Alkyl ketene dimer – New Age Paper Sizing

Structure of the AKD derived from palmitic acid

Structure of the AKD derived from palmitic acid

Alkyl ketene dimers (AKDs) are a family of organic compounds based on the 4-membered ring system of oxetan-2-one, which is also the central structural element of propiolactone and diketene. Attached to the oxetane ring of technically relevant alkyl ketene dimers there is a C12 – C16 alkyl group in the 3-position and a C13 – C17 alkylidene group in the 4-position.

The main application of alkylated ketene dimer is in the sizing of paper and cardboard, as well as in thhydrophobization of cellulose fibers. The products thus modified are distinguished by higher mechanical strengths and less penetration of water, inks, or printing inks.[1]

AKD’s feature hydrophobic alkyl groups extending from a beta-propiolactone ring. A specific example is derived from the dimerization of the ketene of stearic acid. This ketene is generated by pyrolysis of stearoyl chloride.[2] AKD’s react with the hydroxyl groups on the cellulose via esterification reaction. The esterification is competitive with hydrolysis of the AKD. Prior to the development of AKD’s, hydrophobicity was imparted by incorporating rosin into the paper.

Related to AKDs, is alkenyl succinic anhydride which is another substitute used in sizing applications (ASA). As for AKDs, ASA reacts with hydroxy groups of the cellulose to form an ester, anchoring the hydrophobic group to the surface. ASA is prepared by thendne reaction of unsaturated hydrocarbons with maleic anhydride.

A continuous process in which long-chain carboxylic acid chloride and tertiary amine (e. g. dimethyl isopropylamine, dimethylcyclohexylamine or triethylamine) is supplied separately without solvents to a tube reactor, kneader or preferably a twin-screw extruder or planetary roller extruder and reacted at temperatures between 90 and 110 °C, delivers lactone contents of over 90% at short reaction times. Processing is carried out by phase separation or acidic extraction.[19]

 

Alkylated ketene dimers as paper sizing agents

The problems with the acidic (aluminum sulfate-mediated) mass sizing of paper with alkaline-digested colophony resins introduced since the early 19th century led beside the use of alkaline flocculants (such as chalk or calcium carbonate as the alkali reserve) to the search for alternative materials for sizing in a neutral or alkaline environment. In addition to the significantly more reactive alkenyl succinic anhydrides (which do also hydrolyze rapidly in the presence of water) alkylated ketene dimers were preferred surface and mass sizes in the paper industry from the 1960s onwards.

 

Industrially applied AKDs are derived from fatty acids with chain lengths between C14 (myristic acid) to C22 (behenic acid); palmityl (C16) diketene and stearyl (C18) ketene and mixtures thereof are preferably used, as well as fatty acid mixtures from the hydrolysis of animal and vegetable fats. Because of the chain length of the original fatty acids, AKD are waxy solids with melting points between 42oC and about 70 °C. Mixtures of alkylated ketene dimers and water are dispersions at temperatures below 40 °C or emulsions at temperatures above 45 °C. Liquid AKDs are widely used, they are based on unsaturated fatty acids like oleic acid or branched fatty acids, like iso-stearic acid.

Aqueous alkyl diketene dispersions generally contain 10-20 wt% of AKD, as well as active protective colloids (particularly polycations such as cationic starch, copolymers of N-vinylpyrrolidone and quaternized N-vinylimidazole, acylated polyethyleneimines or cationic high molecular weight polyacrylamides with an average molar mass up to 7 million g/mol) and other stabilizers (usually anionic surfactants, for example, lignin sulfonates or condensation products of naphthalene-sulfonic acid sodium salt and formaldehyde). Such stabilized AKD dispersions are active and stable at room temperature for up to three months and also tolerate the addition of different fillers for paper or cardboard (e.g. kaolin, chalk, talc, titanium dioxide, calcium sulfate, aluminum oxide, etc.) from 5 to 25%. The amounts of alkyl ketene dimers used for the sizing of paper and paper products are preferably in the range from 0.15 to 0.8 wt%, sometimes from 0.05 to 0.2 wt%, based on the dry paper stock.

 

Paper sizing with alkylated ketene dimers

For paper sizing with AKD, a three-step process was proposed which, despite controversial discussions in the 1990s, seems to describe the processes that are taking place. 

Decisive criteria for the quality of the hydrophobicity of papers are

  1. The retention of the AKD particles on the wet paper mass on the paper screen
  2. The spreading of the AKD particles on the surface and the penetration in the paper mass
  3. The chemical reaction of the hydroxyl groups of the cellulose (esterification) with the alkylated ketene dimers to form beta-ketocarboxylic esters.

The molecular structure (i.e., molar mass and cross-linking degree), the molar charge density of cationic groups, the exact dosage of the cationic polymer as a dispersion stabilizer and retention aid as well as keeping the other process parameters such as temperature, pH and residence times is crucial.

After removal of excess water – also to avoid hydrolysis of the AKD to the beta-keto acid and subsequent decarboxylation to the ketone –

follows the cracking of the stabilized AKD particles on the base paper mass, the melting of the solid AKD wax (at approx. 90 °C), the spreading of the liquid AKD wax by surface diffusion on the cellulose fibers, and the formation of closed hydrophobic layers. The thickness of the hydrophobic layers depends on the AKD concentration in the dispersion.

Ad 3. The hydrophobization of cellulose fibers with alkylated ketene dimers takes place most effectively in neutral or preferably weakly alkaline media (pH 7.5-9.0). The reaction temperature is generally 90-110 °C, with approximately 40% of the AKD used reacting with the cellulose. After the reaction contact angles of >100° are measured, indicating the hydrophobic character of the AKD-modified model surfaces. The esterification of hydroxyl groups of cellulose fibers was also demonstrated by comparison reactions with 14C-labeled AKD.

The sizing with AKD is suitable for the permanent hydrophobization of newsprint, printing and writing paper and cardboard used as a container for liquids (including foodstuffs such as milk), as well as for the improvement of shape stability and runnability.

Commercial Production

At Advance Chemicals, undergoing robust testing frequently, the production of AKD is strictly under defined and controlled conditions thus giving out world call AKD for application in various grades of paper making.

 

Advantages and Disadvantages of Silicone Defoamers

Industry production and defoaming processes are closely connected. Preventing or controlling is crucial when working in different industries involving aqueous solutions or adhesives. Foaming could influence the appearance and effectiveness of the product, coating weight, increase manufacturer times and expenses, diminish product quality, the flow speed of liquid, and many more other factors.

Advance Chemicals ACCO 0941 silicone-based defoamer is designed to knock down the foam and effectively control and minimize production applications, which could save processing time and money. Our Silicone Based Defoamers are suitable for application in food and beverage, chemical, plastics, pulp and paper, oil and gas, metalworking, construction, and others.

Defoaming agents can effectively remove and suppress the formation of foam. The Silicone-based defoamers are versatile, practical, and economical solutions for controlling foam.

Silicone-based defoamers are ingrained with silicon key ingredients that might be more effective than oil or water-based emulsion. Silicone antifoams are used in processes that involve liquid-gas contact and agitations with the end goal of optimizing manufacturing throughput and productivity.

 

Before you choose an Antifoaming Chemical, it is imperative to peek into its pros and cons.

Advantages of Silicone Based Defoamers

 

  • Wide applications

Due to the chemical structure of silicone oil, it is insoluble in various applications and can be used in myriad industrial uses. It can be blended in oil systems as well as defoaming water systems.

 

  • Lower surface tension

Lower surface tension translates to higher defoaming efficiency. The surface capacity of silicone oil is 20-21 dynes/cm, lower than that of water 72 dynes/cm.

 

  • Thermal stability

An ordinary dimethicone can resist about 150 degrees Celsius for a long time and 300 degree Celsius for a short time, and the Si-O bond does not deteriorate. The silicone defoamer can be used over a wide range of temperatures.

 

  • Good chemical stability

The chemical stability is high, and it’s gruelling to react with other substances. Silicone defoamers can be blended with acids, bases, and salts as their formulation is reasonable.

 

  • Physiologically inert

The properties of silicone oil are non-toxic to humans and animals when added with a semi-lethal dose of more than 349mg/kg of body weight. Therefore, silicone defoamers can be used in food, medical, pharma, cosmetic, and other industries.

 

  • Powerful defoaming

Silicone defoaming breaks the foam, significantly inhibits the foam, and avoids the formation. It is used in small amounts, one part per million of the weight of the foaming medium. It’s not only low cost but also does not pollute defoamed material.

 

Disadvantages of Silicone Based Defoamers

 

  • Poor durability

Silicone-based antifoam is relatively poor durability.

 

  • Oil-soluble

Silicone is oil soluble, and it reduces the defoaming effects in oil systems.

 

  • Temperature resistance

It is not ideal for long-term high-temperature resistance and strong alkali resistance.

 

High-grade silicone defoamer

Advance Chemicals is a defoamer chemical supplier; with unrivaled experience and unparalleled experience, our company has products suitable for all walks of life. We offer food-grade, tech-grade, and agriculture antifoams with various viscosities that are ready to use and concentrated ones.

 

Advance is synonymous with good service and punctual delivery. With a solid customer base, we are the leader in the market for water treatment chemicals as well.

We are renowned as one of the most reliable Pulp & Paper chemical suppliers in India, and offer a range of specialty chemicals.

 

 

Difficulties for persistent control of foam in pulp operations

 

Pulp and paper makers need to reduce excessive foam created in the pulping process, when extracting cellulose fibers from wood, and during the washing process when making products such as Kraft brown-stock. Also due to various contaminants, foam is a permanent trouble during recycling operations. To process, manufacturers use foam control formulations, ‘antifoams’ or ‘defoamers’. To be competitive, pulp manufacturers are constantly seeking to lower costs and to use less water, energy and chemicals. Also to minimize their impact on the environment.

In all these respects, silicone-based antifoam formulations outperform mineral-based products, being easier to use – and at lower dosage – to produce better quality pulp. Silicones provide both greater and more rapid knockdown, and more persistent control of foam, and are stable across the extreme pH and temperature conditions needed to make pulp.

 

A long experience in foam control agents

Advance Chemicals has been helping major clients in Asia for more than 15 years, by continuing to develop our full-range of cutting-edge ACCO range foam control agents, formulations and processing aids.

Our experts work closely with the Pulp and Paper Industry to provide them upstream support by advising on use of the right products in the most efficient way for cost-effective and environmentally safe processes.

 

ACCO​ foam control agents are a comprehensive and highly effective portfolio of products available in different forms, such as compounds and emulsions.

 

A persistent foam control agent

ACCO 0941 is an innovative foam control agent, based on a highly-active silicone compound. Advance Chemicals has specifically designed ACCO 0941 to be the foam control agent of choice for several industries. ACCO 0941 meets all essential criteria in terms of productivity, reliability and quality, to reduce total cost of operations. Benefits include:

  • Excellent foam knock-down
  • Persistent foam control
  • Lower dosage compared to mineral oil-based antifoams
  • Enhanced efficiency of pulp washing
  • Improved drainage of pulp
  • Ease of use
  • Reduced consumption of chemical additives

In case of any technical query related to foaming or related to Pulp & Paper Specialty Chemicals kindly drop us an email of info@advancechemicals.in or submit the form through www.advancechemicals.in

Difficulties for persistent control of foam in pulp operations

Pulp and paper makers need to reduce excessive foam created in the pulping process, when extracting cellulose fibers from wood, and during the washing process when making products such as Kraft brown-stock. Also due to various contaminants, foam is a permanent trouble during recycling operations. To process, manufacturers use foam control formulations, ‘antifoams’ or ‘defoamers’. To be competitive, pulp manufacturers are constantly seeking to lower costs and to use less water, energy and chemicals. Also to minimize their impact on the environment.

In all these respects, silicone-based antifoam formulations outperform mineral-based products, being easier to use – and at lower dosage – to produce better quality pulp. Silicones provide both greater and more rapid knockdown, and more persistent control of foam, and are stable across the extreme pH and temperature conditions needed to make pulp.

 

A long experience in foam control agents

Advance Chemicals has been helping major clients in Asia for more than 15 years, by continuing to develop our full-range of cutting-edge ACCO range foam control agents, formulations and processing aids.

Our experts work closely with the Pulp and Paper Industry to provide them upstream support by advising on use of the right products in the most efficient way for cost-effective and environmentally-safe processes.

 

ACCO foam control agents are a comprehensive and highly effective portfolio of products available in different forms, such as compounds and emulsions.

 

A persistent foam control agent

ACCO 0941 is an innovative foam control agent, based on a highly-active silicone compound. Advance Chemicals has specifically designed ACCO 0941 to be the foam control agent of choice for several industries. ACCO 0941 meets all essential criteria in terms of productivity, reliability and quality, to reduce total cost of operations. Benefits include:

  • Excellent foam knock-down
  • Persistent foam control
  • Lower dosage compared to mineral oil-based antifoams
  • Enhanced efficiency of pulp washing
  • Improved drainage of pulp
  • Ease of use
  • Reduced consumption of chemical additives

In case of any technical query related to foaming or related to Pulp & Paper Specialty Chemicals kindly drop us an email of info@advancechemicals.in or submit the form through www.advancechemicals.in

Paper Machine Runnability – Retention Aid

Retention Aid is the key to cost savings in a paper mill. Retention aids are used at the wet end of a paper mill to improve the retention of fine particles, fillers, additives & sizing agents during the formation of paper. Particularly retention aid is needed to be added in the alkaline paper-making process, but not in the acidic paper-making process because in this process alum helps in retention. Modern paper-making technology is an alkaline paper-making process. Moreover, modern mills operate high-speed paper machine with increased usage of recycled fibers. In this case, the task of retaining is more challenging and paper machine runnability will be troublesome. As a result, the papermaking process becomes less economical. Hence the demand for retention aid is increased to save costs.

The chemical most used as retention aids are polyacrylamide and polyethyleneimine.

Troubles of low retention:

Papermaking is in essence a filtration process. The paper machine wire cloth can be considered as a continuous filter; where a proportion of the solids in the stock is retained and some fine particles are drained through the wire cloth mesh with water and formed white water. The greater part of the white water is returned to the stock, with the result that the concentration of fines and fillers gradually increases. It should be retained otherwise following troubles arise:

  • Fine fiber particles and filler drainage
  • Higher additives and sizing cost
  • Increased deposits
  • Decreased runnability
  • More downtime for cleaning
  • Filling of wet-press felts
  • Bad paper sheet formation
  • Higher sewer losses

 

The function of retention aids

The best retention of fine particles and colloids in the papermaking process normally occurs when the zeta potential is near to zero and retention aid takes care of that. The main functions of retention aids are the following:-

  • Accelerate drainage, hence increasing machine speed
  • Improved retention of fines and fillers
  • Reduced wet-end additives and sizing usage
  • Reduced steam usage due to better surface contact
  • Reduce deposits
  • Reduce sheet breaks
  • Improves paper machine runnability
  • Improved paper sheet formation
  • Increased brightness
  • Cleaner white-water system
  • Reduce downtime for cleaning
    Overall, Increase the productivity

 

Disadvantages of retention aid

If retention aid is used in higher doses, as a result highly flocked sheet is formed. Also, observed are increased paper web break, two-sidedness, and decreased paper machine runnability. Hence to optimize runnability the dosing needs to be optimized.

Importance of Sizing Agents for Paper Making

Introduction

The papermaking process is highly cost-sensitive and the market is extremely competitive. Specialty chemicals have been developed and applied in to assure an efficient process and meet specific end-use paper requirements.

Paper can be classified according to different criteria, either by weight, color or raw material source. Here we talk about woodfree paper, which is a paper made from chemical pulp, without lignin. With woodfree paper, the final performance depends on the quality of the fibrous matrix and the properties of the surface. The surface characteristics are controlled by surface treatments which aim to give specific qualities to the paper, according to its purpose.
Surface treatments are divided into two types:

  1. Mechanical, like calendaring, or 
  2. Chemicals such as coating and surface sizing.

Calendaring and surface sizing are the treatments used while the coating is more common in magazine paper or photographic paper.

Why talk about sizing?
Existing studies on surface sizing focus on evaluating the surface quality of paper, after the application of different solutions, through surface characterization techniques such as contact angle measurement or inverse gas chromatography.

The lack of works exploring surface sizing in a more industrial context contributes to the importance and applicability of the present study. The complexity of the paper structure and the presence of various components make this system quite complex. Thus, to establish a possible process optimization and, consequently, a final improvement of paper characteristics, it is essential to understand the interactions between the various components present in this stage of production.

The Process

For surface sizing, a solution composed mainly of starch is applied to the surface of the paper sheet.

Regarding technology, film size press is the most used, in which a film of the solution is transported and applied to the paper surface by the applicator rollers. This technology allows an independent application of the solution to each side of the paper. Usually, solids content,  viscosity, and temperature are the process control parameters. The penetration of the solution into the paper structure and its uniform surface often determines the printing quality.

The behavior of a liquid on a surface is crucial for homogeneous film formation processes, where properties such as contact angle and surface tension play an important role. Thus, the present work intends to give a deeper understanding of the interactions between the surface sizing solution and the paper surface. More specifically, it aims to measure the contact angle and the surface tension of surface sizing solutions and to relate these properties to starch content and temperature.

What is Surface Sizing?

Surface sizing is a surface treatment whose main objective is to increase the bond between the fibers by filling the pores with a solution composed mainly of starch. This treatment is used to increase the surface resistance, stiffness, and printability, and to control the hydrophilic character of the fibers.

The surface sizing solution is composed typically of starch, sizing agent, optical brightening agents (OBAs), salt, and defoamers.

Starch is the main component of the solution and it acts as a binder to connect vessel segments and loose fibers at the surface. To be used properly, starch needs to be fully dissolved (cooked and disintegrated into amylose and amylopectin) through the process of cooking. Afterward, starch has to be modified to keep its rheological properties and to be protected against retrogradation. Enzymatic or thermal conversion is usually practiced to manipulate the viscosity of the starch solution. On the other hand, the introduction of other functional groups through chemical modifications such as oxidation, esterification, or nucleophilic substitution can give other properties to the starch.

Surface sizing agents are compounds containing hydrophobic groups that repel water molecules and prevent their absorption by the paper sheet. These agents, when combined with starch and applied to the paper surface, form a thin reticular film at the paper surface, impacting certain properties such as smoothness, surface resistance, and hydrophobicity.

For surface sizing, sizing agents can be cationic rosin, AKD, or synthetic polymer compounds like co-styrene maleic anhydride or co-styrene-acrylate. While cation rosin and AKD are preferably applied at the wet end, syntenic polymer compounds were specially designed for surface sizing. Compared to the other available sizing agents, polymer compounds are extremely versatile and compatible with all types of starch, and in some cases, do not need defoamers.

To improve the optical properties of the paper surface, like brightness and whiteness, optical brightening agents are usually applied in surface sizing. There are three types of OBAs used in the paper industry, all based on stilbene molecules. The difference between each one lies in the number of sulfonic substituents, which in turn affect their properties. In general, the whitening effect, solubility, and price increase with the number of sulfonic substitutes, while the affinity to the fibers decreases.

Due to the current high-speed rate of production, together with the heat and friction between the paper and the metal parts of the machine, a favorable environment is created for static electricity to accumulate in the materials. This has serious risks such as production downtime or equipment damage. To overcome the problem is usual to add mono or divalent salt to improve the paper surface conductivity. The addition of a divalent salt, such as calcium chloride, further improves printing quality by enhancing the sharpness of colors on paper.

Defoamers are usually present on surface sizing solutions as a process chemical rather than a functional chemical. Foam is associated with operational problems, reduced efficiency, and surface defects in surface treatments and must be controlled. Defoamers are sophisticated formulations made up of extremely water-insoluble surfactants with the ability to spread rapidly to gas/liquid interfaces, destabilizing the foam lamellae previously stabilized by other surfactants.

Surface sizing performance is affected by the properties of the applied aqueous solution such as composition, viscosity, or temperature, as well as the properties of the paper sheet such as weight, moisture content, porosity, and surface energy, among others. These properties should be adequately controlled to ensure the desired absorption of the aqueous solution into the sheet.

Our range of Sizing Agents be it AKD, Fortified Rosin, Cationic or Anionic Surface Sizing Agent are engineered to cater to all of the aspects mentioned above and ensure smooth runnability of paper machine.

The products codes are as below, and the codes are clickable so that you get the technical details of each product:

  1. ACCO – 0921 – Anionic Surface Size
  2. ACCO – 0922 – Cationic Surface Size
  3. ACCO – 0924 – AKD Emulsion
  4. ACCO – 0925 – Fortified Rosin

Coagulants and Flocculants – Water Treatment at its best!

Uses of flocculation and coagulation in wastewater treatment 

Flocculation and coagulation in water treatment are used to remove suspended solids through a process that destabilizes suspended particles in aqueous solutions. The difference between the two is that, coagulation is the aggregation or agglomeration of particles and agglomeration is the sedimentation of coagulated particles. Its purpose is to remove and neutralize the charge density of the particles through use of coagulant. Thereafter, a flocculant is used to promote particle bonding through flocculation. This allows the larger agglomerated particles to easily separate from the water and settle in the bottle. 

 Common Applications: 

  • Sludge pond Management 
  • Wastewater Solids Dewatering 
  • Wastewater Treatment 
  • Recycled Plastic Wash Water Treatment 
  • Mine Wastewater Treatment 

 

Why Use Flocculants and Coagulants?

 Coagulation: The combined use of agents and coagulants can efficiently and cost-effectively remove suspended particles in aqueous solutions or slurries. Given enough time, some particles will spontaneously settle out of the water. Other particles, however, do not settle out for days or months due to their small particle size and interparticle charge. Coagulants are primarily used to remove very small suspended particles in solutions that do not settle quickly. 

Flocculation: The main function of flocculants is to bind and flocculate suspended particles in water to form larger particles, facilitating sedimentation and removal by the separation process of particles and water. 

 The main purpose of the coagulation/agglomeration process is to remove turbidity from the water. Turbidity is the cloudy appearance of water caused by small particles suspended in the water. Water with little or no turbidity is clear. 

 Turbidity isn’t just a cosmetic issue in water. Highly turbid water can be very difficult or impossible to disinfect properly. Therefore, the maximum permissible turbidity level in water is 0.5 NTU and the recommended value is around 0.1 NTU. (NTU or TU stands for Nephelometric Turbidity Units, a measure of water turbidity.) 

In addition to removing turbidity from water, coagulation and flocculation are beneficial in other ways. This process removes many bacteria floating in the water and can be used to remove colour from water.

Turbidity and color are much more common in surface water than in groundwater. As surface water flows over the surface into streams, through various separate streams, and into rivers, it picks up a large amount of particles. Groundwater needs to be aerated more frequently, while treatment by coagulation and flocculation is common for surface water. 

 

What is aggregation? 

Agglomeration is the process that occurs when the interaction of particles in water becomes destabilized in the presence of another molecule and they join together to form large agglomerated particles that readily settle. Polymer molecules are often used to facilitate this process because they can be tuned to increase or decrease their destabilization potential via the surface charge of the molecule. Higher charge densities can lead to instability. Lower charge densities have less effect on particles in suspension. As a result, technologists are using different combinations of charge, molecular structure, and even elemental composition of flocculants to tailor water treatment protocols for each unique application. 

 

How does flocculant work? 

Used in a wide variety of industries and applications, flocculant works by binding contaminants into flocs or “flakes” that float or sink to the bottom of the water. They help remove suspended solids from wastewater. It can also be used for lime softening, sludge thickening, and solids dewatering. Natural or mineral flocculants include activated silica and polysaccharides, while synthetic flocculants are most commonly based on polyacrylamide

Coagulants can be used alone or in combination with flocculants, depending on the load and chemical composition of the wastewater. Coagulants differ from flocculants in that coagulants are usually salts whereas flocculants are often polymers. They can vary in molecular size (weight) and charge density (% of molecules with either anionic or cationic charge). It is used to “balance” the charge of particles in water, collecting and dehydrating them. Generally, anionic coagulants are used to trap mineral particles, while cationic coagulants can trap organic particles. 

 

Top Flocculant Chemicals 

Our ACCO 090 series of flocculants is a range of flocculants to improve wastewater treatment and reduce overall costs in a wide range of mineral processing applications. We offer a wide range of cationic & anionic, flocculants to meet all your chemical processing needs. 

 

What is coagulation? 

Coagulation is the process of bringing insoluble materials together by manipulating the charge of the particles by adding iron or aluminium salts such as aluminium sulfate or ferrous sulfate to the wastewater stream. is a fairly simple chemical process involving the main purpose of using a coagulant, in addition to removing various particulates from the suspension, is that the process makes the water less turbid.

Negatively charged particles in water are neutralized by the positive charge of the coagulant. This causes suspended matter in the water to combine to form larger flakes. These large flocs begin to sink to the bottom of the water supply. The larger the particle size, the faster the flakes settle

Coagulation helps remove various contaminants that make the water dirty or toxic. There are things like: 

  1. Suspended inorganic precipitates such as iron and some metals 
  2. Certain viruses and bacteria 

 Agglomeration converts industrial waters to their full chemical state, facilitating mechanical filtration. Once the flocs settle to the bottom of the clarifier, equipment such as filter presses can pick up and remove large clumps of these agglomerated particles, returning clean water to the system. The coagulant, clarifier, and filter press combine to deliver maximum water recovery of over 95%. Very little water is actually carried away with the solids, creating a nearly closed-loop process. 

 

Types of Coagulants 

Organic Coagulants 

Organic Coagulants are ideal for solid-liquid separation. It is also suitable if you want to reduce sludge buildup. These coagulants are organic in nature, act at low doses and offer the added benefit of not affecting the pH of the water.

Organic coagulants are typically based on the following formulations: 

Polyamine and Poly DADMAC (Diallyl dimethyl ammonium chloride) – These cationic coagulants work only by neutralizing charges and are the most commonly used organic coagulants. PolyAMINE and PolyDADMAC neutralize the negative charges of colloids in water, forming spongy clumps called “micro-flocs”. They coagulate only by charge neutralization and therefore have no advantage with respect to the sweep flock mechanism (inorganic coagulants are discussed later). 

Melamine Formaldehyde and Tannins – These natural coagulants are somewhat similar to inorganic coagulants in that they coagulate colloidal matter in water and contribute to their own settling flocs. This sweeping floc sedimentation can absorb organic matter such as oil and grease while coagulating unwanted particles in water. Since the sedimentation dehydrates everything to low moisture concentrations, these coagulants It is ideal for operations that produce harmful sludges such as those found in oil refineries. Key benefits of organic flocculants include low dosage, low sludge formation and no pH impact. 

 

Inorganic Coagulants 

Inorganic Coagulants are typically less expensive than organic coagulants, making them a cost-effective solution for a wide range of water treatment applications. It is especially effective when used with low turbidity raw water. 

Inorganic coagulants form aluminium or iron precipitates when added to water. They help purify the water by picking up impurities in the water as they fall. This process is known as the “sweep floc” mechanism. However, this may increase the overall amount of sludge that needs to be treated and removed, so it is not the right choice in all scenarios. The major types of 

inorganic coagulants are: 

Aluminium Sulfate (Alum) – One of the most commonly used water treatment chemicals in industrial processes, alum is the coagulant of choice for many. It is prepared as a liquid and the crystalline form of alum is formed when the liquid is dehydrated. Be aware that alum is a mild hazard and has similar health effects/corrosive properties to dilute sulfuric acid. 

Aluminium Chloride – This coagulant works similarly to alum, but is more expensive. , dangerous and corrosive. Therefore, in processes where alum cannot be used, it is usually chosen only as a second choice. 

Poly Aluminium Chloride (PAC) and Aluminium Chloride (ACH) – These inorganic coagulants are ideal for simple water supplies. 

Ferrous Sulfate and Ferrous Sulfate – Both iron coagulants work similarly to aluminium coagulants, although ferrous sulfate is more commonly used. Ferrous sulfate is generally preferred when a reducing agent is required or when excess soluble iron ions are required. 

Ferrous Chloride – As a waste product from steel production, ferric chloride is the most cost-effective inorganic coagulant. However, it is only used in facilities that live up to its reputation as the most corrosive and dangerous inorganic coagulant.

 

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