This article analyzes the optimal conditions for the immobilization of Eriochrome Black T salt onto fibroin fiber derived from local silk waste, its chemical bonding mechanism, and its characterization through IR analysis, diffuse reflectance spectroscopy, and absorption properties. It was determined that 0.2 grams of fibroin fiber immobilizes 114.7 milligrams of Eriochrome Black T reagent within 30 minutes under optimal conditions of pH 2.11–5.65 and a temperature of 25–30 °C. By immobilizing Eriochrome Black T salt onto the fibroin fiber, a chemical sensor for the determination of metal ions in wastewater was developed. This chemical sensor has been created for the first time.