| Taking the fly ash which emit from power plant of Panzhihua Steel Group Co., Ltd. of Sichuan Province as the research object, influences of mechanical activation, concentrated acid aging, cosolvent addition, calcinations, and microwave-assisted leaching on silicon aluminum and iron strengthened leaching from fly ash were researched. Influence and the mechanism of calcinations have been of the interest. And the best strengthen leaching process was determined. Silicon and aluminum leached from fly ash by alkali leaching in middle temperature, and silicon aluminum and iron leached from fly ash by acid leaching in natural temperature. The stability of acid leaching solution of fly ash was solved by appropriate surfactant. Synthesizing of poly-aluminum ferric silicate sulfate (PAFSS) was synthesized by unique technology of alkali leaching in middle temperature-acid leaching in natural temperature-counteract co-polymerization. PAFSS was applied to simulative wastewater, urban wastewater, industrial coking wastewater and industrial steelmaking wastewater, and the results were well-pleasing. This research has important environmental significance and considerable economic value.The results showed that the rate of silicon aluminum and iron leached from fly ash were 0.18%,10.19%,17.86% respectively in conditions of concentration of H2SO4 was 3mol/L, leaching temperature was 80℃, leaching time was 3h, and slurry concentration was 10%. The leaching rate of silicon aluminum and iron were 4.59%,4.09%,1.98% respectively in conditions of concentration of NaOH was 3mol/L, leaching temperature was 80℃, leaching time was 3h, and slurry concentration was 10%.The leaching rate of silicon and aluminum were 0.45%,11.10% respectively in conditions of ball to powder ratio was 1:3, speed of planetary ball mill was 220rpm, and mechanical activation time was 2.5h by mechanical activation, which increased by 150%, and 9% respectively. The leaching rate of silicon aluminum and iron were 0.30%,8.17%,12.65% respectively in conditions of concentration of H2SO4 was 8mol/L, and aging time was 4h by concentrated acid aging, which increased by 67%,-20% and -29% respectively.The leaching rate of silicon and iron were 23.77%,36.71% respectively in condition of NH4F/FA was 2.0 by cosolvent addition, which increased by 131 times and 106% respectively.The leaching rate of silicon aluminum and iron were 34.40%,58.09%,45.95% respectively in conditions of the mass ratio of sodium was 57.5%, heating rate was 10℃/min, calcination temperature was 850℃, and holding time was 30min by calcination, which increased by 191 times,470% and 157% respectively.The rate of silicon aluminum and iron leached from fly ash were 0.45%,58.08%, 48.85% respectively in conditions of microwave heating temperature was 80℃, microwave holding time was 1h, and slurry concentration was 5% by microwave-assisted leaching, which increased by 150%,470% and 174% respectively.Contrast the strengthened leaching efficiency of various measures and the results show that the rates of silicon aluminum and iron leached from fly ash were highest by calcinations and cosolvent addition; the rates of silicon aluminum and iron leached from fly ash were higher by microwave-assisted leaching and mechanical activation; the rates of silicon aluminum and iron leached from fly ash were low by concentrated acid aging.Fly ash and calcined fly ash were characterized by XRD, SEM and EDS, the results showed that the mechanism of calcinations was that calcinations of the mixture which makes up of fly ash and sodium additives destroyed SiO2-Al2O3 bond of mullite in fly ash, and it generated higher active material, such as NaAlSiO4, Na1.75Al1.75Si0.25O4, K(Na,K)3AlSiO4 and (Na20)o.33NaAlSi04. These substances were more easilier reacted with sulfuric acid and sodium hydroxide solution. Therefore, the rates of silicon aluminum and iron leached from fly ash were strengthened.Acid solution stability was improved by adding P1 of 3% volume ratio at natural temperature acid leaching.(Al+Fe)/Si molar ratio and aging time were major factors of PAFSS effect in the synthesis of fly ash-based inorganic polymer flocculant PAFSS. And the results show that the effect of PAFSS was best in conditions of (Al+Fe)/Si molar ratio was 1.72, aging time was 12h. The technologies of PAFSS synthesis were that:①calcination process:the mass ratio of sodium was 57.5%, the heating rate was 10℃/min, the calcination temperature was 850℃, and the holding time was 30min.②mechanical activation process:ball to powder ratio was 1:3, the speed of planetary ball mill was 220rpm, and the mechanical activation time was 2.5h.③acid leaching process:PI dosage was 3% of the total volume, the concentration of H2SO4 was 3mol/L, the leaching temperature was 25℃, the leaching time was 3h, and the slurry concentration was 5%; alkali leaching process:the concentration of NaOH was 3mol/L, the leaching temperature was 80℃, the leaching time was 3h, and the slurry concentration was 5%④synthesis process:(Fe +Al)/Si molar ratio was 1.72, and the aging time was 12h.PAFSS was applied to simulative wastewater, urban wastewater, industrial coking wastewater and industrial steelmaking wastewater, and the results show that turbidity was 812NTU of simulative waster, and turbidity was 11NTU of treated simulative wastewater by adding 6mL/L PAFSS. Turbidity was 1568NTU, chroma was 50 times, and COD was 11980mL/L of urban waster, and turbidity was 23NTU, chroma was 4 times, and COD was 675mL/L of treated urban wastewater by adding 50mL/L PAFSS. Turbidity was 36NTU, chroma was 8 times, and COD was 156mL/L of industrial coking wastewater, and turbidity was 12NTU, chroma was 4 times, and COD was 112mL/L of treated industrial coking wastewater by adding lOmL/L PAFSS. Turbidity was 2295NTU, and chroma was 40 times of industrial steelmaking wastewater, and turbidity was 27NTU, and chroma was 1 times of treated industrial steelmaking wastewater by adding 10mL/L PAFSS.Contrasting the flocculation efficiency of PAFSS with poly-aluminum chloride (PAC) and poly-ferric sulfate (PFS), the results show that:PAFSS is best than PAC and PFS in capability of removing turbidity, speed of flocs synthesis, volume of flocs, speed of Settlement Velocity, reaction time and Requirement dosage, therefore, the costs of wastewater treatment was lowest. |
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