Chicken Egg Shell Waste Derived Calcium Oxide Based Nanohybrid For Rapid Removal of Heavy Metal Ions from Water: Green Synthesis, Kinetics and Reusability

Abstract The carcinogenic metal ions chromium (Cr +6 ) and lead (Pb +2 ) are prominent water pollutants. To substantiate this, green synthesized SnO 2 nanoparticle (using S. mukorossi extract) was coupled with egg shell derived CaO nanocrystals. Crystalline nature of synthesized catalyst confirmed by PXRD and microscopic study revealed spherical SnO 2 decorated on the irregular surface of CaO. Synthesized nanohybrid followed adsorption and photocatalytic reduction (Cr +6 to Cr +3 ; Pb +2 to Pb 0 ) (Cr +6 : 94 %; Pb +2 : 88 %) phenomenon. Synergism of CaO (51.9 m 2 g −1 ; 2.9 eV) and SnO 2 (13.3 m 2 g −1 ; 3.15 eV) was resulted into plenty of surface area (91.9 m 2 g −1 ), low band gap (2.4 eV), and semiconducting nature of nanohybrid. As compared to Pb +2 removal of Cr +6 was faster due to higher value of reduction potential [Cr +6 /Cr +3 (1.35 eV); Pb +2 /Pb 0 (−0.1262 eV)]. Photocatalyst proved to be effective upto 10 th cycle. SnO 2 @CaO nanohybrid might be considered a potential photocatalyst in industries with sustainable approach.