Synthesis, morphology, and structural properties of graphene oxide (GO) and its composites with transition metal phosphates for application in water purification: A review

Graphene oxide (GO)-based nanocomposites have numerous applications in today's life, with water purification being the leading one. The recently studied GO-based nanocomposites include transition metal phosphates (TMPs) (zirconium phosphate (ZrP), cobalt phosphate (CoP), silver phosphate (AgP), nickel phosphate (NiP), and titanium phosphate (TiP). The modification of GO with transition metal phosphates increases its number of oxygen-containing functional groups, as compared to other GO-based nanocomposites. The TMPs improve the heavy metals adsorption efficiency of GO. Moreover, they generally improve its thermal stability and ion exchange properties, making it ideal for a large spectrum of applications. For water treatment applications, it is crucial to understand the structural and morphological properties of the prepared nanocomposites before studying their effectiveness in purifying water. Thereafter, it is necessary to table out the appropriate method and the relevant tests required to study the effectiveness of the prepared nanocomposite. The effect of pH, interactions between adsorbent and adsorbate, and contact time are some of the important parameters during the adsorption tests of toxic heavy metals. The most toxic heavy metals include mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As). This study is intended to review the GO, transition metal phosphates, and GO-based nanocomposite's morphology and structural properties, as well as their potential use as toxic heavy metal adsorbents in water.