In-situ reduction of heavy metal contaminated soil by hydrocyclone based on axial sorting of particles

Abstract

Soil heavy metal pollution is worsening environmental degradation, with fine soil particles serving key carriers due to their high surface area and porosity. While hydrocyclones are commonly used in soil remediation, the "fish hook effect" limits their ability to separate fine particles effectively. Through particle distribution regulation, we have designed a novel device that integrates particle sorting with hydrocyclone separation via an axial spiral connection, improving the classification of coarse and fine soil particles. Laboratory study demonstrates that B-I sorting hydrocyclone delivers the best overall performance. Compared to the Control, with 8.0 % increase in pressure drop, the separation efficiency improves by 27.4 %, achieving a total efficiency of 91.1 %. Additionally, the d₅₀ and d₈₀ are reduced to 5.4 μm and 17.7 μm, respectively. In practical applications, at an inlet flow rate of 1.6 m³ /h, the Sb concentration at the underflow outlet was 16.6 mg/kg, meeting the first-class land backfill standard (20 mg/kg). Compared to conventional ectopic leaching, this new process reduced soil leaching by 83.9 %, halved the treatment capacity of leaching waste liquid from 50 t/h to 25.5 t/h, and lowered remediation costs from $22.8 to $12.1 per ton. This research underscores the significant potential of hydrocyclones in soil remediation.