Adsorption of Au(III) from aqueous solution using cotton fiber/chitosan composite adsorbents

Two kinds of cotton fiber/chitosan composite adsorbents (SCCH and RCCH) were employed to adsorb Au(III) ions from aqueous solution. The adsorption kinetics and adsorption isotherms of the two fibers for Au(III) were investigated. The experimental results revealed that the adsorption kinetics of SCCH and RCCH fibers for Au(III) was described by the pseudo second-order reaction model. The adsorption isotherm data of Au(III) on the surface of SCCH and RCCH fibers were fitted by linear and non-linear methods of the Freundlich, Langmuir and Redlich-Peterson isotherms. The results confirmed that both linear and non-linear forms of the above-mentioned three models can be used to describe adsorption of Au(III) on the surface of the two fibers and to predict the isotherm parameters. The linear Langmuir and non-linear Langmuir and Redlich-Peterson models are best-fit isotherms for the experimental data. Redlich-Peterson is a special case of Langmuir when the Redlich-Peterson isotherm constant g is set equal to unity. The investigation of adsorption selectivity showed that the SCCH and RCCH fibers displayed strong affinity for gold in the solution and both exhibited 100% selectivity for the gold in the presence of Ni(II), Cd(II), Zn(II), Co(II), and Mn(II).