Optimized adsorptive removal of polycyclic aromatic hydrocarbons from wastewater by low-cost adsorbent using response surface methodology-central composite design.

Polycyclic aromatic hydrocarbons (PAHs) are priority persistent organic pollutants (POPs) due to their toxicity, mutagenicity, and environmental persistence. This study developed a low-cost adsorbent from waste low-density polyethylene (LDPE), carbonized at 500 °C, activated with ZnCl2, and modified with β-keratin extracted from chicken feathers. The keratin-modified LDPE adsorbent (KMLDPEA) was compared with the unmodified LDPE (UMLDPEA). SEM/EDX revealed carbon enrichment from 75.52% to 84.87% for KMLDPEA and 57.45% to 70.06% for UMLDPEA post-adsorption, while FTIR confirmed hydroxyl (3255-3456 cm⁻1) and aromatic (1417-1869 cm⁻1) groups enhancing PAH affinity. Adsorption of five priority PAHs (naphthalene, fluorene, anthracene, fluoranthene, pyrene) was optimized using response surface methodology-central composite design (RSM-CCD) across pH (3-10), dosage (0.2-1.0 g), contact time (10-50 min), temperature (27-37 °C), and concentration (0.01-0.5 mg/L). Optimal conditions (pH 7, 0.8 g, 40 min, 32 °C, 50 min, and 0.23 mg/L) achieved 82-91% removal with KMLDPEA and 65-74% for UMLDPEA. GC-MS confirmed residual PAHs < 0.00001 mg/L, meeting NESREA/SON discharge standards. These findings highlight keratin-modified and unmodified LDPE adsorbents as a sustainable, high-performance activated carbon for industrial PAHs remediation.