PROCESS

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Biosorption Process

Sorption
COLUMNS

Target
METALS

CONVENTIONAL
Metal Removal

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Newer metal-removal processes most often uses (multiple) sorption columns.
Process principles are well established and well understood.

The difference is in the "magic granules" inside the columns - different types of biosorbents for different metals.

Biosorbents perform similarly to much costlier ion exchange resins, they can be also regenerated for multiple re-use resulting in better cost-effectiveness.

In addition, the collected metal can be routinely recovered for re-sale from pre-concentrated column wash solutions.

The scale-up of the process is done by using as many columns as required.

Detail description in a downloadable PDF file

process schematics

The column size can be from a small "canister" size to large ones of up to 2m in diameter and 5m high. While one column is actively operating, another one or two are on stand-by and being regenerated. Flexible process arrangement allows the columns to operate either in parallel or in a serial/combination arrangement

The pilot plant assembly contains the sorption column(s), holding tanks, all operating accessories and essential controls

Biosorption process offers a cost-effective alternative for treating effluents from these industries - as priority clients.
Careful choices must be made where the process can make a good contribution as a part of an overall effluent treatment plan.

Metals to remove

Conventional sorption process columns in operation - a stage expected for the biosorption technology in the near future

Conventional Methods for Removing Heavy Metals Top of page

The conventional methods used so far are usually not adequate any more and the more efficient alternatives tend to be less feasible because of their relatively high costs both operating as well as capital.

PRECIPITATION Conventional precipitation methods of removing heavy metals rely on formation of insoluble precipitates using chemical reagents. The sludges formed must be separated by settling or filtration. There are serious drawbacks: ● The time for precipitation is long. ● Insoluble metal hydroxides or sulfides may be difficult to remove. ● Resulting sludges have to be concentrated prior to their disposal. ● Sludge disposal represents an enormous problem : ● Toxic metal sludges are invariably classified as ‘hazardous substances’ . ● Recovery of metals from sludges is usually not feasible. *Major problem:* Precipitation/separation approach has difficulties in meeting progressively more stringent wastewater criteria.	ION EXCHANGE A contemporary high-performance process using synthetic resins usually packed into a flow-through column. The resin binds metals from solution until it is saturated. Then it the column must be taken out of operation and the desorption-washing procedure follows directly in the column. As the resin gets regenerated for another use it releases the metal in the concentrated form in the wash solution. Deployment of expensive ion exchange resins for large volumes of contaminated wastewater has been economically rather unsustainable. Biosorbents are natural and cheap ion exchangers which operate on exactly the same principle, using the same standard process equipment: columns, pumps, valves and pipes.	REVERSE OSMOSIS The process uses membrane stacks and high pressure. The metal gets concentrated on one side of the membrane, while purified water ends up on the other. Membranes are very expensive and easily foul up. Elevated pressure is also an operating drawback. This high-performance system is an expensive alternative treatment method not feasible for wastewater treatment in most cases. ELECTRO-WINNING METAL RECOVERY: Metal recovery is possible only from concentrated enough solutions. From preconcentrated solutions metals are recovered by "electro-winning" processes. Metals are plated from the solution by electric current applied through special electrodes. Electro-winning is a standard conventional technology used 'for profit' by specialized operators who re-sell the recovered metals. They collect suitably pre-concentrated metal solutions for this type of re-processing.
ENVIRONMENTAL vs RECOVERY CONCERNS: Metal-laden waste solutions usually contain metal(s) at concentrations too low for recovery that is thus not feasible without an effective pre-concentration step. The wastewater toxic metal content, however, is high enough to pose a serious environmental hazard. Biosorption treatment results in low volumes of high-concentration wash solutions suitable for subsequent metal recovery.

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Conventional Methods for Removing Heavy Metals Top of page The conventional methods used so far are usually not adequate any more and the more efficient alternatives tend to be less feasible because of their relatively high costs both operating as well as capital.

Conventional Methods for Removing Heavy Metals Top of page

The conventional methods used so far are usually not adequate any more and the more efficient alternatives tend to be less feasible because of their relatively high costs both operating as well as capital.