Synthesis and characterization of PPy@NiO nano-particles and their use as adsorbent for the removal of Sr(II) from aqueous solutions

In this work, PPy@NiO nanoparticles were synthesized and characterized by XRD, ATR-FTIR, SEM and TEM methods. Synthesized nanoparticles were used for the adsorption of Sr^2 + ions from aqueous solutions. The factors influencing Sr^2 + adsorption, such as adsorbent dosage, pH and initial concentration, were optimized using the central composite design (CCD) of response surface methodology (RSM). The experimental and model predicted values of response (removal %) were in good agreement and ANOVA study suggested that the developed second-order polynomial model is highly significant. The F and P values revealed that this regression is statistically significant. The response optimization plot showed that 98% Sr^2 + removal can be achieved by keeping the metal concentration, pH and dose, 34.6 mg/L, 11.0 and 0.9 g/L respectively. The kinetic studies revealed that the adsorption of Sr^2 + ions on PPy@NiO nanoparticles was rather rapid and Sr^2 + adsorption followed pseudo-second-order model. The maximum adsorption capacity of adsorbent was determined to be 258 mg/g. In this study R_L values for Sr^2 + adsorption on PPy@NiO nanoparticles were less than 1 and greater than 0 for selected Sr^2 + concentrations, which indicate the favourable adsorption of Sr^2 + on nanoparticles. Thermodynamic parameters suggested that Sr^2 + adsorption is spontaneous and endothermic in nature. Present study suggested that PPy@NiO nanoparticles can be efficiently used for the adsorption of Sr^2 + ions.