(1) (2) where, A(ṽ)t is the integral ν(PO) absorbance at time t (min), A(ṽ)e is the predicted integral ν(PO) absorbance at adsorption or desorption equilibria, te is an arbitrary time (i.e., when Phase 1 was switched to Phase 2: te ≈ 37 min), and ka and kd are the adsorption and desorption rate constants (min -1 ), respectively. The concentrations of glyphosate, AMPA, glycine and sarcosine were measured in the effluents with a direct HILIC liquid chromatography mass spectroscopy (LC-MS) method. The instrumentation and details of the LC-MS methodology can be found in Text S1, SI. The concentrations of orthophosphate and ammonium in the effluents were measured using colorimetry. Total soluble Mn was measured using atomic absorption spectroscopy.