Activated Carbon From Waste

Published on 08/05/2011

First Update 08/03/2017

Coconut shells, palm kernel shells and sawdust, other raw materials such as corncobs, rice hulls and vegetable wastes can also be used to produce activated carbon.

From Walnut shells
Walnut shells serve as an alternative source of  Activated Carbon. Adsorption capacity increased with increase in activation temperature but beyond 400 degrees celsius resulted in thermal decomposition. Activation longer than one hour at 375 degrees celcius resulted in a destruction of the micropore size.Activation with ZnCl2 was better than that with CaCl2 and increased with increasing concentrations upto a certain limit beyond which increasing concentrations inhibited activation.Applicability of the activated carbon from walnut shells, as adsorbent  for synthetic copper wastewater, was better for Copper Ions as compared to  carbon from coconut shell.

From Rosa canina seeds
“An activated carbon has been developed from Rosa canina sp. seeds, characterized and used for the removal of methylene blue (basic dye) from aqueous solutions.”

From Corn Cobs
A new absorbent material  made from the remains of corn cob is being used to store natural gas. A nanaporous carbon material is produced from the waste corn which is referred to as the “sponge for natural gas”,where the methane uptake is 120v/v or more. Other materials used to make this adsorbent material , olive pits and coconut shell, are more expensive to produce.Flat low pressure high capacity natural gas tanks for vehicles holding no greater than 500psi of methane have been developed.This  reduced the effects in the event of an explosion because of lower pressure of the storage tank and allowed for more trunk space in cars.

Corn cob dried and crushed is mixed with phosphoric acid (H3PO4),where it serves as an activating agent.Excess phosphoric acid is removed and the mixture is carbonized at 450-650oC in a reactor, after which it is evaporated at 160oC for 3 hours.It is washed with hot water to bring the pH to a neutral point.The washed activated carbon is dried at 110oC and grinded and sieved to a particle size of 40 mesh.Using a hydraulic press and a die the powder and a small quantity of binding agent is pressed into monoliths or briquettes to obtain the highest density .These briquettes are used for storage of natural gas at a targetted capacity of 150v/v .The applications include use in gas based vehicles,transportation of natural gas and adsorption of gas from land fills.

From Oil Palm wastes,cork powder and other agricultural wastes
Adsorption of Sulfur Dioxide on Activated Carbon from Oil-Palm Waste and use of cork powder as source of activated carbon has also been studied.Agricultural wastes could be considered as suitable raw materials for the production of activated carbon.activated carbon was produced by chemical activation with phosphoric acid of agricultural wastes such as bagasse, hard shells of apricot stones, almond, walnut and hazelnut shells,activated carbon from the hard shells of apricot stones have the best adsorption properties and the highest surface  area. This activated carbon could be used in the separation of metal ions from wastewaters.

From pyrolysis of sewage sludges
Activated carbons can also be produced by the chemical activation and pyrolisis of sewage. The adsorbents produced from sewage sludges were able to adsorb dyes from coloured waste waters like saffranine and methylene blue.Methylene blue absorption was faster than that for Saffranine.

From Waste newsprint
Waste paper activated carbon has been  prepared from waste newsprint paper and its adsorption capacities were almost the same as ordinary activated carbon on the market.

From Waste Tyres
Technology is available to burn tires in order to seperate and recover carbides.Some parts of the carbides are active and can be used as active carbon. Water (steam) is added to the system for activation.Steel and generated steam can be recovered seperately.

Methods for treating waste tires include retreading,stockpiling, landfilling, recycling, pulverization, fueling, incineration,and pyrolysis. The simplest means of treating waste tires are landfilling and stockpiling. However,wastetires are not easily biodegradable in landfills and, when stockpiled, the accumulation of water in waste tires provides an ideal breeding ground for disease-carrying mosquitoes and rodents. Moreover, uncontrolled fires have broken out in piles of waste tires, and the emission of gaseous air pollutants during open burning has threatened human health and the safety of nearby communities.Waste tires contain more than 90% organic materialsand have a heat value of 32.6 mJ/kg (14,000 Btu/lb),compared with that for coal of 18.6–27.9 mJ/kg (8000–12,000 Btu/lb). Several attempts have been made to convert waste tires to auxiliary fuel. Among them, pyrolysis is a favorable choice for treating waste tires from environmentaland economic perspectives. Pyrolysis is a typical thermal treatment process in the absence of oxygen (O2),which decomposes waste tires into carbon black, combustible gas, and pyrolysis oil.The combustible gas can be recovered as an auxiliary fuel, while the pyrolysis oil, with a composition similar to that of diesel, can be further distilled as supplemental fuel. Furthermore, waste tires or carbon black could be activated into powdered or granular activated carbon for air pollution control and wastewater treatment.

Rubber separated from waste tires was first carbonized at 500 °C in N2 atmosphere. Next, the obtained chars were activated with steam at 850 °C. As a result, fairly mesoporous activated carbons  were obtained. To further improve the porous properties of the activated carbons, the char was treated with I M HCl at room temperature for 1 day prior to steam activation. This treatment increased mesopore volumes , Furthermore, adsorption characteristics of phenol and a dye, Black 5, on the activated carbon prepared via acid treatment were compared with those of a commercial activated carbon in the liquid phase. Although the prepared carbon had a larger micropore volume than the commercial carbon, it showed a slightly lower phenol adsorption capacity. On the other hand, the prepared carbon showed an obviously larger dye adsorption capacity than the commercial carbon, because of its larger mesopore volume.

From Waste Wood
Activated carbons have been produced from waste wood and have the added advantage of  better utilization of resources and reduction of carbon dioxide generation from waste incineration.Specific surface area and adsorption performance of activated carbons from waste wood were found to be nearly equal to those of commercial activated carbons which could be used for humidity-control in houses and leachate treatment in landfill. Waste wood activated carbon also demonstrated equivalent or superior performance to commercial activated carbons.

From Waste Tea
Activated carbons were prepared by phosphoric acid activation with and without microwave treatment and carbonisation of  waste tea under nitrogen atmosphere at various temperatures and different phosphoric acid/precursor impregnation ratios.

From spent activated carbon from water filters
Spent activated carbon from water purifier (Aqua Guard, India) for the removal of atrazine (2 chloro-4 ethylamino-6-isopropylamino-1, 3, 5 triazine) from wastewaters has also been tried successfully.

From Beer Lees
Activated carbon was successfully produced from beer lees which are the main waste material from a beer-production process, when KOH and CO2 were used as oxidizing agents in activation process.

From combustion ash from low Nox boilers
Coal fired plants now use low NOX boilers to reduce emissions. These burners reduce the NOX but increase the unburnt carbon left after combustion and power plants are left with fly ash and unburnt carbon.This impacts the recycle and reuse of fly ash.One use of combustion waste is as activated carbon.While both anthracite and unburned carbon can produce acceptable activated carbon, unburned carbon is probably less expensive and better for the environment. Unburned carbon, separated from fly ash, does not need cleaning or crushing, nor does it need heating to remove volatile components. Also, while anthracite sells for about $50 a ton, the waste from power plants can be separated for $10 to $15 per ton, and the fly ash could be sold to cement manufacturers.

From Chicken Waste
Preparation of low cost activated carbon from chicken waste is a promising way to produce a useful adsorbent for Hg removal. The activated carbon from chicken waste has the same mercury  capacity as commercial activated carbon.

From Broiler Excreta
Ammonia (NH3) pollution from broiler excreta is a primary concern for broiler industry viability.Activated carbon made from broiler litter is effective for NH3 adsorption originating from litterand provides  an opportunity to not only reuse the manure, but also treat the emissions from or within broiler houses.
The BAC is a much cheaper alternative than commercially produced activated carbons and can be applied directly tohe litter if health of birds are the concern or via a filtration system if air pollution concerns demand compliance to standards.

From Urban Waste
The organic fraction of urban waste is converted to active carbon via an improved pyrolytic process. The active carbon produced has a low ash content, high pore volume and hardnessand the active carbon of the present invention possesses superior characteristics. The urban waste referred to herein includes various types of waste produced in the urban environment. For the purpose of this invention urban waste is defined as waste which includes domestic waste and commercial waste but does not include industrial waste. In this context, domestic waste includes waste produced in an average normal household which comprises food waste, paper products and packaging, plastic products, wood, glass and metal. Commercial waste is the waste produced by the commercial sector. Much of the commercial waste is generated by food establishments, markets, grocery stores and the like.

In the initial stage the waste is sorted for the removal of foreign materials. The waste is then shredded to particle size of about 2cm x 2cm x 2cm, and then dried at a temperature of about 110°C. The dried particulate waste is then transferred to the pyrolysis vessel wherein the pyrolysis is a two stage process conducted at a temperature, preferably, in the range of 1400C to 500°C, in which primary pyrolysis takes place at about 160°C and in the second stage the temperature reaches 3900C. The pyrolysis stage takes about 2 hours. Optionally, matter made of polymeric materials, typically, plastics and rubbers, are removed prior to and/or subsequent to any one of the pyrolysis stages. The charcoal produced in the pyrolysis is crushed to a mean particle size up to about 0.01mm. This charcoal produced in the pyrolysis stage has an ash content of 9-20%. This charcoal is granulated in an extruder with a charcoal: water: oil ratio of about 1: 0.7: 0.15. The subsequent carbonization is carried out at a temperature, preferably, in the range of 110oC to 600°C. The granulated carbon is then carbonized at about 180°C under anaerobic conditions. The subsequent activation is carried out at about 790OC in the presence of steam and combustion gases. The combustion gases used in this stage are mixed with gases from the drying process.

The final purifying of the activated carbon is done by rinsing with an aqueous acidic solution, preferably, 5%-20% HCl solution, until the ash content is 2%-5% followed by washing in water until the water extracts have a pH of 3.5-5. The rinsed activated carbon is finally dried at about 100oC to a final water content in the range of 4%-8%.

The activated carbon obtained by the process of the present invention has an ash content of 2%-5%, a mean pore volume in the range of 0.95-1.2 ml/g  and a hardness in the range 85-95.

From Chlorella Vulgaris and Rice Husk
Chlorella vulgaris and rice husk were selected from microorganisms and agricultural waste, respectively, to create new gold-eluteable adsorbents for adsorption of gold-thiourea complex, and compared with activated carbon.  Although heated-immobilised C. vulgaris had the highest eluteability, it adsorbed less gold. Therefore, heated rice husk could be used as an alternative adsorbent for gold-thiourea pre-concentration.

Activated carbon (AC) of high quality has been produced from rice husk. The production involves two (2) main steps: (1) carbonization of raw material at temperature below 800oC in the absence of air using fixed bed reactor (furnace); (2) activation of resulting char with an alkali. The high-quality activated carbons produced have surface areas of 2,896-3,287 m2/g, methylene blue values of 999-1,050 mg/g and benzene gas adsorption of 167-212%.
References

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