Enhancing the rheology and leachability of fly ash slurry using natural – synthetic mixed surfactant systemfor hydraulic stowing in underground mines

ABSTRACT

The present investigation is intended to develop the stabilization and transportation behavior of fly ash slurry (FAS) using the mixture of the surfactants, namely, Sapindus laurifolia (S. laurifolia, natural) and sodium dodecyl sulfate (SDS, synthetic). In addition to the rheological study, an attempt has been made to remove the toxic and other trace metals through the leaching method to address the safe disposal of FAS for mining backfilling applications. The data obtained from the different rheological studies of ash concentrations in the range of 45–65.8% were fitted to the Bingham plastic model. Addition of synthetic surfactant SDS to natural surfactant S. Laurifolia does enhance the wettability of fly ash (FA) particles by decreasing the surface tension and increasing the zeta potential of the slurry. The effect of other parameters like temperature, mixed surfactant concentration, and FA concentration on the formulation, stability, and leachability of FAS was investigated and reported. The results from the present investigation revealed that the optimum dosages of surfactants for both leaching and transportation of FAS is 0.009 g/cc of saponin and 0.008 g/cc of SDS. The stabilization interaction and leaching mechanism were proposed considering the hydrophobic/hydrophilic property of FA, S. laurifolia, and SDS.

Abbreviations

CMC: Critical micellar concentration; S. laurifolia: Sapindus laurifolia; SDS: Sodium dodecyl sulfate; FA: Fly ash; FAS: Fly ash slurry; η: Dynamic viscosity; τ₀: Yield stress; γ: Applied shear rate; ζ: Zeta potential; τ: Shear stress

KEYWORDS:

• Fly ash
• Sapindus laurifolia
• rheology
• leaching
• SDS
• waste utilization

Acknowledgments

All the authors are thankful to their respective institutions for the support and help provided during the course of this study. The first author is thankful to Dr. Trilochan Sahu, Principal, Government College of Engineering, Keonjhar, India, for his valuable suggestions for improving the quality of the work reported.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Declaration for funding

There is no financial funding component associated for investigation of this work.