ABSTRACT

Red mud is generated at a rate of up to 175.5 million tons per year. The global stockpile of red mud is near 4 billion tons. This material is hazardous with pH values from 11 to 13. Reduction of this waste is critical. Current industry practices for disposal of red mud involve different stockpiling techniques on valuable land area or disposing into critical bodies of water. This review studies processes which can reduce the negative environmental impact of red mud in an economic way. For instance, neutralization of red mud with CO₂ can decrease the pH from 12.5 to 7. Treatment of red mud by this method lessens the negative environmental impact and prepares it for further processing for utilization. The current utilization rate of red mud is very low, only about 3 million tons per year are used as an additive for cement and construction. Red mud contains a large quantity of valuable minerals that can be extracted to both reduce the amount of red mud and provide value to the waste. This review investigates novel methods for treating red mud and extracting minerals like iron, titanium, and rare earth elements using a variety of smelting, direct reduction, and leaching processes. For example, the iron nugget process is a single step method to reduce iron oxides to metallic iron and separate them from red mud. Iron nuggets produced from red mud have an iron grade above 90%, which is comparable to pig iron generated by the blast furnace.

摘要

赤泥的产生速度高达每年 1.755 亿吨。全球赤泥库存接近40亿吨。这种材料的 pH 值在 11 到 13 之间是危险的。减少这种废物至关重要。当前处理赤泥的行业做法涉及在宝贵的土地上使用不同的储存技术或将其处理到关键的水体中。本综述研究了能够以经济的方式减少赤泥对环境的负面影响的过程。例如，用 CO ₂中和赤泥可以将 pH 值从 12.5 降低到 7。通过这种方法处理赤泥减少了对环境的负面影响，并为进一步加工利用做好了准备。目前赤泥的利用率很低，每年只有300万吨左右用作水泥和建筑的添加剂。赤泥含有大量有价值的矿物质，可以提取这些矿物质以减少赤泥的数量并为废物提供价值。本综述研究了使用各种熔炼、直接还原和浸出工艺处理赤泥和提取铁、钛和稀土元素等矿物质的新方法。例如，铁块工艺是将氧化铁还原为金属铁并将其与赤泥分离的一步法。赤泥生产的铁块铁品位在90%以上，