Batch and column studies on removal of methylene blue dye by microalgae biochar

Although industrialization helps us to advance in technology, it produces lots of unwanted pollutants that greatly affect our environment. Textile industries are the most concerned of all of these industries because they use a greater amount of water in their dyeing process and discharge enormous quantities of untreated coloured effluents into the water bodies. Chlorella vulgaris microalgal biomass was converted into biochar to utilize it as an environmental and economical adsorbent to remove dye from wastewater. Microalgal biomass was converted into biochar through the hydrothermal carbonization process at a temperature of 350 °C. The morphological characteristics of the produced biochar before and after methylene blue dye adsorption were analysed using scanning electron microscopy (SEM) analysis. The batch adsorption studies for the removal of well-known methylene blue dye from an aqueous solution were performed by varying parameters. The maximum amount of dye removed by the biochar was 85.74% at an initial dye concentration of 100 ppm, contact time of 60 min, temperature of 30 °C, biochar dosage of 3 g and pH 7, respectively. The adsorption isotherm and kinetics study revealed that the adsorption process followed pseudo-second-order kinetics ( R 2 = 0.9976) with the Langmuir isotherm model ( R 2 = 0.9288). Furthermore, the column adsorption studies were conducted by varying the beads and bed height. When compared to control beads and hybrid beads, the encapsulated beads showed higher removal efficiency of 98% at 60 min. The bed depth service time model was used to optimise column parameters such as initial dye concentration, bed height and flow rate. From this study, it is evident that the Chlorella vulgaris microalgae can be effectively utilized for the production of biochar that has higher dye adsorption efficiency.