A Composite Biosorbent for Treatment of Heavy Metal Waste Streams

 

This purification technology is a means of activating a ceramic substrate and preparing a chitosan gel that coats the surface of the substrate as well as its interstitial spaces. When used in water purification, this biosorbent provides a more efficient and less expensive method for removing heavy metals and other contaminants from water.

This invention provides a novel composite biosorbent for treatment of aqueous waste water streams containing heavy metals. The biosorbent is prepared using chitosan and a support material. Chitosan is a biomaterial derived from deacetylation of chitin from the shells of shrimp, crab, and other arthropods. Chitosan is added onto activated alumina particles, enabling water flow through a columnar structure and providing a greater surface area of sites for attracting heavy metal ions, thereby allowing purification of large volumes of water.

Activation of the alumina (or perlite) with carboxylic acid cleans the surface, increases its reactivity, and facilitates binding of the chitosan to the ceramic. The activation of the ceramic makes it more porous and extends the surface area onto which the chitosan can bind. Spreading the chitosan gel over the largest possible surface area, including the pores, greatly increases the absorption of the gel per given amount of ceramic.

This technology can be used to remove metallic anions (negatively charged) and cations (positively charged) found in aqueous solutions, such as: trivalent chromium cation, hexavalent chromium anion, and the cationic and anionic forms of arsenic. Other metals that can be removed include: lead, copper, nickel, silver, molybdenum and mercury. Water streams containing radioactive materials such as cesium, strontium, thorium and uranium can also be treated with this biosorbent.

Benefits

  • Increased efficiency: Enhanced contact between water and the chitosan gel provides improved purification performance.
  • Ease of use: The material can be used in conjunction with activated carbon and would enable cleaner and simpler processing and purification of water contaminated by heavy metals.
  • Low cost implementation: Chitosan is a naturally-occurring, readily available material.

Applications 

  • Consumer drinking water: The biosorbent is more efficient to use than activated carbon for removing metals. The material could be easily incorporated in under-the-sink units.
  • Wastewater treatment: The chitosan-gel combination is a more effective and less expensive process for removing heavy metals from wastewater in many industrial processes, including metal plating and finishing, mining, and power generation (nuclear and fossil fuels).
  • Groundwater decontamination: The biosorbent can be used in environmental clean-up efforts for removing heavy metals and certain gasoline additives from contaminated groundwater.