Assessment of iron and manganese removal by calcined clay–biomass composite media for decentralised water treatment

Abstract

Access to safe and affordable drinking water remains a major challenge in remote and regional communities, particularly in Australia. In Queensland, raw-water iron (Fe) and manganese (Mn) concentrations can exceed guideline values, reaching up to 13.6 mg/L and 61 mg/L, respectively. This study developed and evaluated KJ25 EcoPellets, a calcined clay–biomass composite produced from locally sourced brick-making clays and agricultural residues, as a potential low-cost medium for Fe and Mn removal. Batch experiments compared KJ25 with conventional media under varying pH, adsorbent dose, initial concentration and contact time. KJ25 demonstrated strong Fe removal and moderate Mn removal under the investigated conditions, generally outperforming the conventional media. Kinetic modelling showed that Fe and Mn uptake were better described by pseudo-first-order and pseudo-second-order models, respectively, with intraparticle diffusion contributing to the time-dependent uptake behaviour. Langmuir modelling provided strong fits for both Fe and Mn, with maximum adsorption capacities of 10.3 and 1.9 mg/g, respectively, highlighting the substantially greater capacity of KJ25 for Fe than Mn. Overall, the results demonstrate the potential of KJ25 EcoPellets as a locally manufacturable, circular-economy-aligned medium for decentralised Fe and Mn treatment, while further validation under real-water and continuous-flow conditions is required before practical drinking-water application.