Experimental Study On Chromium Migration And Transformation In Typical Fine Sand

Chromium salt has been largely produced from last century. Chromium saltis widely used in chemical industry, metallurgy, machinery, etc. The improper stack of chromium slag has caused serious harm to the environment. Cr(VI) is particularly harmful among the contaminants. Different chromium contaminated sites have different soil medium.Theregularity of Cr(VI) migration and transformation is also different. But there is less research on Cr(VI) migration and transformation of chromium contaminated sites at present. Therefore, this article selects three typical fine sands to study from northwest, northeast, north China:yellow fine sand with a small amount of organic matter(S1)、black fine sand with high amount of organic matter(S2)、gray-yellow fine sand with a small amount of organic matter(S3).The batch and column experiments were used to shudy the regularity of Cr(VI) migration and transformation in three kinds of typical fine sand.This study can provide the basis for the removal of Cr(VI). The main results are as follows:Batch experiments show that under the soil p H, S1 and S3 almost not adsorps Cr(VI), but S2 adsorpts Cr(VI) obvious, and the regularity corresponds to the secondary adsorption kinetics.The maximum adsorption amount of S2 is 333.33 mg/kg during 48 hours.This number is got by Langmuir equation under the condition that the solid-to-liquid ratio is 1:30.Column experiments showed that under the condition of natural and high alkali environment,Cr(VI) shows a greater mobility because of the negative charge of the yellow sand; Black fine sand can remove Cr(VI). The reduction of organic matter plays a dominant role under natural condition. The reaction mechanism is complex under high alka condition. The organic matter may have two-tier system. Under the nature condition, Cr(VI) can move easier in gray-yellow fine sand because of the weak electrical adsorption; Gray-yellow fine sand can remove Cr(VI) in high alkali environment. Then Cr(VI) moves slower. Organic matter may play a leading role.