Environment Assessment of Modified Red Mud Utilized in Roadbed

Utilization of red mud in road projects is an effective way to consume large amounts of red mud on a large scale. In order to meet the requirements for road performance, a modified material, Heinchem, has been developed on the basis of extensive experiments, and the long-term environmental risks of red mud modified by this material have been investigated. By collecting and modifying original red mud samples, a series of continuous leaching tank experiments are carried out based on the exposure scenario analysis. According to the leaching content of pollution in the original and modified red mud, the characteristic pollutants are identified. The release mechanism of these characteristic pollutants in the modified red mud is revealed, and the long-term release amount is predicted. Furthermore, in light of the actual road use scenario of the modified red mud, a risk assessment model is established and used to simulate the release, migration, and transformation of characteristic pollutants during the use of modified red mud as roadbed material. The groundwater environmental risk is then assessed. Finally, an acute toxicity test of earthworms and a seed germination test are conducted to investigate the impact of the modified red mud on the farmlands. The results showed that the proposed red mud modified materials have obvious curing effects on V, As, Se, Mo, and F. When the leaching contents of V, Cr6+, Cr3+, As3+, Se4+, Se6+, Mo, and F in the modified red mud were lower than 0.15 mg/L, 0.1 mg/L, 0.2 mg/L, 0.012 mg/L, 0.012 mg/L, 0.012 mg/L, 0.075 mg/L, and 1.2 mg/L, respectively, the environmental risk of modified red mud during long-term road use is acceptable. This study provides a new way for the resource utilization of red mud.

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