| Considering the unoptimistic status of wastewater treatment in our country, it’s imperative to explore a kind of low cost and efficient flocculent. Polyaluminum chloride(PAC) is a kind of inorganic polymer flocculatant which has apparent flocculation behavior, but the general methods of preparing PAC have excessive reliance on aluminium ore, which go against to reduce costs and ease pressure on the environment. This study is aimed to prepare the PAC using calcium reducing slag and coal gangue as raw materials. The main researches are as follows:The optimal condition of activation and acid leaching of coal gangue in this study is determined by single factor experiments. The coal gangue is mechanically grinded to 180μm, calcined at 750℃ for 2h to obtain activated coal gangue, which has the highest leaching rate. Then 20 g activated coal gangue react with 110 m L 20% hydrochloric acid at 95℃ for 3.5h, and the Al2O3 leaching rate of coal gangue could reach above 85%.The curing liquid is obtained when 15 g calcium reducing slag is added to acidic leaching solution, reacting for 4h at 95℃. The solid products are obtained by spray drying or drum drying, the Al2O3 content and basicity are 28.3% and 68.7%, respectively, in accordance with GB/T 22627-2008. It was confirmed as the target product by IR and the weightlessness of PAC was divided into three stages by the result of thermogravimetric analysis.The effect of PAC on the treatment of dyeing wastewater, coking wastewater and domestic wastewater is studied. Specific information as follows:The optimum condition for the flocculation of dyeing wastewater is as follows: the p H is7~8, dosage of PAC is 105mg/L, slowly stirring for 3min~4min, standing for 30 min. Overall consideration, adjusting p H and andding PAM are not necessary. After all, the removal rate of turbidity, chroma and CODCr is 92%, 76% and 78%, respectively.For coking wastewater, the p H should keep between 8 to 10, the dosage of PAC is 170mg/L, after the rapidly stirring for 1 min, the water should keep slow stirring for 2min, and then standing for 20 min, the large and dense flocks would be produced. In the actual operation, there is no need to adjust p H, the combination of PAC and PAM has a synergistic effect in the procedure, it showes that the removal rate of turbidity, chroma and CODCr are increased 15.8%, 5.8%, 15.3% from 95.3% 96.8%, 90.5% after adding to PAM.For the treatment of domestic sewage, the p H should be 7 to 8, the dosage of PAC is 375mg/L, after the rapidly stirring for 1 min, the water should keep slow stirring for 5 min, and then standing for 20 min. The removal rate of turbidity, chroma and CODCr keep above 91%, 80%, 78% without adding PAM.The technological parameters and equipment type of these procedures, pretreatment of raw material,activation of coal gangue,preparation of liquid PAC, drying and packing, are analysised. In addition, project budgetary estinate is also investigated. The results indicate that the project of PAC has the good application value and extensive market prospect. |
PDF Full Text Request