Application of response surface methodology for optimization of Co(II) removal from synthetic wastewater by adsorption on NiO nanoparticles.

The present manuscript deals with the synthesis and application of NiO nanoparticles for the removal of Co(II) ions from synthetic wastewater. NiO nanoparticles were synthesized at 500 °C calcination temperature. Synthesized nanoparticles were characterized by XRD, TEM, SEM and FTIR. TEM revealed the formation of nanosized particles. Central composite design (CCD) of the response surface methodology (RSM) was employed to optimize the important adsorption parameters viz. Co(II) concentration, pH of Co(II) solution and adsorbent dosage. Co(II) adsorption followed pseudo second order kinetic model. Thermodynamic study confirmed the feasibility of Co(II) adsorption and also revealed the exothermic nature of adsorption. Various two and three parameter isotherms were studied and the best fit isotherm was determined by the standard deviation and chi square test. Redlich–Peterson isotherm was found to be the most suitable isotherm for Co(II) adsorption. Langmuir adsorption capacity of nanoparticles was determined to be 149.51 mgg -1 . NiO nanoparticles were found to be efficient in Co(II) adsorption in the presence of anions like Cl − and PO 4 3 − while the presence of SO 4 2 − , NO 3 − NO 3 − and CO 3 2 − decreased their removal efficiency. Significant removal of Co(II) ions was observed in the presence of other cations. [ABSTRACT FROM AUTHOR]