Effective Microporosity for Enhanced Adsorption Capacity of Cr (VI) from Dilute Aqueous Solution: Isotherm and Kinetics

Abstract

The adsorbent pore structure significant to enhanced adsorption capacity of Cr (VI) from dilute aqueous solution is evaluated. As reference, low-cost micro-mesoporous activated carbon (AC) of high basicity, mesoporosity centred about 2.4 nm, and effective microporosity centred about 0.9 nm was tested for removal of Cr (VI) from dilute aqueous solution in batch mode. At pH 2 the low-cost AC exhibited highly improved Langmuir Cr (VI) capacity of 115 mg/g which was competitive to high performance commercial AC. A Comparison with treated characterization results of literature adsorbents/ACs showed that moderate to high effective micropore volume of average pore-size about 0.9 ± 0.1 nm is critical for increased adsorption capacity of Cr (VI) from dilute aqueous solutions. The mesostructure of the tested low-cost AC was associated with rapid kinetics that was fitted by the Pseudo-second kinetics model. While Biot numbers suggested slight significant contribution of intraparticle diffusion. It is hoped that this study may be a useful contribution to development of effective adsorbents for the efficient abatement of toxic Cr (VI) from wastewater and water.