Super-fast removal of cobalt metal ions in water using inexpensive mesoporous carbon obtained from industrial waste material

Inexpensive functionalized porous carbon (PC-KF) as a sorbent was prepared from less useful petroleum matrix leftover and characterized by several analytical and spectroscopic methods. The sorbent is used for the removing Co²⁺ metal ion in water. The optimized conditions were applied: concentration 0.5 mg/L, contact duration 6 min, a dose of adsorbent 0.3 g/L, pH 7.0, and ambient temperature 25 ºC. The removal was very fast, with a maximum amount of 95.5% (1.59 mg/g). The sorption followed Freundlich, Temkin, and Dubinin–Radushkevich isotherm models, indicating multilayers sorption on the heterogeneous surface. The free energy (ΔG^∘) values have a good range and were found to be −2.30, −4.71, and −5.81 kJ/mol at 20 ºC, 25 ºC, and 30 ºC. The value of enthalpy (ΔH^∘) was −10.60 kJ/mol and entropy (ΔS^∘) value was -26.90 kJ/mol K; representing adsorption process is spontaneous as well as exothermic due to both negative values. The kinetics of the adsorption process was concluded to be pseudo-second-order. The sorption process worked at 6 min time and 8.0 pH and, hence, it can be assumed a fast removal method with the economy. Hence, the present method, based on the functionalized porous carbon, could be a good candidate for efficiently removing of Co²⁺ metal ions from polluted water.