What is Poly Aluminum Chloride?
We examine Poly Aluminum Chloride (PAC), a highly significant product in the water treatment sector, and the critical role it performs.
Aluminum, chlorine, hydrogen and oxygen combine to form Poly Aluminum Chloride, an acidic solution.
It is sometimes referred to as Poly aluminum Hydroxide Chloride Sulphate Solution and is clear to slightly yellow in color.
What is the use of PAC?
The most widely used coagulant in the water treatment industry is poly aluminum chloride (PAC).
It is distinguished by the degree of basification; the higher this number, the greater the number of polymers present, which equates to a more effective product in the clarification of water-based products.
The oil and gas sectors, which employ the product as an oil-water emulsion destabilizer with good separation performance, are among its other end users.
This product is crucial to ensure maximum efficiency because, in the case of crude oil, any water content equates to a lower commercial value and greater refining expenses.
As one of the active elements that essentially forms a barrier on the skin and aids in decreasing sweat levels, PAC is also utilized in the manufacturing of deodorants and antiperspirant products.
In the paper and pulp industries, it is used as a coagulant in papermill wastewater.
PAC as an effective coagulant
The benefits of utilizing PAC over alum after considering the various coagulants are that PAC works well with pH ranges of 6–9, whereas alum works better between pH 6.5-7.6, and since PAC works even at temperatures below 10 DC, it can be used in the winter.
Additionally, due to its liquid condition, treated water has better quality and faster reaction times.
Additionally, it has a decreased residual aluminum concentration and operates at all turbidities.
On a per kilogram basis of aluminum, poly-aluminum coagulants are typically twice as expensive as a liquid alum.
However, its use can still be cost-effective with lower coagulant doses and lower pre- and post-treatment alkali doses.
It is appropriate for bulk storage and dosing installations because poly-aluminum chloride solution (10% A1203) is stable for 4 to 5 months when stored at less than 50°C.
Based on a cost comparison, PAC is now being implemented at three of six recently built in-filter/DAF water treatment facilities in Grampians Water Supply Scheme, Victoria.
For the alum option, total chemical expenses come to $76.8/ML, whereas for ACH $63.5/ML; there will be a savings of about 17%.
This example shows how employing ACH coagulant instead of alum can result in cheaper operational costs.
Additionally, superior-quality treated water that is low in TDS, CCPP and SO4 is generated.
PAC advantages
1- can be used in a wide range of PH.
2-Negligible variation of solution PH when PAC is used.
Very low need to correct or adjust the PH value in case of using PAC.
3-Compared to conventional inorganic coagulants, Alkalinity will not be consumed, PH value will not be highly decreased and hence corrosion problems shall not arise.
4-When applying PAC dosage, TDS is not increased.
5-There is a much decrease in pre-chlorination if PAC was used.
6-fast formation of folcs.
7-Very Effective in the removal of dissolved TOC.
8-PAC contains no Iron radicals, this helps with Iron fouling prevention in case of being used in RO pr treatment.
9-Unlike conventional inorganic coagulants, PAC is still very effective at lower temperatures.
10-Much OPEX & CAPEX cost saving.
11-Very easy to handle. Much shipping & Storage cost saving.
key benefits of PAC
1-High purity and quality of water.
2-Excellent coagulation, flotation and sedimentation.
3-Excellent removal of phosphor.
4-Minimal chemical sludge.
5-Low transportation cost.
How does (PAC) water treatment work?
A highly effective chemical for treating water, poly aluminum chloride acts as a coagulant to draw out and collect pollutants, colloidal particles and suspended particles.
This causes floc to form (flocculation), which can then be removed using filters.
The process of coagulation is demonstrated in the image below.
Products made of poly aluminum chloride that is used to treat water are often identified by the percentage of basification.
Basification is determined by how many hydroxyl groups there are in relation to aluminum ions.
Higher basicity results in reduced aluminum concentration and, hence, better performance in terms of pollutant removal.
The procedure that considerably reduces aluminum residuals benefits from the decreased aluminum rate as well.
Difference between PAC and Aluminium Sulphate Coagulants
Since many years ago, the water treatment industry has employed aluminum sulfate as a flocculant to remove contaminants, undesirable colors and general turbidity (haze) from water.
However, this procedure leaves significant residues of aluminum in water sources, necessitating additional filtration and producing enormous amounts of sludge-like waste (referred to as water treatment residuals), which is disposed of in landfills.
It is advantageous to look for solutions that lower these disposal costs because they have a direct impact on the running expenses of water treatment plants.
However, there are well-documented concerns about aluminum toxicity in soil and negative effects on ecosystems that limit this approach.
Waste treatment residuals do have many physical and chemical properties that could also lend to their being re-used for a more sustainable purpose, including use in construction materials and even soil nutrients.
On the other hand, Poly Aluminium Chloride has been created as an alternative.
Because PAC hydrolyzes more readily, achieves better coagulation, and quickly forms flocs, it is a far more effective product.
Additionally, it has lower dosages of aluminum, leaving substantially less sludge waste and aluminum residuals.
References
[1] https://www.monarchchemicals.co.uk/Information/News-Events/873-/What-is-Poly-Aluminium-Chloride
[2] https://www.ripublication.com/ijaer17/ijaerv12n12_36.pdf
