Application of the Principles of the Circular Economy for Obtaining Siliceous Solids with Bio-waste

Circularity is at the core of eco-design, a production methodology in which waste is repurposed and environmental impacts such as raw-material use are reduced through reuse and recycling. The scale of global waste and its proportionate economic and environmental costs is gargantuan. Faced with this entrenched dynamic, how can closed-loop systems become the norm? One answer is to integrate them into circular economies. This model looks to extend the life of products at the use stage, retaining value.

In this research, the sol-gel method is carried out through acid or alkaline hydrolysis, combined with orange or lemon peels generated as urban waste. The main objective was to obtain silica-based materials with the tetraethylorthosilicate precursor using acidic and basic catalysts, of organic and inorganic origin. The solids obtained were characterized with SEM, FT- IR, potentiometric titration and XRD. The primary goal was to use bio-waste to study its influence on the hydrolysis of the sol-gel method and its effect on the morphology and acidity of the synthesized solids.

According to the results, the biowaste used can provide acidity. The acidity values obtained using bio-waste are similar to those of pure silica with acid hydrolysis, showing promising results. Considering that citrus fruits are cultivated and used worldwide, significant amounts of waste are produced, and derivatives such as cellulose, lignin, pectin, pigments, essential oils, etc. can be used. The pharmaceutical, cosmetic, food and even energy sectors have benefited from these by sub-products so far.