Optimization of Synthetic Dye Decolorization Using Agro-Waste-Derived Biocoagulants

Synthetic dyes in industrial effluents pose serious environmental and health risks due to their toxicity and persistence. Conventional chemical coagulants are effective but costly and may cause secondary pollution, prompting the search for sustainable alternatives. This study evaluates agro-waste-based biocoagulants like walnut husk powder (WHP) and date seed powder (DSP), and synthetic coagulant for removing dyes from water. The materials were characterized by Fourier-transform infrared spectroscopy and Scanning Electron Microscopy.

Using Box–Behnken design and response surface methodology, coagulation–flocculation was optimized by varying pH, coagulant dose, and settling time. WHP achieved 89.48% removal of methylene blue at pH 9 and 1000 mg·L⁻¹, while DSP removed 84.12% of malachite green at pH 8.7 and 493.8 mg·L⁻¹. These findings highlight WHP and DSP as effective, eco-friendly, and low-cost alternatives for sustainable dye removal and agro-waste valorization.