Nitrogen and Phosphorus Removal and Recovery from Municipal Wastewater by Means of Adsorption and Ion Exchange

This study focuses on the development of an adsorption/ion exchange process for the removal and recovery of nitrogen and phosphorus from municipal wastewater by means of two innovative materials, G13 geopolymer and Layered Double Hydroxide Pyroaurite. The adsorption isotherms indicate a favorable isotherm trend for both materials, with minimal variations observed before and after the breakthrough tests, highlighting their stable adsorption capacities over multiple cycles. G13 exhibited excellent selectivity for ammonium, achieving a high adsorption yield of 96% and an operating capacity of 8.42 mgN gdry resin−1 at the breakpoint. The N removal process with G13 demonstrated stability over five repeated adsorption/desorption cycles, even at reduced empty bed contact times (EBCTs) of 7.5 min and 5 min. The desorption step optimization led to a fractionated desorption, successfully separating Na+ and NH4+ fractions, with the means of KCl 0.13 N and KNO3 0.67 N. Pyroaurite exhibited exceptional phosphate selectivity, treating 665 bed volumes of municipal wastewater effluent at the BP with a 95% adsorption yield and a 7.5 mgP gdry resin−1 operating capacity. The material was effectively regenerated with NaOH 0.5 N. The study’s innovative contributions involve process optimization, scale-up to a pilot plant, and robust testing over multiple adsorption/desorption cycles.