The removal efficiency of emerging organic contaminants, heavy metals and dyes: intrinsic limits at low concentrations

Abstract

In this work, we exploit Langmuir adsorption isotherms to compare the performance of different materials (adsorbents) in removing organic contaminants (adsorbates) from water. The removal efficiency observed reaches an intrinsic limit at low concentrations. We also demonstrate quantitatively how multi-step adsorption processes achieve better purification efficiency than single-step adsorption performed using much smaller amounts of adsorbent material. We demonstrate how such performance is strongly affected by adsorbent concentration. Only the use of both the parameters obtained from Langmuir adsorption isotherm (Q_m and K_L) modelling allows one to compare materials tested under different experimental conditions by different groups, whereas most published reviews focus only on Q_m which is rather limited for comparing the performance of different materials studied under different conditions. Finally, we present some guidelines for data reporting in future work and reviews.