Eco-friendly lauric acid-diisopropanolamine adjuvant for sustainable enhancement of 27 % Picloram herbicide efficiency

Abstract

Plant-derived adjuvants offer an environmentally friendly solution to reduce reliance on synthetic herbicides. This study developed the lauric acid-diisopropanolamine (LA-DIPA) synergist using food-grade coconut oil components (99 % purity) through a green synthesis process (atom economy: 91.7 %, E-factor: 0.79 kg waste/kg product) and systematically evaluated its physicochemical interactions with 27 % picloram oil dispersion concentrate (ODSC). The LA-DIPA synergist formulation (4.2 % lauric acid, 6.3 % diisopropanolamine, 13 % Span-80/Tween-80 [HLB 11], 76.5 % n-hexanol), optimized via single-factor experiments, significantly enhanced the herbicidal performance of 27 % picloram ODSC. It reduced the contact angle by 23.6 % (59.90° vs. control), lowered surface tension by 14.8 % (32.19 mN/m), shortened leaf penetration equilibrium time by 37 %, and increased droplet retention by 18.5 %. Bioassay results on Boehmeria nivea (B. nivea) demonstrated that LA-DIPA synergist decreased the ED₅₀ of 27 % picloram ODSC from 6.565 to 6.452 mg/L (p < 0.05), maintaining equivalent efficacy even at a 30 % reduced herbicide dosage (2.1 vs. 3 L/hm²). Mechanistic analysis revealed that LA-DIPA synergist disrupts the cuticular barrier and enhances apoplastic transport via amphiphilic action. Life cycle assessment indicated a 45.3 % reduction in carbon footprint (1.68 kg CO₂ eq/kg), with 60.2 % attributable to biogenic carbon sequestration. This study establishes a novel paradigm for sustainable agro-adjuvant development, aligning with 9 Green Chemistry Principles and addressing 3 UN Sustainable Development Goals (SDGs 12, 13, and 15).