Potential of Water Hyacinth Leaves Extract as a Leather Tanning Agent

Abstract

Water hyacinth (Eichhornia crassipes) is listed as one of the worst aquatic plants in the world and its presence in Lake Tana in Ethiopia has been recognized since 2011. Currently, the plant coverage in the lake is increasing and very limited studies have been conducted in the country on practical application of water hyacinth. The aim of this study was to determine the phytochemicals, functional groups and Tannin content of the water hyacinth plant found in the Lake, which could serve as a vegetable tanning agent. Both qualitative and quantitative approaches were used to assess the quality tannin in the plant stem and leaves. On phytochemical analysis of the dried material, the tannin content was found to be 4.1% for leaves and 2.7% for stem parts. As the tannin content of the leaves was higher than the stem parts, leather tanning conducted using the 10% wt and 20% wt leaves and the quality of tanned leathers was evaluated and compared with the leather made from quebracho vegetable tanning material as a control. Most properties of leathers tanned using the leaves met the minimum specified standards for leather product manufacturing, which includes tearing strength > 45 N, percent elongation at break > 42% distension at grain crack > 6.5 mm, and distension at burst >7.8 mm. Even though shrinkage temperature is one of the most important parameters in determining the thermal stability of leather, the leather tanned with leaves extract had a shrinkage temperature of 52°C, which is lower than the standard limit (75°C) for leather product manufacturing. This indicated that, the crosslinking reaction between the hide (collagen fibers) and tannins (leaves) was weaker, implying that the leather would not be as durable or of higher quality. Similarly, the maximum tensile strength of tanned leather was 7.2 N/mm2, which is lower than the standard requirement (20 N/mm2) for leather product manufacturing. Therefore, water hyacinth leaves extract has limited potential as a vegetable tanning agent, and the tanned leather will not be used to make leather products that requires good thermal resistance and strength. On the other hand, the tanned leather may be utilized for leather products that need minimal tensile strain and thermal property requirements such as leather photo frames, sketchbook leather bound, etc. Since water hyacinth tannin is less than ideal as a tanning agent due the minimum shrinkage temperature and tensile strength of the tanned leather, the potential of the plant as a retanning agent should be studied in future.