Enhanced arsenic migration in tailings soil with the addition of humic acid, fulvic acid and thiol-modified humic acid

Humus is an important parameter to affect the environmental fate of arsenic (As) in tailing soil. According to the batch and column experiment, the effects of humus (HS) including humic acid (HA), fulvic acid (FA) on the As release and basic properties of soil were studied in the soil from a mining region. In addition, HA was modified by 3-mercaptopropyltrimethoxysilane (3-MPTS) with different sulfur content (S%) to improve the release capacity of As. The results indicated that HS could destroy the binding of As with Fe, Mn, Al and Ca without affecting the basic properties of tailings soil, thus achieving the co-release of As and associated metals. Besides, the As release capacity of FA (25.47 %) was slightly higher than that of HA (21.90 %). The ability of thiol-modified HAs to release As from tailings soil after being modified with different S% of 3-MPTS was significantly improved, of which 2 % had the best treatment. The thiol groups (-SH) reached 45.00 % of total S. With the increase of S%, the surface thoil content, aromatization degree and total reduction capacity (TRC) of HA increased. The study demonstrated that HS and thiol-modified HA could promote the migration of As and could advance the treatment of heavy metal contaminated tailing soil.