uرض معالجة مجطة جنوب العلمين التابعة لشركة الاسمنت المسلح

CARBOCHEM INC.
PRODUCT DATA
CODE #: 5608

ACTIVATED CARBON

Grade: CARBOCHEM® LQ-900S

Description: High quality virgin granular Activated Carbon produced to tight specifications from selected grades of coal. Specifically designed to remove organic pollutants creating taste and odor problems from municipal water. Physical properties of product provide good abrasion resistance and effective adsorption of both high and low molecular weight contaminants.

Specifications: Iodine Number 900 mg/g min
Abrasion Number 80 min
Ash, Water Soluble 0.5% max
Moisture, as packed 2% max

Typical Properties: Bulk Density 27.5 lbs/cu. ft.
Mesh Size, U.S. Sieve 8 x 30 Mesh
+8 Mesh 10% max
-30 Mesh 4% max
Mean Particle Diameter 1.5 - 1.7 mm NSF Standard: CARBOCHEM® LQ-900S has been certified for ANSI/NSF Standard 61. 12/03

Effective Size 0.8 – 1.0 mm
Uniformity Coefficient 2.1 max
Packing: 25 Kg bags & 500 Kg bags

AWWA Standard: CARBOCHEM® LQ-900S exceeds the minimum requirements of ANSI/AWWA B604-96.



WARRANTY – LIABILITY: Contact CARBOCHEM INC. for details
CARBOCHEM INC.
PRODUCT DATA

CODE #: 5618A

ACTIVATED CARBON

Grade: CARBOCHEM® LQ-816

Description: High quality granular Activated Carbon produced to tight specifications from selected grades of coal. Specifically designed to remove organic pollutants from municipal water including compounds producing objectionable taste and odors. Physical properties of product provide good abrasion resistance and effective adsorption of both high and low molecular weight contaminants.

Specifications: Iodine Number 900 mg/g min
Abrasion Number 80 min
Moisture, as packed 2% max
Ash, Water Soluble 0.5% max

Typical Properties: Bulk Density 27.5 lbs/cu. ft.
Mesh Size, U.S. Sieve 8 x 16 Mesh
+8 Mesh 10% max
-16 Mesh 5% max
Effective Size 1.3 – 1.5 mm
Uniformity Coefficient 1.4 max
Packing: 25 Kg bags & 500 Kg bags

AWWA Standard: CARBOCHEM® LQ-816 exceeds the minimum requirements of ANSI/AWWA B604-96.

NSF Standard: CARBOCHEM® LQ-816 has been certified for ANSI/NSF Standard 61.

12/03





WARRANTY – LIABILITY: Contact CARBOCHEM INC. for details.

326 Lancaster Avenue, Ardmore, PA 19003 USA (610) 645-9200, Fax: (610) 645-5501

Property Test Method Specification Benefit

Iodine Number
(mg/g) ASTM D4607-94 900 min • High surface area
• High adsorption capacity
• Extended service life

Abrasion Number AWWA B604-96 80 min • Less attrition during backwashing
• Lower fines improves efficiency of GAC filter

Moisture ASTM D2867-95 2% max • Economic impact

Water Soluble Ash

Total Ash ASTM D5029-89


ASTM D2866-94 0.5% max


10% max • Minimize leachables


● Minimize inert component
● Improve reactivation yield


Apparent Density
(g/cc) ASTM D2854-96 0.48 min • Reduce loss during backwashing
• Proportional to hardness
• Greater volume activity


Effective Size/ Uniformity Coefficient 1) 0.8 – 1.0 mm
2.1 max • Rate of adsorption
• Shorter EBCT
• Optimize stratification, MTZ
2) 1.0 – 1.2 mm
1.5 max • Lower pressure drop
• Longer filtration cycles

Toxicological Certification: ANSI/NSF Standard 61 & Food Chemical Codex

Quality Assurance: ISO 9001 Certification 12/03


Copyright© 2003 Carbochem



PROJECT: GAC for Municipal Water Treatment


Functionality: Adsorption and/or filtration

Application: Removal of Taste & Odor, trace organics, disinfection by-product precursors, free chlorine and turbidity.

Type of Filters: Gravity – surface water, high volume
Pressure – ground water, low volume

GAC Position: Prior to chlorination to minimize the formation of THM etc.

Recommended EBCT: 7 minutes minimum (producing a shorter MTZ and thus more efficient use of the GAC)


Typical Flow Rate: 3 - 5 gpm/ft2

Backwash Rate: Achieve a bed expansion of 30% minimum (refer to chart)

Pressure Drop: Determined by system requirements (refer to chart)

GAC Specifications:

Iodine Number 900 mg/g min
Abrasion Number 80 min
Water Soluble Ash 0.5% max
Moisture, as packed 2% max
Apparent Density 0.5 g/cc
Backwashed and Drained Density 28 lbs/ft3
Standard Size 8 x 30 mesh
+8 mesh 10% max
-30 mesh 4% max
Mean Particle Diameter 1.5 – 1.7 mm





Quality Certifications: ▪ ANSI/NSF Standard 61
▪ ISO 9002
▪ AWWA B906-96
▪ Food Chemical Codex, Edition 4, 1996

Particle Sizing:

1) Effective Size: 0.8-1.0 mm Uniformity Coefficient: 2.1 maximum
This combination maximizes the adsorption characteristics of the GAC but promotes a larger pressure drop due to stratification. This size is larger than conventional filter sand but comparable to average size anthracite. Recommended to improve performance of filters that have a limited EBCT such as retrofit applications.

2) Effective Size: 1.0 – 1.2 mm Uniformity Coefficient: 1.5 maximum
This combination optimizes filtration performance and produces a lower pressure drop. Recommended for new filters that must sustain a high volume such as deep bed filters.

Typical Service Life, T&O Removal: 3 years

Filter Media Replacement:
• Determined by breakthrough limits.

Recommended Bed Depth: Sand 6”
GAC 36” minimum

Note: Deep bed GAC filters provide the benefit of longer filter run times and yet maintain the required water quality by using larger and more uniform GAC.

Filtration Performance: GAC filter-adsorbers can typically achieve an effluent turbidity of less than 0.3 ntu (depending on the TSS loading on the GAC).

Design Issues:
Parameters such as apparent specific gravity, acid solubility and sphericity (per AWWA B100 and ASTM C128) are mainly applicable to filter media such as sand and fine aggregate rather than activated carbon. GAC has unique properties and characteristics due to its internal pore structure, which are addressed by test methods that have been developed by AWWA and ASTM specifically for activated carbon.

Note: The purpose of this document is to provide a general overview and does not address specific design requirements.


12/03
PROPOSED GAC SPECIFICATIONS




A) Granular Activated Carbon - General Requirements

The Granular Activated Carbon (GAC) shall be virgin product, produced only by steam activation from select grades of bituminous coal. Lignite, peat, wood, sub-lignite or coconut based GAC shall not be accepted nor will reactivated or regenerated material.

Activation of the GAC shall be carefully controlled to produce a material having a high internal surface area with optimum pore size for effective adsorption of a broad range of high and low molecular weight organic contaminants.

The GAC shall be capable of withstanding the abrasion and dynamics associated with repeated backwashing, surface washing and hydraulic transport. The density and particle size shall be designed for packed bed type of operation.
The GAC shall have sufficient density to settle rapidly after backwashing to resume operation of the filter with a low level of floaters.

The GAC shall be supplied from a single factory to ensure consistent quality and contain no soluble inorganic or organic substances that will impair or would otherwise render the water unfit for public use. The GAC shall be visually free of foreign materials such as clay, dirt or other deleterious materials.

The GAC shall conform to the latest edition of AWWA B-604 for GAC and the Food Chemicals Codex (4th Edition, 1996).

B) GAC Supplier Qualifications

The factory producing the activated carbon shall have a minimum of 10 years experience in supplying GAC to the United States for potable water treatment as well as ISO 9001 certification.

The supplier shall demonstrate that the product being offered is suitable for potable water treatment as supported by the following:
(1) ANSI/NSF Standard 61 certification for the manufacturing facility.
(2) Five Municipal references that have used GAC from the designated manufacturer for more than 12 months.
(3) Total quantity of GAC supplied to the U.S. market for potable water treatment to be in excess of 1 million pounds.

For imported GAC, the manufacturing facility should have an official Registration Number as required by the Federal Bioterrorism Regulation for products related to human consumption.







C) GAC Product Specifications:

Iodine No.: 900 mg/g min
Water Soluble Ash: 0.5% ash max
Abrasion Number: 80 min
Moisture, as packed : 2% max
Apparent Density: 0.48 g/cc min
Bulk Density, backwashed and drained: 28 – 30 lbs/ft3
Uniformity Coefficient: 2.1 max
Effective Size: 0.8 – 1.0 mm
Mesh size, U.S. Sieve 8 x 30 mesh
% remaining on top screen 10% max
% through bottom screen 4% max

D) Bid Submittal Requirements:

(1) The bidder shall submit with the proposal a guaranteed certificate of analysis representative of the product being offered.
(2) The bidder shall submit an Affidavit of Compliance stating that the carbon is in compliance with the Bid specifications.
(3) Material Safety Data Sheet for Activated Carbon.
(4) Product literature, including applicable lab reports and product certifications.

E) Analytical Service

The successful bidder shall analyze representative GAC samples taken from each filter annually in terms of Iodine Number, Apparent Density and particle size to determine the degree of saturation and indication of residual effective service life.




12/08

المرشحات المتعددة الاوساط


مكونات المرشح الرملي السريع:
يتكون المرشح الرملي السريع من حوض من الخرسانة مستطيل الشكل يوجد بقاع شبكة الصرف الخاص بالمرشحات بمقاسات معينة.

العوامل المؤثرة في عملية الترشيح

1/ عمق طبقة الوسط الترشيحي
2/ قطر الرمل الخاص بلاوسط الترشيحي
3/ معدل الترشيح
4/ ارتفاع عمود المياه فوق الوسط الترشيحي
5/ كفاء عملية الغسيل للمرشح
6/ كفاءة عملية الترويق التي تسبق الترشيح
7/ نوعيةالوسط الترشيحي

وهناك طريقتان للترشيح :

الأولى وهى القديمة المعروفة بالمرشحات البطيئة
والثانية الحديثة وهى المرشحات السريعة .

- مرشحات الرمل البطيئة :

المرشحات البطيئة تكون بأرضيتها قنوات ثم طبقة زلط وطبقة رمل حرش ورمل ناعم وتتراوح سرعة الترشيح من 2 : 4 متر مكعب ماء لكل متر مسطح من رمل المرشح فى اليوم 24 ساعة وأصبح غير عملى هذا النوع ويتم تنظيفه دوريا كل شهرين بإزالة الطبقة السطحية بسمك من 3 – 5 سم .
- مرشحات الرمل السريعة :
تمتاز المرشحات السريعة على المرشحات البطيئة بزيادة سرعة ترشيحها إلى 200 متر مكعب للمتر المسطح من الرمل يوميا . وكذا بطريقة غسلها ميكانيكا ، وهناك نوعان من هذه المرشحات هى:-

أ – المرشحات بالجاذبية الطبيعية .
ب – المرشحات من ذات الضغط .
أ – المرشحات السريعة بالجاذبية الطبيعية :

تنشأ المرشحات بالجاذبية الطبيعية إما مستديرة وتكون حوائطها الخارجية من الصلب وإما مستطيلة وتكون مبنية بالخرسانة.
وتدخل المياه إلى المرشح من ماسورة المدخل بأعلاه وتوزع فى دائرة الحوض أو بطوله فوق هدار لتنظيم وتوزيع السيب على سطح المرشح ويبلغ ارتفاع المياه فوق رمل المرشح من 30 : 100 سم وتمر هذه المياه

فى طبقة من الرمل يتراوح سمكها بين 30 -90-120-180سم
ويلى ذلك من أسفل

طبقة الزلط المدرج وسمكها من 35 -50-85-145سم

مدرجة من أسفل إلى أعلى كما فى المرشحات البطيئة وفى بعض المرشحات يستغنى عن وضع الزلط بتركيب شبكة سلكية مجلفنة ذات 25 ثقبا فى البوصة الطولية محصورة بين لوحين من الصاج السميك وبكل منها ثقوب على أبعـاد 5 سم وقطر الثقوب العليا ربع بوصة والسفلى نصف بوصة

. أو تركيب أرضية من الاسبستوس الأسمنتى بها ثقوب لتحميل الرمل عليها ويختلف سمك الزلط ومقاسه باختلاف سمك ونوعية الرمل وتخرج المياه بعد ذلك من المرشح بدخولها فى المصافى المركبة على المواسير الفرعية المتوازية المتصلة بماسورة المخرج الرئيسية ومنها إلى خزان المياه المرشحة بعد إجراء عملية التعقيم
- طريقة غسيل المرشح :
نظرا لارتفاع سرعة الترشيح فى المرشحات السريعة من 20 : 30 ضغط للسرعة المتبعة فى المرشحات البطيئة تحتم الضرورة غسل المرشح السريع على فترات قصيرة جدا مرة أو مرتين يوميا على حسب كمية الرواسب الموجودة فى المياه المراد ترشيحها . وقد سبقت الإشارة إلى إزالة الطبقة الهلامية على فترات من سطح المرشح البطئ وهذا غير متبع فى المرشحات السريعة التى يتوفر فيها سهولة غسيل الرمل بدون عناء كبير إذ يسهل فيها غسله بدون إزالته من المرشح . ولتسهيل غسيل رمل المرشح بدون استهلاك كمية كبيرة من المياه يجب تحريك الرمل لتفكيكه وتسهيل فصل الأوساخ عنه عند مرور مياه الغسيل .

ب – المرشحات الرملية السريعة بالضغط

وهى عبارة عن أسطوانة من الصلب محكمة إما رأسية أو أفقية المحور
والنوع الرأسى
يتراوح قطره من نصف متر إلى ثلاثة أمتار
وارتفاعه من مترين إلى أربعة أمتار
وهو يستعمل التصرفات الصغيرة

النوع الأفقى
يتراوح قطره من 2.5 إلى 3.5 متر
ويبلغ طوله حتى سبعة أمتار
وهو يستعمل للتصرفات الكبيرة

. ولا تختلف هذه المرشحات فى داخلها عن المرشحات التى تعمل بالجاذبية فتوجد فيها شبكة لصرف المياه المرشحة تعلوها طبقة من الزلط ثم طبقة من الرمل بنفس مواصفات الرمل والزلط المستعمل فى المرشحات التى تعمل بالجاذبية وطريقة التشغيل هى أن تضغط المياه بعد الترسيب بواسطة طلمبات ذات ضغط عالى إلى المرشحات فتمر فى الرمل والزلط إلى شبكة الصرف ومنها إلى شبكة التوزيع رأسا دون أن تمر على خزان المياه النقية ويستمر هذا حتى يبلغ فاقد عامود الضغط فى المرشح أقصاه – ثم يتم غسله بالطريقة التى سبق شرحها فتتفكك حبيبات الرمل على بعضها ومن ثم باحتكاكها مع بعضها للتخلص مما علق بها من مواد هلامية تخرج مع المياه من المرشح كما أنه لابد من فترة إنضاج للمرشح بعد عملية الغسيل قبل استعمال المرشح ومعدل الترشيح فى هذه المرشحات هو 100 – 150 متر مكعب .
أنواع المرشحات الزلطية :
يتم تقسيم المرشحات الزلطية إلى أنواع طبقاً للأحمال الهيدروليكية والأحمال العضوية وأنواع المرشحات الزلطية هى : المرشحات ذات المعدل البطىء والمرشحات ذات المعدل المتوسط والمرشحات ذات المعدل السريع والمرشحات الخشنة والجدول التالى يوضح المرشحات الزلطية وأنواعها :

أنواع المرشحات الزلطية
الوصف الوحدة مرشحات ذات معدل بطىء مرشحات ذات معدل متوسط مرشحات ذات معدل سريع مرشحات زلطية تحضيرية
نوع مادة الوسط الترشيحى كسر حجارة قطع حديد كسر حجارة قطع حديد خشب أحمد مواد بلاستيكية أى من – المواد السابقة
عمق مادة الوسط الترشيحى متر 1.9-3.0/1.5-3.0/1.5-2.5

المرشحات الزلطية بطيئة المعدل :
الأحمال العضوية لهذه المرشحات حوالى 0.08 كجم /م3/يوم وبصفة عامة فإن المرشحات ذات المعدل البطىء لا تستخدم المياه المعادة ولكن تستخدم سيفون دفق ويتراوح عمق هذه المرشحات من 1.5 – 3.0 متر من كسر الحجارة

المرشحات الزلطية متوسطة المعدل :
وتكون مادة الوسط الترشيحى المستخدمة كبيرة الحجم وتتراوح بين 75- 100مم .

المرشحات الزلطية سريعة المعدل :
ويتراوح عمق مادة الوسط الترشيحى من 0.90 ـ 2.40 متر ، وتكون مقاسات مادة الوسط الترشيحى كبيرة لتجنب الإنسداد ولتحسين التهوية .
المرشحات الكربونية
تختلف عمق مادة الوسط الترشيحى الكربونى بناءا على:-
1)الغرض المطلوب ازالته
2)حجم الحبيبة للكربون النشط
3)عمق طبقة الرمل والزلط الموجودين

وتتراوح عمق طبقة الوسط الكربونى النشط المحبب مقاس 1-3 مم الى ثلث عمق طبقة الرمل الموجودة(10-20-30-40-50سم)
المقاسات القياسية الامريكية والاوروبية للمرشح المتعدد الاوساط السريع الترشيح
العمق=30سم رملx35سم زلطx10سم كربون
العمق=60سم رملx43سم زلطx20سم كربون
العمق=90سم رملx50سم زلطx30سم كربون
المساحة بالمتر المربع=9متر طولx5متر عرض
المساحة بالمتر المكعب=9متر طولx5متر عرضx4متر ارتفاع
References
Integrated design and operation of water treatment facilities
American Water Works Association (AWWA) Specification Valves
Welcome to the premier industrial Valves: AWWA Specification resource. A wide variety of manufacturers, distributors and service companies are featured in our extensive vertical directory to allow ease sourcing and research for Valves: AWWA Specification.
Discuss American Water Works Association (AWWA) Specification Valves & Other Topics
1. ^ a b c Rushton, A, Ward, A S and Holdich, R G (1996). Introduction to Solid-Liquid Filtration and Separation Technology. Wiley VCH. ISBN 978-3527286133
2. ^ a b c d e Coulson, J M; Richardson, J F; Backhurst, J R and Harker, J H (1991). Chemical Engineering. Vol.2, 4th Ed. ISBN 0-7506-2942-8.
3. ^ a b Ives, K J (1990). "Deep Bed Filtration." Chap. 11 of Solid-Liquid Separation, 3rd Ed., Svarovsky L (ed). Butterworths. ISBN 0-408-03765-2
4. AMERICAN Water purification
5. AMERICAN Water treatment
6. American Water Works Association
References
1. ^ Jimmy Wong, Chin Hong Lim, Greg L. Nolen (1997-03-28) (in English). Design of Remediation Systems. CRC Press. p. 226. ISBN 978-1566702171. http://www.amazon.com/Design-Remediation-Systems-Jimmy-Hock/dp/1566702178. Retrieved 2008-09-05.
References

Baker, M.N. and Taras, Michael J. (1981). The quest for pure water: The history of the twentieth century, volume 1 and 2. Denver: AWWA.

Binnie, Chris, Kimber, Martin, & Smethurst, George. (2002). Basic Water Treatment (3rd ed.). London: Thomas Telford Ltd.

Buchan, James. (2003). Crowded with genius: the Scottish enlightenment: Edinburgh's moment of the mind. New York: Harper Collins.

Christman, Keith. (1998). The history of chlorine. Waterworld, 14 (8), 66-67.

Outwater, Alice. (1996). Water: A natural history. New York: Basic Books.

Wilson, Catherine. (1995). The invisible world: early modern philosophy and the invention of the microscope. Princeton, NJ: Princeton University Press.


GRAVITY FILTERS


1. Sanitization Procedure for Empty Filter
• Remove all loose debris and flush filter with water
• Fill filter with chlorinated water at a concentration of 100 ppm chlorine for 12 hours to achieve a minimum residual chlorine level of 25 ppm
• Drain filter and rinse with treated water
• Neutralize chlorinated wastewater as necessary before discharge to sewer

2. Loading GAC
• First add water to the filter equal to 33% of the GAC volume
• The carbon should be pumped into the filter as a water slurry containing approximately 15% GAC by weight (1 Kg/8 liters water)
• During this process all the fines and non-wetted particles will accumulate in the water layer formed above the GAC bed. (NOTE: if the carbon is not loaded hydraulically the new carbon bed should be soaked for 24 hours minimum to ensure adequate wetting)
• This component is removed by backwashing at approx 150 liters/min/m2 until all the fines are removed
• The backwash rate is increased to achieve a bed expansion of 30% for 10 – 15 minutes to allow stratification within the carbon bed
• The backwash cycle should be repeated a second time to ensure complete conditioning

3. Backwashing Procedure During Operation
• Backwashing should commence at an initial rate of 150 liters/min/m2 in an upward direction for 3 minutes to remove any fine material that may exist in the carbon bed
• The backwash rate should then be gradually increased to achieve a bed expansion of 30% for approximately 10 minutes. Typical flow rates are approximately 650 liters/min/m2 with 8 x 30 mesh carbon and 500 liters/min/m2 with 12 x 40 mesh carbon depending on the temperature (refer to Bed Expansion Curves).
• Surface sweeps and air washes should be turned off during the backwashing cycle to prevent GAC losses
• The backwash cycle should be gradually brought to an end over a 3 – 5 minute period to promote stratification within the filter bed
• Backwashing with chlorinated water will help to control microbial growth
12/99

GENERAL INFORMATIONS ABOUT ACTIVATED CARBON PROPERTIES:-


Activated carbon, also called activated charcoal or " Activated coal" is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.[1]
The word activated in the name is sometimes replaced with active. Due to its high degree of microporosity, just one gram of activated carbon has a surface area in excess of 500 m2, as determined typically by nitrogen gas adsorption. Sufficient activation for useful applications may come solely from the high surface area, though further chemical treatment often enhances the absorbing properties of the material. Activated carbon is usually derived from charcoal.

Production
Activated carbon is carbon produced from carbonaceous source materials like nutshells, peat, wood, lignite and coal and petroleum pitch. It can be produced by one of the following processes:
1. Physical reactivation: The precursor is developed into activated carbons using gases. This is generally done by using one or a combination of the following processes:
o Carbonization: Material with carbon content is pyrolyzed at temperatures in the range 600-900 °C, in absence of air (usually in inert atmosphere with gases like argon or nitrogen)
o Activation/Oxidation: Raw material or carbonised material is exposed to oxidizing atmospheres (carbon dioxide, oxygen, or steam) at temperatures above 250 °C, usually in the temperature range of 600-1200 °C.
o
2. Chemical activation: Prior to carbonization, the raw material is impregnated with certain chemicals. The chemical is typically an acid, strong base, or a salt (phosphoric acid, potassium hydroxide, sodium hydroxide, zinc chloride, respectively). Then, the raw material is carbonized at lower temperatures (450-900 °C). It is believed that the carbonization / activation step proceeds simultaneously with the chemical activation. This technique can be problematic in some cases, because, for example, zinc trace residues may remain in the end product. However, chemical activation is preferred over physical activation owing to the lower temperatures and shorter time needed for activating material.


Granular activated carbon (GAC)
Granular activated carbon has a relatively larger particle size compared to powdered activated carbon and consequently, presents a smaller external surface. Diffusion of the adsorbate is thus an important factor. These carbons are therefore preferred for all adsorption of gases and vapours as their rate of diffusion are faster. Granulated carbons are used for water treatment, deodourisation and separation of components of flow system. GAC can be either in the granular form or extruded. GAC is designated by sizes such as 8x20, 20x40, or 8x30 for liquid phase applications and 4x6, 4x8 or 4x10 for vapour phase applications. A 20x40 carbon is made of particles that will pass through a U.S. Standard Mesh Size No. 20 sieve (0.84 mm) (generally specified as 85% passing) but be retained on a U.S. Standard Mesh Size No. 40 sieve (0.42 mm) (generally specified as 95% retained). AWWA (1992) B604 uses the 50-mesh sieve (0.297 mm) as the minimum GAC size. The most popular aqueous phase carbons are the 12x40 and 8x30 sizes because they have a good balance of size, surface area, and headloss characteristics.

Properties
A gram of activated carbon can have a surface area in excess of 500 m2, with 1500 m2 being readily achievable.[3] 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.
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, ammonia, 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.
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 dilited 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 metals (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.




مجموعة تكنولاب البهاء جروب
عقيد دكتور
بهاء بدر الدين محمود
رئيس مجلس الادارة
استشارى معالجة المياه
0117156569/0129834104/0163793775
فاكس/0224024307
TECHNOLABELBAHAAGP@GMAIL.COM
TECHNOLABELBAHAAGP@YAHOO.COM
TECHNOLABELBAHAAGP@HOTMAIL.COM
TECHNOLABELBAHAAGP@LIVE.COM

WEB-SITE
WWW.TECHNOLABELBAHAAGP.GOOGOOLZ.COM