Alginate derived porous graphitic carbon for highly efficient remediation of sulfide from wastewater

Green and bio-derived porous graphitic carbon (PGC) materials were prepared through facile and sustainable method from calcium alginate natural polymer by pyrolysis at 900 degrees C under inert atmosphere and were used to explore the possibility for the remediation of sulfide from wastewater. The graphitic carbon were characterized by N2 adsorption-desorption isotherm, Transmission Electron Microscopy, Raman spectroscopy, Scanning Electron Microscopy, X-Ray Diffraction, Fourier Transform InfraRed spectroscopy and Elemental analysis. The existence of meso-pores in PGC formed by the destruction of ` egg box' model of calcium alginate leads to high meso-pore volume of 0.778 cc/g, comprising 96.77% of total pore volume. In order to evaluate the effectiveness of sulfide removal using PGC, the effect of contact time, initial concentration, dosage, ionic strength and equilibrium isotherms were studied at ambient temperature. The adsorption was fast and reached equilibrium within 3 h with chemisorption playing a significant role. 99.87% sulfide removal was achieved using 17.0 mg of PGC from an initial sulfide concentration of 45 mg/L. An increasing ionic strength (using calcium chloride) decreased the% sulfide removal, while sodium chloride hardly influenced the adsorption capacity. The kinetic studies obeyed pseudo-second-order model while Freundlich isotherm could well explain the equilibrium adsorption. The adsorption mechansims showed that-COOH groups present on PGC are responsible for the removal of sulfide from wastewater. Thus, bio-derived PGC offers promising benefits to the industry for problems associated with the treatment of hazardous sulfide waste water derived from the industrial processes along with easy access to clean water resources.