Adsorption technique is widely used method for the removal of inorganic and organic pollutants from wastewater streams. The advantages of adsorption are:
- Effectiveness (also at low contaminant concentrations)
- Selectivity (tailored adsorbents)
- Regenerability of used adsorbents
- Cost-efficiency (low-cost adsorbents)
In the field of adsorption the focus of LAEC is in nanosorbents including new, low-cost synthesis of these promising materials.
Adsorption materials
Variety of adsorption materials exists for the different applications. Examples of adsorption materials are:
- Activated carbon
- Functionalized inorganic or organic adsorbents: functionalized silica gel, other oxides, and organic polymers
- Biosorbents: microbial material
- Low-cost adsorbents:
o Waste material: agricultural or industrial waste
o Natural adsorbents: zeolites and clay minerals
- Carbon-based nanosorbents: carbon nanotubes and nanoparticles
- Inorganic nanosorbents: semiconductors
- Magnetic nanosorbents: ironoxide nanoparticles
- Low-cost nanosorbents: nano-sized adsorbents prepared from low-cost raw materials and by low-cost methods
Ongoing research in the laboratory
Nanosorbents for heavy metal extraction from low concentrations
There is a demand of real-time determination of minute quantities of metal ions in various process waters, such as mine water, and in natural water. The goal of the project is to develop a measurement system that contains separate units for concentration, measurement, and the possibility of wireless data transfer. Due to their high surface area and/or porous surface structures, nanosorbents are the best alternatives for the basis of the concentration unit. Especially, inorganic metal oxide nanoparticles and nanoporous semiconductors can have desirable properties.
Nanosorbents produced by biosynthesis from natural products and indigenous minerals
Different kinds of chemically synthesized metallic nanoparticles are commercially available. However, their price may be high and their synthesis far from environmentally friendly. Therefore, biosynthetic processes have received a lot of attention as a viable alternative for the development of metal nanoparticles where plant extract is used for the synthesis of nanoparticles without any chemical ingredients. Ongoing research is focused on the biosynthesized silver and gold nanoparticles.
Preparation of activated carbon from natural products
Activated carbon is widely used adsorption material for both inorganic and organic contaminants. However, it remains very expensive material. Therefore, production of activated carbon from low-cost materials has been widely studied in recent years. Activated carbon can be prepared for example from plants or agricultural waste.
Functionalized adsorbents for heavy metal removal
Functionalization of conventional adsorption materials can increase their adsorption efficiency remarkably. Rather simple modification techniques are used to functionalize silica gel and chitosan with chelating agents (EDTA, DTPA) to obtain effective adsorbents for heavy metal removal. These chelating agents form very stable chelates with trace metals. When immobilized on the surface they can act as binding sites for various metal ions. EDTA- and DTPA-modified adsorbents are effective at quite low pH-range and in the presence of organic contaminants such as oxalate. This gives a ground for these materials to be used in various applications.