# Complex Processing of Saponite Waste from a Diamond-Mining Enterprise
## 7 Synthesis of Inorganic Precipitant  
For effective deposition, a calcium aluminosilicate (CAS) reagent was developed with the St. Petersburg Mining University. The calcium aluminosilicate reagent is synthesized in the temperature ranges of the crystallization of tricalcium silicate and tricalciumuluminate [22]. Thus, a method is proposed for obtaining an active coagulant in the wastewater treatment process through the decomposition of the initial silicate reagent. The properties of the coagulant obtained are associated with the structural features of the included  
Figure 3: Granulometric composition of the discharge from the classifier. This composition of the obtained calcium aluminum silicate inorganic coagulant is determined by the ratio in the raw mix, which may vary in a narrow range, including four main minerals: tricalcium silicate, dicalcium silicate, tricalciumaluminate, and quaternary aluminoferrite [11]. The coagulant is a granulated mixture of self-separating slag and may be obtained from a number of clays and hydronic, containing calcium and magnesium silicates including hydroaluminosilicates with thermal treatment at about 1200-1300 \({}^{\circ}\)C. The reagent obtained was tested with an XRD-7000 X-ray diffractometer and the findings are presented in Figure 5. According to the data obtained during the X-ray diffraction analysis of the obtained sample, and according to [PERSON] [23], the primary coagulant is partly tricalcium silicate 3 CaO-SiO2; the composition is presented in more detail in Table 3. \begin{table}
\begin{tabular}{c c c} \hline
**No.** & **Oxide** & **Content, wt\%** \\ \hline
1 & SiO2 & 52.7 \\ \hline
2 & Al2O3 & 5.74 \\ \hline
3 & MgO & 24.1 \\ \hline
4 & Fe2O3 & 9.38 \\ \hline
5 & CaO & 2.9 \\ \hline
6 & K2O & 1.6 \\ \hline
7 & TiO2 & 0.7 \\ \hline
8 & MnO & 0.15 \\ \hline
9 & Na2O & 1.1 \\ \hline
10 & Other & 1.63 \\ \hline \end{tabular}
\end{table} 
Table 2: Oxide composition of sludge. Figure 5: X-ray diffraction pattern of the minerals of the obtained coagulant. The calcium-aluminum-silicate reagent is a mixture of several artificially obtained silicate minerals. The hydrolysis and hydration are described by the following Reactions (2)-(4) [8,24]:  
For the main substance C\({}_{3}\)S:  
\[2(3\text{CaO}\cdot\text{SiO}_{2})+6\text{H}_{2}\text{O}\rightarrow 3\text{CaO}\cdot 2 \text{SiO}_{2}\cdot 3\text{H}_{2}\text{O}+3\text{Ca(OH)}_{2} \tag{2}\]  
The initial hydrolysis of C\({}_{3}\)S can proceed according to the reactions described below:  
\[\text{C}_{3}\text{S}\ (\text{C};\ \text{C}_{2}\text{S})\ \overset{\text{H}}{ \rightarrow}\ \text{C}_{2}\text{S}+\text{Ca}^{2+}+2\text{OH}^{-} \tag{3}\]  
\[\text{C}_{2}\text{S}\ \overset{\text{H}}{\rightarrow}2\text{Ca}^{2+}+\text{H}_{ 2}\text{SiO}_{4}^{2-}+2\text{OH}^{-} \tag{4}\]  
\[2\text{H}_{2}\text{SiO}_{4}^{2-}+2\text{OH}^{-}\rightarrow\ \text{Si}_{2} \text{O}_{7}^{6-}+2\text{H}_{2}\text{O} \tag{5}\]  
A related component is calcium orthosilicate. The structure of calcium orthosilicate (Ca\({}_{2}\)SiO\({}_{4}\)) contains two calcium ions, so when it initially connects to the water, it undergoes hydrolysis:  
\[\text{Ca}_{2}\text{SiO}_{4}+2\text{H}_{2}\text{O}=2\text{C}a_{alg}^{2+}+\text {H}_{2}\text{SiO}_{4,alg}^{2-}+2\text{OH}_{alg}^{-} \tag{6}\]  
When calcium silicates come into contact with water, the chemical interaction with the formation of ions in the solution becomes primarily chemically driven: pure water is pushed to the surface from the interlayer space of the clay mineral saponite. Calcium hydosilicate contains hydroxyl groups, which are shown to have cationic and anionic ion-exchange properties. The reaction when the OH group is replaced with cations in an alkaline medium consists of successive stages [8]:  
* Adsorption: Si-OH + Me(OH)(x-1)+ = Si-OH | HOMe(x-1)+ ;
* Condensation: Si-O-Ca\({}^{2+}\) + An\({}^{2-}\) = Si-O-CaAn.