دراسة جدوى لاستخدام الكربون النشط فى تحلية مياه البحر

Carbon - C

مجموعة تكنولاب البهاء جروب
المكتب الاستشارى العلمى
عقيد دكتور
بهاء بدر الدين محمود
استشارى كيميائى

Chemical properties of carbon

- Health effects of carbon

-Environmental effects of carbon
Atomic number
6

Atomic mass
12.011 g.mol -1

Electronegativity according to Pauling
2.5

Density
2.2 g.cm-3 at 20°C

Melting point
3652 °C

Boiling point
4827 °C

Vanderwaals radius
0.091 nm

Ionic radius
0.26 nm (-4) ; 0.015 nm (+4)

Isotopes
3

Electronic shell
[ He ] 2s22p2

Energy of first ionisation
1086.1 kJ.mol -1

Energy of second ionisation
2351.9 kJ.mol -1

Energy of third ionisation
4618.8 kJ.mol -1

Discovered by
The ancients

Carbon

Carbon is unique in its chemical properties because it forms a number of components superior than the total addition of all the other elements in combination with each other.

The biggest group of all these components is the one formed by carbon and hydrogen. We know a minimum of about 1 million organic components and this number increases rapidly every year. Although the classification is not strict, carbon forms another series of compounds considered as inorganic, in a much lower number than that of the organic compounds.

Elemental carbon exists in two well-defined allotropic crystalline forms: diamond and graphite. Other forms with little crystallinity are vegetal carbon and black fume. Chemically pure carbon can be prepared by termic decomposition of sugar (sucrose) in absence of air. The physical and chemical properties of carbon depend on the crystalline structure of the element.

Its density fluctuates from 2.25 g/cm³ (1.30 ounces/in³) for graphite and 3.51 g/cm³ (2.03 ounces/in³) for diamond. The melting point of graphite is 3500ºC (6332ºF) and the extrapolated boiling point is 4830ºC (8726ºF). Elemental carbon is an inert substance, insoluble in water, diluted acids and bases, as well as organic solvents.

At high temperatures it binds with oxygen to form carbon monoxide or dioxide. With hot oxidizing agents, like nitric acid and potassium nitrate, metilic acid C6(CO2H)6 is obtained.

Among the halogens only fluorine reacts with elemental carbon. A high number of metals combine with the element at high temperatures to form carbides.

It forms three gaseous components with the oxygen: carbon monoxide, CO, carbon dioxide, CO2, and carbon suboxide, C3O2. The two first ones are the most important from the industrial point of view. Carbon forms compounds with the halogens with CX4 as general formula, where X is fluorine, chlorine, bromine or iodine.

At ambient temperature carbon tetrafluoride is gas, tetrachloride is liquid and the other two compounds are solids. We also know mixed carbon tetrahalides. The most important of all may be the dichlorodifluoromethane, CCl2F2, called freon.

Carbon in the environment

Carbon and its components are widely distributed in nature. The estimation is that carbon forms 0,032% of The Earth’s crust. Free carbon is found in big reservoirs like hard coal, amorphous form of the element with other complex compounds of carbon-hydrogen-nitrogen. Pure crystalline carbon is found in the form of graphite and diamond.

The Earth's atmosphere contains an ever-increasing concentration of carbon dioxide and carbon monoxide, form fossil fuel burning, and of methane (CH4), form paddy fields and cows.

No element is more essential to life than carbon, because only carbon forms strong single bonds to itself that are stable enough to resist chemical attack under ambient conditions.

This give carbon the ability to form long chains and rings of atoms, which are the structural basis for many compounds that comprise the living cell, of which the most important is DNA.

Big quantities of carbon are found in the form of compounds. Carbon is present in the atmosphere as carbon dioxide in 0,03% in volume. Several minerals, like limestone, dolomite, gypsum and marble, contain carbonates.

All the plants and live animals are formed by complex organic compounds where carbon is combined with hydrogen, oxygen, nitrogen and other elements.

The remains of live plants and animals form deposits: of petroleum, asphalt and bitumen. The natural gas deposits contain compounds formed by carbon and hydrogen.

Application

The free element has a lot of uses, including decoration purposes of diamonds in jewelry or black fume pigment in automobile’s rims and printer’s ink. Another carbon form, the graphite, is used for high temperature crucibles, dry cell and light arch electrodes, for pencil tips and as a lubricant. Vegetal carbon, an amorphous form of carbon, is used as gas absorbent and bleaching agent.

Carbon compounds have plenty of uses. Carbon dioxide is used in drinks carbonatation, in fire extinguishers and, in solid state, as a cooler (dry ice). Carbon monoxide is used as reduction agent in many metallurgic processes. Carbon tetrachloride and carbon disulphide are important industrial solvents. Freon is used in cooling systems.

Calcium carbide is used to prepare acetylene; it’s used for welding and cutting metals, as well as for preparation of other organic compounds. Other metallic carbides have important uses as heat-resistants and metal cutters.
Health effects of carbon

Elemental carbon is of very low toxicity. Health hazard data presented here is based on exposures to carbon black, not elemental carbon. Chronic inhalation exposure to carbon black may result in temporary or permanent damage to lungs and heart.

Pneumoconiosis has been found in workers engaged in the production of carbon black. Skin conditions such as inflammation of the hair follicles, and oral mucosal lesions have also been reported from skin exposure.

Carcinogenicity- Carbon black has been listed by the International Agency for Research on Cancer (IARC) within Group 3 (The agent is not classifiable as to its carcinogenicity to humans).

Some simple carbon compound can be very toxic, such as carbon monoxide (CO) or cyanide (CN-).

Carbon 14 is one of the radionuclides involved in atmospheric testing of nuclear weapons, which began in 1945, with a US test, and ended in 1980 with a Chinese test. It is among the long-lived radionuclides that have produced and will continue to produce increased cancers risk for decades and centuries to come. It also can cross the placenta, become organically bound in developing cells and hence endanger fetuses.

Most we eat is made up of compounds of carbon, giving a total carbon intake og 300 g/day. Digestion consist of breaking these compounds down into molecules than can be adsorbed to the wall of the stomach or intestine. There they are trasported by the blood to sites where they are utilized or oxidised to release the energy they contain.

Environmental effects of carbon

No negative environmental effects have been reported.

Regeneration / Active Carbon

مجموعة تكنولاب البهاء جروب
المكتب الاستشارى العلمى
عقيد دكتور
بهاء بدر الدين محمود
استشارى كيميائى
Activated carbon is an expensive product. In most of the cases the cost of replacing the saturated carbon would be prohibitive. It should therefore be regenerated, and four methods have been developed for this purpose:

Steam regeneration
This method is restricted to regenerating carbon which has only retained a few very volatile products.

Thermal regeneration
By pyrolysis and burning off of adsorbed organic substances. In order to avoid igniting the carbon, it is heated to about 800 °C in a controlled atmosphere. This is the widely used method and regenerates the carbon very well, but it has two disadvantages: it requires considerable investment in either a multiple-hearth furnace and it causes high carbon losses.

Chemical regeneration
Some process based on the action of a solvent used at a temperature of approximately 100 °C and with a high pH.

Biological regeneration
This method of regeneration has not yet been applied on an industrial scale.

Adsorption / Active Carbon
Activated carbon adsorption

مجموعة تكنولاب البهاء جروب
المكتب الاستشارى العلمى
عقيد دكتور
بهاء بدر الدين محمود
استشارى كيميائى

Adsorption is a process where a solid is used for removing a soluble substance from the water. In this process active carbon is the solid.

Activated carbon is produced specifically so as to achieve a very big internal surface (between 500 - 1500 m2/g).

This big internal surface makes active carbon ideal for adsorption. Active carbon comes in two variations: Powder Activated Carbon (PAC) and Granular Activated Carbon (GAC).

The GAC version is mostly used in water treatment, it can adsorb the following soluble substances:

Datasheet Active Carbon

Adsorption of organic, non-polar substances such as:
Mineral oil
BTEX
Poly aromatic hydrocarbons (PACs)
(Chloride) phenol
Adsorption of halogenated substance: I, Br, Cl, H en F
Odor
Taste
Yeasts
Various fermentation products
Non-polar substances (Substances which are non soluble in water)

Examples from active carbon in different processes:
Ground water purification

The de-chlorination of process water

Water purification for swimming pools

The polishing of treated effluent

Process description:
Water is pumped in a column which contains active carbon, this water leaves the column through a draining system. The activity of an active carbon column depends on the temperature and the nature of the substances.

Water goes through the column constantly, which gives an accumulation of substances in the filter. For that reason the filter needs to be replace periodically.

A used filter can be regenerated in different ways, granular carbon can be regenerated easily by oxidizing the organic matter.

The efficiency of the active carbon decreases by 5 - 10% 1).

A small part of the active carbon is destroyed during the regeneration process and must be replaced. If you work with different columns in series, you can assure that you will not have a total exhaustion of your purification system.

Description of adsorption:
Molecules from gas or liquid phase will be attached in a physical way to a surface, in this case the surface is from the active carbon. The adsorption process takes place in three steps:

Macro transport: The movement of organic material through the macro-pore system of the active carbon (macro-pore >50nm
)
Micro transport: The movement of organic material through the meso-pore and micro-pore system of the active carbon (micro-pore <2nm; meso-pore 2-50nm)
Sorption: The physical attachment of organic material on the surface of active carbon in the meso-pores and micro-pores of the active carbon

The activity level of adsorption is based on the concentration of substance in the water, the temperature and the polarity of the substance. A polar substance (= a substance which is good soluble in water) cannot or is badly removed by active carbon, a non-polar substance can be removed totally by active carbon.

Every kind of carbon has its own adsorption isotherm and in the water treatment business this isotherm is definite by the function of Freundlich
.
The function of Freundlich:
x/m = adsorbed substance per gram active carbon
Ce = concentration difference (between before and after)
Kf, n = specific constants

What is the difference between adsorption and absorption??
When a substance is attached to a surface is is called adsorption, is this case the substance is attached to the internal surface of active carbon.

When a substance is absorbed in a different medium it is called absorption. When a gas is taken in a solution it is called absorption.

Factors that influence the performance of active carbon in water:

The type of compound to be removed. Compounds with high molecular weight and low solubility are better absorbed.

The concentration of the compound to be removed. The higher the concentration, the higher the carbon consumption.

Presence of other organic compounds which will compete for the available adsorption sites.

The pH of the waste stream. For example, acidic compounds are better removed at lower pH.
According to this we can classify some chemicals by their probability of being efficiently adsorbed by active carbon in water:

1.- Chemicals with very high probability of being adsorbed by active carbon:

2,4-D
Deisopropyltatrazine
Linuron

Alachlor
Desethylatrazine
Malathion

Aldrin
Demeton-O
MCPA

Anthracene
Di-n-butylphthalate
Mecoprop

Atrazine
1,2-Dichlorobenzene
Metazachlor

Azinphos-ethyl
1,3-Dichlorobenzene
2-Methyl benzenamine

Bentazone
1,4-Dichlorobenzene
Methyl naphthalene

Biphenil
2,4-Dichlorocresol
2-Methylbutane

2,2-Bipyridine
2,5-Dichlorophenol
Monuron

Bis(2-Ethylhexyl)Phthalate
3,6-Dichlorophenol
Napthalene

Bromacil
2,4-Dichlorophenoxy
Nitrobenzene

Bromodichloromethane
Dieldrin
m-Nitrophenol

p-Bromophenol
Diethylphthalate
o-Nitrophenol

Butylbenzene
2,4-Dinitrocresol
p-Nitrophenol

Calcium Hypochloryte
2,4-Dinitrotoluene
Ozone

Carbofuran
2,6-Dinitrotoluene
Parathion

Chlorine
Diuron
Pentachlorophenol

Chlorine dioxide
Endosulfan
Propazine

Chlorobenzene
Endrin
Simazine

4-Chloro-2-nitrotoluene
Ethylbenzene
Terbutryn

2-Chlorophenol
Hezachlorobenzene
Tetrachloroethylene

Chlorotoluene
Hezachlorobutadiene
Triclopyr

Chrysene
Hexane
1,3,5-Trimethylbenzene

m-Cresol
Isodrin
m-Xylene

Cyanazine
Isooctane
o-Xylene

Cyclohexane
Isoproturon
p-Xylene

DDT
Lindane
2,4-Xylenol

2.- Chemicals with high probability of being adsorbed by active carbon:

Aniline
Dibromo-3-chloropropane
1-Pentanol

Benzene
Dibromochloromethane
Phenol

Benzyl alcohol
1,1-Dichloroethylene
Phenylalanine

Benzoic acid
cis-1,2- Dichloroethylene
o-Phthalic acid

Bis(2-chloroethyl) ether
trans-1,2- Dichloroethylene
Styrene

Bromodichloromethane
1,2-Dichloropropane
1,1,2,2-Tetrachloroethane

Bromoform
Ethylene
Toluene

Carbon tetrachloride
Hydroquinone
1,1,1-Trichloroethane

1-Chloropropane
Methyl Isobutyl Ketone
Trichloroethylene

Chlorotoluron
4-Methylbenzenamine
Vinyl acetate

3.- Chemicals with moderate probability of being adsorbed by active carbon*:

Acetic acid
Dimethoate
Methionine

Acrylamide
Ethyl acetate
Methyl-tert-butyl ether

Chloroethane
Ethyl ether
Methyl ethyl ketone

Chloroform
Freon 11
Pyridine

1,1-Dichloroethane
Freon 113
1,1,2-Trichloroethane

1,2-Dichloroethane
Freon 12
Vinyl chloride

1,3-Dichloropropene
Glyphosate

Dikegulac
Imazypur

*(For this chemicals active carbon is only effective in certain cases).

4.- Chemicals for which adsorption with active carbon is unlikely to be effective.

However it may be viable in certain cases such as for low flow or concentrations:

Acetone
Methylene chloride

Acetonitrile
1-Propanol

Acrylonitrile
Propionitrile

Dimethylformaldehyde
Propylene

1,4-Dioxane
Tetrahydrofuran

Isopropyl alcohol
Urea

Methyl chloride

Factors that influence the performance of active carbon in air:

Type of compound to be removed: In general compounds with a high molecular weight, lower vapor pressure/higher boiling point and high refractive index are better adsorbed.
Concentration: The higher the concentration, the higher the carbon consumption.

Temperature: The lower the temperature, the better the adsorption capacity.

Pressure: The higher the pressure, the better the adsorption capacity.

Humidity: The lower the humidity, the better the adsorption capacity.

Activated carbon filters
مجموعة تكنولاب البهاء جروب
المكتب الاستشارى العلمى
عقيد دكتور
بهاء بدر الدين محمود
استشارى كيميائى
Depending on the type of water, suspended solids concentration, oil and grease, COD, BOD and pesticides contents, activated carbon filters are sized differently, but the basic design data to clarify natural waters is the following:

Filtration velocity 2-8 m3/h.m2

Contact time 10 -30 minutes

Diameter 50 cm to 3m

Filtration area 0,2 to 7 m2

Flowrates 10L/h 100 m3/h

Pressure ratings 4 to10 bar

Vessel Materials Epoxy-coated steel

Polyester composite

Stainless steel (on request)
Bed depth 1 meter min
.
Filtration media GAC

Pesticide removal

COD removal

Dechlorination

Top manhole 2 1/2 to 6" DN 400
Accessories 5-ball or butterfly valves 5-butterfly valves
Options Manometers, degaser, flowmeter
Control Automatic or manual backwash, on timer and.or differential pressure

For pesticide removal only at averal occurence at ppb levels, lifetime of an activated carbon bed can be up to 10 years. For natural organic matter or oil and grease, bed renewal can vary from few weeks to few years.

Desalination Pretreatment
مجموعة تكنولاب البهاء جروب
المكتب الاستشارى العلمى
عقيد دكتور
بهاء بدر الدين محمود
استشارى كيميائى

اماكن استخدام الكربون النشط فى طرق معالجة مياه البحر

Why a pre treatment?

Reverse Osmosis Thin Film Composite membranes are subject to fouling by suspended materials that are present in seawater. Typical seawater RO foulings are:

Fouling Cause Appropriate Pre-treatment

Biological fouling Bacteria, microorganisms, viruses, protozoan Chlorination
Particle fouling sand, clay (turbidity, suspended solids) Filtration

Colloidal fouling Organic and inorganic complexes, colloidal particles, micro-algae Coagulation + Filtration

Optional: Flocculation / sedimentation

Organic fouling Natural Organic Matter (NOM) : humic and fulvic acids, biopolymers Coagulation + Filtration + Activated carbon adsorption

Coagulation+ Ultrafiltration
Mineral fouling Calcium, Magnesium Barium or Strontium sulfates and carbonates Antiscalant dosing

Acidification
Oxidant fouling Chlorine, Ozone, KMnO4 Oxidant scavenger dosing:
Sodium (meta)bilsulfite
Granulated Activated Carbon

Seawater Desalination typical pretreatment processes:

A very cost-effective way to avoid biological fouling is seawater chlorination . Unfortunately, chlorine oxidizes the membrane material, therefore only 1000 ppmh can be tolerated.

A common dechlorination process is the injection of sodium bisulfite or metabisulfite, classified as a chlorine scavenger. Another solution is the use of a granulated activated carbon.

NOM, particles and colloids can be removed by so-called "conventional treatment" consisting of coagulation followed by deep media filtration for low turbidity water . Additional steps such as flocculation and sedimentation are added in case of very turbid shallow seawater.

The non-conventional pretreatment for NOM , particles and colloids is ultrafiltration.

An antiscalant solution should be dosed before the reverse osmosis membranes to disperse calcium carbonate and sulfates precipitates in order to avoid scaling.

Fine filtration (5-micron) is required as a last step before the RO membranes to prevent any debris, sand particles or piping material to damage the membranes.

i

An Overview of Activated Carbon in the Marine Tank
استخدامات الكربون النشط فى تنظيف الخزانات البحرية
مجموعة تكنولاب البهاء جروب
المكتب الاستشارى العلمى
عقيد دكتور
بهاء بدر الدين محمود
استشارى كيميائى

Introduction

The use of activated carbon in Marine aquariums has always sparked debate. In the past opinions ranged from “never use it” to “never be without it.”

Today most aquarists consider activated carbon a beneficial and necessary component of their filtration system.

Although many marine aquarists use activated carbon few know what is being removed or how carbon is beneficial to the marine aquarium. Then the manufacturing processes will be described and its effects on the finished carbon product.

The filtration or sorption mechanism will be discussed in addition to factors affecting activated carbon performance. Lastly techniques for the use of carbon products is provided as well as a “consumer checklist” for evaluation and selection of activated carbon products for use in marine aquaria.

Organic Pollutants in the Marine Aquarium.

The world’s reefs and oceans maintain a perfect balance of metabolic “waste” materials and nutrients via a series of recycling systems.

The marine aquarium however, is quite different than nature relying on synthetic sea salt, artificial lighting, frozen foods, and an extremely high specimen to water ratio.

While inorganic ammonia and nitrite are easily managed with “biological filtration” many organic compounds tend to accumulate resisting microbial degradation.

These natural metabolic compounds remain largely unidentified but include organic acids, phenolics, proteins, carbohydrates, hormones, and antibiotic compounds.

Few of these organics are directly toxic to marine specimens but can stimulate the growth of heterotrophic bacteria thus increasing demand for oxygen in the aquarium, producing carbon dioxide, lower pH, and lowering redox potential.

Excess organics tax ozonation and foam fractionating systems. Certain organics that tint aquarium water yellow also reduce light penetration especially Actinic (420nm) type lighting.

It is difficult to determine exactly which organic compounds are present in the aquarium and what specific effects they might have on different organisms.

It had been observed that “organic laden” aquariums experience more disease problems and reduced fish growth while invertebrates close or cease reproduction.

Some researchers believe that there is a direct relationship between high levels of organics and dense populations of disease organisms in aquaria. Reduction of naturally occurring organic compounds ultimately leads to improved water quality and healthier specimens.

Activated carbon filtration is one of the most effective and easiest methods of removing organics from aquarium systems.

Manufacturing Processes of Activated Carbon.

Many natural substances of base materials are used to make activated carbon. The most common of these are wood, coal, lignite, and coconut shell. The base material is first subjected to a heating process called carbonization. This initial treatment forms a fixed carbon mass full of tiny pores.

The carbonized base material is then activated by a second heat - steam treatment (200-1600 C) while regulating oxygen and carbon dioxide levels.

Activation creates a fast internal pore network and imparts certain surface chemistries (functional groups) inside each particle. Thus activation gives carbon its unique filtering characteristics.

The carbon product may be supplied as granular activated carbon (GAC), powdered activated carbon (PAC), or in pelleted form (compressed PAC). Some carbons are activated or washed with phosphoric acid, zinc chloride, or potassium hydroxide.

These chemically treated activated carbons are unsuitable for use in the aquarium. These products could leach phosphate (an algae promoter), heavy metals, or alter pH.

The Sorption Process: How Activated Carbon Works.

Activated carbon removes organic compounds from aquaria by adsorption and absorption principles. Both processes involve the transfer of the adsorbate (pollutant) from the liquid phase (water) to the solid phase (carbon).

Adsorption is the primary sorption mode relying on electrostatic Van der Walls forces. This attractive “force” forms relatively weak bonds between the carbon and adsorbate.

In theory activated carbon could release or desorb what it removed at some point. But practical experience with aquarium filtration and laboratory experiments show desorption rarely occurs or causes any type of “toxic release”.

Bacteria readily colonize the outer surface of the activated carbon and consume some of the sorbed organics.

The bacterial action reactivates a small portion of the carbon and perhaps prevents desorption.

Absorption refers to the diffusion of a gas or compound into the porous network where a chemical reaction or physical entrapment take place. Ozone for example is absorbed into activated carbon where it oxidizes a portion of the carbon’s surface.

Ozone (O3) is reduced to oxygen (O2) thus “detoxified” and made safe for the aquarium. Ozone does not accumulate or build-up in the carbon structure.

A third process called chemisorption forms an irreversible chemical bond between the carbon surface and the adsorbate. Pollutants are tightly bound to the sorbent.

All three sorption processes occur simultaneously in the aquarium.

The sorption process takes place in three stages:

1) Organic laden water contacts the activated carbon particle.

2) The adsorbate diffuses into the porous network.

3) Sorption onto the carbon occurs.

The sorption process has been described as the activity observed in a parking lot. Vehicles (organics) are moving freely on the main highway (aquarium water).

Gradually vehicles enter the lot (pore) in search of a parking space (sorption site). As the parking lot becomes filled the sorption rate slows down.

Sorption of large organic compounds takes longer than smaller compounds.

The sorption rate is also influenced by water temperature, pH, and salinity, but these factors will not be discussed since they are “constants” in the marine aquarium.

Factors Affecting Activated Carbon Performance.

Over 100 activated carbon products are available. The activated carbon must match the application to obtain the highest water quality.

Carbon products are classified primarily as air phase or liquid phase materials.

Air phase carbons are used to purify air or gas streams such as air conditions systems and gas masks. Air pollutants are typically smaller, low molecular weight compounds, therefore a microporous activated carbon is the most efficient sorbent.

But an air phase carbon has a low efficiency in the marine aquarium. The tiny pores (15 Angstrom) are too small to permit sorption of high molecular weight organics.

A macroporous liquid phase activated carbon has a pore structure large enough (30 Angstrom) to remove typical aquarium pollutants.

The base material greatly influences the pore diameter of the finished carbon product.

Coconut shell typically creates a microporous activated carbon product.

Coconut shell carbons are commonly used for the neutralization of chlorine in tap water.

Chlorine is absorbed into the carbon where it oxidizes the surface and is neutralized.

The disinfection processes such as chlorination create a variety of organic by-products or “surrogates.”

These “smaller” organics are efficiently removed by wood and coconut shell carbon. Lignite, a form of coal, is used to produce macroporous activated carbon.

Wood based activated carbon is an intermediate material having slightly large pores (25 Angstrom).

Other parameters are often used to market carbon products. Total Surface Area (TSA) is a measure of the surface area (M2/g) available for sorption.

It is important to realize that a carbon product may have a relatively high TSA and yet be “locked up” in pores too small for sorption to occur. A measure of microporosity is the Iodine Adsorption Number.

An iodine number of 1000 or higher indicates a highly microporous activated carbon. A microporous activated carbon will also have a relatively high TSA. The Molasses Number is a measure of macroporosity.

A Molasses Number of 400 or higher indicates a macroporous carbon. Some high performance carbon products have a Molasses Number of 1000. As pore size increases, TSA decreases. Both factors must be considered when examining carbon specification sheets.

On occasion Hardness and Abrasion numbers are given. These figures are useful only if the carbon is going to be handled repeatedly as in reactivation processes. Large scale water treatment plants sometimes reactivate their exhausted carbon.

In this case a tougher activated carbon is desirable to resist break down. The marine aquarist cannot reactivate carbon at home. Reactivation requires very high heat in a controlled environment to restore the sorption sites.

Particle size can be important in some filtration systems. Small carbon pieces pack together and reduce flow rates through canister filters. But this reduced flow if not too restrictive will increase contact time for sorption processes. Most aquarium carbon products range in size from 1.4mm to 4.75mm in particle size.

Crushing a spoonful of carbon into a powder will not create more surface area. It will expose more of the surfaces already contained in the carbon.

This will increase the rate of sorption but not the amount of pollution removed.

Thus a poor activated carbon cannot be improved by crushing into smaller particles.

Ash is the trace inorganic material left behind after the activation process.

The chemical nature of the ash varies with the type of base material and fluctuates even with the same type of carbon. Iron and calcium oxide are common ash constituents. Water soluble ash will be leached out of the carbon by rinsing or soaking the carbon in water.

Quality activated carbons are acid washed to remove most of these inorganic “leftovers.” Unfortunately many carbon products are washed with phosphoric acid.

It would appear that the selection of activated carbon products can be made by comparing specification figures. Unfortunately this is not the case.

In _Seawater Aquariums_ Spotte (1979) sums up activated carbon selection with the following quote: “There are no valid theories that allow selection of the best activated carbon in any single case without experimentation.”

Under laboratory conditions we have observed that two brands of activated carbon with similar specifications give vastly different sorption rates and capacities. Some highly priced “marine” carbons are less effective than lower priced “all purpose” products. One of the most used (and abused) evaluation techniques is the removal of a dye from water.

All this test indicates is the ability of various carbons to removed a particular dye such as methylene blue. One filter cartridge manufacturer designed a test showing how well their cartridge removed malachite green from a jar of water compared to other brands.

We found that their product did remove more malachite green than all other brands. But the removal was caused by the polyester cartridge’s unique ability to bind with malachite green, not the activated carbon in the cartridge.

Even if all the carbon was removed from the product it still outperformed all other competitors! But this test worked only for malachite green.

This same cartridge tested on any other dye or naturally pollutant gave the poorest sorption rate and capacity of all filter cartridges tested. Several important lessons are illustrated here. Aquarists use activated carbon to remove a variety of natural organic compounds from saltwater aquariums.

A carbon product must be evaluated using these same pollutants under aquarium conditions in addition to the lab bench. Removal of a single pollutant is not an adequate test of a carbon product. This often results in invalid product claims and aquarists dissatisfaction with product performance.

Scientific studies must include adsorption isotherms: the relationship between the amount of substance sorbed and its residual concentration in the surrounding water.

Chemical oxygen demand (COD), biological oxygen demand (BOD), and total organic carbon (TOC) are also invaluable tools for analysis. Lasers may be used in the future to help evaluate water quality and the performance of activated carbon in aquaria. Marine aquarists do not have the laboratory facilities necessary to conduct sorption studies. The aquarists must rely on advertisements and recommendations by aquarium shops and friends.

Some aquarium books promote certain brands or types of carbon, mainly because the author(s) sells that type of carbon product rather than impartial scientific study or review of current filtration literature. Aquarists must be wary of the assumption that all expensive carbon products are superior to lesser priced items. To be sure quality activated costs “more” but price alone does not guarantee good performance.

Nine activated carbon products were tested for phosphate contamination. Five of these contained phosphate, including so called “marine” carbons.

Another misconception is that “good carbon fizzes” or releases bubbles when placed in water. some of the most active carbons release no bubbles at all. Ability to “fizz” is not considered an indication of quality by waste treatment engineers or the activated carbon industry.

The marine aquarist can evaluate several brands of activated carbon in the home aquarium. Each brand is used in the aquarium until the aquarist “feels” it needs to be changed. Observations should be recorded such as water clarity and color as well as foaming in the foam fractioner. pH levels should remain relatively stable.

The same volume of activated carbon must be used in each test. If Brand A was used at one cup/55 gallons then Brand B must be used at the same rate. Activated carbon is used by volume rather than by weight, aquarists simply fill up their carbon bag or canister filter.

Weight is not a consideration in aquarium testing. The higher grade carbon products should keep the water cleaner and permit better light transmission by removing the organics.

Many reef aquarists can judge their water quality (organic loading) by the appearance of certain invertebrates. The particular species will be different in each aquarium but in general the specimen closes up, shrinks, or looks “poor” when water quality declines.

A reduction of organics via fresh carbon, a water change, or new air stones in the foam fractioner usually perks up the “indicator species”. It must be stressed that in all tests the aquarium population and feeding regime must be equal.

Do not test Brand A with six fish, then add several pieces of live rock, then proceed to evaluate Brand B. Obviously the organic load is increased, invalidating all subsequent data.

Using Activated Carbon in the Marine Aquarium

The principle of sorption requires aquarium water to come in contact with the activated carbon.

As contact is increased sorption also increases maximizing removal of pollutants. Some water treatment plants add powdered activated carbon to a large agitated vessel of water.

Sorption (purification) is rapid because of the small particle size and optimal contact with the adsorbate.

Optimal contact is essential when using this “once through” methodology. Water has only one “chance” to be purified as it passes through the treatment process. Tap water filters are another example.

Once the water exits the filter it cannot be “put back” and refiltered if some impurities were not removed. Aquarium filtration employs the dilution principle. A small portion of the total aquarium volume is removed, filtered, and replaced on a continuous basis.

The idea is to remove pollution faster than it accumulates in the aquarium. This is why filter manufactures make different size filtration systems, they are matched to the volume of the aquarium.

If the filter is too small or the flow rate too slaw the pollutants build up faster than the filter can dilute them. As activated carbon becomes exhausted the sorption rate slows down and organics begin to accumulate. Replacing the activated carbon with fresh material continues the purification process.

Ideally aquarium water should be prefiltered before contact with activated carbon. Prefilters reduce the amount of particulate matter captured in between the carbon particles. Canister filters often provide an activated carbon chamber with prefiltration capabilities. Special carbon contractors maximize contact time and allow for floss fiber as a prefilter.

Contrary to some authors, bags of activated carbon placed in the water flow work quite well. Laboratory studies have shown that bags of carbon or resins can remove substantial quantities of organic pollutants, medications, water hardness, and heavy metals. Actual performance depends on the flowability of the bag material, sorbent partical size, and amount of sorbent in the bag.

Aquarists often ask how much activated carbon should be used in the aquarium. Some carbon products give recommendations while others give no indication at all. Independent research has shown that “more is better” when using activated carbon.

When filtering municipal water or aquarium water a greater quantity of carbon will work faster and longer than a lesser amount. A rough guide would be two U.S. cups (480 c.c.) per 55 gallons (280 L.) of aquarium water.

Some aquarists use more or less depending on their filtration system and quality of the carbon product they use. Most carbon products last about six weeks in a marine “fish” aquarium.

Reef aquaria produce more organics than a regular aquarium and may require more frequent replacement. Activated carbon cannot be reactivated by boiling in water or heating in an oven, the temperature is too low to destroy the sorbed pollutants and restore sorptive capacity.

تركيب الفلتر الكربونى النشط

مجموعة تكنولاب البهاء جروب
قطاع تصنيع وحدات معالجة المياه

عقيد دكتور
بهاء بدر الدين محمود
استشارى معالجة المياه

اعتمادا على نوع المياه ، وتركيز المواد الصلبة العالقة والزيوت والشحوم، والحد من الشوائب كمبيدات الآفات، وتتنوع مرشحات الكربون المنشط من حيث الحجم ولكن معالم التصميم الأساسي لترشيح المياه واحدة كما يلي :

سرعة الترشيح 2-8 مترمكعب/ساعة/متر مربع

فترة التلامس 10 -30 دقيقة/مرة

قطرها 50سم-3متر

مساحة سطح الترشيح 0.2-7 متر مربع

معدل التدفق 10لتر-10متر مربع

الضغط المسموح به 4-10بار

تصنيع الجسم الخارجى من الصلب المجلفن المعالج بالايبوكسى

الجسم الداخلى من البوليستر

الفولاذ المقاوم للصدأ (حسب الطلب)

سمك سرير الكربون 1 متر
.
الوظائف التى يقوم بها فلتر الكربون

الترشيح

إزالة المبيدات الحشرية

يقبل إزالة الرائحة

إزالة الكلور

لإزالة المبيدات فقط عند حدوث averal على المستويات جزء في البليون، يمكن عمر سرير الكربون المنشط يمكن أن تصل إلى 10 اعوام وبناءا على نوع المواد العضوية الطبيعية أو الزيوت والشحوم، يمكن تجديد سرير الكربون من أسابيع قليلة إلى سنوات قليلة

اماكن استخدام الكربون النشط فى معالجة مياه البحر

مجموعة تكنولاب البهاء جروب
قطاع الاستشارات الكيميائية

عقيد دكتور
بهاء بدر الدين محمود
استشارى كيميائى

مجالات استخدام الكربون النشط فى الانواع المختلفة من معالجة المياه:-

1-الأغشية الرقيقة لاجهزة التناضح العكسي تتعلق بها المواد الموجودة في مياه البحر. وتسمى ب foulings لمياه البحر هي :

وتصبح هذه الملوثات هى السبب الرئيسى لاستخدام الكربون النشط لبقاء الاغشية صالحة للاستعمال وتعمل بكفاءة.

2-والملوثات البيولوجية كالبكتيريا والكائنات الدقيقة والفيروسات واالجراثيم الاولية الجسيمات وقاذورات الرمل والطين (التعكر ، المواد الصلبة العالقة)

الترشيح+امتصاص الكربون النشط

3-والملوثات الغروية العضوية وغير العضوية ، والجسيمات الغروية والطحالب الدقيقة

التخثر + الترشيح+امتصاص الكربون النشط

4-اختياري : التندف / الترسيب

الملوثات العضوية الطبيعية اولمواد الغير العضوية (تصنيفه) : الأحماض الدبالية وfulvic ، البوليمرات الحيوية

التخثر +امتصاص الكربون المنشط + + الترشيح

5-الملوثات المعدنية الناتجة من املاح الكالسيوم والباريوم والمغنيسيوم أو السترونتيوم الكبريتات والكربونات

التخثر + الترشيح الفائق+امتصاص الكربون النشط

6-تحمض
الملوثات الناتجة من أكسدة الكلور ، والأوزون ، وزيادة جرعات برمنجنات البوتاسيوم المؤكسد

الصوديوم ميتا سلفيت +حبيبات الكربون المنشط

عمليات تحلية مياه البحركمعالجة نموذجية :

وهناك طريقة فعالة جدا من حيث التكلفة لتجنب تلوث البيولوجي وهى كلورة مياه البحر. ولكن، والكلور يؤكسد المواد المكونة للغشاء ، يمكن المعالجة بالكلور الى ان نصل الى 1000بى بى ام فقط

عملية إزالة الكلور شيوعا هو حقن بيسلفيت الصوديوم أو ميتابيسلفيت ، تصنف على أنها عملية ازالة الكلور الزائد اوبحل آخر هو استخدام الكربون المنشط المحبب.

يمكن إزالة الجسيمات والغرويات من "وسائل العلاج التقليدية" مما تتألف من التخثر تليها الترشيح لجعل نسب التعكر منخفضة. تضاف خطوات إضافية مثل الترسيب والترسيب في حالة مياه البحر الضحلة عكر جدا.

والمعالجة غير التقليدية للجسيمات ، وتصنيفه الغرويات والترشيح الفائق.

وينبغي اضافة مزيلات للقشور والملاح قبل أغشية التناضح العكسي لتفريق رواسب من كربونات الكالسيوم وكبريتات من أجل تجنب انسداد مسام الاغشية.

مطلوب ان تكون مسام اغشية الترشيح (5 - ميكرون) كطريقة امنه للتخلص من حبيبات الرمل أو مواد صلبة اخرى تؤدى إلى تلف الأغشية.