Graphene oxide–coated pyrolysed biochar from waste sawdust and its application for treatment of cadmium-containing solution: batch, fixed-bed column, regeneration, and mathematical modelling

Cadmium being a heavy metal, which is also a known pollutant, had a wide variety of usage in many industries like electro-plating industries, phosphate fertilizers, batteries, mining, stabilizers, pigments, and alloys. In this study, sawdust was used to produce the nanocoated adsorbent. Sawdust is non-hazardous low-cost waste materials and easily available. Thermally activated biochar was produced from sawdust and coated with graphene oxide nanomaterials in two different methods, and the synthesized nanocomposite was used to remove cadmium present in solution. Batch study was performed to optimize different parameters for better removal. Experiments were performed and the best condition optimized for removal of cadmium was found to be pH 7.5 and temperature 35 °C or 308.15 K, with 1 g/L adsorbent dose, and within 2 h, i.e. 120 min, above 55.68 mg/g removal capacity was attained with initial metal concentration of 50 mg/L. The modified saw dust composite was more effective in removal of cadmium than the normal sawdust-based composites. The characterization of the nanocomposite was done to know the internal structure of the composite. The continuous fixed-bed column study was performed, and the study followed Admas–Bohart model. The batch and column study results showed that this nanocoated composite can be an alternative for the treatment of pollutant present in the solution. The regeneration of the composite showed a sustainable use of the composite for the treatment of pollutant.