Application of photothermal floats for mine water disposal

Ross Monasmith, Montana Tech

A publishable paper submitted for degree fulfillment of a master of science in environmental engineering.


Photothermal materials can efficiently translate incoming solar radiation into water evaporation. The application of photothermal materials to enhance evaporative water disposal may be limited by material durability, scale formation, and interactions between the photothermal materials and variable water chemistries. Granular activated carbon (GAC) was chosen as a photothermal material based on previous results (Monasmith et al. 2019, pending review). Using a custom-built bench-scale evaporation platform, evaporation trials were performed to determine the effect of water quality, GAC grain sizes, and float adhesives on water evaporation rates. Adhesives to attach the GAC to HDPE floats were tested for bond strength and durability, and the adhesive’s effects on GAC’s evaporative properties were measured by contact angle, water retention, and surface area analyses. No significant differences were discovered between grain sizes, adhesives, or water quality in the evaporation tests (p > 0.05). As water leaves the evaporative surface, scale will form, and possibly change the photothermal properties of the material. Scale formation from three test waters was observed and characterized by SEM imagery and EDS, but did not lead to any significant changes in evaporative performance of the floats. Consistent evaporation rates were measured in the bench scale evaporation scale chamber regardless of varying GAC grain size, adhesive type, and water quality, indicating the potential versatility of GAC in photothermal water disposal. Further experiments should focus on durability for pilot scale applications, and may inform the use of passive evaporation techniques for water management and disposal.