Macroalgae and coal-based biochar as a sustainable bioresource reuse for treatment of textile wastewater

Conventional wastewater treatment technologies are energy-intensive and environmentally un-friendly due to the use of synthetic and expensive chemicals. This study investigates the potential of macroalgae and coal-based biochar (control) to remove methylene blue from simulated wastewater as well as real textile wastewater. The macroalgae and coal-based biochars adsorb more than 90% of methylene blue from simulated wastewater in only 10 min on their active surface sites. The distinct feature of the current study is that macroalgae-based biochar shows high dye removal efficiency (75%) even in real textile wastewater. Macroalgae-based biochar also shows 67% dye removal efficiency for second regeneration cycle. Langmuir isotherm (> R² = 0.954) and pseudo-second-order models (R² = 0.999) are well fitted to describe the monolayer homogenous biosorption and process kinetics, respectively. Thermodynamic analysis indicates that methylene blue biosorption on macroalgae and coal-based biochars is a spontaneous and endothermic process following physiosorption. The maximum biosorption capacity with macroalgae-based biochar is 353.9 mg g⁻¹ at 303 K, which is approximately 27% higher than any previous biochar study on the treatment of methylene blue. It demonstrates that macroalgae-based biochars can be used as a promising alternative adsorbent to activated carbon for textile wastewater treatment. [Figure not available: see fulltext.].