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Molecules. 2019 Jun 1;24(11). pii: E2094. doi: 10.3390/molecules24112094.

Wetting Behavior and Maximum Retention of Aqueous Surfactant Solutions on Tea Leaves.

Zhu F1,2,3, Cao C4, Cao L5, Li F6, Du F7, Huang Q8.

Author information

1
Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China. gzzbszf@163.com.
2
Institute of Plant Protection, Guizhou Academy of Agricultural Sciences, Guiyang 550006, China. gzzbszf@163.com.
3
Department of Applied Chemistry, College of Science, China Agricultural University, Beijing 100193, China. gzzbszf@163.com.
4
Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China. ccao@ippcaas.cn.
5
Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China. caolidong@caas.cn.
6
Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China. fmli@ippcaas.cn.
7
Department of Applied Chemistry, College of Science, China Agricultural University, Beijing 100193, China. dufp@cau.edu.cn.
8
Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China. qlhuang@ippcaas.cn.

Abstract

In this research, the maximum retention and wetting behavior of surfactant solutions (N-200, N-300, Tween-80, Morwet EFW, DTAB, SDS) on the surfaces of tea leaves was investigated based on surface free energy, surface tension, the contact angle, adhesion work, and adhesion force. The results showed that the contact angles of all surfactant solutions were kept constant with low adsorption at the tea leaf-liquid interfaces below 0.005%. With an increase in concentration, the contact angle of Tween-80 decreased sharply because the adsorption of molecules at the solid-liquid interfaces (ΓSL') was several times greater than that at the liquid-air interfaces (ΓLV). Adhesion work decreased sharply and then reached a minimum at the critical micelle concentration (CMC), but then increased until reaching a constant. Moreover, a high adhesion force did not indicate better wettability, as it does with rose petals and peanut leaves. For tea leaf surfaces, an increase in the contact angle brought about an increase in the adhesion force. In addition, the maximum retention for Morwet EFW is at different concentrations compared to N-200, N-300, Tween-80, DTAB, and SDS, where the maximum retention of Morwet EFW on tea leaves was 6.05 mg/cm2 at 0.005%.According to the mechanisms of wetting behavior on plant surfaces, a recipe for pesticide formulation can be adjusted with better wettability to reduce loss, improve utilization efficiency, and alleviate adverse effects on the environment.

KEYWORDS:

maximum retention; surfactants; tea leaves; wetting behavior

Conflict of interest statement

Funding: This research was funded by the National Key R&D Program of China, grant number (No. 2017YFD200302) and the Guizhou Science and Technology Infrastructure Program, grant number (No. [2017]2582).

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