Recovery of PO_4~(3-) from Aqueous Solutions Using La/GO Composites And Adsorption/desorption Process

摘要

Graphene oxide (GO)/Lanthanum oxide (La_2O_3) composites (abbreviated as La/GO) were employed as adsorbents to study the removal of orthophosphate (PO_4~(3-) ) from industrial effluents. The effects of different adsorbents and composite ratio for PO_4~(3-) adsorption was first investigated. The adsorption performance under various water quality factors and the adsorption/desorption operations were then studied. La/GO showed the best performance on PO_4~(3-) adsorption as compared to other adsorbents. The adsorption amounts of PO_4~(3-) were 49.94 and 148.44 mg/g with initial concentrations of 50 and 200 mg/L, respectively. The adsorption amounts of PO_4~(3-) increased as the solution ionic strength increased but decreased as the solution pH value decrease probably due to the increase of H~+ which enhances the surface positively charged surface of La/GO. In the alkaline conditions, the adsorption amounts of PO43 decreased probable because of the competitive adsorption between PO_4~(3-) and OH~-. In the temperature experiments, PO_4~(3-) is easily adsorbed in the high temperature indication that adsorption process is endothermic. From the results of Langmuir model, adsorption of PO_4~(3-) to La/GO surface is s monolayer adsorption. Thermodynamics indicate that adsorption process is spontaneous. Desorption results indicated adsorbed PO_4~(3-) on La/GO could be readily desorbed by NaOH solution and could be employed in the cyclic recovery with adsorption/desorption of PO_4~(3-) from wastewater. In summary, the La/GO composites possess good performance for adsorption/desorption of PO_4~(3-) and possibly become promising adsorbents for PO_4~(3-) recovery in wastewater treatment of high-tech industrial effluents.