Preparation of hierarchical porous activated carbons from different industrial lignin for highly efficient adsorption performance

Business cost concern of solid adsorbents has motivated the production of porous activated carbons from waste biomass materials. In this work, three hierarchical porous activated carbons (HPAC) are obtained using hardwood alkali lignin (HPAC-H), sodium lignosulfonate (HPAC-L), and softwood alkali lignin (HPAC-S) as precursors and potassium hydroxide (KOH) as inorganic template and activation agent. their morphology and structure are characterized by Scanning electron microscopy (SEM), Nitrogen adsorption/desorption isotherms, X-ray diffraction spectroscopy (XRD), the Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS). Furthermore, the microscopic morphology of HPAC-H is rough surface with irregular pores and channels with uniform diameters; HPAC-L is hollow spheres of different sizes; and HPAC-S is solids particles with honeycomb pores. And they have a hierarchical porous structure with macro-meso-micropore. Moreover, HPAC-H exhibits the highest specific surface area (2852 m(2)center dot g(-1)), the largest total pore volume (1.50 cm(3)center dot g(-1)) and the highest oxygen content (10.61 at%) as compared to HAPC-L (2397 m(2)center dot g(-1), 1.37 cm(3)center dot g(-1), and 9.13 at%) and HAPC-S (2518 m(2)center dot g(-1), 1.41 cm(3)center dot g(-1), and 9.59 at%). In adsorption tests, the adsorption data of three activated carbons fits well with the Langmuir and Freundlich equations. The maximum methylene-blue (MB) adsorption capacity onto HPAC-H, HPAC-L, and HPAC-S calculated by Langmuir equation is 1671.66 mg center dot g(-1), 1182.84 mg center dot g(-1), and 1409.32 mg center dot g(-1), respectively. The excellent absorption capacity should be benefited from high surface area, the improved interconnected macro-meso-microporous framework and enriched surface functional groups. The obtained high-performance hierarchical porous activated carbons can afford a noteworthy potential for removing dye from wastewater.