Na ₂ CO ₃ solid-state impregnation of Prunus Endoocarp Biochar (PEB) for enhanced removal of naphthalene from aqueous solution: characterisation and optimisation modelling

This study presents a greener and sustainable approach by developing an efficient adsorbent from Prunus Endocarp Biochar (PEB), modified through solid-state impregnation with sodium carbonate (Na2CO3@PEB). The synthesised adsorbents were evaluated for the removal of naphthalene from aqueous solutions using laboratory-scale batch experiments. Surface characterisation by Scanning Electron Microscopy, Brunauer–Emmett–Teller and Fourier Transform Infrared Spectroscopy confirmed successful modification of PEB. SEM images revealed a microporous structure with irregular pore distribution, while BET analysis showed a significantly enhanced surface area of 128.83 m2 g−1 for Na2CO3@PEB. FTIR spectra indicated the presence and shifting of functional groups responsible for effective surface interactions. Optimisation was done at various experimental conditions and achieved maximum removal efficiency of 99.3% at pH 5.5, contact time of 60 min, 10 mg/L initial concentration and 0.025 g/L adsorbent dose. The Na2CO3@PEB exhibited a higher monolayer adsorption capacity (115.4 mg/g) compared to pristine PEB (95 mg/g). Adsorption data fitted well with the Langmuir isotherm, supports monolayer adsorption, while kinetic analysis followed a pseudo-second-order model, supporting chemisorption. Thermodynamic studies also confirmed that the process is spontaneous and endothermic with increased randomness during adsorption. Thenceforth, a Na2CO3@PEB stands a strong potential as a sustainable and eco-friendly adsorbent for naphthalene removal from wastewater.