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WASTE VALORIZATION OF SPENT COFFEE GROUNDS: A SUSTAINABLE ROUTE FOR BIO-COMPOSITE MATERIALS IN A CIRCULAR ECONOMY

Mousa Ahmad

Abstract

This study examines the potential of chemically modified spent coffee grounds (SCG) as reinforcement for epoxy bio-composites. SCG was subject to three different modifications - citric acid, acetylation with acetic acid, and potassium permanganate oxidation. Modified SCG was incorporated into epoxy resin at an 80/20 weight ratio, and the resulting composites were evaluated using flexural and impact tests. Fourier transform infrared (FTIR) data revealed that each chemical modification induced distinct structural modification within the SCG powder. Citric acid promoted the formation of ester groups. While acetylation produced a marked reduction in hydroxyl group intensity. The KMnO₄ treatment also induces minor but significant changes in the 900–1200 cm−1 fingerprint region. These modifications result in oxidative changes to the hydroxyl groups of the polysaccharide components, leading to the creation of new oxidized moieties within the cellulose and hemicellulose fractions. The results showed that citric acid-treated SCG exhibited the best mechanical performance with reference to the other modified samples. It displayed an increase of approximately 20% in impact strengths and 40% in flexural strength. This was attributed to enhanced interfacial bonding with the epoxy matrix. In contrast, potassium permanganate-treated and acetylated SCG produced noticeably weaker mechanical properties. This was due to fiber degradation or insufficient interfacial adhesion resulting from the treatment process. The results establish a clear performance, making citric acid treatment provide the highest mechanical reinforcement, whereas potassium permanganate and acetylation yield relatively weaker improvements.

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