Thiocyanate removal by metal impregnated activated carbon and mechanistic understanding

Abstract Activated carbons impregnated with metal-HCl containing aqueous solutions effectively eliminate thiocyanates. This study investigated the adsorption capability of thermally activated carbon (AC1), impregnated with metals like copper (AC2), zinc (AC3), iron (AC4) and zinc with HCl (AC5) for thiocyanate. The synthesized materials were analyzed using BET, SEM, FT-IR and X-ray Photoelectron Spectroscopy. The highest removal efficiencies were 59%, 73%, 80% and 93% for AC1, AC2, AC3, AC4 and AC5, respectively. Moreover, a batch-mode operation was used to investigate the equilibrium and adsorption kinetics of thiocyanate in aqueous solutions onto AC5 (carbon impregnated with HCl and zinc). A study was conducted to ascertain the impact of the initial dose and thiocyanate concentration. By contrasting the pseudo-first-order and second-order kinetic models, the study sought to assess the rate constants and adsorption mechanism of the thiocyanate system. The pseudo-second-order equation was successfully fitted by the kinetic data. The adsorption isotherm data is well-modelled by the Freundlich and Langmuir isotherms. Graphical Abstract