河口沉积物对砷的吸附性能及影响因素

Adsorption of Arsenic in Estuarine Sediments and Its Influencing Factors

对比分析了砷在辽东湾营口河口外侧近海域沉积物和河口内侧河流段沉积物上的含量和吸附行为,并探讨了主要影响因素。结果表明,海域沉积物和河流段沉积物中As含量分别为7.5和4.0 mg/kg,相对于As的效应临界浓度TEL值7.2 mg/kg,海域沉积物中有一定的As污染。河口外侧近海域沉积物由于铁锰铝等金属和有机质含量较高,对A(sⅢ)和A(sV)的吸附量大于河口内侧河流沉积物,并且A(sⅢ)在沉积物上的吸附量均大于A(sV)。2种沉积物对A(sⅢ)和A(sV)的吸附动力学符合准一级模型,吸附等温线符合修正后的Langmuir方程。河口外侧近海域沉积物对A(sⅢ)和A(sV)的吸附容量和速率随着初始浓度的增加而增大。偏碱性条件利于A(sⅢ)的吸附,偏酸性条件利于As(V)的吸附。溶液中共存阴阳离子对砷在沉积物上的吸附具有较大影响。

Arsenic concentrations and adsorption behavior on both estuarine marine sediment and estuarine fiver sediment of Liaodong Bay were compared. The influence of arsenic initial concentration, pH value and other ions in water on arsenic adsorption was studied. Results showed that the concentrations of As in sediments from estuafine marine sediment were 7.5 mg/kg which was higher than the threshold effect level（TEL）, implying As contamination there. Higher adsorption capacity for As （ Ⅲ ） and As （V） was observed on the marine sediment which contained more organic matter and iron, manganese,, and aluminum metals. The amount of adsorption for As（ Ⅲ） was higher than that for As（V） in both sediments. Adsorption kinetics for As（Ⅲ ） and As（ V ） can be satisfactorily fitted by pseudo-first-order model. A modified Langmuir equation may describe well the As（ Ⅲ ） and As（V） adsorption on the samples. With the initial concentration of As（ Ⅲ ） and As（V） increased, adsorption capacity and rate of As（ Ⅲ） and As（V） rose. Best adsorption environment of As（ Ⅲ ） was acidic while As（V） was alkaline. The coexistence ions in water showed an obvious influence on the adsorption of arsenic in the sediments.