砷是一种广泛存在于自然环境且毒性很大的类重金属元素。由于自然作用和一些人为活动，使得部分砷进入水环境中，造成地下水体砷污染，危害公众健康。砷污染是亟待解决的全球性环境问题之一，受到研究者的广泛关注。

砷在水体中主要以砷酸盐As(Ⅴ)和亚砷酸盐As(Ⅲ)两种无机形式存在，其中As(Ⅲ)比As(Ⅴ)具有更强的可溶性、毒性和迁移性，较难以去除。在众多除砷技术中，吸附法因其操作简单、成本低廉、吸附材料可再生等优点备受关注。但是现有的吸附材料通常很难在较广pH范围内同时高效去除水体中的As(Ⅲ)和As(Ⅴ)，因此开发新型、高效、具有广泛应用性的吸附剂具有重要意义。

本研究利用铁氧化物和铜氧化物对As(Ⅴ)的高吸附性能与锰氧化物对As(Ⅲ)的氧化性能，采用氧化还原/共沉淀法一步合成铁铜锰复合氧化物吸附剂。此外，为了拓展铁铜锰复合氧化物的应用范围，以壳聚糖为黏合剂，制备了颗粒状铁铜锰复合氧化物，实现粉末吸附剂的颗粒化。采用多种技术，对制备的吸附剂进行了详细表征；并对其砷去除性能及机理进行了系统研究，主要研究结果如下：

1. 采用氧化还原/共沉淀法制备了铁铜锰复合氧化物，该吸附材料是由许多纳米级粒子团聚而成，为无定型结构，具有较大的比表面积（162.3 m²/g）。铁铜锰复合氧化物对As(Ⅲ)和As(Ⅴ)都具有良好的吸附效果，在溶液pH为7.0时，对As(Ⅲ)和As(Ⅴ)的最大吸附容量分别为131.3 mg/g和105.4 mg/g，吸附效果优于其他文献中报道的粉末吸附剂。铁铜锰复合氧化物在较广泛pH范围（3.0 ~ 9.0）内对As(Ⅲ)和As(Ⅴ)均具有良好的吸附效果。而且该吸附材料具有良好的再生性能，用氢氧化钠溶液处理使吸附的砷有效脱附，可多次重复使用。

2. 铁铜锰复合氧化物对As(Ⅴ)的吸附主要是通过金属氧化物表面的羟基与As(Ⅴ)进行离子交换，形成稳定的内层络合物，达到去除效果。铁铜锰复合氧化物对As(Ⅲ)的去除过程，不仅存在吸附作用，还存在氧化还原反应。铁铜锰复合氧化物中的锰氧化物主要作用是将As(Ⅲ)有效地氧化成As(Ⅴ)，铁氧化物和铜氧化物主要作用是对砷起吸附作用，同时铜氧化物的存在有助于加强复合氧化物间的协同作用，拓宽吸附剂的pH适用范围，增强砷吸附性能。

3. 以壳聚糖为黏合剂，采用滴加成球法制备了颗粒状铁铜锰复合氧化物吸附剂。颗粒状铁铜锰复合氧化物对As(Ⅲ)和As(Ⅴ)也具有出良好的吸附性能，在pH为7.0时，最大吸附容量分别达到56.5 mg/g和24.0 mg/g。颗粒状铁铜锰复合氧化物吸附材料也具有良好的再生性能，可多次重复使用。利用颗粒状铁铜锰复合氧化物进行连续动态吸附柱实验。当水力停留时间为10 min，As(Ⅲ)初始浓度为259.4 μg/L时，吸附柱达到穿透（即出水口砷浓度达到10 μg/L）时，可处理5200个柱体积的模拟含As(Ⅲ)地下水。As(Ⅴ)初始浓度为260.4 μg/L时，吸附柱达到穿透时，可处理3500个柱体积的模拟含As(Ⅴ)地下水。

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(Ⅴ)] and arsenite [As(Ⅲ)]. As(Ⅲ) is much more soluble, toxic, mobile and more difficult to remove than As(Ⅴ). 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(Ⅲ) and As(Ⅴ) 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(Ⅲ) and As(Ⅴ), which combined the high adsorption capacity of iron oxide and copper oxide to As(Ⅴ) and oxidation performance of manganese oxide to As(Ⅲ). 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 m²/g). The synthetic Fe-Cu-Mn trimetal oxide adsorbent had high adsorption capacities of As(Ⅲ) and As(Ⅴ), especially As (Ⅲ). At pH 7.0, the maximum adsorption capacities of As(Ⅲ) and As(Ⅴ) on Fe-Cu-Mn trimetal oxide adsorbent were 131.3 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(Ⅲ) and As(Ⅴ) 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(Ⅴ) was removed by ion exchange, forming inner-sphere complex on surface of the adsorbent. The removal mechanism of As(Ⅲ) is an oxidation coupled with adsorption approach. Mn oxide in adsorbent is mainly responsible for As(Ⅲ) 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(Ⅲ) and As(Ⅴ)adsorption. At pH 7.0, the maximal adsorption capacities were 56.5 and 24.0 mg/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 μg/L As(Ⅲ) and 260.4 μg/L As(Ⅴ) were respectively treated before breakthrough (10 μg/L).