Adsorption characteristics of malachite green dye onto novel kappa-carrageenan-g-polyacrylic acid/TiO2-NH2 hydrogel nanocomposite

Batch adsorption experiments were carried out for the removal of malachite green (MG) cationic dye from aqueous solution using novel hydrogel nanocomposite that was prepared by graft copolymerization of acrylic acid (AA) onto kappa-carrageenan (kappa C) biopolymer in the presence of a crosslinking agent, a free radical initiator and aminosilica-functionalized TiO2 nanoparticles (kappa C-g-PAA/TiO2-NH2). The factors influencing adsorption capacity of the adsorbents such as initial pH value (pH(0)) of the dye solutions, TiO2-NH2 content (wt%), initial concentration of the dye, amount of adsorbents, and temperature were investigated. The adsorption capacity of hydrogel nanocomposite for MG was compared with hydrogel. The adsorption behaviors of both adsorbents showed that the adsorption kinetics and isotherms were in good agreement with a pseudo-second-order equation and the Langmuir equation. The high adsorption capacity (q (m)= 666-833 (mg/g)) and the favorable heterogeneity factor (n = 1.2-1.5) calculated from isotherm equations show the efficiency of the novel adsorbents.