Structural and adsorptive properties of boron- and phosphorous-doped graphene oxide: Insight into effective removal of Pb(II) and As(III)

Abstract

Graphene oxide (GO) doped with heteroatoms are gaining interest in depollution of water because of their large surface area. This paper presents for the first time the comparative adsorptive properties of boron- and phosphorous- doped GO (B-GO and P-GO) to remove Pb(II) and As(III) ions from water. The doped GO were synthesized by two-step approach and fully characterized using various analytical techniques to demonstrate their distinct structural and adsorptive features. The Brunauer-Emmett-Teller (BET) surface areas of B-GO (127.4 m2g−1) and P-GO (144.4 m2g−1) were higher than that of pristine GO (77.4 m2g−1) due to insertion of dopants during synthesis. The defects in the doped GO were higher, which were seen in measurements of band intensity ratio of defect band to graphene band in the Raman spectra of B-GO, P-GO, and pristine GO as 1.02, 1.17, and 0.84, respectively. The XPS studies revealed that 96.9 % PO and 3.1 % of PC moieties were present in P-GO. Whereas in B-GO, 93.4 % C2BO/CBO2 and 6.3 % BC moieties were present. Thermodynamic and kinetic measurements of adsorption of Pb(II) and As(III) onto doped GO and pristine GO were determined under different experimental conditions of pH, adsorbent dose, and co-existing ions. Results were interpreted using linear and non-linear isotherms and kinetic modelling. The Langmuir binding capacities of P-GO were 388.1 mgg−1 and 157.4 mgg−1 for Pb(II) and As(III) ions, respectively, which were higher than B-GO and pristine GO. Higher adsorption capacity of P-GO was delineated on the basis of functional moieties, surface defects, smaller particle size, and larger surface area. The renewability experiment showed a negligible decrease in adsorption capacity of P-GO even after five repeated cycles. Column studies supported the applicability of P-GO as an effective adsorbent for removing metal ions in the continuous system.