Arsenic oxides are removed by passing them through ?

Arsenic oxides, such as arsenious oxide (As₂O₃) and arsenic pentoxide (As₂O₅), are toxic compounds commonly produced during metallurgical or industrial processes involving arsenic-bearing ores. To minimize environmental contamination and health hazards, these oxides must be effectively removed from gases or water.

One of the most efficient methods of removal is by passing arsenic oxides through ferric hydroxide [Fe(OH)₃]. Ferric hydroxide acts as an adsorbent and precipitating agent, reacting chemically with arsenic compounds to form ferric arsenate (FeAsO₄) — a highly insoluble and stable compound that can be easily separated.

The reaction can be represented as:

Fe(OH)3+H3AsO4→FeAsO4+3H2OFe(OH)₃ + H₃AsO₄ → FeAsO₄ + 3H₂OFe(OH)3+H3AsO4→FeAsO4+3H2O

In this process:

• 
  

  Arsenic acid (H₃AsO₄) or dissolved arsenic species interact with ferric hydroxide.

  
  


• 
  

  The result is an insoluble ferric arsenate precipitate, effectively removing arsenic from the system.

  
  

Ferric hydroxide has a strong affinity for arsenic ions (As³⁺ and As⁵⁺) due to its surface chemistry, which allows it to form stable chemical bonds with arsenic oxides or their hydrated forms. This property makes it widely used in water purification and industrial gas scrubbing systems to control arsenic emissions.

Other hydroxides, such as sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)₂), and aluminium hydroxide (Al(OH)₃), are less effective because they either form soluble arsenates or do not adsorb arsenic efficiently. Among all, ferric hydroxide provides the best combination of chemical reactivity and adsorption capability.

Thus, ferric hydroxide is the preferred and most effective material for the removal of arsenic oxides, both in environmental and industrial applications, helping reduce the toxic impact of arsenic compounds on ecosystems and human health.