Kinetics and capacities of non-reactive phosphorus (NRP) sorption to crushed autoclaved aerated concrete (CAAC)

Abstract

With growing interest in resource recovery and/or reuse, waste materials have been considered a promising alternative for phosphorus (P) adsorption because they are low-cost and easily accessible. Crushed autoclaved aerated concrete (CAAC), as representative construction waste, has been extensively studied for P removal in ecological technologies such as treatment wetlands. However, most of the previous studies focused on the adsorption of orthophosphate, namely reactive phosphorus, and lacked attention to non-reactive phosphorus (NRP) which is widely present in sewage. This study presents the first investigation on the potential and mechanism of CAAC removing four model NRP compounds. Adsorption isotherm and kinetics of NRP onto CAAC indicate that the removal of NRP was a chemisorption process and also involved a two-step pore diffusion process. The desorption experiment shows that different NRP species showed varying degrees of desorption. Most NRP was irreversibly adsorbed on CAAC. Among the model compounds considered in this study, the adsorption capacity and hydrolysis rate of organophosphorus were much less than that of inorganic phosphorus. Moreover, the adsorption of different NRP species by CAAC in the mesocosm study was different from the results of laboratory adsorption experiments, and the possible biodegradation was essential for the conversion and removal of NRP. The findings confirmed the validity of CAAC for NRP removal and the potential advantages of CAAC in terms of costs and environmental impact. This study will contribute to a better understanding of NRP conversion and environmental fate and that can be the basis for a refined risk assessment.