The bio-adsorbent that I'm using has this weird behavior the first question is that I have been reading every quote online saying that non-linear fitting is a way better approach than linear fitting for me the linear fitting does not show good R^2 values except for Redlich-Peterson in every studied pH in linear form, but the R^2 Values for other linear models are between 95% and 85% for non-linear fitting this amount for the studied model of Langmuir, Freundlich, Sips, Temkin are worse between 94-70% the adj-R^2 values I am quite confused since the matter showed outstanding sorption capacity reaches equilibrium in less than 10 min showed high porosity and I believe that the adsorption process is multi-phase containing ion exchange, surface sorption, how can I interpret the adsorption isotherm

second question is that for redlich Peterson in linear form, i got 99.99% R square value but the plotted data is lnCe in X axis and ln(Ce/qe) y Axis the K parameter is missing i guess how can i find K parameter if this is right?