Triclosan is a broad-spectrum bacteriostat and an antimicrobial agent popularly used in hygiene and health care products. The current paper presents a cost-effective and simpler process of synthesis of triclosan from 2,5-dichlorophenol and potassium 2,4-dichlorophenolate by using p-xylene as a solvent under solid-liquid phase transfer catalysis (S-L PTC), at 120 degrees C. It leads to 100% selectivity of the product ill comparison with a liquid-liquid PTC process. A novel mathematical model is developed to determine simultaneously the rate constant and anion exchange equilibrium Constant from the same set of data. This will be helpful in reactor design and scale-up. The activation energy and Gibbs free energy for a combined ion exchange and partitioning of ion pairs are calculated.