1 HLB value of surfactant and selection of deinking agent of waste paper
Surfactant is an indispensable agent in deinking agent, which determines the quality of the whole deinking agent formula. There are many kinds of surfactants, and the range of use is also very wide, which can be used as dispersant, collector, wetting agent, filter aid and anti-precipitation agent in the production of waste paper deinking. When the surfactant is added to the hydropulper or to the waste pulp before flotation, the hydrophobic group will bind to the ink, grease and dirt, while the hydrophilic group end remains in the water.
2 HLB value and characteristics of surfactants
The HLB value can reflect the hydrophilic strength of the surfactant, and it is generally believed that the turning point of hydrophilic and lipophilic is 10, that is, surfactants with an HLB value greater than 10 are mainly hydrophilic, while those with an HLB value less than 10 are lipophilic. Surfactants with different HLB values have different properties and have different effects in deinking applications. According to the relationship between hydrophilic and lipophilic equilibrium values of various surfactants, that is, HLB values and surfactant properties, the characteristics of surfactants with different HLB values and their influence on whiteness after ONP deinking are given in Table 2.
3. Selection of waste paper deinking agent
According to the relationship between the HLB value of the surfactant and the properties of the surfactant, all the surfactants with an HLB value of 8 to 18 or greater than 18 are suitable for being the emulsifier of the 0/W type dispersion system: surfactants with an HLB value in the range of 3 to 6 are suitable for being the emulsifier of the W/0 type dispersion system, and the deinking system is generally a 0/W type dispersion system. Surfactants with HLB values in the range of 8 to 18 or greater should be selected as emulsifiers. There is an obvious correlation between HLB value and deinking efficiency, so HLB value can be used as one of the basis for selecting deinking agent. Zhang Changhui et al.  have shown that HLB value between 12 and 15 is more appropriate.
We can find out the HLB value of various surfactants by referring to the chemical manual and using the calculation formula (1) and (9) to find out the more suitable surfactant. In the formulation of deinking agent, the HLB value of anionic and non-ionic surfactants is greater than 8, which is suitable for waste paper deinking agent.
In practical applications, multiple surfactants with different HLB values can be mixed. According to the desired HLB value, the formulations of various surfactants are determined by using the admissibility of the HLB value of surfactants, and the compatibility of various surfactants is given full play to obtain better results.