Use of Corn Oil as an Alternative Medium in Cotton Dyeing with Direct Dyes: Reducing Salt and Water Usage and Assessing Oil Reusability

Alternative methods, such as the use of vegetable oils, are being evaluated to reduce water consumption in textile dyeing processes. This study assessed the effectiveness of using corn oil in dyeing cotton with direct dye, aiming to reduce salt concentration and allow oil reuse. Initially, the oil-to-water ratio was investigated, and dyeing with 70% oil and 30% water resulted in the highest color strength, with a K/S value of 13.74 ± 0.58. At the same time, the conventional process yielded a K/S of 12.87 ± 0.77. Subsequently, salt concentration was reduced by 50%, achieving a K/S of 16.91 ± 0.77. Regarding FTIR analyses, no changes were observed in the transmittance bands of oil-based dyeing compared to the conventional process. The possibility of reusing corn oil was studied for the 70% oil and 30% water formulation with a 50% reduction in salt. After three dyeing cycles, the K/S obtained showed no significant difference from the first dyeing cycle, demonstrating the feasibility of reusing corn oil. The kinetic studies showed that dye adsorption mechanisms on the substrate, in both aqueous and oily phases, follow a pseudo-first-order kinetic model. The isotherm analyses revealed that the Langmuir model was most suitable to represent dyeing in the aqueous phase, indicating favorable adsorption and dye-fiber solid interaction. In contrast, data from the oily phase did not fit well with the Langmuir or Freundlich models. This may be attributed to dyeing occurring through the aqueous phase. In contrast, the oily phase serves only as a transport vehicle for the dye, without direct interaction between the dye and fiber.