Activated carbon davao

20/09/2022

Function Of Activated Carbon For Gold Mining

Activated carbon is widely used in the absorption of gold cyanide complexes in gold processing. This process can be applied to the clear solution through a fluidized bed column or participate in the process of leaching on the tank and the separation of carbon. Activated carbon in the cyanide process gold or commonly referred to as activated charcoal is charcoal made from coconut shell charcoal, charcoal or wood or coal. The most widely used is granular activated carbon from coconut shell charcoal. With specific processing of the activation process such as treatment with high pressure and temperature, can be obtained activated carbon has a surface in the area. Glanural activated carbon derived from coconut shells are produced by pirolis with temperature 600-900 degrees Celsius by using an inert gas (argon or nitrogen) or by oxidation or combustion.

Adsorption of gold complexes (especially ion disianoaurat) on activated carbon is the basis of modern techniques for gold extraction process. This process is very effective and has become a major factor in improving the productivity of the gold mining industry over the last 25 years (S., Mansooreh, Tahereh Kaghazchi, 2007). Carbon is very actively used in the process of recovery of dissolved gold, either by introducing direct to the CIL (carbon-in-leach) or CIP (carbon-in-pulp) tanks after leaching. Activated carbon adsorbs dissolved gold from gold leach pulp complex to be absorbed through the pores of the carbon.The most cost-effective process is to create adsorption of the dissolved gold onto activated carbon, resulting in an Easier solid-solid separation based on size To Achieve this ore particles must typically be Smaller than 100 μm while the carbon particles must be larger than 500 μm. Adsorption is achieved by Contacting the activated carbon with the agitated pulp. This can be done while the gold is still being leached with the CIL-process, or following leaching with the CIP-process. The CIL-process offers the advantage of Countering the adsorption of gold on carbonaceous or shale ore particles, but is more expensive due to less efficient adsorption, Increased gold inventory and Increased fouling and abrasion of the carbon.

Activated carbon in contact with a pulp containing gold can typically recover more than 99.5% of the gold in the solution in 8 to 24 hours, Depending on the reactivity of the carbon, the amount of carbon used and the mixer's efficiency. The loaded carbon is then separated from the pulp by water or screens That are swept hydrodynamically, thus Preventing blinding by the near sized carbon particles. The pulp residue is then either thickened to separate the cyanide containing solution for recovery / destruction of the cyanide, or sent directly to the tailings storage facility from the which the cyanide containing solution is recycled to the leach plant.

The gold adsorbed on the activated carbon is recovered from the carbon by elution, typically with a hot caustic aqueous cyanide solution. Gold was obtained by the method of cementation or by elektrorefining of the solution, while the carbon can be reused. Activated carbon can be reused by washing with dilute hydrochloric acid (HCl) to remove metallic impurity and neutralized with caustic soda. Reactivation is then performed first using a rotary kiln at a temperature of 730 degrees Celsius for 20 minutes. Generally, 10% of carbon lost in the process due to abrasion. During the process, the performance of carbon has decreased so that the efficiency of carbon sequestration need to be monitored and if necessary the addition of new carbon. In traditional mining usually carbon that has been filled with gold complexes directly in the fuel. Dust from the burning of carbon was then taken to be melted.

Contained metal can be purified directly. This is done because of cost considerations and technology.When carbon is not used to adsorb the gold dissolved in the above-Mentioned leach slurry, the gold bearing solution must be separated from the solids components utilizing filtration or thickening units. The resultant solution, Referred to as pregnant solution, is subjected to Further treatment (other than by carbon absorption) to recover the dissolved gold

20/09/2022

What is activated carbon?

Thursday, 21 July 2011 01:58 administrator

Activated carbon is a porous material containing carbon, which has highly advanced pore texture，and is a excellent absorbent, per gram of activated carbon adsorption area as much as the equivalent of eight tennis courts. The absorption of activated carbon is reached by physical absorption force and chemical absorption force, besides carbon which contains a little hydrogen, nitrogen oxygen and ash, the structure is accumulated by carbon form six ring content. Because of six ring carbon irregular arrange, the activated carbon has the characters of microporous volume and high surface area.

Activated carbon is constituted by various carbonaceous materials, which contains wood, sawdust, coal, coke, peat, lignin, nut shell, hard nut shell, sugar cane pulp, bone, lignite, petroleum residue and etc. The coal and coconut shell have become the most commonly employed raw material to produce activated carbon. Activated carbon manufacturing basically divide into two major processes.First, include dehydration and carbonization, heating materials, drying in the temperature 170℃ to 600℃ and making the original organic carbonized about 80%.Second, it is to make carbonized content activation, which is finished through the activator of steam and carbon reaction. In the Heat-sink reaction, it is mainly produce the mixed gases composed by CO and H2 to burn Heating carbonized content to proper temperature(800℃--1000℃),which is used to burn all biodegradable materials. So the activated carbon has advanced mesoporous molecular, large specific area and strong absorption capacity. The pore of activated carbon can divide into three types according to aperture size. Macro pore: radius 1000---1000000A Filter pore: radius 20----1000A Micro pore: radius---20A

Because of different raw material, activated carbon has different size of aperture. The coconut shell activated carbon has the smallest aperture. The wood based activated carbon usually has the biggest aperture, and is used to adsorb larger molecules and almost dedicated in liquid phase. The first type granular activated carbon is used in urban water treatment field, which is made of wood and called wood charcoal. The aperture size of coal based activated carbon is between them. In the coal based activated carbon, lignite activated carbon has more filter space and larger average pore size than anthracite activated carbon, so it can effectively remove macromolecular organic matters in water.

Usually activated carbon is used in water treatment, which does not need larger surface area, but should have more filter pore and larger average pore size.

The usages of activated carbon

Activated carbon has high efficiency air purification function, can build comfortable and clean environment, also can care for human health, it is invisible air filters. Activated carbon uses the function of physical adsorption and chemical decomposition combined can decompose harmful gases such asmethanol, ammonia, benzene, ci******es, lampblack etc. and all kinds of unusual smell, especially carcinogenic aromatic substances. It has strong adsorption capacity, is a common adsorbent, catalyst or catalyst carrier, and can easy fully touch with harmful gases in air. Activated carbon uses own pore adsorption to adsorb the harmful gases molecular into pore, then blow out fresh and clean air. So the family partnership can’t do without activated carbon.

Activated carbon is widely used in all aspects of industrial and agricultural production, such as petrochemical industry non-alkali deodorization (refined de-mercaptan), ethylene desalination water (refined packing), catalyst carrier (platinum, palladium, rhodium and etc.), water purification and wastewater treatment, the power plant water treatment and protection in electric power industry, chemical catalyst and carrier, gas purification, solvent recovery and the decolorization and refining of oil in chemical industry, beverage, wine, MSG liquor in food industry and refining, decolorization of foodstuff, gold extraction and tail liquid recovery in gold industry, wastewater treatment, waste gas and harmful gas treatment, gas purification in environmental protection industry, and related industries cigarette filter, wood floor moisture proof, adsorbing odor, automotive gasoline evaporation of pollution control, the preparation of various impregnanting liquid and etc. Activated carbon will have a good development prospect and broad markets in the future.

20/09/2022

The Properties of Activated Carbon

Wednesday, 13 July 2011 07:01 administrator

A gram of activated carbon can have a surface area in excess of 500 m2, with 1500 m2 being readily achievable. Carbon aerogels, while more expensive, have even higher surface areas, and are used in special applications.

Under an electron microscope, the high surface-area structures of activated carbon are revealed. Individual particles are intensely convoluted and display various kinds of porosity; there may be many areas where flat surfaces of graphite-like material run parallel to each other, separated by only a few nanometers or so. These micropores provide superb conditions for adsorption to occur, since adsorbing material can interact with many surfaces simultaneously. Tests of adsorption behaviour are usually done with nitrogen gas at 77 K under high vacuum, but in everyday terms activated carbon is perfectly capable of producing the equivalent, by adsorption from its environment, liquid water from steam at 100 °C and a pressure of 1/10,000 of an atmosphere.

James Dewar, the scientist after whom the Dewar (vacuum flask) is named, spent much time studying activated carbon and published a paper regarding its absorption capacity with regard to gases. In this paper, he discovered that cooling the carbon to liquid nitrogen temperatures allowed it to absorb significant quantities of numerous air gases, among others, that could then be recollected by simply allowing the carbon to warm again and that coconut based carbon was superior for the effect. He uses oxygen as an example, wherein the activated carbon would typically absorb the atmospheric concentration (21%) under standard conditions, but release over 80% oxygen if the carbon was first cooled to low temperatures.

Physically, activated carbon binds materials by van der Waals force or London dispersion force.

Activated carbon does not bind well to certain chemicals, including alcohols, glycols, strong acids and bases, metals and most inorganics, such as lithium, sodium, iron, lead, arsenic, fluorine, and boric acid.

Activated carbon does adsorb iodine very well and in fact the iodine number, mg/g, (ASTM D28 Standard Method test) is used as an indication of total surface area.

Contrary to a claim repeated throughout the web, activated carbon does not adsorb ammonia.

Carbon monoxide is not well absorbed by activated carbon. This should be of particular concern to those using the material in filters for respirators, fume hoods or other gas control systems as the gas is undetectable to the human senses, toxic to metabolism and neurotoxic.

Substantial lists of the common industrial and agricultural gases absorbed by activated carbon can be found online.

Activated carbon can be used as a substrate for the application of various chemicals to improve the adsorptive capacity for some inorganic (and problematic organic) compounds such as hydrogen sulfide (H2S), ammonia (NH3), formaldehyde (HCOH), radioisotopes iodine-131(131I) and mercury (Hg). This property is known as chemisorption.

Iodine number

Many carbons preferentially adsorb small molecules. Iodine number is the most fundamental parameter used to characterize activated carbon performance. It is a measure of activity level (higher number indicates higher degree of activation), often reported in mg/g (typical range 500–1200 mg/g). It is a measure of the micropore content of the activated carbon (0 to 20 Å, or up to 2 nm) by adsorption of iodine from solution. It is equivalent to surface area of carbon between 900 m²/g and 1100 m²/g. It is the standard measure for liquid phase applications.

Iodine number is defined as the milligrams of iodine adsorbed by one gram of carbon when the iodine concentration in the residual filtrate is 0.02 normal. Basically, iodine number is a measure of the iodine adsorbed in the pores and, as such, is an indication of the pore volume available in the activated carbon of interest. Typically, water treatment carbons have iodine numbers ranging from 600 to 1100. Frequently, this parameter is used to determine the degree of exhaustion of a carbon in use. However, this practice should be viewed with caution as chemical interactions with the adsorbate may affect the iodine uptake giving false results. Thus, the use of iodine number as a measure of the degree of exhaustion of a carbon bed can only be recommended if it has been shown to be free of chemical interactions with adsorbates and if an experimental correlation between iodine number and the degree of exhaustion has been determined for the particular application.

Molasses

Some carbons are more adept at adsorbing large molecules. Molasses number or molasses efficiency is a measure of the mesopore content of the activated carbon (greater than 20 Å, or larger than 2 nm) by adsorption of molasses from solution. A high molasses number indicates a high adsorption of big molecules (range 95–600). Caramel dp (decolorizing performance) is similar to molasses number. Molasses efficiency is reported as a percentage (range 40%–185%) and parallels molasses number (600 = 185%, 425 = 85%). The European molasses number (range 525–110) is inversely related to the North American molasses number.

Molasses Number is a measure of the degree of decolorization of a standard molasses solution that has been diluted and standardized against standardized activated carbon. Due to the size of color bodies, the molasses number represents the potential pore volume available for larger adsorbing species. As all of the pore volume may not be available for adsorption in a particular waste water application, and as some of the adsorbate may enter smaller pores, it is not a good measure of the worth of a particular activated carbon for a specific application. Frequently, this parameter is useful in evaluating a series of active carbons for their rates of adsorption. Given two active carbons with similar pore volumes for adsorption, the one having the higher molasses number will usually have larger feeder pores resulting in more efficient transfer of adsorbate into the adsorption space.

Tannin

Tannins are a mixture of large and medium size molecules. Carbons with a combination of macropores and mesopores adsorb tannins. The ability of a carbon to adsorb tannins is reported in parts per million concentration (range 200 ppm–362 ppm).

Methylene blue

Some carbons have a mesopore (20 Å to 50 Å, or 2 to 5 nm) structure which adsorbs medium size molecules, such as the dye methylene blue. Methylene blue adsorption is reported in g/100g (range 11–28 g/100g).

Dechlorination

Some carbons are evaluated based on the dechlorination half-value length, which measures the chlorine-removal efficiency of activated carbon. The dechlorination half-value length is the depth of carbon required to reduce the chlorine level of a flowing stream from 5 ppm to 3.5 ppm. A lower half-value length indicates superior performance.

Apparent density

Higher density provides greater volume activity and normally indicates better quality activated carbon.

Hardness/abrasion number

It is a measure of the activated carbon’s resistance to attrition. It is important indicator of activated carbon to maintain its physical integrity and withstand frictional forces imposed by backwashing, etc. There are large differences in the hardness of activated carbons, depending on the raw material and activity level.

Ash content

It reduces the overall activity of activated carbon. It reduces the efficiency of reactivation. The metal oxides (Fe2O3) can leach out of activated carbon resulting in discoloration. Acid/water soluble ash content is more significant than total ash content. Soluble ash content can be very important for aquarists, as ferric oxide can promote algal growths. A carbon with a low soluble ash content should be used for marine, freshwater fish and reef tanks to avoid heavy metal poisoning and excess plant/algal growth.

Carbon tetrachloride activity

Measurement of the porosity of an activated carbon by the adsorption of saturated carbon tetrachloride vapour.

Particle size distribution

The finer the particle size of an activated carbon, the better the access to the surface area and the faster the rate of adsorption kinetics. In vapour phase systems this needs to be considered against pressure drop, which will affect energy cost. Careful consideration of particle size distribution can provide significant operating benefits.

20/09/2022

20/09/2022

Useful Activated carbon for the environment

The activated carbon which has adsorbent function with micro pore is useful for world environment preservation.

The main applications are to help create pleasant envornment for living, through improving the water quality, deodorizing, removing soil contaminant and dioxin.

20/09/2022

Absorption with Activated Carbon

To solve the problems presented by the classic scheme of cyanidation, the absorption with activated carbon was developed, which also dates back to the past century, which in its beginnings was of very restricted use, due to the fact that the recuperation of precious metals absorbed in the carbon had to be performed by flotation or by baking and burning. In the present, there are various alternatives which exist for desorbing the precious metals and to be able to pass them previously to electrodepositation. In this process columns of absorption are used, in which the the contact is performed in countercurrent in variousreservoirs in series in which the solution advances from down to up in a compatible form with the velocity of sedimentation and granulometry of the carbon. Other more recent equipments of design are the columns of fluidized beds, as is the case of the Nimcix developed by the Angloamerican.

Finally, we can mention the system used in Cripple Creek, United States, which consists in a species of special containers which contain the carbon, which is fluidized by the solution (5).once the conjunction of containers is loaded it is transferred to the section of elusion in which they fulfill the role of reactors of elusion. These containers are of steel covered with a special plastic for resisting acid washings, if it is necessary. This system is also used in Australia and in Zimbabwe. One recent innovation was installed in Whim Creek Consolidated, United States, in which the containers instead of piling in the form of columns are disposed in a carroussel.

The elusion of carbon can be effectuated through hot solutions of NaOH and NaCN at atmospheric pressure, which was the first in being used successfully, or the use of pressurized reactors for working with this same type of solutions from above the point of boiling and the use ofethanol or glycol for working under the point of boiling (6). In all these alternatives the carbon can be regenerated and reused many times.

The electrodepositation is performed fundamentally in cylindric cells Zadra type, from which different designs exist. In the present time, rectangular cells are preferred, for the reason of rationalization of the space and its handling, but what is essential still remains the same: electrolite of NaOH – NaCN and cathodes of wool of steel.

Curiously, the use of the activated carbon has meant a higher use of the precipitation with Zinc, but now starting with the eluision. The first company in using it in the Untied States was the Freeport McMorand Gold Inc., and posteriorly, it was introduced in Equity Silver, Canada.