Velocity dependent contact angle hysteresis of Rhamnolipid biosurfactant on peat

Of all organic materials employed in soilless culture systems, peat is commonly employed as a substrate for crop production. However, the properties of peat may not provide optimal water availability and aeration conditions due to the development of substrates water repellency (WR). Although synthetic surfactants are used to ameliorate WR, their negative environmental impacts demand for an alternative approach. In the past decade, biosurfactants have drawn attention due to their low toxicity, biodegradability and, could potentially be used as an alternative. However, to the best of our knowledge, the rate and extent to which biosurfactant may reduce the contact angle (CA) form on peat surface is currently not investigated. The main objective is this study is to quantify the interplay between Rhamnolipid biosurfactant and WR peat. The study is involved with measurements of dynamic advancing and receding CA of aqueous biosurfactant on peat surface at different velocities and aqueous concentrations, using Wilhelmy plate method. For concentration ranged from 20 to 200 mg/l, the results clearly demonstrated a velocity dependence in the first cycle of advancing/receding CA, and significant reduction in CA hysteresis at higher velocities. In the four subsequent cycles, further reduction in CA and CA hysteresis could be observed for the Rhamnolipid demonstrating its aid to peat wettability. However, for water, higher advancing and receding CA was observed even after five consecutive cycles. In our presentation, the results of advancing and receding CA of Rhamnolipid and water on peat surface will presented and possible mechanism will be discussed.

Keywords: Peat, water repellency, Biosurfactant, advancing and receding contact angle, velocity