复合型絮凝剂聚合氯化铝铁的合成

Synthesis of composite flocculant polyaluminum ferric chloride

粉煤灰中含有铝、铁,可以用其制备聚合氯化铝铁絮凝剂。但是,粉煤灰中的铝、硅以复杂的玻璃体红柱石形式存在,酸溶性非常差,需要通过焙烧破坏其中的SiO2—Al2O3键,提高其酸溶性。在粉煤灰中通过添加一定量赤泥来调节混合物中铝铁比值关系,然后用改性粉煤灰和盐酸为主要原料,制备聚合氯化铝铁絮凝剂。粉煤灰活化最佳条件:粉煤灰与赤泥的质量比为0.3、焙烧温度为750℃、焙烧时间为2 h。粉煤灰中铝铁溶出最佳条件:盐酸浓度为7 mol/L,液固比为3.5 mL/g,反应温度为85℃,反应时间为2.0 h,在此条件下铝铁溶出率高达90.5%。将所得溶液陈化18 h即得到聚合氯化铝铁(PAFC)絮凝剂。絮凝实验结果表明:制得的PAFC的絮凝性能优于聚合氯化铝(PAC)、聚合氯化铁(PFC)。

Fly ash can be used to prepare composite flocculant polyaluminum ferric chloride （ PAFC ）, as it contains a- luminum and iron. But the existence of aluminum-silieon in fly ash is in the form of complex vitreous mullite phase, which is hardly soluble in acidic solutions. Therefore,it is necessary to sinter fly ash to destroy SiO2--Al2 O3 bonds so as to improve its solubility in acid. Proper amount of red mud was added to fly ash to adjust the ratio of aluminmn and iron. Finally, PAFC flocculant could be prepared with modified fly ash and hydrochloric acid as main raw materials. Experimental results showed that the optimum activation conditions of fly ash were as follows ： mass ratio fly ash to red mud was O. 3, sintering temperature was 750 ℃, and sintering time was 2 h ; the optimum aluminum and iron leaching conditions were as follows ： concentration of hydrochloric acid was 7 mol/L,liquid-to-solid ratio was 3.5 mL/g, reaction temperature was 85℃, and reaction time was 2. O h. Under those conditions the leaching rate of aluminum and iron reached 90.5% and PAFC flocculant could be obtained after aging the as-prepared solution for 18 h. Flocculation tests showed that PAFC is superior to either PFC or PAC.