Green Synthesis and Evaluation of Antimicrobial Soap from Bio-Oil of Water Hyacinth and ZnO Nanoparticles Derived from Waste Plantain Peel

Abstract

This study explores a sustainable approach to soap production through the green
synthesis of Antimicrobial soap using bio-oil extracted from Eichhornia crassipes
(water hyacinth) and zinc oxide (ZnO) nanoparticles biosynthesised from waste
Musa paradisiaca (plantain peel). Water hyacinth, an invasive aquatic plant, and
plantain peels, an agro-waste, were utilised to address environmental waste issues
while enhancing public health through eco-friendly hygiene innovations. Bio-oil
was obtained via pyrolysis, while ZnO nanoparticles were synthesised using
aqueous plantain peel extract as a reducing and stabilising agent. Phytochemical
screening revealed the presence of antimicrobial constituents such as flavonoids,
tannins, and saponins in both materials. Soap formulations containing 0%, 5%,
10%, and 15% ZnO nanoparticles were produced and evaluated for pH, foaming
ability, stability, and antimicrobial efficacy against Escherichia coli,
Staphylococcus aureus, and Pseudomonas aeruginosa. The 10% ZnO soap
demonstrated optimal balance with acceptable foaming, skin-friendly pH, and
significant inhibition zones (up to 26 mm), suggesting a synergistic antimicrobial
effect of phytochemicals and nanoparticles. The soap also maintained structural
stability over six weeks. This work exemplifies a circular economy model by
transforming environmental and agro-waste into high-value antimicrobial
products, offering potential for commercialisation and application in underserved
communities. The study contributes to sustainable development goals related to
health, sanitation, and responsible consumption. It sets a foundation for largerscale
green product development.