Environmental Technology & Innovation 11 (2018) 49–63 Contents lists available at ScienceDirect Environmental Technology & Innovation journal homepage: www.elsevier.com/locate/eti Efficiency of waste clinker ash and iron oxide tailings for phosphorus removal from tertiary wastewater: Batch studies Thandie Veronicah Sima a, b , Moatlhodi Wise Letshwenyo a, b, *, Lesedi Lebogang a, c a Botswana International University of Science and Technology, Faculty of Engineering and Technology, Botswana b Department of Civil and Environmental Engineering, Botswana c Faculty of Sciences, Department of Biological Sciences and Biotechnology, Private Bag 16, Palapye, Botswana highlights • Adsorption of phosphorus onto iron oxide tailings and clinker ash. • Adsorption onto both media was described by Pseudo second order model. • Intraparticle diffusion was not solely controlling the rate of adsorption. • Tailings and clinker capacities were 1.29 mg P g −1 and 0.29 mg P g −1 respectively. • Tailings had greater potential for regeneration compared to clinker ash. article info Article history: Received 7 September 2017 Received in revised form 9 April 2018 Accepted 17 April 2018 Available online 25 April 2018 Keywords: Adsorption Phosphorus removal Clinker ash Iron oxide tailings abstract Phosphorus removal from wastewater using waste materials as novel adsorbents has been gaining attention. This work exploits and compares phosphorus adsorption capacities of iron oxide tailings and clinker ash waste from the copper–nickel mine (BCL LTD) in Botswana. The surface heterogeneity of the media was investigated using scanning electron microscope, which revealed a highly porous structure of clinker ash as compared to iron oxide tailings. The chemical and mineralogical composition was determined using the X-ray Fluorescence and X-ray Diffractometer respectively. The adsorption kinetics, equilibrium isotherms and regeneration potential of the media were investigated through batch experiments at room temperature using real wastewater. XRF results revealed 25.1% of iron oxide in tailings and 5.3% for clinker ash. The concentrations of aluminium oxide were 5.4% and 11.7% for tailings and clinker ash respectively. Small amounts of phosphorus were present in both media before the experiment and there was an increase of phosphorus in used tailings whereas in clinker ash there was a reduction of phosphorus suggesting retention of phosphorus by tailings and desorption by clinker ash. Pseudo second order model best described the kinetics of adsorption onto both media with R 2 values of 0.99 for both media compared to pseudo first values of 0.98 and 0.96 for tailings and clinker ash respectively, suggesting that chemisorption was the dominant force. Intra-particle diffusion model revealed that intra-particle diffusion was not the solely rate controlling mechanism but other mechanisms such as mass transfer were involved as well. The equilibrium data for both iron oxide tailings and clinker ash were best described by Langmuir model, which suggested a monolayer adsorption process with homogeneous distribution of energies. The batch results (Langmuir) indicate that iron oxide tailings have * Corresponding author at: Botswana International University of Science and Technology, Faculty of Engineering and Technology, Botswana. E-mail addresses: thandie.sima@studentmail.biust.ac.bw (T.V. Sima), letshwenyom@biust.ac.bw (M.W. Letshwenyo), lebogangl@biust.ac.bw (L. Lebogang). https://doi.org/10.1016/j.eti.2018.04.008 2352-1864/© 2018 Elsevier B.V. All rights reserved.