Peak at 42.4 might be due to the presence of residual MnO2 that would form from KMnO4 during the synthesis of Graphene Oxide.

In article  RSC Adv., 2015, 5, 81831 it is stated "The XRD spectrum of GO (Fig. 4a) exhibited a sharp diffraction peak at 2q ¼ 10.5, corresponding to an interlayer spacing (d001) of 0.8423 nm, typical of highly oxidized GOs.24 A less intense peak at 42.4, commonly observed in graphitic substances, was also recorded."  could you please tell me about this

 A less intense peak (101) at around 2θ = 43 degree in case of graphite oxide is most probably due to the defects in the GO system.

I agree with Biju Majumdar,peak at 2θ = 42.4° might be attribute to trace MnO2

the peak at 2θ = 42.4° is attributed to un-exfoliated Graphene Oxide Sheets

You can wash the sample well with a dilute acid and redo the XRD if the peak disappears its definitely coming from trace MnO2.

I agree with Dr Hiran, the peak is attributed to the traces of MnO2... so you should wash it with dilute nitric acid

I am getting XRD peaks of graphene oxide in such a manner could somebody tell me what is the defect...u attach the file below