<p>This study presents a comprehensive experimental and theoretical investigation of Catechol adsorption onto pinecone-derived activated carbon (PB600) for water remediation applications. Adsorption equilibrium data were modeled using four statistical physics-based isotherm formulations, systematically fitted to the experimental results. Convergence was evaluated through rigorous error analysis using reduced chi-square (χ²), residual sum of squares (RSS), coefficient of determination (R²), and adjusted <InlineEquation ID="IEq200"> <EquationSource Format="TEX">\(\text R^2_\text{adj}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mtext>R</mtext> <mtext>adj</mtext> <mn>2</mn> </msubsup> </math></EquationSource> </InlineEquation>. Among the tested scenarios, the monolayer adsorption model with a single energy level provided the best fit, revealing a maximum adsorption capacity (<i>Q</i>ₘₐₓ) of 263.8 mg·g⁻¹ at 298 K. The stereographic analysis showed that the occupation number (<i>n</i>) remained below unity across all temperatures, indicating a horizontal molecular orientation and a multi-point attachment mechanism on the adsorbent surface. The thermodynamic insights derived from the accurate model parameters revealed that surface accumulation is exothermic and spontaneous, as evidenced by the negative values of internal energy and Gibbs free energy. The adsorption energy values remained consistently below 40 kJ·mol⁻¹, confirming that the process is driven by physisorption involving van der Waals forces, π–π interactions, and hydrogen bonding. Additionally, entropy increased with both temperature and concentration, suggesting enhanced molecular disorder at higher loading. A temperature-driven transition in adsorption behavior was observed around 302 K, beyond which the density of receptor sites (<i>N</i>ₘ) increased sharply, indicating thermally induced structural changes in the adsorbent and improved site accessibility. The outcomes demonstrate the potential of PB600 as a high-performance and renewable bio-adsorbent. Its strong adsorption capacity under moderate conditions, combined with low-energy binding characteristics, positions it as a promising material for scalable, eco-friendly treatment of phenolic pollutants. These findings support future development of hybrid or modular filtration systems tailored for real-world applications in industrial and decentralized water purification.</p>