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Particles finer than 0.1 μm (10 −7 m) in water remain continuously in motion due to electrostatic charge (often negative) which causes them to repel each other. [citation needed] Once their electrostatic charge is neutralized by the use of a coagulant chemical, the finer particles start to collide and agglomerate (collect together) under the influence of Van der Waals forces.
Sodium silicate (Na 2 SiO 3) is a typical example. Usually, in higher pH ranges, in addition to low ionic strength of solutions and domination of monovalent metal cations, the colloidal particles can be dispersed. [21] The additive that prevents the colloids from forming flocs is called a deflocculant.
Finings’ actions may be broadly categorized as either electrostatic, adsorbent, ionic, or enzymatic.. The electrostatic types comprise the vast majority; including all but activated carbon, fining yeast, PVPP, copper sulfate, pectinase and pectolase.
Before fermentation, pectin-splitting enzymes and, for white wine, fining agents such as bentonite may be added to the must in order to promote the eventual agglomeration and settling of colloids. [1] Pectins are structural molecules in the cell walls of fruits which have the important function of 'gumming' plant cells together.
They are thus often used as thickeners, emulsifiers, conditioners, clarifying agents, and even drag reducers. They are used in water treatment and for oil recovery. Many soaps, shampoos, and cosmetics incorporate polyelectrolytes. Furthermore, they are added to many foods and to concrete mixtures (superplasticizer).
Before the water enters the clarifier, coagulation and flocculation reagents, such as polyelectrolytes and ferric sulfate, [4] can be added. These reagents cause finely suspended particles to clump together and form larger and denser particles, called flocs, that settle more quickly and stably.
An enzyme added to fruit to increase juice yield. Also used as a clarifying agent in fruit wines when added to wine or must to eliminate pectin hazes. Perlant French term for a very lightly sparkling wine with less effervescence than a crémant or pétillant Perlite
A sewage sludge thickener. Thickening is often the first step in a sludge treatment process. Sludge from primary or secondary clarifiers may be stirred (often after addition of clarifying agents) to form larger, more rapidly settling aggregates. [9]