Activated carbons from waste Cassia bakeriana seed pods as high-performance adsorbents for toxic anionic dye and ciprofloxacin antibiotic remediation

Waste Cassia bakeriana seed pods were used for porous carbon production in a facile pyrolysis process. The carbons were highly efficient adsorbents for methylene blue, congo red and ciprofloxacin antibiotic from aqueous media. The experimental results demonstrated that despite moderate surface area of 283.4 m2/g, KOH activated carbon (PSAC-KOH) exhibited the highest adsorption capacity for congo red reported to date for carbon-based adsorbents (970 mg/g). PSAC-KOH also demonstrated a high adsorption capacity at 600 mg/g for ciprofloxacin. Raman spectroscopy, X-ray diffraction and X-ray Photoelectron spectroscopy analysis of the carbons demonstrated an extensive graphitic characteristic, while Fourier transform infrared spectra of PSAC-KOH suggested a high proportion of aromaticity which promotes adsorption mechanisms including electrostatic and π-π interactions. Pseudo-second-order kinetic model fitting suggested a rate-controlling chemisorption mechanism. The utilization of waste Cassia bakeriana seed pods for carbon production may create new opportunities to develop sustainable and highly efficient adsorbents for water remediation.