Synthesis of anti-photolysis lignin-based dispersant and its application in pesticide suspension concentrate.

In the formulation of pesticide Suspension Concentrate (SC), some photosensitive pesticides are easily decomposed in the preparation. In this study, a hindered amine modified lignosulfonate (SL-Temp) with anti-photolysis function was synthesized using 4-amino-2,2,6,6-tetramethylpiperidine (Temp) and Sodium Lignosulfonate (SL) to solve this problem. The obtained SL-Temp was used as a dispersant to prepare 5% SC of avermectin, which shows good physical stability. The decomposition rate of the avermectin in SC after accelerating hot storage is 0%, which is much lower than 6.1% when SL was used as the dispersant. After being exposed to UV irradiation for 60 hours, the highest retention rate of avermectin is 87.1% when SL-Temp was used as the dispersant, which is much higher than 73.6% when SL was used as the dispersant, and also higher than 76.3% when a small molecule antioxidant (BHT) was added to the formulation. QCM-D studies revealed that the SL-Temp adsorption layer on avermectin particles can compete to absorb partial ultraviolet rays, hinder the penetration of ultraviolet light, and scavenge the free radicals produced by photooxidation, so as to protect avermectin from degradation.

Preparation of self-dispersed lignin-based drug-loaded material and its application in avermectin nano-formulation.

In this work, the anionic and cationic lignin-based drug-loaded materials (SL/CTAB) with strong hydrophobicity were prepared by using Sodium Lignosulfonate (SL) via self-assembly. The obtained SL/CTAB was used as drug-loaded material and emulsifier to prepare avermectin nano-formulation, which can be automatically dispersed into nano drug-loaded nanospheres in water. The cold and hot storage experiments show that the physical and chemical stability of the nano-formulation is good. The nano-formulation exhibits controlled-release performance, and the cumulative release amounts range from 56.27% to 87.33% in 62 h. Meanwhile, the release rates slow down with increasing SL/CTAB dosage. After UV irradiation for 50 h, the retention rates of avermectin in the nano-formulation range from 46.67% to 63.41%, which is 2.18-2.96 times higher than commercial avermectin Emulsifiable Concentrate (EC). The experiment of simulated rainwater scour-resistance shows that the affinity of lignin-based nano-formulation to the Epipremnum aureum leaves is higher than EC formulation.

Synthesis of a Hindered Amine-Grafted Lignin-Based Emulsifier and Its Application in a Green Emulsifiable Concentrate.

4-Amion-2,2,6,6-tetramethylpiperidine (Temp) was grafted into sodium lignosulfonate (SL) to obtain hindered amine-modified lignosulfonate (SL-Temp). Then, the polymer surfactant (SL-Temp-CTAB) was prepared using cetyltrimethylammonium bromide (CTAB) and SL-Temp. Obtained SL-Temp-CTAB was used as an emulsifier to prepare a green emulsifiable concentrate (EC) of avermectin (AVM), which shows good emulsifying property and storage stability. The prepared AVM green EC can form AVM-loaded microspheres with nanometer particle size distribution after emulsification in water. After ultraviolet irradiation for 70 h, the AVM retention rate of the green EC prepared using SL-Temp-CTAB was 75.8%, which is much higher than that of commercial EC (0.4%) and the green EC prepared using unmodified SL (31.4%). Moreover, the AVM green EC prepared using SL-Temp-CTAB has slow-release performance, and the release equilibrium time is 5.3 times the commercial EC. Therefore, the newly prepared AVM green EC using a lignin-based functional emulsifier shows good antiphotolysis and slow-release performance compared to the traditional EC.