Application of red-mud based ceramic media for phosphate uptake from water and evaluation of their effects on growth of Iris latifolia seedling.

In the present study, we have produced red-mud based ceramic media (RMCM) as an adsorbent for removal of phosphate from aqueous solutions, and their application in a constructed wetland. Phosphate adsorption to RMCM was investigated by varying initial phosphate concentration, contact time, and temperature. Adsorption of phosphate to the surface of RMCM was confirmed by scanning electron microscope and energy dispersive X-ray spectroscopy. The surface area and pore volume of RMCM decreased significantly after phosphate adsorption. Experimental equilibrium data followed Langmuir and Sips model better than the Freundlich model. Kinetic data followed both pseudo first order and pseudo second order reactions. Thermodynamics suggested the phosphate adsorption process onto RMCM to be endothermic and spontaneous, and physisorption dominated. Fourier transform infrared spectrumof phosphate adsorbed RMCM did not show any PO specific bands thus ruling out role of chemical forces in phosphate adsorption. Overall, phosphate adsorption on RMCM was driven by physisorption. The RMCM promoted biomass growth and increased the surface area of roots in Iris latifolia. Together with RMCM, I. latifolia augmented removal of phosphate from aqueous solution. Based on their phosphate removal performance and plant-growth promoting effects, we believe that RMCM can be effectively used in constructed wetlands.