Highly porous biobased graphene-like carbon adsorbent for dye removal: Preparation, adsorption mechanisms and optimization

Dyes containing wastewater are generally produced in enormous quantities by the textile, dyeing, paper and pulp, tannery, and paint industries. Adsorption is used widely for dye removal because it is easily applied, non-toxic, inexpensive, and highly efficient. Graphene and graphene-based materials are attractive adsorbents, owing to their high specific surface areas and strong pi-pi interactions. However, graphene production process is demanding, costly, and requires several toxic chemicals. Thus, uncomplicated, and economical graphene-like carbon preparation by biomass pyrolysis has attracted attention. In this study cellulose-derived graphene-like carbon (CGLC) was obtained by pyrolyzing cellulose with FeCl3/ZnCl2. FeCl3 facilitates the synthesis of CGLC via the template effect, while ZnCl2 can produce a porous structure. The CGLC produced was characterized using the Brunauer-Emmett-Teller method, scanning electron microscopy, X-ray diffraction, Raman, Fourier transform infrared, and X-ray photoelectron spectroscopic analyses. We confirmed that the CGLC had a low ID/IG of 0.64 and a crystalline structure when cellulose was pyrolyzed with FeCl3. In addition, ZnCl2 produced a porous CGLC with high specific surface areas (2069.22 m(2) g(-1)). The CGLC was then used for adsorptive cationic and anionic dye (Rhodamine B and Congo Red) removal to investigate its applicability as an adsorbent. The maximum CGLC adsorption capacities for Rhodamine B and Congo Red were 572.8 and 220.7 mg g(-1), respectively, which indicate that CGLC can remove both cationic and anionic dyes. The adsorption mechanism may involve physical adsorption, such as pi-pi interactions and van der Waals bonds.