Characterization and adsorption performance of nano-hydroxyapatite synthesized from Conus litteratus waste seashells for Congo red dye removal

Abstract

In this research, nano-hydroxyapatite synthesized from Conus litteratus seashells (Ss/nHAp) and the potential of Ss/nHAp as an adsorbent for eliminating Congo Red (CR) dye from aqueous solutions were explored. The synthesized Ss/nHAp was subjected to characterization using various techniques, including XRD, XPS, FTIR, Raman, BET, FESEM etc. in order to understand the material thoroughly. Batch adsorption experiments were conducted to establish the optimal conditions for removing the dye, considering variables such as adsorbent dosage, contact time, pH and initial dye concentration. 85% of the CR dye was eliminated within a short span of 10 minutes using a minimal adsorbent dose of 0.1 g, under neutral pH and room temperature, showcasing its efficiency. The adsorption process adhered to pseudo second order kinetics and was best fitted by the Langmuir isotherm model, with a maximum adsorption capacity (q_max) of 24 mg g⁻¹. The material's reusability was demonstrated through regeneration studies, with efficiency slightly decreasing to 74% by the fifth cycle due to adsorbent loss. This study establishes Ss/nHAp as a low-cost, eco-friendly, and effective adsorbent for dye-contaminated water treatment, paving the way for future applications in industrial wastewater remediation.