Research on the Negative Externalities Evaluation for the Development of Weathered Crust Elution-Deposited Rare Earth Ores

Table 1

Weathered crust elution-deposited rare earth ore process characteristics and negative external effects [3].

Process	First generation	Second generation	Third generation
Leaching process	Barrel leaching, pool leaching	Pool leaching, heap leaching	In situ leaching
Leaching agent		⟶mixed ammonium salt
Characteristics	Simple source and cheap leaching agent	Low concentration leaching, improving economic and social benefits	Intact mountains and vegetation, little infrastructure, and low cost, improving efficiency
Negative externalities	Inefficiency leaching, soil salinization, destruction of mountain landscape, and vegetation growth	Tailing piles occupy a large amount of land, destroy the ecological environment, and cause soil erosion	Contamination of groundwater; improper injection is at risk