Arsenic (As) and antimony (Sb) both appear in group 15 of the periodic table, with antimony appearing directly under antimony. They have complex chemical behaviours, and both are used as alloying agents. The most common emission of antimony into the human environment is a result of coal burning or antimony smelting, with typically low concentrations in water except for areas affected by acid mine drainage (AMD), mining tailings dams, or from dissolution from metal plumbing or fittings. Arsenic concentrations in water can be naturally high in areas containing volcanic rock or sulfide minerals, and can also be introduced to the environment through industrial effluents and mining wastes.
Arsenic is detrimental to human health, with main long-term ingestion associated with cancer, skin lesions, developmental effects, cardiovascular disease, neurotoxicity and diabetes. The World Health Organisation guidelines for drinking water are 20 ppb for antimony, and 10 ppb for arsenic.
Methods commonly used for removing arsenic and antimony from water are membrane methods such as reverse osmosis (RO), ion exchange, coagulation-flocculation, or precipitation. All of these methods have different efficiencies and suitability depending on the concentration in the feed water. pH changes and changes of the oxidation state of arsenic can be required to improve the removal efficiency. Drawbacks to these methods include high chemical consumption, issues with waste disposal, and potentially high energy usage.
Our CIF® (continuous ionic filtration) technology can be used to reduce or remove arsenic and antimony, with our iron impregnated resins able to target these species. The process is a robust combination of physical filtration and ion exchange which achieves high recoveries with a tolerance to variable feed flowrates and concentrations.
If the concentrations are too high for our ion exchange process, we can also provide conventional precipitation or granular activated carbon (GAC) methods as part of our flow sheet to achieve a product water specification.
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