Holmium doped La2O3 and its composite with graphitic carbon nitride for the removal of atrazine and chlorpyrifos from wastewater

Herein, the co-precipitation method was employed for the synthesis of rare earth metal oxide La 2 O 3 , Holmium doped La 2 O 3 , and its composite with 2D layered material i.e. graphitic carbon nitride (g-C 3 N 4 ) to study their photocatalytic behavior towards organic pollutants . Pollutants employed to study are pesticides that include atrazine and chlorpyrifos . Structural, spectral, morphological, and elemental analysis were done by XRD , FTIR , SEM , and EDX respectively. Optical bandgap calculations showed the decrease in band edge positions of the bare La 2 O 3 from 5.02 eV to 3.39 eV by doping of Ho in La 2 O 3 lattice. The photocatalytic degradation efficiency of prepared samples was evaluated using a dual beam UV-Visible spectrophotometer. Experimental investigation showed that the prepared composite i.e. Ho doped La 2 O 3 @g-CN had remarkable photodegradation activity of about 60 % and 86 % towards the atrazine and chlorpyrifos respectively. While the pristine La 2 O 3 showed only 41 % and 65 % degradation activity and Ho doped La 2 O 3 showed 52 % and 75 % removal efficiency for atrazine and chlorpyrifos respectively by using 0.03 g/100 mL of photocatalysts under solar light exposure of about 80 min. The enhanced degradation activity of composite (g-C 3 N 4 /Ho@La 2 O 3 ) as compared to its other counter parts is due to its increased surface area and more active sites provided by g-C 3 N 4 for electrons trapping to cause a delay in electron-hole pair recombination rate. The enhanced surface area also played a key role in adsorbing more pollutant molecules for degradation.