Coal mine waste characterization and defluoridation property.

Area of Science:

• Environmental Science
• Materials Science
• Water Treatment

Background:

• Fluoride contamination is a global water scarcity issue requiring effective mitigation strategies.
• Existing adsorbents for fluoride removal are often costly or unavailable.
• Coal mining generates substantial waste, such as shale, with underutilized potential.

Purpose of the Study:

• To investigate the efficacy of shale, a coal mining waste, as an adsorbent for fluoride removal from aqueous solutions.
• To analyze the impact of weathering on shale's defluoridation properties.
• To evaluate shale's adsorption capacity and suitability for water treatment.

Main Methods:

• Shale samples (weathered and fresh) were collected, crushed, and characterized using XRD, SEM, and FTIR.
• Batch adsorption experiments were conducted using synthetic fluoride solutions to determine optimal conditions (pH, contact time, particle size).
• Adsorption kinetics and isotherm models (pseudo-second order, Freundlich) were applied to analyze the adsorption process.

Main Results:

• Weathered shale achieved a maximum defluoridation efficiency of 47.05%, surpassing fresh shale (40.02%) at 3 ppm fluoride.
• Adsorption followed pseudo-second kinetics and Freundlich isotherm, with capacities of 23.66 mg/g (weathered) and 21.33 mg/g (fresh).
• Characterization revealed increased porosity and clay content in weathered shale, with XRD confirming F- adsorption onto minerals like Villiaumite and Fluorite.

Conclusions:

• Weathered shale is a highly effective, low-cost adsorbent for fluoride removal from contaminated water.
• Shale adsorption requires no significant pH adjustment and produces minimal suspended solids, potentially eliminating the need for secondary treatment.
• Utilizing shale waste offers a sustainable and economical solution for addressing fluoride contamination in water resources.