The use of red mud as an immobiliser for metal/metalloid-contaminated soil: A review.

TLDR: Overall red mud amendment is likely to contribute to lowering the PTE availability in contaminated soil, suggesting the toxicity from PTEs was reduced by red mud, as well as indirect effects due to changes in soil properties.

About: This article is published in Journal of Hazardous Materials.The article was published on 2017-03-05 and is currently open access. It has received 167 citations till now. The article focuses on the topics: Red mud & Environmental remediation.

Figures

Table 1. Red mud pH and total metal/metalloid concentrations (mg kg-1 dry weight) and country of production as reported in the literature. Summary statistics for red mud composition and EU limits for metals/metalloids in sludge for application to agricultural land are stated at the foot of the table.

Table 3. Pot experiments: effect of red mud amendment of metal-contaminated soils on metal concentrations in plants and plant biomass yield.

Fig. 1. (a) Annual alumina production worldwide and in China. Global data from International Aluminium Institute [8]. Data for China from National Bureau of Statistics of China [9]. (b) Regional distribution of alumina production in 2015. Data from International Aluminium Institute [8].

Table 5. Effect of red mud amendment of metal/metalloid-contaminated soils on soil properties and microbial activities.

Fig. 2. Preliminary proposed scheme for assessing the use of red mud to remediate contaminated soil.

Table 2. Summary of studies assessing the effect of red mud on metal/metalloid mobility in soil using single chemical extractants.

Frequently asked questions

Q1. What are the contributions in this paper?

This review focuses on the applicability of red mud as an amendment for metal/metalloid-contaminated soil. The varying properties of red muds from different sources are presented as they influence the potentially toxic element ( PTE ) concentration in amended soil. Bacterial activity was intensified in red mud-amended contaminated soil, suggesting the toxicity from PTEs was reduced by red mud, as well as indirect effects due to changes in soil properties. Red mud remediation of metal/metalloid contaminated sites has the potential benefit of reducing red mud storage and associated problems. 

Q2. What are the future works in this paper?

In applying this scheme it should be recognised that: ( i ) further studies, particularly at the field scale, will help to define critical thresholds, and ( ii ) site-specific risk assessments are required, to include, amongst other considerations, PTE mobility in the red mud and soil and site factors which might enhance mobilisation ( discussed below ). Although there is the possibility of increasing the remediation effectiveness of red mud through pre-treatment, more research is required on how different pre-treatment methods influence the effectiveness of red mud for remediation of contaminated soil. ( 1 ) Fractionation studies have shown that metals in red mud are mainly associated with the less reactive phases, suggesting that they are not readily mobile under natural or even moderately acidic or reducing conditions. An appropriate pre-treatment method, such as neutralising red mud with seawater, may be helpful to improve the fixation of Cu in amended soils.