Removal of anionic Dye Congo Red from aqueous solutions using CuO Nanoparticles: Isotherm, Kinetics and Thermodynamic studies

Most of dyestuffs discharged into environment from textile industries are toxic and can cause serious dangers harms to aquatic and human lives. Unfortunately some of them are difficult to biodegrade by microorganisms. Therefore; they require proper treatment before discharge into the rivers or environment. Among the various water treatment methods used for dye removal, adsorption and biosorption are more popular and economic. In this research, CuO nano-particles (termed as CuO NPs) were used for removal of Congo red dye as a typical anionic dye (termed as CR) from aqueous solutions. Adsorption experiments were conducted in a batch system. CuO NPs were prepared by chemical precipitation method under optimized conditions. X-ray Diffraction (XRD) and scanning electron microscopy (SEM) were used for characterization of the prepared adsorbent. The effects of several factors, including pH, contact time, initial dye concentration, adsorbent dosage, temperature, and ionic strength on sorption were evaluated. The experimental data were also analyzed by Langmuir and Freundlich adsorption models. Based on the linear regression analysis (R2) it was found that equilibrium data fitted well with Freundlich isotherm. Equilibrium adsorption data were also examined by pseudo-first-order and pseudo-second-order models and their respective rate constant were estimated. It was found that sorption of CR dye onto CuO NPs is fitted very well with pseudo-second-order kinetic model. Using the equilibrium concentration constants obtained at different temperature, important thermodynamic parameters were also calculated. The results indicate that CuO NPs adsorbs CR dye very efficiently and can be used as an effective adsorbent for removal of anionic dyes from aqueous solution such as textile wastewaters.

Keywords:

Adsorption , Congo Red , CuO Nanoparticles , Batch system , Isotherm , Kinetics