Enhanced Removal of Phosphate from Aqueous Solution Using Plant Mediated Synthesized Reduced Graphene Oxide and Nano Zero-Valent Iron (rGO-nZVI) Composite: Synthesis, Characterization, Kinetic, Adsorption and Desorption Studies

Phosphorus (P) is an essential nutrient for all living organisms. However, excessive phosphorus input can damage aquatic ecosystems by overgrowth of algae, known as eutrophication. The present work studied the synergistic effect between reduced graphene oxide (rGO) and zero-valent iron nanoparticles (nZVI) on the phosphate removal ability from aqueous solution. Rice and wheat husk were used as agricultural waste for GO synthesis. rGO-nZVI composite was synthesized by the green method, using green tea extract. UV–Visible, XRD, SEM, EDS, FTIR, and Zeta potential identification techniques have confirmed the successful formation of the composite. The nZVIs were spherical and uniformly distributed on the rGO surface. A comparison of phosphate adsorption results with GO and rGO-nZVI adsorbents showed that the synthesized composite has improved the adsorption properties of GO. The effect of pH, contact time, adsorbent dosage, and initial adsorbate concentration have been intensively studied. The adsorption and kinetic mechanisms follow the Freundlich isotherm and pseudo-second-order kinetic models, respectively. The maximum adsorption obtained from the Langmuir was 16.99 mg/g. Phosphate has little reversibility due to its specific adsorption. rGO-nZVI composite is promising in water purification due to its ability to reduce phosphate in water.

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