Recycling Used Cooking Oil into High-Quality Liquid Soap: An Optimized Sequential Green Pretreatment Protocol

Mohammed Hasan Alwan

Authors

Mohammed Hasan Alwan University of Tikrit

Keywords:

Waste Cooking Oil, Green Pretreatment, Liquid Soap, Saponification, Circular Economy, Resource Recovery, Sensory Evaluation

Abstract

This research provides an innovative laboratory procedure for producing quality liquid soap from waste cooking oil (WCO). The two-step sequential green pretreatment improved quality: acid value was reduced from 1.50 ± 0.05 to 1.10 ± 0.03 mg KOH/g and 400 nm absorbance went from 0.50 ± 0.02 to 0.38 ± 0.01. Saponification of the pretreated oil yields high-quality liquid soap (13.0 ± 0.5% active) with pH of 8.5 ± 0.1, which is safe for skin; has good foam stability (88%); and aroma-free, confirmed by formal sensory test. The product showed good physical/chemical stability throughout a four-week accelerated storage test. The procedure is based on utilizing non-toxic materials that are readily available, allowing for a functional and sustainable circular economy solution for WCO.

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