Preparation And Granulation Of Fe-Cu-Mn Trimetal Oxide Adsorbent And Their Arsenic Adsorption Properties

Arsenic,a ubiquitous element in the environment,is well known and extensively concerned with high toxicity.It is generally introduced into the water and groundwater through natural processes and some human activities,which poses a significant threat to human health.Arsenic pollution has become one of the urgent environmental problems and attracted attention of researchers all over the world.In natural water environments,arsenic exists in two predominant species,arsenate[As(?)]and arsenite[As(?)].As(?)is much more soluble,toxic,mobile and more difficult to remove than As(?).Compared with other treatment techniques for arsenic removal,adsorption is regarded as one of the most promising methods due to its simple operation,low cost and reusability.However,most reported adsorbents are difficult to remove As(?)and As(?)from water simultaneously over a wide pH range.Therefore,it is of great significance to develop new,efficient and widely applied adsorbents for arsenic removal.In this research,a novel Fe-Cu-Mn trimetal oxide adsorbent was developed aiming at simultaneously effectively removing both As(?)and As(?),which combined the high adsorption capacity of iron oxide and copper oxide to As(?)and oxidation performance of manganese oxide to As(?).Moreover,the granular Fe-Cu-Mn trimetal oxide(GFCM)was fabricated using chitosan as adhesive to expand its application range.This adsorbent was well characterized with various techniques and its arsenic adsorption performance and removal mechanisms were investigated.The following results were obtained.1.The Fe-Cu-Mn trimetal oxide adsorbent was synthesized via a facile one-step oxidation-coprecipitation method.The synthetic Fe-Cu-Mn trimetal oxide was composed of many aggregated nanograins with amorphous structure and a high BET surface area(162.3 m~2/g).The synthetic Fe-Cu-Mn trimetal oxide adsorbent had high adsorption capacities of As(?)and As(?),especially As(?).At pH 7.0,the maximum adsorption capacities of As(?)and As(?)on Fe-Cu-Mn trimetal oxide adsorbent were131.3 mg/g and 105.4 mg/g,respectively,which were better than that of adsorbents reported in other literatures.The synthetic Fe-Cu-Mn trimetal oxide adsorbent had good adsorption effect on As(?)and As(?)over a wide range of pH(3.0~9.0).The Fe-Cu-Mn trimetal oxide was well regeneratable and the adsorbed arsenic can be desorbed with NaOH solution and reused again.2.As(?)was removed by ion exchange,forming inner-sphere complex on surface of the adsorbent.The removal mechanism of As(?)is an oxidation coupled with adsorption approach.Mn oxide in adsorbent is mainly responsible for As(?)oxidation,while Fe and Cu oxides are dominant for adsorbing arsenic.Moreover,Cu oxide contributes to enhance arsenic adsorption performance of the Fe-Cu-Mn trimetal oxide over a wide pH range.3.A novel adsorbent of granular Fe-Cu-Mn trimetal oxide(GFCM)was fabricated by using chitosan as adhesive.The GFCM was effective for both As(?)and As(?)adsorption.At pH 7.0,the maximal adsorption capacities were 56.5 and 24.0mg/g,respectively.The granular Fe-Cu-Mn trimetal oxide was well regeneratable.The GFCM can be easily used in the flow-through system.The experimental results of column tests demonstrated that about 5200 and 3500 bed volumes of simulated groundwater containing 259.4?g/L As(?)and 260.4?g/L As(?)were respectively treated before breakthrough(10?g/L).