| The eutrophication has become a serious environmental problem to Chinese water body, with total nitrogen and total phosphorus being the primary contaminants. Phosphorus pollution is one of the top pollutants in Chinese natural water. Industrial sewage discharged from sewage treatment plant is high phosphorus concentrated, which will exacerbate eutrophication. To solve the problem, further treatment of P-containing wastewater is important. The preferable further phosphorus removal technique is the application of high-efficiency, low-cost phosphorus removal coagulant at present. So a kind of coagulant had been prepared by using a kind of industry waste residue in this paper.The phosphorus removal coagulant was prepared based on industrial waste through acid treatment. The composition of residue and the self-made phosphorus removal coagulant were analyzed by XRD, XRF, IR and SEM. A series of experiments were conducted to study the influence of factors such as acid concentration, response time, reaction temperature, solid-to-liquid ratio, etc.The composition of self-made coagulant was analyzed by XRF, XRD, IR, SEM, the results of which showed that the main mineral composition were goethite, hematite, fibroferrite, gibbsite, quartz, etc. The moisture content of goethite, fibroferrite and gibbsite were10.14%,38.26%and34.64%respectively. Infrared analysis showed that the main groups of self-made coagulant were Si-O-Si,Fe-OH, A1-OH and H-OH. The molecular formula of fibroferrite is Fe(OH)SO4ยท5H2O, which is the primary composition of coagulation. Polymeric Ferric Sulfate were generated in the process that sulfuric acid neutralized a portion of hydroxyl, from which we can know polymers such as polymeric ferric sulfate may exist in the self-made coagulant.The removal efficiency of the self-made coagulant on simulated P-containing water samples, domestic sewage samples and East Lake water samples were studied in the research. For the simulated P-containing water (initial P concentration1.82mg/L and initial pH9.13), the removal rate of phosphorus can reach97%with dosage of0.3g/L, and final P concentration and pH can reach0.05mg/L and6.81respectively. The removal rate for domestic sewage samples (initial P concentration 2.5mg/L and initial pH7.96) and East Lake water samples (initial P concentration1.04mg/L and initial pH8.11) could reach94.48%and95.58%. The final P concentration can reach0.013mg/L and0.046mg/L respectively when the dosage is0.2g/L and0.1g/L. The total phosphorus in treated domestic sewage and East Lake water can reach the I class and II class water standards in GHZBI (GB3838-2002). Meanwhile, other indexes such as COD, TP, SS were also reduced to meet the requirement of relevant national standard. A mass of flocs emerged in the process of coagulation, which were big and tightly bound, and could settle to the bottom of the beaker fast.The self-made coagulant, ferric sulfate, aluminium polychlorid and a foreign coagulant were compared by conducting coagulation experiments. To get the final P concentration of less than0.1mg/L from domestic sewage with initial P concentration2.1mg/L and initial pH8.69, the dosage of the foreign coagulant, polymeric ferric sulfate, the self-made coagulant and aluminium polychlorid were0.2g/L,0.2g/L,0.3g/L and0.4g/L respectively. The self-made coagulant flocs settled fast and could settle completely in only10minutes. The self-made coagulant had promising industrial applications due to the low production costs. The results indicated that the self-made coagulant and flocculant products at home and abroad behaved similarly in the aspects of dosage, P removal effect and floc size, and it provided new ways for multipurpose utilization of waste. |
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