## 3 Results and Discussion  
### Development of Optimal Dust Suppressant Formula  
#### 3.1.1 Performance Requirement and Formula Composition of Dust Suppressant  
According to the influencing factors of fugitive road dust concentration, this paper has researched the road condition factor and developed a kind of environmentally friendly dust suppressant comprising organic components for the humectant, hygroscopic agent, coagulant, surfactant, etc. Its dust suppression principle is to control the fugitive road dust concentration by changing the moisture content, evaporation rate, and particle size ratio of road dust. The technical characteristics of the suppressant are shown in Table 2.  
Based on the \"Soil moisture determination method\" (GB 7172-87), Glycol (BS1), sucrose (BS2), and triethanolamine (BS3) were selected as preliminary moisturizers. The changes in the water loss rates of dust samples at 65 \({}^{\circ}\)C and under natural conditions are shown in Figures 1 and 2 through monomer experiments with different concentrations of humectants. According to Figures 1 and 2, the order of moisture retention at 65 \({}^{\circ}\)C is BS1 \(>\) BS2 \(>\) BS3, and the order of moisture retention under natural conditions is BS2 \(>\) BS3 \(>\) BS1, showing that the higher the concentration, the better the moisturizing performance will be. Based on the results of the moisturizing test under different conditions, BS2 demonstrates the best moisturizing performance. Therefore, BS2 was selected as the humectant monomer. Its concentration range was determined to be from 3% to 6% in light of both its hygroscopicity and economic efficiency. The organic solvents glycerin (XS1), triethanolamine (XS2), trimethyllop propane (XS3), and the mixture of glycerin and magnesium chloride (XS4) were selected as the hygroscopic agents. The performance of each hygroscopic agent was evaluated by the moisture content rate and its increment of dust samples. The moisture content rate variation curves for different concentrations of hygroscopic agent monomers are shown in Figure 2. According to Figure 2,XS4 andXS1 demonstrate the best hygroscopic performance. However, in view of the compound reagent ofXS4, whose main component is XS1, and the strong hygroscopicity ofXS1 in a single component, XS1 was selected as the best hygroscopic agent. Its concentration range was set from 3% to 6% in light of its economic efficiency. Subsequently, another reagent in XS4 can serve as a hygroscopic and moisturizing enhancer to optimize the hygroscopic and moisture-retention performance of the dust suppressant. \begin{table}
\begin{tabular}{c c} \hline
**Composition of Dust Suppress** & **Technical Characteristics of the Suppressant** \\ \hline Humectant & It can resist evaporation, thus reducing the evaporation rate of the water contained in dust itself and the water absorbed by dust. The road dust is kept wet in this way, and the dust suppression duration of the dust suppressant can also be prolonged. \\ Hygroscopic agent & It serves to absorb moisture from the air when the ambient humidity is high. Thus, the moisture content rate of road dust and the road surface humidity can be increased so that the dust will not be easy to raise. \\ Coagulant (mainly) & It serves to delay water evaporation and bond the fine dust, so as to add weight to dust, to shorten the sedimentation time of fugitive dust, and thus to enhance the effect of the dust suppressant. \\ Surfactant & It serves to reduce the surface tension of dust suppressant solution and accelerate the speed for road dust infiltration. \\ \hline \end{tabular}
\end{table} 
Table 2: The technical characteristics of the suppressant. Polyacrylamide (NB1), methylcellulose (NB2), cassava starch (NB3), sodium polyacrylate (NB4), and sodium carboxymethyl cellulose (NB5) were selected as raw materials of the coagulant. The viscosity value and the bonding effect were adopted to evaluate the bonding performance of each coagulant.