Removal of Reactive Red 195 and Methylene Blue dyes by adsorption on the surface of cobalt hydroxide-supported polystyrene waste particles

Waste-derived polystyrene microparticles loaded with cobalt hydroxide were prepared and tested as adsorbents for water treatment. The structure of the obtained adsorbent was analyzed by FT-IR, SEM-EDX and XRD techniques. Two dyes, namely, Reactive Red 195 and Methylene Blue were used to evaluate the adsorption behavior of the adsorbent toward anionic and cationic dyes, respectively. The effects of solution pH, contact time, temperature and adsorbent dose on the adsorption process were investigated. The adsorption data were analyzed using the Langmuir and Freundlich isotherms and the pseudo-first and pseudo-second order kinetic models. The thermodynamic parameters of the adsorption process (changes in enthalpy, entropy, and Gibbs free energy) were estimated. The maximum adsorption capacities estimated using the Langmuir model were 37.20 and 32.06 mg g(-1) for Reactive Red 195 and Methylene Blue, respectively. The pseudo-first-order equation provided the best description for the adsorption kinetics. The evaluated thermodynamic parameters for adsorption indicated that the process was endothermic, random, and spontaneous. These results suggest that the cobalt hydroxide-loaded polystyrene waste could serve as an effective adsorbent for the removal of dyes from water.