FORAGER® - Type M Granular
for the removal of heavy metal and inorganic contaminants

GENERAL PROPERTIES

Type M FORAGER® absorbent is an amine-containing polymer having selective affinity for heavy metals in cationic and anionic states in aqueous solution. It is currently available in 10/40 mesh granular form and in sponge form.

The polymer functions by forming coordination complexes preferentially with ions of transition group heavy metals, namely those metals classified in groups IB through VIIIB of the Periodic Table and generally characterized in having incomplete inner rings of electrons or being otherwise capable of existing in more than one valence state. By comparison, metals such as calcium, magnesium and aluminum, having complete inner rings of electrons and single valence states, show poor affinity for the polymer. The polymer provides ligand sites that surround the metal and form a coordination complex. The order of affinity of the polymer for metals is influenced by solution parameters such as pH, temperature and total ionic content. However, the following affinity sequence of some representative ions can generally be expected:

When employed as a stationary bed in a tank or column through which an aqueous stream flows, absorption bands are produced generally in accordance with the affinity sequence. In certain situations, strongly absorbed species will displace less strongly absorbed species. This characteristic may be employed to separate ions. When utilized in an upward flow fluidized bed, or in rotating drums, simultaneous absorption of a number of ionic species will occur in amounts relative to initial concentration and affinity sequence.

At saturation, the polymer will contain between about 6% and 20% (dry weight basis) of absorbed ions, depending upon the affinity of the polymer for the ion, and its molecular weight. This represents an absorption capacity of about 1.0 meq of absorbed ion/dry gram of polymer. A recently developed augmentation process is available for doubling the saturation capacity of the polymer. The presence of commonly abundant innocuous ions such as Na+, K+, Ca++, Mg++, Al+++, Cl-, SO4-- will not adversely affect the absorption capacity of the polymer

APPLICATIONS

FORAGER Type M absorbent finds greatest use in removing toxic species in ppm and ppb concentrations from industrial wastewater, groundwater, landfill leachate, municipal process streams and acid mine drainage waters. The absorbent is particularly useful in remediating waters containing less than about 100 ppm of targeted species, and especially where treated effluent concentrations below 1 ppb are sought. The Type M absorbent is often employed as a polishing operation following an upstream treatment such as a precipitation process. Type M is uniquely capable of absorbing metals such as mercury, lead, nickel and cadmium which are chelated by EDTA or other synthetic or naturally occurring chelating agents.

The Type M product, in granular form, is generally utilized as a stationary bed in a tank , as shown in Figure1, wherein the ratio of bed height (H) to bed diameter (D) is between 1.5 and 4.0. The impedance to flow (shown in Fig. 2) is about 75% greater than granular activated carbon of the same mesh size distribution.

Removal efficiencies of greater than 90% are obtainable at residence times of 2 minutes. Figure 3 illustrates the relationship between residence time and removal efficiency for the particular case of an influent stream having 20 ppm Cu++ and pH 7.0.

Type M can be employed to treat streams in the pH range of 3 to 11.5. For example, in an EPA Superfund Evaluation, Type M polymer in sponge form was shown capable of 95% removal of 1 ppm each of lead, copper and cadmium from groundwater at pH 3.1. Performance features such as removal efficiency, saturation content, flow impedance, and order of affinity can be expected to vary with pH. Such performance features can also vary throughout the effective temperature range of 1ºC-45ºC. In general, however, the rate of absorption will increase with increased temperature.

The operating cost in using an absorbent such as FORAGER Type M can be expressed as cost per gram of metal removed, based upon one time use of the absorbent followed by disposal. Such operating cost, namely the selling price of a cubic foot of Type M granules, divided by the saturation capacity of the cubic foot for a particular metal, is currently in the range of 45 cents to 90 cents per gram of metal absorbed. It should be noted however, that the cost of ultimate disposal of metal saturated absorbent may be a significant factor in the overall cost of a remediation.

Disposal to landfill in 55 gallon drums may cost between $200 and $700 per drum, depending upon the contents of the drum and geographic location. Because the Type M product at saturation contains more absorbed metals than is typical of other absorbents such as granular activated carbon (GAC), fewer drums are needed for disposal. Furthermore, metal-saturated Type M will generally pass the EPA TCLP test, thereby possibly qualifying as non-hazardous waste with attendant lower disposal cost.

HANDLING

The Type M granular absorbent is marketed in water-swollen form, containing about 55% water. Drying is to be avoided because cycling between wet and dry states can cause attritional degradation to finer particles.

The Type M granules are preferably used in tanks constructed of fiberglass, stainless steel, or coated metal, equipped with a top closure lid and capable of operating at pressures up to 50 psi. The bottom of the tank should be equipped with a grate having 1/4" apertures, and a 40 mesh stainless steel screen atop the grate. The tank should have at least 40% empty space above the bed to accommodate bed expansion upon backwashing.

The granules are preferably added to a water-filled tank, thereby forming a bubble-free bed having a height/diameter in the range of 1.5 to 4.0. A preliminary backwash is desirable to lift any fine particles out of the tank. Such particles are non-toxic and biodegradable. Downflow is the preferred treatment mode. If initial trials show too high a pressure drop, then either the flow rate should be diminished, the bed should be made shallower, or a tank of larger diameter is needed.

In calculating the contact time, it can be assumed that the drainage volume of the bed is about 50% of its geometric volume. For example, a bed of 20" diameter and 40" height has about 27 gallons of drainage volume. A flow of 9 gal/min will produce a contact time of 3 minutes. In subsequent trials, faster flows should be tried.

In a full-scale continuous flow remediation, two, and preferably three absorption beds should be employed in staged series flow relationship wherein the upstream bed can be changed out and placed back on line as the downstream bed. This assures that the granules will be utilized to saturation while providing maximum efficiency of metals removal.

FORAGER Type M granular absorbent has a limited life expectancy, and is best used as soon as received. It is desirable to design flow rates and vessel sizes so that the upstream bed will become saturated within about six months of service. If long term storage is required prior to use, storage at cool or refrigerated temperatures is recommended.

The saturation content of absorbed metals will be in the range of 500 to 1000 grams/cubic foot of bed. Once the saturation value is determined for a specific application, the running time to saturation can be predicted based upon a consideration of the flow rate and average concentration of the targeted metal.

If, in the course of operation, the pressure drop increases because of accumulation of fine particles within the bed, a backwashing should be conducted to remove the particles with the overflow water. If a sight glass tube or small diameter transparent pipe containing some granules can be associated with the exit line from the tank, a visually observable color change can in some cases be used to monitor the state of saturation of the bed within the tank.

In some applications, particularly where a low affinity ion (e.g. Fe++, Ni++, Ca++) has been absorbed, desorption can be achieved to permit re-use of the granules. However, in the case of strongly absorbed ions such as mercury, lead, cadmium and copper, desorption is not recommended

Removal of the saturated granules from the tank can be achieved with a slurry pump, elongated digging devices, or inversion and dumping. There are several disposal options. The saturated granules can be loaded into 55 gal. drums for shipment to landfill. In those instances where the metal-saturated granules do not pass the TCLP test, fixative agents such as sulfides, silicates, phosphates or concrete powder may be added to the drum. Such treatment may achieve non-hazardous waste status with attendant reduced disposal cost.

Alternatively, the granules can be incinerated. Because the polymer is aliphatic, substantially no hazardous aromatic species occur in the stack gas. However, careful attention must be given to removal of species such as NOx and volatile metals. Biodegradation of the granules can also be achieved under long-term monitored conditions of temperature, moisture and microbial activity.

Evaluation samples are available upon request.

NON-WARRANTY All data, statements and recommendations contained in this publication are based upon the best information available and are believed to be reliable. However, all such data, statements and recommendations are given gratis, and Dynaphore, Inc. assumes no obligation or liability, and makes no warranty either express or implied, with regard to the data, statements and recommendations given or the application of the products covered in this publication, or the results obtained; all such data, statements and recommendations being given and accepted at the user’s risk. Nothing printed in this publication is to be construed as permission, or a recommendation to practice any patented invention without a license. Although no adverse physiological effects have been observed in the course of our handling of FORAGER® products, the user assumes all risk of its use and handling. No statement herein contained shall be taken as a recommendation of any action or use without independent investigation and the practice of such safety precautions as may be indicated in the particular circumstances to protect health and property.

PATENTS ISSUED AND PENDING