Preparation, RSM Optimization and Awareness of Orange-Peel - Activated Carbon for Effective Phenol Adsorption from Water

Abstract

Phenolic compounds are priority aquatic pollutants due to their high toxicity (LD₅₀ ≈ 317 mg kg⁻¹), persistence in conventional treatment processes, and secondary pollution potential. Adsorption is a promising remediation strategy; however, the performance of orange-peel-derived activated carbon (OPAC) varies with activation methods, and systematic optimization is limited. In this study, OPAC was synthesized via a single-step phosphoric acid activation at 400 °C for 60 min. Its suitability for phenol adsorption was confirmed through Brunauer-Emmett-Teller (BET) analysis (812 m² g⁻¹, primarily mesoporous), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD). Batch adsorption experiments were optimized using Box Behnken response surface methodology, considering pH (1.2–8.8), contact time (30–150 min), adsorbent dose (0.2–2 g L⁻¹), and initial phenol concentration (10–50 µg L⁻¹). Optimal conditions (pH 5, 150 min, 2 g L⁻¹, 10 µg L⁻¹) achieved 96.9% phenol removal. Adsorption kinetics followed a pseudo-second-order model (R² = 0.995), and equilibrium data fitted the Langmuir isotherm (maximum adsorption capacity: 10.1 mg g⁻¹). Thermodynamic analysis indicated spontaneous physisorption (ΔG° = −18.4 kJ mol⁻¹). Reuse studies showed adsorption efficiency decreased to 82% after five cycles, maintaining phenol concentrations below 1 mg L⁻¹. A validated public awareness questionnaire (Cronbach’s α = 0.795, n = 32) demonstrated societal relevance. The combination of optimized adsorption performance and community awareness highlights OPAC’s practical potential for decentralized water treatment and policy adoption.