What is selective flocculation?

Selective flocculation utilizes the differences in the physical-chemical properties of the various mineral components in the mixed suspension. It is based on the preferential adsorption of an organic flocculant on the particular solids to be flocculated, leaving the remainder of the particles in suspension.

What is the process of flocculation?

4 Flocculation. Flocculation is a process by which a chemical coagulant added to the water acts to facilitate bonding between particles, creating larger aggregates which are easier to separate. The method is widely used in water treatment plants and can also be applied to sample processing for monitoring applications.

Is alum used as flocculants?

Alum is one of the most widely used, dependable flocculants in the municipal market. It adds cationic, tri-valent metal ions to the water that neutralize the surface charges and react with the water alkalinity to form metal hydroxide precipitates that encapsulate fine colloidal particles.

For which flocculation process is used?

Coagulation-flocculation is a chemical water treatment technique typically applied prior to sedimentation and filtration (e.g. rapid sand filtration) to enhance the ability of a treatment process to remove particles.

What is coagulation and flocculation process?

Coagulation is the destabilization of colloidal particles brought about by the addition of a chemical reagent called as coagulant. Flocculation is the agglomeration of destabilized particles into microfloc and after into bulky floccules which can be settled called floc.

What is the next step after flocculation process?

Conventional plants separate coagulation (or rapid-mix) stage from flocculation (or slow-mix) stage. These stages are followed by sedimentation, and then filtration.

How is alum used as a flocculant?

There are numerous ways to use alum as a flocculant, including to crush it into a powder before adding it to water, stirring and decanting or stirring the whole stone in the water for a few seconds and waiting for the solids to settle.

Is alum a catalyst?

Alum (KAl(SO4)2·12H2O) is an inexpensive, efficient, and nontoxic catalyst used for the synthesis of 2-[3-amino-5-methyl-5-(pyridin-3-yl)-1,5-dihydro-4H-1,2,4-triazol-4-yl]propanoic acid derivatives in aqueous media by the reaction of 3-acetyl pyridine (1), amino acids (2)/(6), and thiosemicarbazide (4) at 80°C.

What is controlled flocculation?

Controlled flocculation (caused by additives): additive molecules cause the pigment particles to form a network; no direct pigment-pigment contact. Such “controlled” flocculates can be destroyed by low shear forces.

What is macro flocculation?

Polymers bridge the flocculant from micro to macro flocculant, meaning that the mass of particles collecting together gets bigger. This chemical also binds the collected mass together so that it does not easily disintegrate even when the water is slightly agitated.

Why alum is used as coagulant?

When alum is added to water, it reacts with the water and results in positively charged ions. Coagulation removes colloids and suspended solids from the water. These particles have a negative charge, so the positively charged coagulant chemicals neutralize them during coagulation.

What is particle flocculation?

Flocculation, in the field of chemistry, is a process by which colloidal particles come out of suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent.

What is the flocculation method?

Flocculation is usually considered as a primary harvesting method to increase the particle size of algae cells before dewatering and drying (Rastogi et al., 2018 ).

What are the conditions for microalgal flocculation?

Microalgal flocculation could occur under alkaline conditions (pH > 10) by coprecipitation with Mg 2+ and/or Ca 2+ [73], while inorganic flocculants, i.e., iron chloride and aluminum sulfate, need acidic conditions for effective microalgal flocculation [44,74].

What is the best flocculant for algae flocculation?

Advanced flocculants such as polyferric sulfates, prepolymerized metal salts, nonanionic polymer Magnafloc LT-25, ultrasound, pH modification, electrolytes, synthetic polymers, natural polymers including cationic starch, Moringa oleifera seed flour, and chitosan are used as novel algal flocculation agents ( Wan et al., 2015 ).

How long does it take for flocculation to complete?

Once floc has reached it optimum size and strength, water is ready for sedimentation. Design contact times for flocculation range from 15 or 20 minutes to an hour or more, and flocculation requires careful attention to the mixing velocity and amount of mix energy.