| Flocculation is a kind of method and technique of purifying water in common use. But the conventional flocculants such as polyaluminium chloride (PAC) and polyacrylamide (PAM) in water treatment are prone to produce secondary pollution, the aluminum ions that is produced from hydrolysis of PAC in water come into human body via feed water and cause various diseases such as anaemia and brain dementia, crylic acid and amine that are produced from hydrolysis of PAM would harm human health too. So how to prepare a kind of flocculant which is highly ecological safety is a very important subject and an urgent task in water treatment field recently. On the other hand, pyrite cinders are the solid waste of sulfuric acid industry. The comprehensive utilization of pyrite cinders is very important because the comprehensive utilization can not only control the cinder pollution, but also recover the resource. Therefore, a kind of high ecological safety flocculant-PFC was prepared from pyrite cinders, and the flocculation efficiency, flocculation mechanism, the ecological safety were studied. The main research contents and results of this paper are included as following:1.The method of preparing PFC from pyrite cinder is: The extraction liquid was collected by dissolving pyrite cinders using hydrochloric acid and divided into part A and part B. Certain amount of NaOH was added into A with aeration to get Fe (OH) 3 colloid; Oxidant and stabilizer reagent were added into B, and the obtained Fe (OH) 3 colloid were put into B, stirred until the colloid was dissolved, then some basification reagent was added into it to adjust the basification. The reaction system was cured for some time to get PFC products.2.The optimum process conditions of hydrochloric acid dissolution which were get by single factor experiments and orthogonal experiment were as follows: the mass fraction of hydrochloric acid of 30%, the mass ratio of pyrite cinder and hydrochloric acid of 0.35:1, the temperature of 95℃and the time of 1.5h。3.The best reaction conditions of preparing PFC from pyrite cinders were as follows: the volume ratio of extraction B to extraction A(VB:VA) of 3.2:1, the molar ratio of NaOH to the total Fe in extraction A(nNaOH:nFeA) of 3.5:1, the molar ratio of stabilizer W to the total Fe(nw:nFe) of 0.06:1, the molar ratio of basification reagent to the total Fe(nB:nFe) of 0.3:1, the curing time of 3.5h and the curring temperature of 85℃.4.The flocculation efficiency of PFC was studied by Jar test. PFC was used to treat kaolin simulated wastewater, and the impact of different dose, pH and different turbidity wastewater on the flocculation efficiency of PFC were studied. Results showed that the flocculation efficiency of PFC was better with the increase of the dosage, but when the dosage reached certain value, the flocculation efficiency would decrease. The flocculation efficiency of PFC under basic condition was better than that under acid condition, and PFC has a wider pH scale application than PAC. PFC has good flocculation efficiency on different turbidity wastewater.5.In a certain range, the flocculation efficiency and the congregation degree were improved with the rising of basification. The flocculation efficiency of PFC whose basification was 9.007% was better than PFC whose basification was 14.615%. PFC whose basification was 9.007% was used to treat municipal wastewater and beer wastewater, the removal rates of turbidity, absorbency and COD in municipal wastewater can reached 96.26%,95.81% and 92.77%, and the removal rates of turbidity, absorbency and COD in beer wastewater can reached 91.99%,86.24% and 82.41%.6.The flocculation mechanism of PFC was simply discussed. And the flocculation mechanism was the joint action of neutralizing charges, absorption and bridging, enmeshments. They don't happened alone, but happened together. And the degree of the primary and secondary of diverse mechanisms were different with different kind of wastewater.7.The ecological safeties of ferric chloride (FC), polyferric sulfide (PFS), polyferric chloride (PFC) were studied by the terrestrial ecotoxicological methods of seed germination and root elongation. Results show that polyferric chloride is the most highly ecological safe flocculant. |
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