Sustainable adsorptive removal of eriochrome black T Dye using Cladophora glomerata biochar

Water contamination by synthetic dyes poses a serious threat to aquatic ecosystems and human health, thus urgently requiring cost-effective and sustainable remediation strategies. In this research work, Cladophora glomerata algae were pyrolyzed at a slow rate (10°C/min) at 350°C for two hours in order to produce high efficiency value-added biochar and were used for the removal of an azo dye called Eriochrome Black T (EBT) from water through adsorption. The adsorbent was characterized by using various physicochemical analyses and experimental techniques. According to proximate and EDS analysis, the chosen biochar is a rich source of nutrients, including Ca, K, Mg, and P as well as carbon (47.67 wt%), oxygen (40.04 wt%), and other elements. A higher yield of 67% means that less weight is lost during pyrolysis, which allows for the production of more amount of biochar. FTIR data show that Peaks at 3853 cm-1 and 2312 cm-1 in the spectra of biochar were linked to the stretching frequency of the OH group. The abundance of OH functional groups imparts a negative charge to the biochar, providing potential active sites for dye biosorption. SEM images identified diatoms on the algal surface, diatoms are a component of ash that are present in the biochar sample. The maximum dye uptake capacity (qm) was 58.55625 mg/g at pH 2, 60 ppm dye concentration, 0.1 g biochar dosage, and 120 min of equilibrium time at room temperature. The adsorption followed the Langmuir isotherm model (R² = 0.9711) and pseudo-second-order kinetics (R² = 0.9992, K₂ = 0.006139 g/mg.min, qt = 58.47953 mg/g). Thermodynamic analysis shows that the adsorption process is endothermic (ΔH° = 6.92621 KJ/mol-1) and spontaneous (ΔG° < 0). These results demonstrate that Cladophora glomerata-derived biochar is a highly efficient and sustainable adsorbent for removing synthetic dyes from water.