Study On The Preparation And Adsorption Properties Of Zirconium-Based Oxides/Graphene Composites

Phosphate and sulfate ions are the important source of water pollution. Due to the strong affinity to phosphorus and sulfate, zirconium-based oxides have a great potential in the water treatment field. While the particle agglomeration, difficult solid-liquid separation have restricted its industrial application. Graphene material can be used as adsorbent support materials due to its good physic-chemistry properties and large surface area.In this work, graphene oxide（GO） were prepared by improved hummers method.Zirconia/graphene composites（ZrO₂/rGO） were rapidly synthesized by hydrothermal and microwave-hydrothermal with Zr（OH）₄/rGO as precursor which was prepared by ultrasound-stirred-coprecipitation. Phosphate and sulfate adsorption of Zr（OH）₄/rGO and ZrO₂/rGO were systematically studied. The mainly results were shown as follows:ZrO₂/rGO composites with zirconia nanopowder anchored on graphene were successfully fabricated with the hydrothermal temperature at 200 oC for 30 min. The proportion of GO and ZrOCl₂·8H₂O is 20.3:79.7（by mass ratio） named G20.ZrO₂/rGO composites with complete crystallization were successfully synthesized only for 5min in the microwave hydrothermal method.The PO₄^3- adsorption properties of zirconium-based oxides/graphene shown that G20 samples performed the best adsorption capacity. The adsorption capacity of Zr（OH）₄/rGO and ZrO₂/rGO composites decreased as the pH value increased, and The adsorption capacity increased with the increasing phosphate concentration and the solution temperature. The maximum adsorption capacities of Zr（OH）₄/rGO and ZrO₂/rGO composites is 81.84 mgP/g and 63.58 mgP/g respectively. The adsorption kinetics of these two adsorbents accords with the pseudo-second-order model and isothermal adsorption complied with the Langmuir isotherm equation. The results of its recycling properties shown the adsorption capacity decreased a little of the Zr（OH）₄/rGO samples, which may be caused by the partly dissolved and losing of Zr（OH）₄ during the primary adsorption process with the solution. The recycling absorption capacity of phosphate for ZrO₂/rGO samples is almost the same as the initial adsorption performance.The SO₄^2-adsorption properties of zirconium-based oxides/graphene were similar to the PO₄^3- adsorption.The maximum SO₄^2- adsorption capacities of Zr（OH）₄/rGO and ZrO₂/rGO composites is 226.8 mg/g、242.18 mg/g respectively. The adsorption kinetics of these two adsorbents accords with the pseudo-second-order model. But the isothermal adsorption complied with the Freundlich isotherm equation.