Valorization of Waste Orange Peel to Produce Shear-Thinning Gels

Abstract

A laboratory experiment was developed to introduce students to waste valorization. This is the process of reusing, recycling, or composting from wastes, useful products, or sources of energy. In this laboratory experiment, waste valorization is demonstrated through transforming waste orange peel (WOP) into a marmalade-type gel by extracting a pectin-based mixture (or sol) and forming a gel in combination with an acidified sugar solution. Upon isolating the pectin sol, students examined how the rheological properties varied as a function of temperature using capillary viscometry. Gelation was followed via rotational viscometry, and non-Newtonian, shear-thinning properties were demonstrated by monitoring the viscosity change as a function of spindle RPM. In addition to providing a safe and green alternative to the traditional borax-cross-linked poly(vinyl alcohol) gel for students to study, this experiment demonstrates that valuable products for everyday use can be created from household waste such as WOP. Students making the transition from a first to second year undergraduate chemistry program within a natural-sciences degree have successfully conducted this laboratory experiment.

Faculty perspectives regarding the integration of systems thinking into chemistry education

“…When such an experiment was performed in Brazil, waste orange peel was selected as the substitute feedstock given that its disposal in landfill is an issue of national importance. Therefore, in addition to acting as a learning resource, the experiment aids in reducing the issues surrounding the disposal of this 'waste', advocating for a transition from a linear to a circular economy (Mackenzie et al, 2019). This demonstrates that the experiment is accessible and transferable while illustrating how systems thinking can be used to help solve global problems.…”

Efficacy and sustainability of natural products in COVID-19 treatment development: opportunities and challenges in using agro-industrial waste from Citrus and apple

“…As one of the major commercialized natural products, Citrus already have a well-established production chain. Several studies have evaluated the reuse of its industrial waste, although its waste usage to promote value-added products is still not as consolidated as the production of industrialized products, such as juices or frozen pulps 97 , 98 . Citrus waste valorization has many branches, such as the extraction of phenolic compounds and flavonoids, carotenoids, pectin, limonoids, and even essential oils 99 , 100 .…”

International Perspectives on Green and Sustainable Chemistry Education via Systems Thinking

“…17 To embed systems thinking more deeply, students turned to a different system where they designed a laboratory experiment based on valorizing waste orange peel by extracting a pectin sol and, in combination with a sugar solution, formed a marmalade-based product in which the rheological behavior could be investigated. 18 This system allowed students to directly consider the life cycles of materials in a more systemic fashion. In doing so, students could reflect on where materials come from, how they are transformed and used, and what happens at the end of their life spans.…”