In most sites I find online, I see that the Gibbs free energy of adsorption is negative. But, it is also said that physisorption is a reversible adsorption, suggesting that $\delta G=0$ which contradicts the original premise.
Hence, what exactly is the correct free energy change associated with physisorption?
From comments I learn that the reversibility is not used in the conventional thermodynamics sense but rather in the chemical reaction sense (refer). But, I don't see how it applies here since physisorption doesn't involve any bond formation.
NCERT chapter claiming the $\delta G = 0$ and reversibility condition