Hydrogen peroxide and high-temperature heating differently alter the stability and aggregation of black soil colloids

Chemical oxidation and high-temperature heating have been widely used for the decontamination of soils polluted by hydrocarbons and the removal of soil organic matter. Chemical oxidation and high-temperature heating decreased the stability of soil colloids, but the difference in colloidal stability and aggregation behaviors of soil after chemical oxidation and high-temperature heating is not clear. In this study, taken black soil as an example, we tested the stability profiles of black soil colloids (BC), hydrogen peroxide (H₂O₂) treated black soil colloids (BC_H₂O₂), and 350 °C treated black soil colloids (BC_350 °C) in three salt solutions (NaCl, CaCl₂, and Na₂SO₄) with different salt concentrations. The stability of soil colloids in salt solutions was in the order of BC > BC_350 °C > BC_H₂O₂. The salt concentrations at which three colloids started to be unstable were much lower for CaCl₂ solution than those for NaCl and Na₂SO₄ solution. Salt concentrations that suspension started to be unstable were similar in NaCl and Na₂SO₄ solution for all the three colloids, but the colloidal stability profile in NaCl solution decreased faster than that in Na₂SO₄ solution when the suspension was unstable. The stability profiles of three colloids at the fast aggregation stage could be well fitted with the proposed exponential model, and model parameters (t₀ and S_max) could reflect the stability behaviors of soil colloids in various salt solutions.