Recovery of metal values from pre-concentration of coarser size fraction of printed circuit boards by froth flotation

Abstract

The E-waste Printed Circuit Boards (PCBs) are rich in metal content and processing these wastes for extracting the metal values and removing the non-metallic constituents is a prospective proposition. Froth flotation methodology was observed to be a propitious process technique for rejecting plastics from the comminution product. It has been shown for the first time that nearly reagent-free flotation of relatively coarse size (-1.0 mm) pulverized e-waste is feasible with a reasonably good product at a high yield and excellent recovery. In the present research work, enrichment of ground 1.0 mm PCB powder was investigated through flotation route by varying the operating variables such as frother dosage, pulp density, air flow rate and rotational speed of impeller. The liberation studies accomplish that liberation of metal value from non-metallic constituents at -1.0 mm size is excellent and the particulate system is significantly rich in metal value, containing around 23% metal. In-depth study of froth flotation kinetics is primarily focused on high rejection of plastics and also identification of optimum operating conditions for the same. Single-stage flotation enhances metal content from 23% to over 37%, contributing a mass yield of around 75% with recovery of nearly 95% metal values, suffering nominal loss of around 4% metal value only, while effectively rejecting 32% of the materials in feed through float fraction. Systematic quantification of e-waste flotation performance accentuated on kinetics, supported by statistically designed experimental campaign, comprising integration of features ranging from liberation to optimization, statistical analysis and modeling efforts, evidence novelty.