A comprehensive study on the influence of pH for dewatering performance and filter cake characteristics in solid–liquid separation of clean coal

Abstract

The pH of solution significantly influences the interplay between polymer flocculants and clean coal, thereby affecting dewatering performance. Herein, a comprehensive study on the influence of pH for dewatering performance of clean coal was investigated from the perspectives of particle interaction and filter cake structure. The results reveal that as the solution transitions from acidic to alkaline, the filtration rate diminishes and the cake moisture content elevates, regardless of flocculant presence. Atomic Force Microscope (AFM) measurements indicated a reduction in the adhesion force of particles as the pH increases. CT analysis demonstrated that the filter cake porosity at pH 4 is markedly greater than those at pH 7 and 10. Upon reaching a pH of 10, the cake porosity further decreases to 5.41%, while the ratio of isolated pores to total pores increases to 17.15%. In acidic environments, the development of pore space in filter cake is more uniform and well connected, which indicates a substantially lower capillary pressure compared to that at pH 7 and pH 10. The Lattice Boltzmann Method (LBM) simulation results indicate that the permeability of the cake formed at pH 10 is notably lower than that of pH7 and pH4.