Cellulose and wood derived activated carbons from Pinus sylvestris: comparative performance in methylene blue adsorption

Abstract

This work describes the preparation of eco-friendly activated carbons from redwood (Pinus sylvestris L.) sawdust and cellulose extracted from the same source, activated with H₃PO₄ under optimized carbonization conditions. The materials were comprehensively characterized by FTIR, SEM, TGA, XRD, and BET analyses, revealing superior textural uniformity and surface functionality for the cellulose-derived carbon (AC-CRW) compared with its wood-based counterpart (AC-RW). Adsorption experiments demonstrated consistently higher methylene blue uptake by AC-CRW, with the Langmuir isotherm and pseudo-first-order kinetics providing the best fit. Under optimal conditions (24 h impregnation, 1 : 2 impregnation ratio, 650 °C), AC-CRW achieved a maximum capacity of 314.07 mg g⁻¹, markedly surpassing AC-RW (218.78 mg g⁻¹). Thermodynamic analysis further confirmed that adsorption was spontaneous, endothermic, and entropy-driven, with higher ΔH° and ΔS° values for AC-CRW underlining its superior thermal sensitivity. Regeneration tests showed excellent reusability, with AC-CRW retaining 93.5% of its initial efficiency after five cycles. These findings highlight the benefit of cellulose isolation in tailoring porous carbons and establish Pinus sylvestris-derived activated carbons as sustainable, high-efficiency adsorbents for dye-contaminated wastewater treatment.