Husks, peels and other forms of fruit waste can be exploited to nurture evolving renewable energy and water supply technologies. These materials can find new value by transformation into 2D layered molybdenum carbide (MXene), which features superior light-to-heat conversion capabilities for use in solar-powered water purification systems.

A two-stage calcination process involving acid treatment and carbonization was devised by researchers from Nanyang Technological University, Singapore, and the Indian Institute of Science Education and Research to enable production of this useful material from fruit waste serving as the carbon source. The process was applied to coconut husk, orange peel and banana peel; the MXene sheets fabricated were employed to design a solar absorber in a solar still for water desalination.

As reported in Chemistry — A European Journal, the waste-derived MXenes demonstrated excellent light-to-heat conversion efficiency of 90%, almost 30% higher than that of commercial solar absorbers. The material production process also proved more economical relative to commercial alternatives since one of the reactant sources was obtained without cost from fruit waste.

[See also: Car and construction components derived from lemon peels, almond shells]

The photothermal layer made from coconut husk has the highest photothermal conversion efficiency of 94% and the highest evaporation rate of 1.52 kg/m²/hour under one sun illumination. The MXene —equipped solar still prototype delivered a water production rate 50% greater than that of an existing solar still and provided purified water that met the World Health Organization drinking water standard.