The co-transport of Cd(II) with nanoscale As2S3 in soil-packed column: Effects of ionic strength.

Abstract To observe the co-transport of Cd(Ⅱ) with nanoscale As2S3 (nAs2S3) in a soil-packed column under different ionic strength (IS). A soil-packed column experiment with Cd(Ⅱ) and nAs2S3 was conducted. The results show that the transport of Cd(Ⅱ) was facilitated remarkably in the presence of nAs2S3, and nano-associated-Cd(Ⅱ) was the major migration type. However, the co-transport of Cd(Ⅱ) and nAs2S3 was affected by IS. The Cd(Ⅱ) concentration in the effluent to initial Cd(Ⅱ) concentration decreased from 38.75% to 29.95% and 22.28% as IS increased from 1 mM to 10 mM and 50 mM. When IS was 1 mm, 10 mm and 50 mm, the retention of nAs2S3 increased from 74.29% to 78.95% and 85.9% respectively. The agglomeration and sedimentation of nAs2S3 were the main reason for the rise of retention. Due to the increase of retention and reduction in adsorption capacity of nAs2S3 to Cd(Ⅱ), the ratio of migration in the form of nano-associated-Cd(Ⅱ) reduced from 53% (IS 1 mM) to 27.4% (IS 10 mM) and 18.2% (IS 50 mM). During the transport, the IS promoted desorption of Cd(Ⅱ) from nAs2S3 so that more soluble Cd was monitored in the effluent as IS increased. In general, these findings can provide references for controlling the risk caused by the co-transport of nAs2S3 and Cd(Ⅱ) in saline-alkali soil.