Experimental research on the injectable xanthan gum gel intercepting barrier of simulated Cr(VI) contaminated aquifer

Due to the unreasonable discharge of industrial waste, a large amount of heavy metal pollutant Cr(VI) enters the underground environment, which seriously threatens human health and ecological environment. The high mobility of Cr(VI) in groundwater environment makes it difficult to repair. A green, economic and effective interception method is urgently needed to improve the ability of groundwater Cr(VI) pollution control. In this paper, sodium metabisulfite is selected as a reducing agent, and Cr³⁺ generated from Cr(VI) in groundwater is used as an xanthan gum crosslinking agent to form a gel blocking barrier. The influences of various components on gel time and viscosity changes and the blocking effect of gel barrier on aquifer are studied. The results indicate that (1) in the system with Cr(VI) concentration up to 200 mg/L, xanthan gum solution with 0.4% mass concentration can form gel with certain mechanical strength within 1.5 h. (2) The gel has salt resistance and is suitable for common aquifers. Na⁺ and K⁺ of 2.5−5 g/L can promote the gel. (3) The injected gel blocking barrier can significantly reduce the coefficient of permeability of medium sand media to 1×10⁻⁷ cm/s, which can meet the demand of groundwater blocking. Injection-type gel barriers are formed without the introduction of harmful substances. After the interception, injection-type gel barriers can be naturally degraded by biological action without long-term changes under the aquifer hydraulic conditions. This study provides a theoretical basis for the construction of gel barrier in chromium contaminated groundwater.