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

Reduction of Cr(VI) to Cr(III) by Activated Carbon Cloth through Adsorption and Electrochemical Processes

“…Most of the pores (88%) on CC were micropores, defined as pores with width <2 nm, based on IUPAC classification, and 12% of the pores on CC were mesopores, described by width in the interval of 2 and 50 nm. The pore size distribution of CC makes it a suitable material for the adsorption of chromate ions in solution because chromate ions have a radius of 0.5 nm , and can readily enter the pores on CC with radius larger than 0.5 nm. , The material properties of CC are summarized in Table .…”

“…The pore size distribution of CC makes it a suitable material for the adsorption of chromate ions in solution because chromate ions have a radius of 0.5 nm 45,46 and can readily enter the pores on CC with radius larger than 0.5 nm. 47,48 The material properties of CC are summarized in Table 1.…”

Variable diffusivity homogeneous surface diffusion model and analysis of merits and fallacies of simplified adsorption kinetics equations

“…The dimensionless time (TA) is: (72) where DA is the surface diffusion coefficient of the incoming ion (A). The parameter ai is the ratio of the surface diffusion coefficients of the incoming ion (A) to the ion initially in the solid phase (B).…”

“…Paterson's approximation has been used in isotopic exchange studies, as for example the exchange of sodium and cesium ions on hydrous zirconia [65], sodium and cesium ions on titanium(IV) antimonite [66], and molybdate ions on calcium molybdate [62]. Furthermore, it has been used for systems that follow non-linear isotherms, such as the removal of organic cations by clinoptilolite [67], the ion exchange of calcium on zeolite A [68], the ion exchange of several metals on clinoptilolite [69], the adsorption of a herbicide on bituminous shale [70], the adsorption of basic dye onto zeolitic materials synthesized from fly ash [63], the removal of U(VI) by hydrogels [64], the ion exchange of copper on weak acid resins [71], and the adsorption of Cr(VI) on sawdust [72]. A discussion on this issue is done later in this section.…”