Synthesis And Performance Of TiO₂-based Adsorbent For Arsenic Removal

As is known to all，the arsenic pollution is very serious harmful both to humanhealth and ecological systems in surface water. Arsenate [As（V）] and arsenite [As（III）]as two primary forms of the inorganic arsenic, play an very important role in thearsenic pollution of the water. At present, the research of arsenic removal in thedrinking water has become a very important research subject of the environmentalscience around the world. This paper have synthesized two different kinds ofadsorption materials, Including titanium dioxide nanotube arrays （TiO₂NTs） andreduced graphite oxide/titanium dioxide （rGO/TiO₂）, which were used to estimate theadsorptivity of the As（V） and As（III） in aqueous solution. The effects factors of initialAs（V） and As（III） concentration, contact time, and solution pH have been investigated.Moreover, some of the regeneration ability has been studied. The results were asfollows:（1） The amorphous titanium dioxide nanotube arrays （TiO₂NTs） were preparedby a simple anodization process without subsequent calcination at high temperature,and the effectiveness of amorphous TiO₂NTs as adsorbents in removing arsenite[As（III）] and arsenate [As（V）] was investigated. The kinetics and equilibrium ofremoving both As（III） and As（V） were studied by separate batch experiments. Theapparent values for Langmuir monolayer sorption capacities were28.9mg/g for As（III）and24.7mg/g for As（V） at pH7, respectively. Kinetics studies indicated that theadsorption process on TiO₂NTs followed pseudo-second-order rate mechanism. TheTiO₂NTs not only were effective for arsenic removal without a pre-oxidation of As（III）to As（V） and/or adjusting the pH value of water before the adsorption process, butalso can be separated and recovered easily from the solution. Moreover, Arsenicadsorption of TiO₂NTs remains stable over a broad pH range. The TiO₂NTs haveexcellent stability and regeneration, and they can be used repeatedly at least fivetimes.（2） Graphene oxide was prepared from graphite powder according to the methodof Hummers and the reduction of the graphene oxide in water with hydrazine hydrate.Then the titanium oxide was loaded in the reduced graphite oxide through the TiCl4hydrolysis process, obtaining the reduced graphite oxide/titanium dioxide （rGO/TiO₂）.Adsorption of As（V） and As（III） on rGO/TiO₂has been studied, the result indicatedthat the apparent values for Langmuir monolayer sorption capacities were28.034 mg/g for As（III） and18.783mg/g for As（V） at pH7, respectively. Kinetics studiesindicated that the adsorption process on rGO/TiO₂followed pseudo-second-order rateequation and the As（V） and As（III） reached the adsorption equilibrium at180min and240min, respectively. The rGO/TiO₂was effective for arsenic removal without apre-oxidation of As（III） to As（V） and/or adjusting the pH value of water before theadsorption process, and arsenic adsorption of rGO/TiO₂remained stable in the pHfrom3to9, the adaptability was stronger than TiO₂NTs.