Application of oxidised activated red mud to treat phosphorus-contaminated water

Environmental context Red mud originating from Vietnam is used in the treatment of phosphorus-contaminated water. Suitability of a pseudo first order (PFO) model to describe the kinetics of phosphorus adsorption on O-RM was confirmed, with the adsorption process reaching an equilibrium after 20 min. Findings of this study will contribute to the industrial application of low-cost materials in wastewater treatment. Rationale Oxidised activated red mud (O-RM) materials have a high adsorption capacity for phosphorus, are easy to synthesise, are low-cost, have a short adsorption time and are readily applicable in practice. Methodology Morphological and compositional analysis of O-RM materials was performed by energy-dispersive X-ray (EDS), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Surface area and porosity was examined by Brunauer, Emmett and Teller (BET) method as well as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Phosphorus content was measured by a colourimetric method based on the ISO 6878:2004 standard. Results This study investigated the activation process of red mud using an oxidation method at a temperature of 373.15 K (100°C). The O-RM has a large surface area with preserved key components such as FeO(OH), Fe2O3, AlO(OH), and Al(OH)3. As a result, O-RM became an efficient adsorbent for phosphorus with high adsorption capacity (218.15 mg g−1) and short adsorption time (20 min). O-RM is inexpensive, easy to synthesise, stable, reusable and environmentally friendly material which makes it a highly promising option for treating phosphorus-contaminated wastewater. Discussion The morphology and chemical composition of O-RM including FeO(OH), Fe2O3, AlO(OH) and Al(OH)3 was confirmed. Factors affecting the phosphorus adsorption process onto the O-RM, such as pH, contact time, adsorption thermodynamics, stability, reusability of the material and the influence of other ions, were also studied and validated.