P0 ph

Laskowski has reviewed the mechanism of the action of surface-active reagents in flotation. He said that frother molecules have an uneven distribution of polar and non-polar groups which cause them preferentially to orientate at the air-water interface with the polar groups forming a liquid film around the bubble by hydrogen bonding with the water and the non-polar groups forming a gaseous film within the bubble. They may be classified into five groups:

1. Aliphatic alcohols with a single hydroxy group R-OH, where R is either a straight-chain alkyl group with five to eight carbon atoms or a branched chain with six to sixteen carbon atoms. Typical of the branched alcohols are methyl iso-butyl carbinol (MIBC), di-acetone alcohol and 2-ethyl hexanol. These frothers produce fine-textured, fairly selective froths.

2. Cyclic alcohols. These are represented by pine and eucalyptus oils of which the active components are the terpene alcohols typically a-terpineol. These are traditional frothers and are still used usually in combination with other frothers and collectors in 30% of the world's copper concentrators.

3. Phenols of which cresylic acid a mixture of cresols and xylenols, is the most commonly used.

4. Alkoxyparaffins of which the most successful is 1,1,3-triethoxybutane, have come into use in sulfide flotation as they seem also to have collector specificity.

5. Finally the polyglycols, particularly polypropylene glycol, these are available as commercial products with the general formula R(X)nOH, where R is either H or CnH2n +1 and X is either ethylene oxide (EO) -CH2CH2O-, propylene oxide (PO) -CH2CH(CH3)-O- or butylene oxide (BO) -CH2CH2CH(CH3)-O-. In the PO and BO frothers the propylene and butylene groups are hydrophobic and the ether oxygen and the hy-droxyls are hydrophilic. Varying the relative length of the hydrophobic to hydrophilic groups in the molecule permits tailoring the molecule to a specific application.

Bubble stability in pulp The crucial property of a bubble in an aerated flotation cell relates to its ability to survive the collision and attachment of a particle without bursting. Although it is possible to observe that the addition of frothers does increase the stability of a single bubble, a coherent quantitative stability model does not exist. This will need to relate to the ability of its water film surrounding the bubble to withstand local disturbances. This ability is thought to be related to dynamic changes in surface tensions in the film following the local decreases in frother concentration after distortion has occurred following impact with a particle.

The effect of frother concentration on the surface energy of the solution has been used by Laskowski to characterize the surface activity of various frothers as related to their molecular structure. This is based on the application of the Gibbs adsorption isotherm, where r is the surface excess of the surface-active agent, a its activity in the bulk solution and yLV is the bubble-liquid interface energy:

This implies that a decrease in a, the surfactant activity, at the gas-liquid interface following local surface increases, will be associated with a very sensitive surface tension y increase.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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