Removal of Chromium(VI) from aqueous solution using guar gum–nano zinc oxide biocomposite adsorbent

• Published in: Arabian journal of chemistry 2017-05, Vol.10 (S2), p.S2388-S2398
• Main Authors: Khan, Tabrez A., Nazir, Momina, Ali, Imran, Kumar, Ajeet
• Format: Article
• Language: English
• Subjects: Adsorption; Chromium(VI); Guar gum–nanozinc oxide biocomposite; Isotherms; Kinetics; Thermodynamics
• ISSN: 1878-5352; 1878-5379
• DOI: 10.1016/j.arabjc.2013.08.019

Guar gum–nano zinc oxide (GG/nZnO) biocomposite was used as an adsorbent for enhanced removal of Cr(VI) from aqueous solution. The maximum adsorption was achieved at 50min contact time, 25mg/L Cr(VI) conc., 1.0g/L adsorbent dose and 7.0 pH. Langmuir, Freundlich, Dubinin–Kaganer–Radushkevich and Temkin isotherm models were used to interpret the experimental data. The data obeyed both Langmuir and Freundlich models (R2=0.99) indicating a multilayer adsorption of Cr(VI) onto the heterogeneous surface. The linear plots of Temkin isotherm showed adsorbent-adsorbate interactions. Moreover, the energy obtained from DKR isotherm (1.58–2.24kJ/mol) indicated a physical adsorption of the metal ions onto the adsorbent surface, which implies more feasibility of the regeneration of the adsorbent. GG/nZnO biocomposite adsorbent showed an improved adsorption capacity for Cr(VI) (qm=55.56mg/g) as compared to other adsorbents reported in the literature. Adsorption process followed pseudo-second order kinetics; controlled by both liquid-film and intra-particle diffusion mechanisms. Thermodynamic parameters (ΔGo, ΔHo and ΔSo) reflected the feasibility, spontaneity and exothermic nature of adsorption. The results suggested that GG/nZnO biocomposite is economical, eco-friendly and capable to remove Cr(VI) from natural water resources.