Electrochemical Behavior of Tannin Solutions under Microwave Irradiation

Vegetable tannin extract has an important use as a tanning agent in leather industry. The electrochemical behavior of tannin solutions, as a critical factor, greatly affect vegetable tanning. In this work, we have investigated the particle size, Zeta potential and conductivity of Commercial Acacia Mangium extract solutions (CAME) and Commercial valonia extract solutions (CVE) under water bath heating (WBH) and microwave irradiation heating (MIH). The heating conditions were selected as follows: time, 5 min, 15 min, 30 min, 60 min and 120 min; temperature, 30°C, 40°C and 50°C. It was found that the particle size of both CAME and CVE decreased under MIH while Zeta potential increased compared with WBH. Furthermore, the features become more and more significant with the irradiation temperature and time. And the conductivity of CAME and CVE increased more with the temperature under MIH in comparison to WBH. As a result, in the condition of microwave irradiation, tannin extract can easily penetrate into skins and then crosslink well with the collagen owing to the small tannin particle size and stable solution system, hence microwave may contribute to the penetration of tannin extracts in the skin and the binding properties with collagen in vegetable tanning.