Graphite particle electrodes that enhance the detoxification of municipal solid waste incineration fly ashes in a three-dimensional electrokinetic platform and its mechanisms

Abstract

This paper investigated the application of graphite particle electrodes to the removal of Zn, Pb, Cu, and Cd from municipal solid waste incineration (MSWI) fly ashes in a three-dimensional (3D) electrokinetic reactor. The influences of the voltage gradient, mass ratio of graphite powers to fly ashes, nitric acid concentrations, proposing times, and liquid-solid (L-M) ratios on the remedial efficiencies of MSWI fly ashes were comprehensively studied in an orthogonal deign and a sequential double-factor setup. Significant analysis showed that changes in the mass ratios and nitric acid concentrations both had a statistically significant effect on the removals of Zn and Pb. Proposing times and L-M ratios both remarkably affected the removals of heavy metals (HMs) in a 3D electrochemical system. The graphite powers had a narrower distribution interval and slightly larger surface areas compared with MSWI fly ashes, which relented pH gradients over the time in the electrochemical experiments and minimized the bubble barricade caused by the hydrolysis. The particle electrode had increased the residue factions of Zn, Pb, Cu, and Cd in S1 region by approximately 216%, 136%, 309%, and 950%, respectively, compared with the raw MSWI fly ashes. The addition of graphite powders to a two-dimensional (2D) electrochemical process strengthened hydrolysis reactions, shortened time for the redistribution of pH balance, decreased the tortuosity of migration path, and increased the desorption concentrations of HMs in the sample area.

Keywords: A three-dimensional electrokinetic process; Enhancement; Heavy metal removal; Municipal solid waste incineration fly ashes; Particle electrodes.