Synthesis, characterization, and performance of graphene oxide and phosphorylated graphene oxide as additive in water-based drilling fluids

Graphene oxide (GO) and phosphorylated graphene oxide (PGO) have been synthesized from graphite electrode waste (GrW) or spent pot lining (SPL) from industrial aluminum wastes. The graphite waste was successfully recovered from the industrial aluminum wastes by alkaline and acid leaching method. The GO was then synthesized according to modified Hummers method in room temperature. The addition of oxygen into graphite structure was indicated by the formation of new vibrational bands at 3344, 1727, and 1069 cm⁻¹ in the infrared (IR) spectrum, and the increase of oxygen content was confirmed by energy dispersive X-ray (EDX). The formation of single or few layers of graphene is confirmed through X-ray diffraction (XRD) analysis which show a down shift of 2θ peak and longer interlayer distance. Additional phosphate group to graphene oxide in functionalization process, in order to enhance the dispersion of graphene in water, was confirmed by scanning electron microscopy-energy dispersive X-ray (SEM-EDX). The effect of heat treatment on phosphorylated graphene oxide (PGO) was investigated by calcination at different temperatures (200–500 °C). The Fourier transform infrared (FTIR) spectroscopy and EDX results indicated that heat treatment decreased the oxygen containing group in PGO. An addition of GO as additive in water-based drilling fluids resulted in better rheology properties (plastic viscosity (PV) reduced from 10 to 7 cp and yield point (YP) increased from 11 to 15 lbs/100 ft²), an increase in fluid loss control performance (filtrate volume decreased from 6 mL to 3.6 mL and filter cake thickness reduced from 1.06 to 0.33 mm), and an increase in lubricity ability (lubricity coefficient reduced from 0.158 to 0.119). In the alkaline environment, the bentonite particles are negatively charged, and GO may also turn to be negatively charged. The repulsive static interaction might reduce the plasticity. The zeta potential of the GO and PGO was measured to be −38.90 and −41.23 mV, indicating that both are not easily agglomerated. The additional PGO as additive in water-based drilling fluids showed a negative impact due to significant pH decreased of drilling fluid.