Study On The Preparation Of Poly-silicic-aluminum-ferric Coagulant From Fly Ash And The Simulation Of Coagulation Flocs

In this paper, poly-silicic-aluminum-ferric coagulant was prepared by adding potassiumferrate to extracts of silicon-iron-aluminium oxides from fly ash, the extracts were got byroasting, acid leaching the roasted product. Using the coagulant to treat simulation wastewaterwith disperse yellow brown, and investigated the results of coaguration experiments, and thecorrelation of the results of experiments and fractal structure of flocs was studied throughintroducing fractal dimension. applying fractal theory in water treatment, building DLA, DLCAmodels and statistically analysed the relationships between main parameter of models andsimulation results, applying the models in the simulations of flocs and used appearance of flocsand its fractal dimension as an evaluation criterion, analyzing feasibility of simulating flocswith models by comparing, characterizing properties of coagulant finally.(1) The best conditions of extracting were got by single factor experiment as follows: thesieve mesh which filtrated fly ash was200, mole ratio of Na2CO3/SiO2was0.5, calcinationtemperature was800℃, calcination time was1.5h, concentration of HCl was4mol/L, time ofacid leaching was2h, the ratio of liquid to solid was10:1, the respective ratios of extraction ofFe2O3, Al2O3and SiO2was71.32%,78.93%,69.37%by the conditions.(2) Adding potassium ferrate to the extracts which was got through the best conditions ofextracting, poly-silicic-aluminum-ferric coagulant was prepared by orthogonal experiments,and the best polymerization condition was determined by investigating removal rate ofsimulated dyestuffs wastewater, experimental results showed: adjusting pH value to2.0with2.0mol/L NaOH solution firstly, continuely adjusted the value to1.4with1.0mol/L NaOH,activation time was4h, mole ratio of Fe/Al/Si was1.1:3:10, reaction temperature was60℃,time of ageing was2h, the results of flocculation experiments with coagulant was prepared bythese conditions as follows: turbidity removal ratio was up to97.2%, the highest ratio ofcolority removal was up to98.7%. The results also showed that there was a good correlation instudying the relationships between the ratios of removal of and fractal dimension of flocs bybring fractal dimension.(3) The relationship of parameters and simulation results were analyzed statistically withDLA and DLCA model that was established by MATLAB, the fractal dimension of actual flocs were measured with ImageJ, the fractal dimension of simulated flocs were measured by turningradius method, and analyzed their correlation of the two kinds of appearance of flocs andcorresponding fractal dimensions. The experimental results showed: the two models both hadgood application potential in simulating the flocs of dyestuffs wastewater.(4) The properties of poly-silicic-aluminum-ferric coagulant were characterized byadvanced instruments and analytical method, and mechanism of coagulation were discussedsimultaneously, the results of research showed: copolymer of poly silicic acid of highpolymerization degree and incidental polymetals were contained in coagulant, the morphologyof the copolymer were long chain and intertwined, its branching-like structure and mulantennaeprovided good effects of coagulation with conditions, and combined charge neutralization oftraditional metal salt coagulants and absorption with bridge of polysilicic.