原渣和浸出渣的产物分别为奥辉石和沸石ZSM-5。结果表明，BFS的酸浸导致矿相向辉石相转变。在水热处理过程中，原料中CaO和MgO的初始组成显著影响ZSM-5沸石的形成。随着杂质的减少，浸出渣成功转化为ZSM-5沸石。然而，合成的晶体呈现出独特的球形形态。通过中和将酸性渗滤液对环境的影响降到最低，确保了安全处理并增强了浸出过程的可持续性。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Cleaner Waste Systems

CiteScore

2.60

自引率

0.00%

发文量