Application and mechanistic insights of a washing/microwave/ultrasonic ternary pretreatment for enhancing barite flotation in waste drilling fluids.

A quantity of recoverable barite exists in high-density waste drilling fluid. Based on the inefficiencies and complexities of existing recycling methods, a novel pre-treatment approach which includes clean-breaking, high-speed washing, ultrasonic dispersion, and microwave heating and a new depressant (Gellan Gum) was proposed. The floatability, separation efficiency and mechanism were discussed by SEM, adsorption capacity, zeta potential measurements and contact angle tests. The results of reverse flotation experiments results indicated that secondary water washing proves highly effective in enriching a significant quantity of barite solid phase. Subsequent microwave-ultrasonic and flotation can obtain barite of high quality with recovery and density reaching 81.5% and 4.238 g/cm, respectively. It can be utilized directly in the preparation of drilling fluid. Mechanism studies shown that the per-treatments substantially enhances the barite grade while effectively eliminating low-density solid phases adhering to the barite surface, thus exposing additional contact points between the constituents so as to improve flotation separation. This new recovery scheme has environmental advantages and great reference value for the separation of barite within high-density waste drilling fluids.