OPTIMIZATION OF MICROWAVE-ASSISTED HYDROTROPIC FRACTIONATION OF RAMIE (Boehmeria nivea L.) USING RESPONSE SURFACE METHODOLOGY

The optimization of the fractionation of ramie fiber using microwave assistance and a urea solution as the hydrotropic agent was evaluated in this study through response surface methodology (RSM). A central composite design, a commonly used matrix design in RSM, was implemented. The independent variables for this research included the liquid-to-solid ratio, hydrotrope concentration, and duration of hydrotropic fractionation. At the same time, the yield, lignin content, and cellulose content of the pulp served as the dependent variables. A series of second-degree polynomial equations were developed to establish the relationship between pulp yield, lignin content, and cellulose content with the parameters of the fractionation process, including both the antagonistic and synergistic effects of these parameters. The significance of the process parameters was determined through the analysis of variance, and information regarding the most influential variables on pulp yield, lignin content, and cellulose content was derived from Pareto charts. The highest yield of the fractionation process was achieved with microwave-assisted fractionation of ramie fiber at a liquid-to-solid ratio of 43.40, a hydrotrope concentration of 36.82, and a fractionation time of 73.63 minutes. The lowest lignin content in the pulp was obtained during microwave-assisted fractionation at a liquid-to-solid ratio of 25.59, a hydrotrope concentration of 3.18, and a fractionation time of 6.36 minutes. Conversely, the maximum cellulose content in the pulp was realized during microwave-assisted fractionation at the same liquid-to-solid ratio of 43.40, hydrotrope concentration of 36.82, and fractionation time of 73.63 minutes. © 2025, Publishing House of the Romanian Academy. All rights reserved.