Abstract

Significantly unexploited red mud contains 0.5–1.7 kg/ton of rare earth metals (REMs) and 14–45% Fe, 5–14% Al, 1–9% Si, 1–6% Na, and 2–12% Ti which is currently being stockpiled. Reasonably, the red mud can be a suitable secondary resource of REMs, and other valuable metals, if not for the contained base metals. Stockpiled red mud locks down these technologically important and supply chain critical metals. Though quantitatively minor, the value perspective of REMs in red mud is significant. Global red mud inventory could reach 4 billion tons by 2020 and being generated 120–150 million tons per year worldwide. Analysis indicated that industrial-scale valorization could unlock approximately $4.3 trillion worth of REMs from stockpiled red mud. The current review discusses the valorization of red mud through metal value recovery which is an industrial waste circular economy challenge. Unlike other reported reviews, the current review intensively discusses circular economy challenges and opportunities associated with the red mud valorization. Finally, a suitable conceptual sequential metal recovery process has been proposed based on a comprehensive review of various processes which can technically be a feasible process for sequential recovery of various metal values from the red mud. Comprehensive cutting-edge research, broader risk assessment, and cost and benefit analysis of the proposed process can ensure broader valorization. Broader valorization can address several issues through the proposed process like; (i) metal value recovery, (ii) REMs circular economy, (iii) closed-loop process with the industry, and (iv) lower the futuristic carbon economy, simultaneously.

摘要

大量未开发的赤泥含有 0.5-1.7 千克/吨的稀土金属 (REM) 和 14-45% 的铁、5-14% 的铝、1-9% 的硅、1-6% 的钠和 2-12% 的钛，其中目前正在囤货中。合理地，赤泥可以是 REMs 和其他有价值金属的合适的二次资源，如果不是因为所含的贱金属。储存的赤泥可锁定这些技术上重要且供应链关键的金属。虽然数量上较小，但 REMs 在赤泥中的价值前景很重要。到 2020 年，全球赤泥库存可能达到 40 亿吨，全世界每年产生 120-1.5 亿吨。分析表明，工业规模的增值可以从储存的赤泥中释放价值约 4.3 万亿美元的 REM。当前的评论讨论了通过金属价值回收实现赤泥的增值，这是一个工业废物循环经济挑战。与其他报告的评论不同，当前的评论集中讨论了与赤泥增值相关的循环经济挑战和机遇。最后，基于对各种工艺的全面审查，提出了一种合适的概念顺序金属回收工艺，该工艺在技术上是从赤泥中连续回收各种金属价值的可行工艺。全面的前沿研究、更广泛的风险评估以及拟议过程的成本和收益分析可以确保更广泛的价值。更广泛的估值可以通过提议的流程解决几个问题，例如：(i) 金属价值恢复，(ii) REMs 循环经济，