Chromium(VI) adsorption by Codium tomentosum: evidence for adsorption by porous media from sigmoidal dose–response curve
2018
Anandaraj, B. | Eswaramoorthi, S. | Rajesh, T. P. | Aravind, J. | Suresh Babu, P.
Adsorption of Cr(VI) using native and chemically modified marine green macroalgae Codium tomentosum biomass and its adsorption kinetics were studied under specific conditions. Maximum Cr(VI) removal occurred at pH 2 for both untreated and acid-treated biomass. However, base-treated biomass exhibited maximum adsorption at pH 6 due to the hydrolysis of methyl esters present in the cellulose, hemicellulose and lignin molecules resulting in carboxyl groups (COO⁻) on the surface. The effect of adsorbent dose revealed that untreated and acid-treated biomass follows Henry’s linear isotherm, while base-treated biomass exhibited sigmoidal curve indicating energetic heterogeneity on the adsorbing surface. The monolayer adsorption capacity of untreated, acid-treated and base-treated biomasses was 5.032 ± 0.644, 5.445 ± 0.947, 3.814 ± 0.559 mg g⁻¹, respectively. Adsorption was found to follow Ho and McKay’s pseudo-second-order kinetic model with decreasing pseudo-second-order rate constant (K ₂, g mg⁻¹ min⁻¹) of 0.088 ± 0.037 (acid-treated), 0.019 ± 0.003 (untreated) and 0.012 ± 0.003 (base-treated).
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