Study On The Preparation And Application Of Fly Ash Inorganic Coagulant

The activation of the coal fly ash was studied in this paper firstly. And the activation methods of other researchers were summarized. The Na2CO3 melting methods which are used to increase the acid lixiviate property of fly ash were put forward. Based on the activation of the fly ash, series experiments of synthesis and application in papermaking wastewater of the fly ash coagulant were studied. And satisfied results were obtained. The main studies and conclusions were as followed:1. The influence of the quantity of solubility promoter, NaCl and NaF, to solubilization ratio of Al2O3 from fly ash was studied when the HC1 is used as solvent. The results suggested that the quantity of NaCl, which was added to the fly ash, has no effect on the solubilization ratio of aluminum. But the quantity of NaF has obvious influence on the solubilization ratio of aluminum. The trend is that with the quantity's increasing of NaF the solubilization ratio of aluminum also increased. The highest solubilization ratio is 20.45%. When the quantity is over 15.8%, the ratio begins to decline.2. Hydrochloric acid is used to solubiliz the fly ash after it is baked with CaO in the muffle. The aluminum chloride is obtained. The results suggested that the quantity of CaO has influence on the solubilization ratio of aluminum under the temperature of 850 C. The highest solubilization ratio is 14.3%.3. The fly ash is baked with Na2CO3 in the muffle, and then the sinter is solubilized by hydrochloric acid. The aluminum chloride is obtained at last. The results showed that the quantity of Na2CO3 has distinctly influence to the solubilization ratio of aluminum under the temperature of 850 C. When it was added, to 25%, the highest solubilization ratio is obtained by 53.2%.4. By using fly ash and pyrite roasting residue as primary raw materials, the polymeric aluminum ferric silicate (PAFSi) is synthesized by a series of sodium dissolves and acid dissolves procedure on the base study of the activation of fly ash. During sodium dissolves process, the sodium hydroxide to fly ash ratio and the reaction temperature are the main effects of the solubilization ratio of silicon and aluminum. Experiment results indicated that the optimum condition is alkali/ash =0.74:1 (OH/(0.5Si+Al))=2:3, molar ratio), temperature=150 C, reaction duration =lh. A highest solubilization ratio is obtained by 60.9% under the optimum condition. During pyrite roasting residue acid dissolves process, the main reaction factor is temperature, with the temperature's increase, so do the ferric solubilization ratio. When the reaction temperature is up to 106 C, by using 6M hydrochloric acid. The ferric solubilization ratio will rapidly increased to 99% within 0.5 hour.5. During the study of the synthesize of the inorganic flocculants made from fly ash, the ratio between Al, Fe and Si, the pH value of the flocculants, the ageing temperature and duration and so on were studied by single factor experiments. Through orthogonal experiments, the optimums conditions of synthesize of the inorganic flocculants (PAFSi) are found. They are as follows, Si:Al:Fe=1: 0.7:0.5, pH value of the flocculants=1.1, ageing temperature=60 C, ageing time=1hour.6. A series jar tests were take by using the synthesized flocculants (PAFSi), polymeric aluminum chloride (PAC) and polymeric ferric sulfate (PFS). The results suggested that compared with PAC and PFS, PAFSi has the strongest turbidity removal ability during the treatment to the simulative wastewater. The fly ash inorganic flocculants (PAFSi) also has excellent manifest in treating papermaking wastewater, and the removal ratio of chroma, turbidity and CODcr is respectively up to 99.1%, 98.5%, and 65.6%.