Removel Experimental Researching On Arsenic,Cadmium And Lead Of Formation Compound Mg-Al Hydroxides

Arsenic and heavy metal pollution has been a global pollution problem, and has caused wide public concern. Arsenic has strong toxicity, and it is carcinogenic. Cd and Pb are more common heavy metal pollutants. If the untreated waste water which contained those heavy metal pollutants ions and arsenic ions discharged into natural water bodies will heavily pollute the environment and also harm the human health.Since the compound Mg-Al hydroxides (MgxAly(OH)2·nH2O) can be formed in the process of coagulation, and high degree of polymerization of aluminum based coagulants are conducive to form more compound Mg-Al. Under a certain range of pH, the coagulant dosage is positive proportional to the amount of compound Mg-A1 which formed in that process. Therefore, in this experiment, we use different methods to make a kind of water which contains As, Cd and Pb ions, and through the method of coagulation and agitation to form a certain amount of compound Mg-A1 hydroxides under the conditions of a certain amount of time, pH, appropriate amount of coagulant to study its effectiveness on removing As, Cd, Pb ions, and the characterization removed, the author draws a conclusion as below:pH is the most crucial factor which not only determines whether it can form compound Mg-A1 and its structure, but also shows that under the proper pH, compound Mg-Al hydroxides has the strongest ability to remove As, Cd, Pb. Other influence factors are: appropriate coagulant (AI13 and AICI3) dosage, Mg2+concentrations and concentration of different pollution ions, MgO alternative NaOH pH adjustment. Those factors are all affect the forming status of compound Mg-A1 hydroxides and its removing effectiveness.Through the experiment of Pb, Cd, it shows that the coagulation AI13 indeed played a positive role in promoting removing ions, and its ability to remove As, Cd, Pb ions is better than AICI3. Second, according to some characteristics, it shows that the form of Mg-Al composite was amorphous, with a huge surface area, and the composition is relatively complex. Under a certain range of pH, coagulant dosage 0.06 mmol/L, the higher polymerization degree's AI13 can form lager composite particles than AICI3 does, and it can illustrate the compound Mg-Al hydroxides do have further positive facilitation on removing polluted ions.