Leaching toxicity and deformation failure characteristics of phosphogypsum-based cemented paste backfill under chemical solution erosion.

Abstract

In order to explore the potential environmental and safety risks of phosphogypsum-based cemented paste backfill (PCPB) in mines, aiming at the actual problems of different acidity and alkalinity of the groundwater environment where PCPB is located, the chemical solution erosion test, element concentration determination test, uniaxial compressive strength (UCS) test, and microscopic analysis test of PCPB were carried out. The effects of three different chemical solutions, HCl solution, NaOH solution, and pure water on the leaching toxicity and deformation failure characteristics of PCPB were analyzed. The kinetic equations of pH value of PCPB in the HCl and NaOH solutions, the leaching models of total P and fluoride, and the UCS erosion model of PCPB were established. The research shows that the pH value of PCPB is weak alkaline or alkalinity, when it reaches dynamic equilibrium in different chemical solutions. The leaching concentration of total P is higher than the Class III standard of surface water; the leaching concentration of fluoride is higher than the Class III standard of surface water, the Class III standard of groundwater, and the Class I standard of sewage. In the early stage of chemical solution erosion, scanning electron microscope (SEM) images show that the hydration product C-S-H gel and Aft are intertwined and firmly combined. The research results have important engineering practice and application value in mine environmental governance and safety management.