UV–Visible Spectrophotometric Evaluation of Activated And Pristine Cow Dung Bio-Adsorbents For Dye Removal

Abstract

The discharge of dye-containing wastewater from textile, printing, paper, and allied industries poses a significant environmental challenge due to the persistence and toxicity of synthetic dyes. The development of low-cost, eco-friendly, and sustainable adsorbents has become an important strategy for wastewater remediation. In the present study, pristine cow dung charcoal (CDC) and phosphoric acid-activated cow dung charcoal (ACDC) were investigated as bio-adsorbents for the removal of four synthetic dyes, namely Methyl Orange (MO), Methyl Red (MR), Thymol Blue (TB), and Eriochrome Black T (EBT), from aqueous solutions. The prepared adsorbents were characterized using X-ray diffraction (XRD) to investigate their structural characteristics. Adsorption performance was evaluated using UV–Visible spectrophotometry under optimized experimental conditions. The reduction in absorbance after adsorption confirmed the removal of dye molecules from aqueous media. Activated cow dung charcoal exhibited higher adsorption efficiency than pristine cow dung charcoal for all investigated dyes. The highest removal efficiency was observed for Eriochrome Black T, followed by Methyl Orange, Thymol Blue, and Methyl Red. The enhanced adsorption performance of ACDC may be attributed to the development of additional active adsorption sites and changes in the surface characteristics induced by phosphoric acid activation. The findings demonstrate that activated cow dung charcoal is an inexpensive, renewable, and environmentally sustainable adsorbent with considerable potential for wastewater treatment applications. This study further highlights the conversion of agricultural waste into value-added adsorbent materials and supports sustainable circular-economy approaches for industrial wastewater management.