An multifunction Zn0.3Mn0.4O4 nanospheres for carbon dioxide reduction to methane via photocatalysis and reused after five cycles for phosphate adsorption.

The Zn 0.3 Mn 0.4 O 4 Nanospheres (ZnMnONs) were synthesized for the photocatalytic reduction of CO 2 to CH 4 . The average particle size was 70.1 nm and having composition of Zn, Mn and O are about 18.93, 21.30 and 59.77 wt% respectively. The catalysts were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), IR spectra and UV–vis spectrophotometer. Zn 0.3 Mn 0.4 O 4 is used for efficient photocatalytic CO 2 to methane which is an important component in a future sustainable post carbon energy system. It was reached to 2.65 μmol/g of CH 4 yield, and the photocatalyst presented a potential for reducing CO 2 emission. The recovered nanospheres sample from methane production is further used for phosphate adsorption for exploring its multifunction application. The maximum% adsorption observed at 200 mg of adsorbent concentration at 40 min of agitation time. The adsorption study follows the first order of kinetics, Langmuir isotherm graph deduced the q max value at 125 mg/g & Freundlich equilibrium isotherm also shows the linear plot. The essential features of the Langmuir isotherm can be expressed in terms of a dimensionless constant called separation factor. The value of R L indicates the shape of the isotherms to be either unfavorable (R L  > 1), linear (R L  = 1), favorable (0 < R L  < 1) or irreversible (R L  = 0). It was observed that the value of R L was in the range of 0–1 and finally the Thermodynamic parameter related to the adsorption process ΔG shows the value at −4587.24 J mol −1 . [ABSTRACT FROM AUTHOR]