TECHNOLOGIES / IN-SITU CHEMICAL FIXATION FOR ARSENIC
Innovative Arsenic Fixation Process Combines Iron, Oxygen, and Chemistry for Success.
Although iron (with and without peroxide) has been used for years to precipitate and fix arsenic, achieving consistent distribution under in-situ conditions has often remained a challenge. Direct injection of iron salts often results in premature iron loss due to sorption to the native soil matrix, undermining the success of the treatment. ISOTEC’s Innovative Arsenic Fixation (IAF) process addresses this challenge by optimizing iron distribution and enhancing the fixation chemistry, offering a more effective and reliable solution at your site.
ISOTEC’s Innovative Arsenic Fixation (IAF) process utilizes a carefully balanced formulation of reagents to optimize the radial distribution of iron and supply dissolved oxygen. This process enables the co-precipitation of arsenic by forming an iron-arsenic oxyhydroxide complex. The IAF process requires both iron and arsenic to be present in groundwater in their oxidized states (Fe+3 and As+5) while providing dissolved oxygen to facilitate the oxyhydroxide formation. A key feature of the IAF process is the use of a chelated iron catalyst and stabilized hydrogen peroxide. When combined in-situ, they enhance both the chemical fixation and the physical distribution of reagents in the groundwater.
Chelating agents stabilize iron at neutral pH in the subsurface, while stabilized hydrogen peroxide serves as the oxygen source. The extended interaction between the peroxide and iron (which lasts several hours) generates a slightly oxidizing environment. This process produces an abundance of dissolved oxygen from the decomposition of the hydrogen peroxide, oxidizing the arsenic from As+3 to As+5 and the iron from Fe+2 to Fe+3.
Additionally, the chelating agents and stabilizers slow the decomposition of hydrogen peroxide. This slower decomposition allows sufficient time for gas expansion, resulting in a significant radius of influence (ROI) through displacement. It also ensures that the chelated iron and stabilized peroxide are effectively distributed throughout the ROI, remaining available to support the fixation chemistry.
