Synthesis and characterization of silver/calcium Oxideactivated carbon Nano-composite for the removal of phosphate from wastewater

Abstract

Excessive phosphate concentration in wastewater discharged into the environment is the main cause of eutrophication in aquatic environments. Adsorption methods are widely used for removing phosphate from wastewater because of their simple design, treatment efficiency and recovery of the adsorbents. Developing adsorbents with appreciable morphology will create new approaches for better phosphate adsorption performance. In this study, Silver/calcium oxide-activated carbon nano-composite was synthesized by wet impregnation methods and characterized using Ultraviolet-Visible spectroscopy (UV-Vis) to confirm the formation of silver nano-particles. Fourier Transform-Infrared spectroscopy (FT-IR) was used to study the functional groups, whereas Scanning Electron Microscope coupled with Energy Dispersive X-ray spectroscopy SEM/EDS was used to study morphology and elemental composition. An X-ray diffractometer (XRD) was used to study the crystallographic nature of the nano-composite. The UV-Vis spectra obtained gave a maximum absorption peak of around 420 nm, confirming the formation of silver nano-particles. FT-IR showed the calcium-oxygen bond formation and established the silver and activated carbon functional groups. SEM/EDS verified the coating of silver on the surface of calcium oxide-activated carbon and the presence of phosphate on the adsorbent after adsorption, which further confirmed that the adsorbent had removed phosphates from the water. The XRD results further confirmed the materials' properties and the presence of peaks that corresponded to silver. The nano-composite was applied in the removal of phosphate from wastewater samples. Batch adsorption studies were carried out to study the effects of various experimental parameters (adsorbent dose, initial phosphate concentration, and pH) on phosphate adsorption. The results from the experiments showed that the best condition for phosphate adsorption was achieved at an adsorbent dose of 0.02 g, initial phosphate concentration of 40 mg/L, contact time of 45 minutes, and pH of 7 with percentage removal of 99.9 % and an adsorption capacity of 45.8 mg/g. The adsorbent was then used to test its efficiency in removing phosphates from real wastewater samples. The percentage of phosphate removed by the synthesized adsorbent was 90 % of the real wastewater sample. This study suggests that Silver/calcium oxide-activated carbon nano-composite is a promising adsorbent for phosphate removal from aqueous solution and real wastewater samples.