Research On Preparation Of Polymeric Aluminum Ferric Chloride And Its Compounds

The waste liquid generated during the purification process of hydrochloric acid leaching the diatomite has to be used by the commission of Diatomite Research Institute of Linjiang. The liquid contains Al³⁺, Fe³⁺ and Cl^- which are the raw materials to prepare polymeric aluminum ferric chloride（PAFC）. Using the liquid to prepare PAFC can turn waste into treasure. The organic matters have become the main pollutants of water, and suspended and colloidal ones except the dissolved organic ones（DOM） can be removed by coagulation. In order to remove the DOM by coagulation, composition of PAFC has been studied to remove DOM by coagulation.Firstly, the effects of parameters such as aluminum iron molar ratio, basicity, polymerization agent and p H during the preparation process of PAFC using the waste liquid on the performance of PAFC have been studied. The preparation conditions have been optimized and the PAFC prepared by waste liquid has been characterized. The optimal conditions were: Al/Fe molar ratio, the dosage of polymerization agent, polymerization temperature polymerization time, and basicity are respectively 9:1, 0.145g/m L, 30℃, 24 h, 1.9. Under the preparation conditions, Al₂O₃ and Fe₂O₃ content of PAFC were respectively 7.51% and 1.48%, and its basicity was 63.33%, the effective type of metal hydrolysis product（Mb with lower polymerization degree） was accounted for 34.20%, the zeta potential was 10.02 m V.Secondly, the application conditions during PAFC’s treatment of DOM has been discussed. The results showed that the PAFC was insensitive to changes of water temperature, it has a wide range of p H, 5.0-9.0 and exhibited better DOM removal capacity in the lower dosage compared with commercially available coagulants. At the dosage of 4.0 mg/L, total organic carbon（TOC） and chemical oxygen demand(COD_Cr) removal rate can reach 43.60% and 39.30%.Finally, PAFC is compounded with other moleculars, such as inorganic high molecular polysilic acid, organic high polymer polyacrylamide（PAM） and powered actived carbon, to remove DOM in simulated water samples. The compounding conditions has been investigated. The result shows that polyaluminum ferric silicate chloride shows good property to remove DOM when（Al+Fe）/Si molar ratio, polymerization temperature, polymerization time and dosage are respectively 10:1, 30℃, 15 h and 3.5 mg/L. PAFC/PAM shows good property when the concentration of PAM, m（PAFC）/m（PAM） and adding sequence are respectively 0.5 mg/L, 3:1 and PAFC first. PAFC and powered active carbon shows good property when m（PAFC）/m（Powered active carbon） and adding sequence are respectively 2:1 and powered active carbon first. Under the above optimized conditions, all showed good removal ability for DOM, and the removal rates of TOC and CODCr respectively reached 62.40%, 86.31%, 95.61% and 58%, 82%, 92.80%.