Highly efficient removal of hazardous aromatic pollutants by micro-nano spherical carbons synthesized from different chemical activation methods: a comparison study
Glucose-derived micro-nano spherical activated carbon (GAC) was synthesized through two-stage and three-stage chemical activation processes in different impregnation ratios (K2CO3: precursor). GAC was characterized by nitrogen adsorption/desorption isotherm, point of zero charge, scanning electron microscope, and Fourier transform infrared. The prepared spherical GAC and commercial non-spherical AC were applied to remove a cationic dye (methylene green 5; MG5), an anionic dye (acid red 1; AR1), and phenol. The batch adsorption experiments were conducted to analyse the effects of different operation conditions (i.e. solution pH, contact time, initial adsorbate concentration, temperature, and desorbing agent) on the adsorption process. The adsorption equilibrium was rapidly reached in kinetic experiments with a removal rate of 47–83% (within 1 min). The three-stage process-synthesized GAC exhibited the highest adsorption capacity, with the maximum adsorption capacity reaching at 1365 mg/g for MG5, 562 mg/g for AR1, and 322 mg/g for phenol adsorption. The process of MG5 and AR1 adsorption was endothermic (+ΔH°), while phenol adsorption was exothermic (–ΔH°). The primary adsorption mechanism was pore filling and π-π interactions. The pore of spherical GAC might be easily enlarged than that of non-spherical AC when the temperature of solution increased. Therefore, the spherical activated carbon can server as a green promising and renewable adsorbent for efficiently remove hazardous aromatic pollutants from aquatic environment.
